Office of Transportation                  EPA420-R-06-006
United States     and Air Quality                     March 2006
Environmental Protection 	
Agency
         EPA Technical Study on the
         Safety of Emission Controls
         for Nonroad Spark-Ignition
         Engines < 50 Horsepower

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                                        EPA420-R-06-006
                                             March 2006
                    on the          of
                            for
                           < 50
  Assessment and Standards Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency

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Executive Summary
The purpose of this technical study is to assess the incremental impact on safety of applying the advanced emission
control technology expected to meet the new emission standards under consideration for particular subcategories of
nonroad engines and equipment, focusing on the risk of fire and burn to consumers in use. The study will be part of
the rulemaking record for the proposed standards and satisfies the provisions of section 205 of PL 109-54, which
requires the Environmental Protection Agency (EPA) to assess potential safety issues, including the risk of fire and
burn to consumers in use, associated with the proposed  emission standards for nonroad spark-ignition (SI) engines
under 50 horsepower (hp).   As is discussed below, this technical  study concludes that new emission standards
would not increase the risk of fire and burn to consumers in use. In fact, in a number of circumstances the study
demonstrates a directional decrease in risk.

This study evaluates new exhaust and evaporative emission standards for nonhandheld (NHH) and handheld (HH)
equipment in the Small SI engine category and outboard (OB) and personal watercraft (PWC) engines and vessels
in its Marine SI engine category. The new emission standards addressed by this study include:

       New catalyst-based hydrocarbon plus oxides of nitrogen (HC+NOx) exhaust emission standards for NHH
        engines;

       New HC+NOx and carbon monoxide (CO) exhaust emission standards for OB/PWC engines and vessels;

       New fuel evaporative emission standards for NHH and HH equipment; and

       New evaporative emission standards for OB/PWC engines and vessels.

The following summarizes EPA's assessment of the incremental impact on safety of new standards in each of these
four areas.  For each new  standard,  EPA concludes that the forthcoming Phase 3  emission  standards may be
implemented without any incremental increase in risk of fire or burn to consumers in use. Furthermore, the testing
and analysis also indicates that compliance with the Phase 3 emissions standards will most likely reduce the risk to
consumers of operating Phase 2 products in these subcategories.

Exhaust emission standards for NHH engines: We conducted the technical study of the incremental risk of catalyst-
based HC+NOx emission standards for NHH engines on several fronts.  First, working with the Consumer Product
Safety Commission (CPSC), EPA evaluated CPSC reports and databases  and other outside sources to identify those
in-use situations which create fire and burn risk for consumers. Six basic scenarios were identified for evaluation.
Second, EPA conducted extensive laboratory and field testing of both current technology (Phase 2) and prototype
catalyst-equipped advanced technology engines  and equipment (Phase 3) to assess the emissions performance and
thermal characteristics of the engines  and equipment.   EPA also contracted with Southwest  Research Institute
(SwRI) to conduct design and process Failure Mode and Effects Analyses (FMEA) comparing Phase 2 and Phase 3
compliant engines and equipment to evaluate incremental changes in risk probability as a way of evaluating the
incremental risk of going from Phase 2 to Phase 3 emission standards. Our technical work and subsequent analysis
of all of the data and information strongly indicate that catalyst-based standards can be implemented without an
incremental increase in the risk of fire or burn to the consumer.  In many cases, the designs used for catalyst-based
technology can lead to an incremental decrease in such risk.

Evaporative  emission standards for NHH and HH engines and equipment: EPA also evaluated the incremental risk
of fire and  burn to  consumers for the evaporative emission  standards we are  considering for NHH and  HH
equipment. For both subcategories we are considering fuel tank and fuel hose permeation standards similar to those
in place for  other nonroad SI engines and vehicles, such as all-terrain vehicles and off-highway motorcycles. In
addition, for NHH equipment we are considering running loss controls designed to reduce emissions related to  fuel
in the tank evaporating to the atmosphere during equipment operation. Working with CPSC, EPA evaluated CPSC
databases to  identify those in-use situations which create fire and burn risk for consumers. Fuel leaks from tanks or
fuel hoses on HH and NHH equipment were identified as the major safety concern for evaluation.

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Fuel tanks used on HH and NHH equipment are constructed of different types of materials using different processes
and each has a potentially different approach to controlling tank permeation emissions. EPA evaluated both current
and treated fuel tanks in the laboratory for several years and identified no incremental  safety risk related to the
technologies for reducing permeation emissions. Most fuel hoses meet American Society for Testing and Materials
(ASTM) and Society  of Automotive Engineers (SAE) standards, and the types of fuel hoses needed to reduce
permeation are  in widespread use today. In fact, some lawn and garden equipment already uses low permeation
hose.

Beyond this, in situations where custom fuel hoses are used there are the ASTM and manufacturer specific test
procedures and requirements  that  assure proper  in-use  performance.  With regard  to  fuel  tanks, there are
manufacturer specific  test procedures and  requirements which manufacturers apply to current products and will
continue to use in the future.  The emissions  durability portion of EPA's permeation test procedures inherently
includes the types of evaluations needed to identify the potential for leaks in-use. The FMEA conducted by SwRI
also  looked at systems interaction between  engine  modifications and the fuel system  and determined  that
permeation controls and running loss controls on NHH  fuel tanks would not increase the fire and burn risk
probability but  could  in fact lead to directionally better systems from a safety perspective.  Overall, there  is  no
incremental  safety risk in applying  advanced technology  to  reduced evaporative emissions from HH and NHH
engines and equipment, and to some degree the use of technology can lead to an incremental decrease in risk.

Exhaust emission standards for OB/PWC engines and vessels: EPA is also considering new HC+NOx and CO
exhaust emission standards for OB/PWC engines and  vessels.  The US Coast Guard (USCG) keeps a close watch
over marine safety issues,  and USCG, as well as  several other  organizations,  including SAE, Underwriters
Laboratories (UL), and the American Boat  and Yacht  Council (ABYC), already have safety standards which apply
to engines and fuel systems  used  in these vessels.  The  four-stroke and two-stroke direct  injection engine
technologies that  are  likely to be used  to meet the  exhaust emission  standards being considered by EPA for
OB/PWC are in widespread use in the vessel fleet  today.  These  more sophisticated engine  technologies are
replacing two-stroke carbureted engines. These four-stroke and two-stroke direct injection engines meet applicable
USCG and ABYC safety standards and future products will do so as well. The proposed emission standards must be
complementary to the already existing safety standards and our analysis indicates that this is the case. There are no
known safety issues with this technology compared to the two-stroke carbureted engines and arguably the newer
technology engines provide  safety benefits  due to improved engine reliability in use. Based on the applicability of
USCG and ABYC safety standards and the  good in-use experience with advanced technology engines in the current
vessel fleet, EPA believes new emission standards would not create an incremental  increase in the risk of fire or
burn to the consumer.

Evaporative emission standards for OB/PWC engines  and vessels:  EPA also analyzed the  incremental impact on
safety  for the fuel hose and fuel tank  permeation and fuel tank  diurnal evaporative  emission standards it is
considering for marine vessels.  As with the exhaust emission standards, the proposed  emission standards must
complement existing USCG,  ABYC, and SAE test procedures and safety standards related to fuel hoses for marine
vessels and USCG, UL, and ABYC standards and test  procedures covering portable and installed fuel tanks.  All of
these standards are designed to address the in-use performance of fuel systems with the goal of eliminating fuel
leaks.  The low permeation fuel hoses needed to meet the Phase 3 requirements would need to pass these standards,
and evidence indicates that this would occur.  In fact, fuel hoses meeting these requirements are available today.
The  low permeation fuel tanks needed to meet the Phase  3 requirements would also need to  pass the applicable
USCG,  UL, and ABYC standards;  work  conducted  by EPA and vendors supplying  the marine tank  industry
indicates that the technology needed to meet these standards can be applied without an incremental increase in risk
over current systems.

EPA is also considering fuel tank diurnal emissions standards for fuel tanks used on Marine SI engines and vessels.
For PWC and  portable OB fuel tanks,  this  would likely  entail the use of venting control technology  already
commonly used in these tanks.  For vessels with installed fuel tanks this would likely employ the use of activated
carbon canisters to capture this vapor. Such canisters have been used safely on automobiles  for more than 30 years
and a prototype fleet run last summer revealed no safety concerns. Overall, there should be no incremental increase
in risk  of fire  or burn to consumers in applying advanced technology to reduce evaporative emissions  from

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OB/PWC engines and vessels.  In fact, the reduction of permeation emissions is likely to incrementally decrease
safety risks from fire in the under floor areas on boats where the tanks and hoses are installed.

In summary, EPA has evaluated the incremental impact on safety focusing on the risk of fire and burn to consumers
associated with the advanced technologies expected to meet the new emission standards EPA is considering for the
Small SI engine  and Marine SI engine categories under 50 hp.  Laboratory and field testing, the FMEA analyses,,
the mandatory and consensus test procedures and standards which apply to these engines and fuel systems, and the
availability of certain components  and engines which already meet the Phase 3 standards lead EPA to conclude that
new  emission standards would not cause  an incremental increase in  risk of fire or burn to consumers in use.
Instead,  compliance with  the  new standards  should reduce certain safety  concerns  presented by current
technologies.

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TABLE OF CONTENTS


EXECUTIVE SUMMARY	1

LIST OF ACRONYMS	7

1.   INTRODUCTION	9
  A.    BACKGROUND	9
  B.    OVERVIEW	11

2.   EPA'S APPROACH TO ASSESSMENT OF THE SAFETY ISSUE	13

  A.    SCOPE OF ASSESSMENT	13
  B.    THE SMALL SI ENGINE ASSESSMENT	13
  C.    MARINE SI ASSESSMENT	13

3.   TECHNICAL BACKGROUND ON NONHANDHELD ENGINES	15

  A.    CURRENT TECHNOLOGY	15
    Class I engines	16
    Class II engines	18
  B.    CURRENT SAFETY STANDARDS	21
  C.    IN-USE SAFETY EXPERIENCE	23
    CPSC Databases:	24
    Discussion of CPSCData	27

4.   SCENARIOS FOR EVALUATION OF NHH ENGINES AND EQUIPMENT	29

  A.    SUMMARY OF OTHER INFORMATION CONSIDERED	29
  B.  SAFETY SCENARIOS FOR EVALUATION	30
    Scenario 1: Contact burns	30
    Scenario 2: Debris fire:	30
    Scenario 3: Fires due to fuel leak	31
    Scenario 4: Fires related to refueling	31
    Scenario 5: Fire related to storage and shutdown	31
    Scenario 6: Ignition misfire	31
    Scenario 7: Fire due to rich operation	32

5.   NHH TEST PROGRAM	33

  A.    ENGINE SELECTION	33
  B.    ENGINE MODIFICATIONS	34
    Class I- 10 g/kW-hr systems	34
    Class II- 3.5 g/kW-hr HC+NOx system	40
    ClassII- 8.0g/kW-hr HC+NOx systems	43
  C.    INFRARED THERMAL IMAGING	45
  D.    LABORATORY TEST PROCEDURES	46
    Operation over the Federal A-Cycle	46
    Hot Soak Testing	47
    After-fire Testing	47
    Misfire Testing	48
    Simulated Rich Operation	49
  E.    FIELD OPERATION	49
    Acquisition ofIR Thermal Images in the Field	54

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6.   TEST RESULTSCOMPARISON BETWEEN EPA'S PHASE 3 PROTOTYPES AND CURRENT
ENGINE SYSTEMS	55
  A.    EMISSIONS RESULTS	55
  B.    LABORATORY TEST RESULTS	55
    Surface temperature measurements by infrared thermal imaging - Class I Side-valve Engines	55
    Infrared thermal imaging - Class IOHV Engines	59
    Infrared thermal imaging - Class II OHV Engines	77
    Muffler outlet temperatures - Class I and Class II Engines	89
    Run-on after-fire testing	89
    Ignition misfire testing	90
    Rich Operation	94
  C.    FIELD TESTING RESULTS	96
    Surface Temperature Measurements by Infrared Thermal Imaging Taken During Grass Cutting Operations..97
    Results of Hot-Soak Tests Conducted in the Field.	98
    Idle Testing	103

1.   DESIGN AND PROCESS FAILURE MODE  AND EFFECTS ANALYSES (FMEA) TO ASSESS NHH
INCREMENTAL SAFETY RISK	104

  A.    BACKGROUND	104
  B.    THE WORK CONDUCTED BY SwRI	105
  C.    DESIGN FMEA	107
  D.    PROCESS FMEA	109
  E.    FMEARESULTS	109
  F.    DISCUSSION OF DESIGN FMEAs FOR CLASSES I AND II	110
  G.    CONCLUSION	Ill

8.   CONCLUSIONS - IMPACT OF PHASE 3 EXHAUST STANDARDS ON CLASS I AND  CLASS II
NHH ENGINES	130
  SCENARIO 1: CONTACT BURNS	130
    Scenario Description: Thermal burns due to inadvertent contact with hot surface on engine or equipment. ..130
    Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:	130
    Conclusions Based on FMEA of Burn Safety	134
  SCENARIO 2: DEBRIS FIRE	134
    Scenario Description: Grass and leaf debris on engine/ equipment	134
    Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:	134
    Conclusions Based on FMEA of Debris Fire Safety	135
  SCENARIO 3 FUEL LEAK	136
    Scenario Description: Fires due to fuel leaks on hot surfaces	136
    Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:	136
    Conclusions Based on FMEA of Fuel Spills or Leaks	137
  SCENARIO 4: REFUELING-RELATED	138
    Scenario Description: Fires related to spilled fuel or refueling vapor	138
    Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:	138
    Conclusions Based on FMEA of Refueling-Related Safety	138
  SCENARIOS: STORAGE AND SHUTDOWN	139
    Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:	139
    Conclusions Based on FMEA of Shutdown and Storage Safety	139
  SCENARIO 6: IGNITION MISFIRE	140
    Scenario Description: Engine malfunction which results in an ignitable mixture of unburnt fuel and air in the
    muffler	140
    Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:	140
    Conclusions Based on FMEA of Ignition Misfire	141

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  SCENARIO 7: RICH OPERATION	142
    Scenario Description: Fire due to operation with richer than designed air-to-fuel ratio in engine or catalyst.
    	142
    Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:	142
    Conclusions Based on FMEA of Rich Operation	143

9.   SAFETY  ANALYSIS  OF  SMALL  SI   ENGINE  EVAPORATIVE  EMISSIONS  CONTROL
TECHNOLOGIES	144
  A.    CURRENT TECHNOLOGY	144
    Fuel Evaporative Emissions	144
    NHH Equipment	144
    HH Equipment	145
  B. CURRENT SAFETY STANDARDS	145
  C. IN-USE SAFETY EXPERIENCE	146
    NHH Equipment	146
    HH Equipment	146
  D. EMISSION CONTROL SYSTEM DESIGN AND SAFETY	147
    NHH Equipment	147
    HH Equipment	150
  E. CONCLUSION	151

10. SAFETY ANALYSIS FOR MARINE SI	152
    Marine Engines	152
    Marine Vessel Fuel Systems	153
  B. IN-USE SAFETY EXPERIENCE	153
    Marine Engines and Vessels	153
  C. CURRENT SAFETY STANDARDS	154
    Marine Engines	154
    Marine Vessel Fuel Systems	155
  D. EMISSION CONTROL SYSTEM DESIGN	156
    Marine Engines	156
    Marine Auxiliary Engines	156
    Marine Vessels	156
    Fuel tanks	757
    Diurnal Emissions Control	158
  E. ASSESSMENT OF SAFETY IMP ACT OF NEW EMISSION STANDARDS	158
    New Exhaust Emission Standards for OB/PWC	158
    New Exhaust Emission Standards for Marine Auxiliary Generators	158
    Fuel Hose Permeation Standards	159
    Fuel Tank Permeation Standards	160
    Fuel Tank Diurnal Emission Control Standards	160
  F. CONCLUSION	161

APPENDIX A - BASIC PRINCIPLES OF INFRARED THERMAL IMAGING	162
  IR TEMPERATURE BASICS	162
  CONDUCTIVE HEAT TRANSFER	162
  CONVECTIVE HEAT TRANSFER	162
  RADIATIVE HEAT TRANSFER	162
  HOW THE IRFLEXCAMT AND IR SNAPSHOT CAMERA'S CONVERT RADIANCE TO TEMPERATURE	163

APPENDIX B: EMISSIONS RESULTS	165

APPENDIX C - FMEA OF SMALL SI EQUIPMENT AND ENGINES	168

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List of Acronyms
ABYC         American Boating and Yacht Council
ANSI          American National Standards Institute
ASAE         American Society of Agricultural Engineers
ASTM         American Society for Testing and Materials
BP             Barometric Pressure
C             Degrees Celsius
CAA           Clean Air Act
CAD           Crank Angle Degrees
CARB         California Air Resources Board
Class I         Nonhandheld Engines <225cc
Class II         Nonhandheld Engines >225cc and less than 19kW
CO            Carbon monoxide
CFR           Code of Federal Regulations
CPSC          Consumer Product  Safety Commission
cpsi            Cells per square inch
CVS           Constant Volume Sampler
E85            mixture of 85% ethanol and 15% gasoline
ECU           Engine Control Unit
EFI            Electronic Fuel Injection
EPA           Environmental Protection Agency
ETC           Electronic Throttle  Control
EVOH         Ethyl Vinyl Alcohol
F             Degrees Fahrenheit
FMEA         Failure Modes and  Effects Analysis
FR             Federal Register
g/kW-hr        Grams per kilowatt hour
HC            Hydrocarbons
HOPE         High-Density Polyethylene
NHH           Non-handheld
HH            Handheld
hp             Horsepower
INDP          In-Depth Investigations (CPSC database)
IPII            Injury/Potential Injury Incident (CPSC database)
IR             Infrared
ISO            International Standards Organization
kW            Kilowatt
LEV           Low Emission Vehicle
MAP           Manifold Absolute  Pressure
MIL           Malfunction Indicator Light
NEISS         National Electronic Injury Surveillance System (CPSC database)
NIST           National Institute of Standards and Testing
NFIRS         National Fire Incident Reporting System
NFPA         National Fire Protection Association
NOx           Oxides of nitrogen
NVFEL         National Vehicle and Fuel Emissions Laboratory
OB            Outboard
OEM           Original Equipment Manufacturers
OHV           Overhead Valve
OPEI           Outdoor Power Equipment Institute
Pd             Palladium
PGM           Platinum Group Metal
Ph2            Phase 2

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Ph3            Phase 3
Pt             Platinum
PWC          Personal Water Craft
Rh             Rhodium
ROM          Ride On Mower
RPN           Risk Priority Number
S AE           Society of Automotive Engineers
SD/I           Sterndrive/Inboard
SI             Spark Ignition
SwRI          Southwest Research Institute
TDC           Top dead center
TPS           Throttle Position Sensor
UL             Underwriters Laboratory
US             United States
USD A         United States Department of Agriculture
USCG         United States Coast Guard
VR            Variable Reluctance
WBM          Walk Behind Mower
WOT          Wide open throttle
XLPE          Cross-link polyethylene

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1.      Introduction
A.
BACKGROUND
Over the past 15 years, the Environmental Protection Agency (EPA) has implemented emission control programs
for nonroad engines and equipment. Section 213 of the Clean Air Act (CAA)  authorizes EPA to  set emission
standards for nonroad engines and equipment that "achieve the greatest degree of emissions reduction achievable
through the application  of technology which the  Administrator determines will be available for the engines or
vehicles  to  which such  standards shall  apply  giving  appropriate consideration to the cost of applying such
technology within the period of time available to manufacturers and to noise, energy, and safety factors associated
with the application of  such technology."  Section 216 of the  CAA  defines a nonroad engine as "an internal
combustion engine (including the fuel system) that is not used in a motor vehicle or a vehicle used solely for
competition." Nonroad engines are used in a variety of nonroad vehicles and equipment and are primarily powered
by diesel or gasoline. Gasoline-powered engines are frequently referred to as spark-ignition (SI) engines.

EPA's nonroad program regulates nonroad engines and equipment  in seven general engine categories.   These
categories are further divided into various subcategories or groups depending on what approach is most useful in
distinguishing the particular product and application from others.  For example, certain subcategories describe an
engine's or an equipment's application (i.e. snowmobile, personal watercraft, nonhandheld equipment) while other
subcategories include engines of a certain size  (i.e. SI engines < 19kW (25hp)).  Therefore, each of these seven
engine categories contains further divisions, including engines and equipment with a wide range of horsepower or
performance characteristics. Table  1-1 illustrates the nonroad program and its applicable regulations for these
various subcategories.

                                  Table 1-1 EPA Nonroad Engine Program
Engine Categories
1 . Locomotives engines
2. Marine diesel engines
3. Other nonroad diesel engines
4. Marine SI engines
5. Recreational vehicle SI engines
6. Small SI engines (SI engines < 19
kW (or < 30 kW if total
displacement is < 1 liter))
a. Handheld (HH)
b. Nonhandhled (NHH)
7. Large SI engines (SI engines > 19
kW (or > 30 kW if total
displacement is < 1 liter))
Applicable
Regulations
40 CFR Part 92
40 CFR Part 94
40 CFR Parts 89,
1039
40 CFR Part 91
40 CFR Part 1051
40 CFR Part 90
40 CFR Part 1048
Date of Last
Significant Rule
April 16, 1998
December 29,
1999
June 29, 2004
October 4, 1996
November 8, 2002
a. Jan 12. 2004
b.Mar 30,1999
November 8, 2002
Code of Federal
Regulation
Citation
63 FR 18978
64 FR 73300
69 FR 38958
61 FR 52088
67 FR 68242
a. 69 FR 1824
b. 64 FR 15208
67 FR 68242
Applicable
Standards
Exhaust
Exhaust
Exhaust
Exhaust
Exhaust &
Evaporative
Exhaust
Exhaust &
Evaporative
Section 428(b)  of the 2004 Omnibus Appropriations bill (PL 108-199) required EPA to consider new emission
standards for nonroad SI engines under 50 horsepower (hp). For purposes of this discussion, 50 hp is about 37
kilowatts (kW). The first three categories in Table  1-1  are only diesel engines so they are not covered by the

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provisions.  As shown below, the remaining four categories are all SI engines, with all or at least some or their
product offerings below 50 hp.
                                Table 1-2 SI Engine HP Distribution
SI Engine Category
Marine SI
Recreational SI
Small SI
Large SI
Engine Subcategory
Outboard
Personal Watercraft
Sterndrive/Inboard
All Terrain Vehicle
Off-Highway Motorcycle
Snowmobile
Handheld
Nonhandheld
None
Estimated % < 50 hp
65
<5
0
100
100
2
100
100
40
Standards for Marine SI engines were last promulgated in 1996 and are presently ending their phase-in period.
Recreational SI engine standards were promulgated in 2002, and are beginning their phase-in in 2006.  Small SI
engine standards for nonhandheld (NHH) engines (containing Classes I and II) were last promulgated in  1999 and
finish their phase-in next year, 2007.  Standards for handheld (HH) (containing Classes III-V) are catalyst-based in
many cases and the implementation  approach was  revised in a 2004 technology review.   These engines do  not
complete their phase-in until 2010.   Finally, two phases of standards for Large SI engines were promulgated in
2002, with catalyst-based standards and a new test cycle required for 2007.

Based on its assessment of these categories, EPA intends to propose revisions to the emission standards for Marine
SI engines and Small SI NHH engines and equipment for exhaust and evaporative controls and HH equipment for
evaporative controls. Under section 205 of the appropriations bill funding EPA for fiscal year 2006 (section 205 of
PL 109-54) EPA, in coordination with other appropriate federal agencies, must complete and publish a  technical
study analyzing the potential safety issues associated with the proposed standards for engines <50hp, including the
risk of fire and burn to consumers. The technical study is to be completed and published before the publication of
the notice of proposed rulemaking. This safety  study satisfies the requirements of this provision and will also be part
of the supporting information in the rulemaking.

The safety analysis for NHH exhaust emissions is presented in Chapters 3 through 8. The  safety analysis  for
evaporative control requirements for  NHH and HH are presented in Chapter 9 and for Marine  SI requirements in
Chapter 10. The proposed rule is also expected to include the first ever exhaust and evaporative  emission standards
for sterndrive/inboard (SD/I) engines  and vessels as  part of our authority under section 213.  However, they are  not
addressed in this safety study as they are all over 50hp.   The impact on safety of new standards for these engines
and vessels will be addressed in the proposal.

As part of the assessment for the rulemaking,  EPA  evaluated the performance of the current technology  for NHH
engines and equipment (studies for HH and  Marine SI were not conducted).   EPA's initial  efforts focused on
developing a baseline for emissions and general engine performance so that we could assess the potential for new
                                                   10

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emission standards for engines and  equipment in this  category. This  process  involved  laboratory and  field
evaluations of the current engines and equipment.  As part of this assessment EPA also reviewed engineering
information and data on existing engine designs and their emissions performance. Using information and experience
gathered in this effort, EPA initiated a testing program designed to  evaluate improvements to the emissions
performance of these gasoline engines and to assess the potential safety impacts associated with the use  of more
advanced emission control technology.

The  technology approaches  assessed by EPA for meeting  the new  standards  for  Class  I  (< 225cc engine
displacement) and Class II (>225 cc)  NHH engines include exhaust catalyst aftertreatment and improvements to
engine and fuel system designs.  In addition to its own testing and development effort, EPA also met with engine
and equipment manufacturers to better understand their  designs and technology  and to determine the  state of
technological progress beyond EPA's Phase  2 standards. EPA's research, development, and  testing evaluation
efforts included laboratory and real world field assessments of potential technology applications. In the course of
this work EPA conducted both thorough evaluations  of  laboratory and field emissions performance as well as
separate assessments of safety issues. The engines EPA used for developing these improved emissions factors were
maintained based on manufacturer specifications. Every engine in the field evaluation was maintained at a level at
least as rigorous as called for in the  manufacturer's requirements.

The central focus of our safety assessments for NHH engine exhaust standards has been to understand the potential
incremental safety impact of the application of catalyst-based exhaust emission controls on Class I and  Class II
engines. EPA's engineering analysis of the safety of exhaust and evaporative emission controls  for NHH  and HH
engines and equipment focused on five areas:

    1.  Engineering analysis and emission testing  of current technology Class I and Class II engines and Class I
        and Class  II engines with properly designed emission  control systems  capable of achieving  exhaust
        emission reductions beyond the Phase 2 standards  (catalyst-based advanced prototype systems).

    2.  Exhaust  emission and  safety assessment testing of Class I  and Class II engines  in both  a stock
        configuration and equipped with advanced prototype emission control systems.  Engines were tested both
        in the  laboratory  and in the field over a  broad  range of operating conditions;  external exhaust system
        surface  temperatures were measured using infrared thermal imaging while temperatures  for lubricant,
        cylinder head and exhaust gases were measured using thermocouple probes.

    3.  Laboratory analysis  of significant off-nominal  operating conditions  that were identified by engine
        manufacturers, original equipment manufacturers (OEMs), and EPA staff.

    4.  Assessment of the potential safety impacts of evaporative emission control requirements.

    5.  The completion of design Failure Mode and Effects Analyses  (FMEA) for  Class I and Class II engines
        used in walk-behind and ride-on mowers and three process FMEAs for consumer use of lawn equipment.
        These studies were conducted as an additional tool for identifying potential safety concerns in going from
        Phase 2 to potential Phase 3 standards.

With regard to marine  SI, we focused on safety issues  related to  incorporating upgraded fuel systems and engine
modifications for both outboard and personal watercraft engines.  We also assessed the potential incremental safety
impacts of evaporative emission control requirements for marine SI vessels.

B.      OVERVIEW

The remainder of this report is comprised of nine chapters. Following this Introduction, Chapter 2 explains EPA's
basic approach to its assessment of the safety issue. Chapters 3 through 8 address only NHH engines. Chapter 3
gives background on small SI NHH engine technology, the relevant applicable safety standards, in-use experience
related to the safety concerns of interest.  Chapter 4 describes the safety issues and concerns raised by the various
parties and identified by EPA and identifies the scenarios  to be assessed along with the causal factors.  Chapter 5
describes in detail the test methods  employed by EPA while Chapter 6 presents the results of the testing.  Chapter 7
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describes the design and process FMEAs conducted by Southwest Research Institute (SwRI)  and discusses the
safety results in the context of potential Phase 3 standards.  Chapter 8 presents EPA's technical conclusions for the
Small SI engine category by assessing the concerns identified in Chapter 4 in light of the technical information and
analyses presented in  Chapters  5 through  7.   Chapter 9 addresses the evaporative control requirements for
equipment powered by Small  SI engines.  Finally, Chapter 10 assesses the potential safety impact evaporative and
exhaust emission standards for Marine SI engines and vessels as discussed above. The appendices to this report
contain relevant data and technical information referred to in the text.
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2.      EPA's Approach to Assessment of the Safety Issue
A.      SCOPE OF ASSESSMENT
As mandated by Section 205, this study addresses four subcategories of nonroad engines and equipment containing
SI engines under 50 hp for which EPA intends to propose revisions to the emission standards. These two categories
are commonly referred to as Small SI and Marine SI. As explained in Chapter 1, the four subcategories include HH
and NHH, in the Small SI engine category, and outboard and personal watercraft engines (OB/PWC), in the Marine
SI engine category. The study does not address the EPA categories where EPA is not intending to propose  revisions
to the emission standards. This study also does not address safety issues concerning Marine SI vessels powered by
SD/I engines. EPA intends to propose exhaust and evaporative standards for this Marine SI subcategory. EPA will
address any safety concerns related to SD/I requirements as part of the proposed rule.

For Small SI and Marine SI we are considering new exhaust and/or evaporative emission standards. With  regard to
the Small SI category we are considering new exhaust and evaporative standards for nonhandheld equipment and
new  evaporative standards for handheld equipment.  For Marine SI engines we are  considering new exhaust and
evaporative standards for both outboard engines and personal watercraft.

B.      THE SMALL SI ENGINE ASSESSMENT

The small SI engines and equipment that we considered in this study have been commercially marketed for over 50
years, are commonly found across the United States (US), and have relatively frequent usage.  For example, EPA
estimates that there are over 52  million residential and commercial walk behind lawn mowers and ride-on lawn,
garden, and  turf equipment in-use in the United States today.  EPA estimates that these are used about 3  billion
hours per year. Thus, there is a large  amount of in-use experience with the performance of this equipment over time.
As successive generations of engines and equipment have entered the marketplace there have been improvements to
address consumer satisfaction, performance, safety, and emissions, among other factors. Over this time, consumers
have had a variety of types of performance experiences with this equipment. In some cases problems are related to
engine or equipment design while in others they are  related to human interactions.  It is not uncommon for both
factors to contribute to a problem.

It is not the purpose of this study to review  or generally assess safety or performance issues with  current small  SI
engines and equipment in-use. This study instead looks at the incremental impact on safety of moving from current
Phase 2  standards to new Phase 3 hydrocarbon plus oxides of nitrogen (HC+NOx) exhaust emission standards for
nonhandheld Small SI Engines which are nominally a 35-40 percent reduction over current Phase  2  emission
standards, as well as fuel evaporative emission control requirements for all  Small  SI engines Although it was
necessary to understand the performance of Phase 2 products in order to fully characterize the baseline used for this
incremental safety analysis, this study does not assess and does not draw any conclusions on what safety risks, if
any,  are presented by current equipment. Instead, EPA took current equipment as the baseline, and evaluated the
incremental impact on safety of moving from this baseline to equipment applying more advanced emissions control
technology.  The study does not address any issues not related to the potential proposed rulemaking for small  SI
engines, such as concerns about carbon monoxide (CO) exposure or refueling problems related to portable gasoline
containers.

C.      MARINE SI ASSESSMENT

EPA intends to propose revisions to the exhaust and evaporative emission standards for Marine SI engines. As with
Small SI engines, the study addresses the incremental impact on safety of going from the current EPA standards to
the standards under consideration. The study addresses both outboard engines and personal  watercraft.
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3.      Technical  Background on  Nonhandheld  Engines

A.      CURRENT TECHNOLOGY

The scope of this study included Class I and Class II engine systems, which relate to residential walk-behind and
riding lawn mowers, respectively. Residential lawn mower equipment was chosen for the following reasons:

    1.   Lawn mowers and  the closely-related category of lawn tractors represent the largest categories of
        equipment using Class I and Class II nonroad SI engines. EPA estimates that over 47 million walk-behind
        mowers and ride-on lawn and turf equipment are in-use in the US today.

    2.   These equipment types represent the majority of sales for Small SI engines.

    3.   CPSC data indicates that more thermal burn injuries associated with lawn mowers occur than with other
        NHH  equipment; lawn mowers therefore  represent the largest thermal  burn risk for these classes of
        engines.

    4.   General findings regarding advanced emission control technologies  for residential  lawn and garden
        equipment carry over to commercial lawn and turf care equipment as  well as to other NHH equipment
        using  Class I and Class II engines.  Lawn mower design  and use characteristics pose unique safety
        implications not encountered by other NHH equipment using these engines (i.e. a mower deck collects
        debris during operation whereas a pressure washer collects no debris).  Thus, other NHH equipment may
        employ similar advanced  emission control technologies for meeting the proposed  standards without a
        corresponding concern regarding the safety issues analyzed in this study.

Information in EPA's nonroad emissions model estimates suggests about 1.5 billion lawn mower use events per
year for residential  lawn care equipment.1 Much of the equipment is typically operated and refueled by the general
public. The equipment  is operated under conditions where  grass-clipping and similar debris  are often present,
particularly during  side-discharge or mulching grass cutting operations. Refueling  operations typically occur from
portable containers  with no automatic cut-off, and can result in fuel spillage.

Class I product, mostly walk-behind mowers, are produced by both integrated and non-integrated manufacturers.
Integrated manufacturers make both the engine and equipment, non-integrated manufacturers make only one of the
two. In almost all  cases the fuel  tank  and muffler are part of the  Class  I engine when it  leaves the engine
manufacturer. Based on manufacturer estimates provided as part of EPA's emission certification program, there are
about 14 million Class I and Class II engines produced per year. In Class II, which also has integrated  and non-
integrated manufacturers, it is  not uncommon to  have  the fuel tank and/or muffler added by the equipment
manufacturer.  According to the Outdoor Power Equipment Institute (OPEI), there were about 9 million  lawn and
garden units produced  in the 2005 model year with  the remainder comprised  primarily of  pressure  washers,
generators, tillers, snow throwers, construction, and commercial equipment.  Table 3-1 below  shows the current
Phase 2 emission standards for Class I and Class II engines.
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                                Table 3-1 EPA Phase 2 Emission Standards
Engine Class
Class I
Class II
HC+NOx Standard
(g/kW-hr)
16.1
12.1
CO Standard
(g/kW-hr)
610
610
Final Phase-In Year
for Large
Manufacturers
2007
2005
Regulatory Useful
Life (hours)
125,250, or 500
250, 500, or 1000
Crankcase must be closed. The HC+NOx standards do not apply to  engines used in snow equipment. Emission
averaging is allowed to meet the HC+NOx standard. There are no evaporative emission control requirements for
Class I or Class II. The useful life category is determined by the manufacturer.
EPA evaluated the incremental change in key safety parameters for the modification of lawn mowers and lawn
tractors from Phase 2 emissions compliance to meeting potential Phase 3 HC+NOx emission standards  of 10.0
g/kW-hr for Class I and 8.0 g/kW-hr for Class II.  These standards would be 35-40 percent more stringent than
Phase 2 emission standards on Federal certification fuel. The Phase 3 standards would not change the CO emission
standard for NHH engines.

The potential Phase 3 emission standards would also include measures for controlling fuel evaporative emission
requirements. While we looked at the full range of potential evaporative controls, our present program is focused on
fuel tank and fuel hose permeation emissions, running loss controls, and diffusion losses from freely vented fuel
caps. The fuel systems for Class I and Class II equipment consist of rubber fuel hoses and open-vented fuel tanks
which may be constructed out of metal or plastic.  Based on information supplied by manufacturers we estimate that
about 80 percent of Class I and 90 percent of Class II equipment are equipped with plastic fuel tanks.  Fuel hoses
used today  are typically  made out of  inexpensive  nitrile  rubber and there  are  general industry  consensus
performance standards related to hoses which apply.

The following discussion explains the  design elements for the type of emission control technology that could be
used to achieve the potential  Phase 3 emission standards discussed above.  These  technical  discussions and
information presented below are derived from more than two years of laboratory and field work conducted by EPA
in assessing current Phase 2 engine technology and developing prototype Phase 3 systems.

The North American automotive market is now entering its fourth decade of high-volume production of  exhaust
catalysts for light-duty gasoline-powered vehicles since the introduction of catalysts on Chrysler vehicles in 1975.
With the advent of Federal Tier 2 and California Low Emission Vehicle (LEV) II exhaust emission standards, light-
duty and medium-duty vehicles are equipped with catalysts and engine  management systems that control NOx, HC,
and CO emissions with greater than 99 percent efficiency relative to previous, non-catalyst engines.

Class  I and Class II nonroad SI engines face a number of engineering, safety, and cost challenges that can differ
substantially from those of light duty automotive applications. As a result, Class I and Class II exhaust emission
control systems differ from that of light-duty gasoline vehicles but share some common elements with emission
control systems that are now being applied to small-displacement on-highway motorcycles.

In addition, Class I and II equipment can make use of the advances in materials technology and fuel system designs
that have been made in the automotive industry over the past several decades.  These approaches to improved fuel
containment are now being applied to other nonroad applications in anticipation of upcoming evaporative emission
standards.

Class I engines
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Class I engines  typically  are equipped with integral  exhaust  and fuel systems and are  air-cooled.  Significant
applications include  walk-behind lawn mowers (largest segment), pressure washers, generator sets and pumps.
There are both overhead valve (OHV) and side-valve (SV) engines used in Class I, but side-valve engines are the
predominant type in Class I, particularly in lawn mower applications. They currently represent about 60 percent of
Class I sales. Exhaust catalyst design for Class I engines must take into account several important factors that differ
from automotive applications:

     1.   Air-cooled engines run rich of stoichiometry to prevent overheating when under load. Because of this, CO
        and HC emissions can be high. Catalyst induced oxidation of a high percentage of available reactants in
        the exhaust in the presence of excess oxygen (i.e., lean of stoichiometric conditions) can result in highly
        exothermic exhaust reactions and increase heat rejection from the exhaust.  For example, approximately 80
        to 90 percent of the energy available from catalyst-promoted exhaust reactions is via oxidation of CO.

    2.   Air-cooled engines have significant HC and NOx emissions that are typically  much higher on  a brake-
        specific basis than water-cooled automotive engine types.  Net heat available from HC oxidation and NOx
        reduction at rich of stoichiometric conditions is considerably less than that of oxidation of CO at near
        stoichiometric or lean of stoichiometric conditions due to the much lower concentrations of NO and HC in
        the exhaust relative to CO.

    3.   Most  Class I engines do not have 12-volt DC electrical systems to power auxiliaries and instead are pull
        start.  Electronic controls relying on 12-volt DC power would be difficult to integrate onto Class I engines
        without a significant cost increase.

    4.   Most  Class  I  engines  use  inexpensive stamped mufflers with internal baffles.  Mufflers are typically
        integrated onto the engine and may or may not be placed in the path of cooling air from the cooling fan.

    5.   The regulatory emission test cycles (A-cycle, B-cycle), manufacturer's  durability cycles and some limited
        in-use operation  data  indicate that  emissions  control should focus  primarily on light and part load
        operation.

These factors would  lead to exhaust catalyst designs for small engines that should differ somewhat from those of
light duty gasoline vehicle exhaust catalysts.  Design elements specific to  Class I Phase 3 exhaust catalysts would
include:

     1.   Catalyst substrate volume would  be sized relatively small so as to be space-velocity limited.  Catalyst
        volume for  Class  I Phase 3  engines would be approximately 10 to 25 percent of the  engine  cylinder
        displacement, depending on cell count, engine-out emission levels, and oil consumption. Catalyst substrate
        sizes would be compact, with typical catalyst substrate volumes of approximately 1 to 3 cubic inches. This
        would effectively limit mass transport to  catalyst sites at moderate-to-high load conditions and reduce
        exothermic reactions occurring when exhaust temperature is highest. This is nearly the opposite of the case
        of typical automotive  catalyst designs.  Automotive catalyst volume  is typically 50  to 100  percent of
        cylinder displacement,  with the chief constraints on catalyst volume being packaging and cold-start light-
        off performance.

    2.   Catalyst precious metal loading (Pt-platinum, Pd-palladium, Rh-rhodium)  would be kept relatively low,
        and formulations would favor NOx and  HC selectivity over CO selectivity.  We estimate that typical
        loading ratios for Phase 3 would be approximately in the range of 30 to  50 g/ft3 (approximately 50 percent
        of typical automotive loadings at light-duty vehicle Tier 2 emission levels) and can be Pt:Rh, Pd:Rh or tri-
        metallic.  Tri-metallic platinum group metal (PGM) loadings that replace a significant fraction of Pt with
        Pd would be less selective for CO oxidation and would also reduce the cost of the catalyst.  Loading ratios
        would be similar or higher in Rh than what is typically used for automotive applications (20-25 percent of
        the total PGM mass in small SI) to improve NOx selectivity, improve rich of stoichiometry HC reactions
        and reduce CO selectivity.
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    3.  Catalysts would be integrated into the muffler design.  Incorporating the catalyst into the muffler would
        reduce surface temperatures, and would provide more surface area for heat rejection.  This is nearly the
        opposite of design practice used for automotive systems, which generally  try to  limit heat rejection  to
        improve cold-start light-off performance. The design for Class I Phase 3 engines  would have somewhat
        higher surface area and somewhat larger volume than many current  Class I muffler designs in order  to
        promote exhaust heat rejection and to package the catalyst,  but  would be similar to  some higher-end
        "quiet" Class I muffler designs.  Appropriately positioned stamped heat-shielding and touch guards would
        be integrated into Class I Phase 3 catalyst-muffler designs in a manner similar to many Class I Phase 2
        mufflers.   A degree of heat rejection would be available via forced convection from the cooling fan,
        downstream of cooling for the cylinder and cylinder head.  This  is the case with many current muffler
        designs. Heat rejection to catalyst muffler surfaces to minimize "hot spots" can also be enhanced internally
        by turning the flow through multiple chambers and baffles that  serve as sound  attenuation within the
        muffler, similar to the designs used with catalyst-equipped lawn mowers sold in Sweden and Germany.

    4.  Many Class I Phase 3 catalysts would include passive secondary air injection to enhance catalyst efficiency
        and allow the use of smaller catalyst volumes. Incorporation of passive secondary air allows halving  of
        catalyst substrate volume  for the same catalyst efficiency over the regulatory cycle. A system for Class I
        Phase 3 engines would be sized small enough to provide minimal change in exhaust stoichiometry at high
        load conditions so as to limit heat rejection, but would be provide approximately 0.5 to 1.0 points of air-to-
        fuel  ratio change at conditions of 50 percent of peak torque and below in order to  lower HC emissions
        effectively  in engines operating at air-to-fuel ratios similar to those of current Class I Phase 2  engines.
        Passive secondary air systems are preferred. Mechanical or electrical air pumps are  not necessary.  Passive
        systems include stamped  or drawn Venturis or ejectors integrated into the muffler,  some of which may
        incorporate an air check-valve, depending on the application.  Pulse-air injection is also a form of passive
        secondary air injection.   Pulse air draws  air into the exhaust port through a check-valve immediately
        following the closure of the exhaust valve. Active secondary air (air pump) systems were not considered in
        this  analysis since  they may be cost prohibitive for use in Class I  applications  due to  the need for a
        mechanical accessory drive or 12-volt DC power.

    5.  Class I engines are typically turned off via  a simple circuit that grounds the input side of the ignition coil.
        Temperature fail-safe capability would, if appropriate, can be incorporated into the engine by installing a
        bimetal thermal  switch in parallel with the ignition grounding circuit used for turning the engine off.  The
        switch can be of the inexpensive bimetal disc type in wide-spread use in numerous consumer  products
        (furnaces, water-heaters, ovens, hair dryers, etc.).  To  reduce cost, the bimetal switch could be a non-
        contact switch mounted to the engine immediately behind the muffler, similar to the installation of bimetal
        sensors currently used to actuate automatic chokes on current Phase 2 Class I lawn mower engines.

Class II engines

Almost all Class II engines are air-cooled. Unlike Class I engines, Class II engines are not typically equipped with
integral exhaust systems and fuel tanks.   Significant applications  include lawn tractors (largest segment),
commercial turf equipment, generator sets and pumps.  Overhead valve engines have largely replaced side-valve
engines in Class II, with  the few remaining side-valve engines certifying to the Phase  II standards using emissions
credits or being used in snow thrower type applications where the HC+NOx standards do not apply. Class II engines
are typically built more robustly than Class I engines. They often use cast-iron cylinder liners, may use either splash
lubrication or full-pressure lubrication,  employ high volume  cooling fans and in some  cases,  use significant
shrouding to  direct cooling air. Exhaust catalyst design practice for Class II engines will differ depending on the
level of emission control. Class II engine designs are more suitable for higher-efficiency emission control systems
than most Class I engine designs. The design factors are somewhat similar to Class I:

    1.  Class II engines  are mostly air-cooled, and thus must run rich of stoichiometry at high loads. The ability  to
        operate at air-to-fuel ratios rich of  stoichiometry  at  high load  may  be more critical for some  Class  II
        engines than for Class I  engines due to the longer useful life requirements in Class II.  The  engines
        incorporate more advanced fuel metering and spark control than is typical in Class I, in order to  meet the
        more stringent Class II Phase 2 emission standards (12.1 g/kW-hr HC+NOx in Class  II versus 16.1 g/kW-
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        hr in Class I).  The heat energy available from CO oxidation is typically somewhat less than the case in
        Class I because of slightly lower average emission rates.

    2.  As with Class  I engines, air-cooled Class  II engines have significant HC and NOx emissions that are
        typically much higher on a brake-specific basis than water-cooled automotive engine types, but generally
        with a  somewhat higher fraction of NOx in the total regulated HC+NOx emissions and lower CO
        emissions than is the case for Class I engines.

    3.  Most Class II engines are equipped with 12-volt DC electrical systems for starting.  Electronic controls
        relying on 12-volt DC power could be integrated into Class II engine designs.  Low-cost electronic engine
        management systems are extensively used in motor scooter applications in Europe and Asia.  Both Kohler
        and Honda have  introduced Class II  engines in North America that use electronic engine management
        systems.

    4.  Class II engines use inexpensive stamped mufflers with internal baffles similar to Class I, but the mufflers
        are often not integrated  onto the engine design and may be remote mounted in a manner more typical of
        automotive mufflers.  Class II mufflers are often  not placed in the direct path of cooling air from the
        cooling fan.

    5.  As with Class  I, the regulatory cycles (A-cycle,  B-cycle), manufacturer's durability  cycles and  some
        limited in-use operation data indicate that emissions control should focus primarily  on light and part load
        operation.

Taking these factors into account would point towards exhaust catalyst designs that differ from those of light duty
gasoline exhaust catalysts and differ in some cases  from Class  I systems. Elements specific to Class II Phase 3
emission control system design using carburetor fuel  systems would include:

    1.  Catalyst substrate volume would be sized  relatively small  so  as to be  space-velocity limited.  Catalyst
        volume for Class II Phase 3  engines would be  approximately 33-50 percent of the engine  cylinder
        displacement, depending on cell count, engine-out emission levels, oil consumption and the useful life
        hours to which the engine's emissions are certified. Catalyst substrate sizes would be very compact within
        typical mufflers used in  Class II, with typical  catalyst substrate volumes of approximately 3 to  12  cubic
        inches.  This would effectively limit mass  transport to catalyst sites at moderate-to-high load conditions
        and reduce exothermic reactions occurring when exhaust temperature is highest.

    2.  Catalyst precious metal loading would be kept  relatively low, and formulations would favor NOx and HC
        selectivity over CO selectivity to minimize heat concerns.  We estimate that typical loading ratios for Phase
        3 would be approximately in the range of 30 to 50 g/ft3 (approximately 50 percent of typical automotive
        loadings) and could be Pt:Rh, Pd:Rh or tri-metallic. Tri-metallic PGM loadings that replace a significant
        fraction of Pt with  Pd would be less selective for CO oxidation and would also reduce the cost of the
        catalyst.   Loading ratios would be similar or higher in Rh than what  is typically used for automotive
        applications (20-25 percent of the total PGM mass in small SI).

    3.  Catalysts would be  integrated  into the muffler design.  Incorporating the catalyst into the muffler would
        reduce surface temperatures relative to the use  of a separate catalyst component. The catalyst for Class II
        Phase 3 engines would be integrated into mufflers  that are similar in volume to today's  Class II Phase 2
        mufflers.  Appropriately positioned stamped heat-shielding and touch guards would be integrated into
        Class II Phase 3 catalyst-muffler designs in  a manner similar to current product.  Class II engines  typically
        have a much higher volume of cooling air available downstream of the cylinder than Class I engines.  Heat
        rejection from the cylinder and cylinder head  increases the temperature of the  cooling air, but  it is still
        sufficiently below the temperature of exhaust system components to allow its use for forced cooling.  Thus
        a degree of heat rejection would be available via forced convective cooling of exhaust components via the
        cooling fan. However, this would require some  additional ducting to supply cooling air to exhaust system
        surfaces along with careful layout  of engine and exhaust components within the design of the equipment
        that it is used to power.   Integrated catalyst-mufflers can also use exhaust energy for ejector cooling (see
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        chapter 6).  Heat rejection to catalyst muffler surfaces to minimize "hot spots" can also be enhanced
        internally by turning the flow through multiple chambers and baffles that serve as sound attenuation within
        the muffler.

    4.  Some applications may include secondary  air injection to enhance catalyst efficiency.  Incorporation of
        passive secondary air allows halving of catalyst substrate volume for the same catalyst efficiency over the
        regulatory cycle. In many cases, this may not be necessary due to the lower engine-out emissions of Class
        II engines.  In cases where secondary air is used, it could  either  be a passive  system similar to the
        previously  described Class I systems, or an active system with an engine driven pump.  Pump drive for
        active  systems could be  either 12-volt DC electric or via crankcase pulse, and pump actuation could be
        actively controlled using an electric solenoid or solenoid valve.  The use of active systems is an option but
        seems unlikely.

    5.  Class II engines are typically turned off via a simple circuit that grounds the input side of the ignition coil.
        As with Class I engines temperature fail-safe capability could be incorporated into the engine by installing
        a bimetal thermal switch in parallel with the ignition grounding circuit used for turning the engine off,
        although application of this may not be suitable for use with ride-on equipment.

    6.  Higher catalyst efficiency,  considerably lower exhaust emissions levels, and improved fuel consumption
        are possible with Class II engines, but temperature considerations  might necessitate the use of electronic
        engine management and  open-loop fuel injections systems. In such a case, the design and integration of
        the emission control system would  more closely resemble automotive applications, but still with some
        differences.

Elements specific to Class II Phase 3 emission control system design using electronic engine management to reduce
emissions beyond the nominal 35 percent reduction target would include:

    1.  Electronic fuel and spark control.  Fuel metering would be via a low-cost open-loop fuel injection system
        similar to systems currently in production for motor scooters in Europe and Asia.  Such systems  use far
        fewer  sensors  and components  and  simpler Engine  Control Units  (ECU)  than typical  automotive
        applications. Open loop fuel mapping can be based on feedback of manifold absolute pressure (MAP) and
        engine oil temperature, with injection timing based on a magnetic signal from the flywheel or an inductive
        signal from the ignition system. Air-to-fuel ratio and spark timing can also be tailored at moderate to light-
        load conditions to favor engine-out control  of HC and CO emissions while still operating sufficiently rich
        of stoichiometry to allow good NOx conversion over the catalyst.  Such a control strategy would reduce
        heat rejection from the catalyst and provide improved engine protection and reduced exhaust temperature
        at high-load conditions.  Secondary air injection into the exhaust would not be necessary.

    2.  Larger catalyst volume with higher precious  metal loading.  Improved air-to-fuel ratio and spark  control
        allows the use of larger catalyst volumes (50 to 75 percent of engine displacement) with a higher precious
        metal loading than is possible with carbureted engines that have higher engine-out CO levels at light to
        moderate loads.  The advanced engine control system discussed in item 1 above would reduce engine out
        CO emissions and thus catalyst exotherms related to further CO oxidation.

    3.  Catalysts integrated into the muffler design. Catalysts would be integrated into mufflers similar in design
        to the  systems described for carbureted Class II  engines. Muffler volume would be similar to existing
        designs.

    4.  Misfire detection software would be integrated into the ECU that could:

            a.   notify the user that engine servicing  is necessary via illumination of a malfunction indicator light
                (MIL);

            b.   place the engine in a "limp mode" in the event that an engine operating condition is encountered
                that has potential safety, engine durability, or emission control system durability implications:
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            c.   could shut-down the engine under extreme circumstances.

            d.   ECU software could also integrate an input from a bimetal thermal switch for MIL illumination,
                "limp mode" initiation, or engine shut-down.

B.      CURRENT SAFETY STANDARDS

An appendix to the  SwRI report lists over 30 mandatory and voluntary standards which are, to varying degrees,
applicable to small SI equipment and in some cases specifically to nonhandheld engines.3 The majority of these are
voluntary American National Standards Institute (ANSI) and Society of Automotive Engineers (SAE) standards. US
Department  of Agriculture (USDA) requirements  are  primarily applicable  to  handheld equipment such as
chainsaws. American Society of Agricultural Engineers (ASAE), International Standards Organization (ISO), and
the American Society for Testing and Materials (ASTM) all have surface temperature requirements.

The existing ANSI standards for turf care equipment standards are  sponsored by  the Outdoor Power Equipment
Institute. These ANSI standards address engine and equipment safety for small gasoline engines.  The predominant
standards followed by the Class I and Class II engine and equipment manufacturers are ANSI B71.1, American
National Standard for Consumer Turf Care Equipment-Walk-Behind Mowers and Ride-On Machines with Mowers-
Safety Specifications and ANSI B71.4, American National Standard for Commercial Turf Care Equipment - Safety
Specification for Consumer Lawn Care and  Commercial Lawn Care Equipment.3'4  They are designed to address
operator and by-stander safety. The ANSI standards apply to the engine and exhaust system as well as the complete
equipment product.  Within the ANSI standards for residential lawn care equipment, there are three sections that
discuss  touch burn safety and prevention of fuel ignition during refueling, with two sections referring to walk-
behind mowers and one section referring to ride-on lawn equipment.

       From ANSI B 71.1, Part II: Walk-Behind Mowers: ,American National Standard for Consumer Turf Care
        Equipment-Walk-Behind Mowers and  Ride-On Machines  with Mowers-Safety Specifications,  Part II:
        Walk-Behind Mowers:

            o   "5.2 Heat protection - A guard or shield shall be provided to prevent inadvertent contact with any
                exposed components that are hot and may cause burns during normal starting and operation of the
                machine."

            o   "5.3 Fuel ignition protection -  Overflow gasoline shall be diverted away from the muffler outlet
                area."

       From ANSI B 71.1, Part III: Ride-on mowers, lever steer mowers, lawn tractors, and lawn and garden
        tractors:

            o   "15.2 Heat protection - A guard or shield shall be provided to prevent inadvertent contact with
                any exposed components that are hot and may cause burns during normal starting, mounting, and
                operation of the machine."

       From ANSI B 71.4, Figure 3, American National Standard for Commercial Turf Care Equipment - Safety
        Specification,  In section 4.2.4, Operation,  Service, Maintenance  Instruction (figure 3),  the following
        information is required in the instruction manual:

            o   Clean grass and debris from cutting units, drives, mufflers, and engine to help prevent fires. Clean
                up  oil or fuel spillage.

            o   Let engine cool before storing and do not store near flame.
' The SwRI report and its appendices are in located in Appendix C of this study.
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            o   Shut off fuel while storing or transporting. Do not store fuel near flames or drain indoors.

In general these ANSI standards primarily focus on safety labeling, operator instructions, manuals, and a series of
safety tests regarding equipment operation, mower deck safety, prevention of ejection of objects from the deck and
equipment maneuverability. No design standards or surface temperature criteria are specified, nor are standardized
test procedures provided for fire or touch burn safety for lawn care equipment.  There are  no ANSI standards
specific to fuel tanks or fuel hoses.

       ASAE Standard S440.3 Safety for Powered Lawn and Garden Equipment5  addresses hot surfaces  in
        section 9 stating:

            o   9.1.7 Hot surfaces (engine, hydraulic, transmission, etc) that exceed  a temperature of 90C
                (194F) for  nonmetallic surfaces, or 80C (176F) for metallic  parts while operating at 21C
                (70F), except surfaces  of equipment intended primarily  for winter use, which shall be  at 5C
                (41F).  All  surfaces which exceed 65.5C (150F) at 21C  (70F) ambient and which might be
                contacted by the  operator  during normal starting,  mounting,  operating, or refueling shall be
                indicated by  a safety sign located on or adjacent to the surface.

       ISO standard 5395 section 2.2.3 addresses heat protection stating6:

            o   A guard or shield shall be provided to prevent accidental contact with any exposed engine exhaust
                components  greater than 10 cm2 and with a hot surface temperature greater than 80 C at 20 C
                (+/- 3C ) ambient temperature during normal operation of the machine.

       ASTM Standard  C1055-03, the Standard Guide  for Heated System Surface Conditions that Produce
        Contact Burn Injuries recommends  first determining the  acceptable contact time and level of burn
        severity7.  They list an acceptable contact time of 5 seconds for industrial processes and 60 seconds for
        consumer items.  The maximum operating surface temperature can then be derived from two equations
        given in  the standard.  A recommendation to install jacketing or insulation is made if the injury level
        exceeds the chosen criteria;  a redesign to the system is recommended if the  criteria still cannot be met after
        installing protective measures. Nominally a value of 70C is established as a level above which action is
        necessary.

The CPSC  issued a regulation, 16 CFR Part 1205, to prevent users and bystanders from coming into contact with
mower blades8. There are no Federal regulations, standards, or test procedures related to addressing fire or burn risk
with residential lawn equipment.

 There are machine standards for noise and other operator and by-stander impacting characteristics in the European
Machinery  Directives.  These machine standards are  referred to during the engine design process.  Most of the
machine standards focus on the safety of the cutting blades.    There are also installed engine operating tests
designed to address heat exposure of stationary or parked tractors. These specifically focus on grass browning and
surface temperature tests. These tests involve dumping the  engine load and either letting the engine idle for two to
three minutes or shutting the engine off. These tests are typically designed to address the level of distress caused to
the grass.

There are a range of threshold temperature  specifications that equipment manufacturers require of their  engine
suppliers for surface temperatures and exhaust temperatures.  Most temperature requirements are for functionality
rather than for safety.  These include issues related to ventilation, tire side wall heating (for exhaust exiting near the
rubber front tires), and oil degradation protection.

In the same vein, it should be noted that in discussions with EPA all engine and equipment manufacturers indicated
that they have various proprietary tests they use to address  in-use safety. These are applied when engines and fuel
systems are completed by the original engine manufacturer, and it is often the case that the engine manufacturer
                                                   22

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works  with and advises the  equipment manufacturer on  safety specifications and  requirements for the safe
application of engines, mufflers, and fuel tanks as appropriate.

C.      IN-USE SAFETY EXPERIENCE

Assessing incremental impact on safety risk from applying more advanced emission control technology requires a
thorough understanding  of the problems and in-use safety experience with current  products.  To conduct this
assessment EPA coordinated closely with CPSC. The staff of CPSC provided copies of relevant CPSC technical
reports and provided detail and synopses of relevant information from four key databases.  EPA also reviewed
CPSC's public website which contained information on voluntary recall actions.

The technical reports provided by CPSC include the following:

       U.S. Consumer Product  Safety Commission.  (2004). Hazard Analysis of Power Lawn Mower Studies
        Calendar Years 2003 and 1993. Washington DC: Adler, P.; Schroeder, T.9

        This report examined data collected from 1983 through 1993 to evaluate the effectiveness of the mandatory
        standard addressing blade contact injuries and the ride mower portion of the voluntary ANSI/OPEI B71.1.
        Blade-contact and  thrown  object hazards were  examined  with walk behind and ride-on mowers.
        Additionally,  rolling/tipping over hazard was examined in ride-on mowers. All other hazards, including
        hot surfaces contact and fire/flame, were categorized as 'other' and were not further addressed by this
        report.

       U.S.  Consumer  Product Safety  Commission. (2003). Hazard  Screening  Report Yard and  Garden
        Equipment (Product Codes 1400-1464). Washington DC: Rutherford,  G., Marcy, N., Mills, A.10

        This report compared the risk of different products within the Yard and Garden Equipment category  based
        on 2001 injury data and 2000 death data. Lawn mowers represented the largest cost associated with  injury
        and deaths. A common hazard among all yard and garden equipment was a leaking fuel system which was
        mostly reported with riding mowers and walk behind mowers. No further information was given specific
        to lawn mowers.

       U.S. Consumer Product  Safety Commission.  (1993).  Ride-On Mower Hazard Analysis  (1987-1990).
        Washington DC: Adler, P.11

        This report provides  a detailed hazard analysis of lawn  mowers for reporting periods 1987-1990;  a
        comparison was made with lawn mower hazard patterns from 1983-1986.  Table 6 indicates  that for the
        periods 1983-86 and  1987-90, 5-6 percent of all injuries associated  with ride-on mowers treated in US
        hospital emergency rooms are burns.  Lacerations and burns from a hot surface contact occurred to  hands
        and accounted for 77 percent of all hand injuries.

       U.S. Consumer Product  Safety Commission.  (1993). Deaths Related to Ride-On  Mowers:  1987-1990.
        Washington DC: David, J. A.12

        A follow-up report to CPSC Rider-On Mower Hazard Analysis (1987-1990) indicates that for the period
        1987-1990, 2.5  percent  of  deaths were  fire-related  and indicates the fraction of fire-related  hospital
        emergency room visits to be five percent for 1983-1986 and two  percent for 1987-1990., There  are
        approximately 850 hospital visits related to touching hot  surfaces, and nine deaths related to fire for ride-on
        mowers for the period 1987-1990. It should be noted that these figures cover only ride-on mowers.

       U.S. Consumer Product Safety Commission. (1988). Hazard Analysis, Ride-On Mowers.  Washington DC:
        Smith, E.13
                                                  23

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        This report gives an estimated 6 percent of in-use injuries as being thermal-burn related, such as a hot
        muffler or exhaust pipe.  In most cases the engine was reported as being off, but the mower was still in use,
        which can include making repairs, maintenance, fueling, getting on/off, lifting, pushing, or other.

       U.S. Consumer Product  Safety Commission.   Thermal  Burn Contact-Related  Injuries Associated with
        Gasoline-Engine Powered Equipment, 1990-19981 Washington DC: Adler, P.14

        This report discusses thermal burns exclusively from contact related injuries on gasoline engine powered
        equipment for the period 1990 -  1998.  This report discusses gasoline engine powered equipment such as
        walk  behind and riding mowers,  chainsaws,  rotary tillers, brush cutters.  A contact burn injury is
        characterized by inadvertent contact with hot components or surfaces on the equipment.  Based on the
        National Electronic Injury Surveillance System (NEISS) database there were an estimated average of 2,200
        contact burn injuries treated in U.S.  hospital emergency rooms during the 9 year period.  Of these, 17
        percent were related to the lower arm/leg and 68 percent were on the hand or  finger.  First and second
        degree burns are  53  percent of the total. Table 3 of this report indicates that 41 percent of burns were
        related to the muffler, 13 percent related to the exhaust tailpipe, 13 percent related to engine components,
        and 33 percent related to other surfaces. Muffler contact thermal burns were the dominant risk in all the
        engine-powered equipment discussed in this report.

In addition, CPSC provided EPA focused extracts related to fire and burn incidents from four different databases.

    1.  CPSC's NEISS database is  comprised of a sample of  hospitals that are  statistically  representative of
        hospital emergency rooms nationwide. From the data collected, estimates can be made of the numbers of
        injuries associated with consumer products and treated in hospital emergency departments.

    2.  CPSC's Injury/Potential Injury  Incident File (IPII) contains summaries, indexed by consumer product, of
        Hotline reports, product-related newspaper accounts, reports from medical examiners,  and letters to CPSC.

    3.  CPSC's In-Depth Investigations (INDP) file contains summaries of reports of investigations into events
        surrounding product-related injuries or incidents. Based on victim/witness interviews, the reports provide
        details about incident sequence, human behavior, and product involvement.

    4.  The National Fire Incident Reporting System (NFIRS) is a database of fires attended by the fire service.
        NFIRS provides data at the product level and is not a probability sample. The information from the NFIRS
        database results are weighted up to the National Fire Protection Association (NFPA) survey to provide
        national annual product-level estimates.

US  CPSC's public  website contains information on voluntary manufacturer recalls dating back over 30 years. In
reviewing this website, EPA reviewed recalls  related to small gasoline-powered equipment such as lawn mowers,
generators, pumps, pressure washers, utility vehicles, snow throwers, go-karts, tractors, and engines.  In these nine
categories, EPA identified 32 recall actions  that were related to either fire  or burn risk on gasoline-powered
equipment.

CPSC Databases:

Working closely with CPSC staff, EPA reviewed the databases and recall events to identify those which might have
a bearing on this safety study. Each of these is discussed below.

NEISS:  CPSC's National Electronic Injury  Surveillance System reported a  total  of 475 thermal burn injuries
related to gasoline-fueled lawn mowers that were treated in hospital  emergency rooms over  the five year period
2000-2004.15 The product codes used to create  this dataset included walk behind mowers, riding lawn mowers, lawn
tractors and lawn mower product  codes that do not specify the type of mower.  Based on this period sampling of
NEISS reported cases, there were an estimated  19,072 lawn mower thermal burns  injuries treated in emergency
rooms around the United States. Ninety six percent of these injuries were treated and released. Most of the victims
                                                   24

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(51%) suffered hand injuries.  Other body parts that were injured frequently were finger, lower arm, and lower leg
(about 15%, 13%, and 8% of the cases, respectively).

The descriptive narratives of the NEISS reported cases were reviewed to determine hazard patterns that resulted in
thermal burn injuries.  The following hazard patterns were identified:

           Contact Burn: An individual contacts a hot lawn mower component and receives a burn.
           Refueling-Related Fire: Ignition of fuel vapor when an individual was refueling.

In addition, there were two NEISS  hazard patterns  (shown below) which either had a significant user behavior
component to the problem, which is not a technical issue, or were inadequately described in the records to allow a
laboratory or field assessment of the incremental risk. These two items are assessed primarily in the FMEA.

           Unspecified: The running lawn mower caught fire/exploded for reasons unspecified.
           Maintenance: An individual is performing lawn mower maintenance activities when a fire occurs.

Table 3.2 shows the annual NEISS estimates for both thermal burn injuries associated with gasoline fueled lawn
mowing equipment from 2000-2004 and the portion of these burns that were due to the victim contacting a hot lawn
mower component.  There was an estimated average of 3,814 thermal burn injuries per yearb with contact burns
accounting for 88% (3,375) of these injuries. There  were no significant differences among the years studied,  nor
were there any significant trends detected over these five years.
 Note:  The 2000-2004 NEISS estimates are larger than the 1990 - 1998 estimates in report 6, [Thermal Burn Contact-Related
Injuries Associated with Gasoline-Engine Powered Equipment, 1990-1998, Adler, P., because the 2000-2004 data set  included
additional product codes such as lawn mowers not specified, tractors other or not specified, powered lawn mowers not specified.
                                                   25

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                                               Table 3-2
                           Annual Estimates of Emergency Room Treated Thermal
                          Burns From Gasoline-Fueled Lawn Mowing Equipment1
Year
2000
2001
2002
2003
2004
Total
Mean
Estimate of
Thermal Burn
Injuries
3,509
4,256
4,354
3,587
3,365
19,072
3,814
Proportion of Thermal
Burn Injuries due to
Contact
92% (3,236)
85% (3,626)
92% (3,985)
84% (3,026)
89% (3,002)
88% (16,875)
88% (3,375)
IPII and INDP: Gasoline-powered lawn mower records related to thermal burn injuries or potential injuries were
obtained from CPSC's Injury/Potential Injury Incident File and In-Depth Investigation files.17  For the five year
period of January 2000 through December 2004, there were 466 IPII records and 87 INDP records. There were
cases  of some duplication in the NEISS, IPII/INDP records because the emphasis was in finding scenarios that can
lead to thermal burn injuries rather than removing duplicate records. EPA and CPSC reviewed every record in these
databases, with the purpose of identifying the prevalence of problems with engine or equipment systems affected by
EPA's potential new exhaust and fuel evaporative emission standards. Several hazard patterns were identified from
the INDP and IPII records that caused or could potentially cause fire  and thermal burn injuries.   These hazard
patterns fall into two  basic categories.   In the  first, the hazards identified are directly  traceable  to a technical
performance or failure in a component or subsystem on the engine  or are the effect of the  characteristics and
performance of the equipment itself. These are shown below:

       Fuel Leaks: fuel leaks  from tank installed on equipment, faulty fuel hose or primer bulb, or from faulty or
        malfunctioning carburetor

       Debris Fire: Ignition of grass or leaves from hot components on the lawn mower

       Shutdown/Storage:  A  lawn mower  stored or used near  combustibles/flammable materials or near an
        ignition source such as an appliance with a pilot light results in a fire.

       Engine Backfire/Misfire: The lawn mower backfires resulting in either noise or fire/flames.

       Contact Burn: An individual contacting a hot lawn mower component that results in a burn

       Refueling Related Fire: Ignition of fuel liquid or vapor related to refueling

In addition, there were three hazard patterns (shown below) which either had a significant user behavior component
to the problem which is not a technical issue or were inadequately described in the records to allow a laboratory or
field assessment of the incremental risk.  These three items are assessed primarily in the FMEA.

       Maintenance:  An individual performing lawn mower maintenance activities that results in a fire

       Tip Over: A riding lawn mower tips over when in use resulting in fuel leaks.  It is believed that fuel leaks
        from the overturned lawn mower are primarily from the vented gas cap or from the carburetor. In some of
        these records, the individual becomes trapped under the riding lawn mower.

       Unspecified: For reasons unspecified, the running lawn mower catches fire/explodes
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NFIRS: The National Fire Incident Reporting System is based on firefighter and first responder reports on incidents
to which they respond.  The data  compiled by the US Fire Administration and  the National Fire Protection
Association is not as complete or precise as that from the NEISS. Nonetheless, the data provided by CPSC estimates
that for 2002 there were 100 fires involving gasoline-fueled lawn mowing equipment and estimates that there were
10 injuries associated with these fires.18

CPSC RECALL INFORMATION

The CPSC  website publishes Recalls and Product Safety News, where manufacturers, in cooperation with CPSC,
voluntarily  recall products that pose  a safety hazard to consumers.19 Recall notices published during the period of
January 2000 to December 2004 were reviewed.  During this period there were a total of 22 lawn mowers or lawn
mower engine recalls due to safety issues related to  fire and thermal burn injuries. These 22 recall notices affected
approximately 850,000 lawn mower units. Table 3-3  identifies the following hazard patterns from the recall notices:

Table 3-3:  Fire/Burn Risk Related Recall Events for Small Gasoline-powered Lawn/Garden Equipment
Problem
Category
Fuel Tank
Leaks
Fuel Hose
Leaks
Backfire
(Misfire)
Refueling Vapor
Ignition
Other
Number Recalls
11
5
2
1
o
J
Years Issued
2000-2004
2000-2004
2002
2001
2000-2004
Years Affected
1995-2004
2001-2004
1998-2001
1998-2001
1999-2003
Incidents
Reported
2229
5
25
28
27
Total Equipment
Involved
742,054
4660
34,000
39,000
28,300
EPA also identified about 10 other CPSC recalls related to small engines which either were not applicable to lawn
and garden equipment or occurred outside of the five year evaluation period. Most of these were related to fuel
tanks and fuel hoses. This type of problem was also identified in the 2000-2004 lawn mower equipment recalls.

Discussion of CPSC Data

Taken as a whole, the reports and data provided by CPSC are consistent and indicate that the following types of
incidents should be of primary technical concern when evaluating the  incremental impact on safety of the more
advanced emissions control technology:  burns due to contact with hot surfaces, fuel tank leaks, fuel hose leaks,
refueling vapor ignition, debris fires,  shutdown and storage related fires, engine backfire/misfire, and carburetor fuel
leaks.

In the chapters which follow, EPA identifies causative factors which might be contributing to these hazard patterns
and their occurrence in use, and presents data and technical analyses assessing the incremental impact on these
hazard patterns of potential Phase 3 exhaust and fuel evaporative emission standards for Class I and Class II engines
and equipment.
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1   "Estimated Number of Refueling Events for Residential Mowing Equipment," EPA memorandum from Phil
Carlson, March 3, 2006, Docket EPA-HQ-OAR-2004-0008-0331.
2 U.S. Code of Federal Regulations, Title 40, Part 90, 90.103, Tables 2 and 3.
3 ANSI B71.1-2003, "American National Standard for Consumer Turf Care Equipment - Walk-Behind Mowers and
Ride-On Machines with Mowers - Safety Specifications", American National Standards Institute, 2003.
4 ANSI B71.4-2004, "American National  Standard for Commercial Turf Care Equipment - Safety Specifications"
American National Standards Institute, 2004.
5  ASAE S440.3, "Safety for Powered Lawn  and Garden Equipment", American Society  of Agricultural and
Biological Engineers, St. Joseph, Michiganwww.asabe.org, March 2005.
6 ISO 5395, "Power lawn-mowers, lawn tractors,  lawn and garden tractors, professional mowers, and lawn and
garden tractors with mowing attachments ~  Definitions, safety requirements  and test procedures", International
Organization for Standardization, Geneva, Switzerland, 1990.
7 ASTM C1055-03, "Standard Guide for Heated System Surface Conditions That Produce Contact Burn Injuries",
ASTM International, 2003.
8 U.S. Code of Federal Regulations, Title 16, Part 1205.
9 Docket EPA-HQ-OAR-2004-0008-0321.
10 Docket EPA-HQ-OAR-2004-0008-0322.
11 Docket EPA-HQ-OAR-2004-0008-0323.
12 Docket EPA-HQ-OAR-2004-0008-0332.
13 Docket EPA-HQ-OAR-2004-0008-0329.
14 Docket EPA-HQ-OAR-2004-0008-0320.
15 Docket EPA-HQ-OAR-2004-0008-0327.
16 U.S. Consumer Product Safety  Commission, National Electronic Injury  Surveillance System database, 2000-
2004.
17 The Injury/Potential Injury Incident File (IPII) can be found at Docket EPA-HQ-OAR-2004-0008-0325.  The In-
Depth Investigation (INDP) files can be found at Docket EPA-HQ-OAR-2004-0008-0326.
18 "NFIRS Data on Gasoline-Fueled Lawn Mowing Equipment, 2002," CPSC memo from Risana Chowdhury to
Susan Bathalon, December 7, 2005, Docket EPA-HQ-OAR-2004-0008-0324.
19    U.S.    Consumer   Product   Safety    Commission,    "Recalls   and    Product    Safety    News",
http://www.cpsc.gov/cpscpub/prerel/prerel.html
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4.  Scenarios for Evaluation of NHH Engines and  Equipment

A.      SUMMARY OF OTHER INFORMATION CONSIDERED

In this chapter, EPA identifies the key scenarios used in evaluating the incremental impact on safety associated with
advanced emission control technology for NHH engines and equipment.  The scenarios cover a comprehensive
variety of in-use conditions or circumstances which potentially could lead to an increase in burns or fires.  These
may occur presently or not at all, but are included because of the potential impact on safety if they were to occur.
EPA is not identifying these as conditions that will in fact occur, but more as potential or hypothetical conditions
should be evaluated. The focus of the analysis is therefore on the incremental impact on the likelihood or that the
severity of these  scenarios  and  the potential  causes occurring from using  more advanced  emissions control
technology.

In addition to using the CPSC reports and databases, EPA considered additional inputs in identifying the scenarios
for evaluation. These included the following:

       OPEI briefing to EPA entitled:  "Discussion of Off-Nominal Operating Conditions for Catalyzed Small
        Off-Road SI Engines and Lawn/Garden Equipment," Oct 26, 2005.:

OPEI identified nominal and off nominal conditions and laid out concerns which occur in the lab versus in the field.
According to OPEI,  off nominal  conditions  are defined as  unintentional and unavoidable  conditions during
equipment operation which are non-trivial infrequency and may be high consequence events leading to significant
increase in fire and heat-related safety hazards. The four general categories of off nominal conditions identified by
OPEI include:

                i.  An increase in the amount of air present in the muffler/catalyst region

                ii.  Air/Fuel ratio changes affecting catalyst conversion efficiency

               iii.  Increase of unburned fuel into muffler/catalyst or on hot surfaces of the equipment

               iv. Changes in the cooling air flow management system

       National Association of State Fire Marshals memorandum from Margaret Simonson to James Burns,
        "Recommendations  for Independent Research Project on Fire Safety of Measures being Considered to
        Reduce Emissions of Small Engines in Outdoor Power Equipment," September 22, 2004.2

       Memorandum, from Charles Burnham Applied Safety and  Ergonomics to Margaret Simonson, National
        Association of State Fire Marshals entitled, "Request for Data: Air Quality Measures for Small Engines
        Used with Outdoor Power Equipment," June 18, 2004.3

       Letter from William Guerry, Collier, Shannon, Scott, to Jackie Lourenco entitled Re: "CARB's Catalyst
        Durability Study." September 10, 2002.4

       "Lawn-Mower Related Burns," Journal of Burn Care and Rehabilitation, Volume 21, No.8, pp. 403-405.5

       "Literature Survey  on Garden  Machinery  (lawnmowers)" prepared by Dutch  Consumer and  Safety
        foundation for the Inspectorate for Health Protection and Veterinary Public Health, November 3, 2002.6

       Discussion with the National Institute for Standards and Testing (NIST), December 6, 2005.7

       "Durability of Low Emissions Small Off-Road Engines," Southwest Research institute, April, 2004.8
                                                 29

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       Information from  meetings, workshops, and  discussions with engine  and equipment manufacturers
        including but not limited to:

            o   OPEI Presentation to US EPA, May 23, 2005.9

            o   Public  Consultation Meeting,  The International Consortium  for  Fire  Safety, Health, and
                Environment and US EPA, Briggs and Stratton Corporation, October 5, 2005.10

In addition to these references, EPA has gained valuable empirical experience in the field testing conducted over the
past two years.  This testing has increased our understanding of potential failure modes and added to the scope and
depth of our planned assessment.
B.      SAFETY SCENARIOS FOR EVALUATION

There are a number of ways in which the scenarios of concern could be identified for evaluation and discussion.
EPA elected an approach which closely mirrors the problems identified in the CPSC data, while including the other
concerns identified in the other sources described in A. above. This  provides a comprehensive and methodical
approach to analysis and discussion which is provided in the chapters which follow.


Scenario 1: Contact burns

Scenario Description: Thermal burns due to inadvertent contact with hot surface on engine or equipment.

Potential Causes:

        a.   muffler surface temperature increases due to debris inhibiting flow of cooling air

        b.  higher temperatures on mower deck or around muffler due to higher radiant heat load from   muffler
            or engine

        c.   muffler temperature increase due to air-to-fuel ratio enleanment caused by calibration drift over time,
                fuel system problems or air filter element mal-maintenance

        d.  exhaust gas leaks increase surface temperatures

        e.   misfueling: use of highly oxygenated fuel such as E85 (mixture of 85% ethanol and 15% gasoline)

Scenario 2: Debris fire:

Scenario Description: Grass and leaf debris fires on engine/equipment.

Potential Causes:

        a.   muffler temperature increases due to debris inhibiting flow of cooling air, debris trapped in tight areas
            blocks air flow, dries out and heats up

        b.  higher temperatures on mower deck or around muffler due to higher radiant heat load from muffler or
            engine or exhaust system leaks

        c.   muffler temperature increase due to A/F ratio enleanment caused by calibration drift over time, air
            filter element mal-maintenance, or exhaust system leaks
                                                   30

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        d.   exhaust gas leaks increase surface temperatures




        e.   misfueling: use of highly oxygenated fuel such as E85




Scenario 3:  Fires due to fuel leak




Scenario Description: Fires due to fuel leaks on hot surfaces.




Potential Causes:




        a.   faulty fuel tank




        b.   faulty fuel line or connection




        c.   tip-over during maintenance




        d.   tip over in operation




        e.   faulty carburetor




        f.   heat affects fuel tank or fuel line integrity






Scenario 4: Fires related to refueling




Scenario Description: Fires related to spilled fuel or refueling vapor.




 Potential Causes:




        a.   fuel spilled on hot surfaces




        b.   spilled fuel evaporates or refueling vapors lead to fire indoors






Scenario 5: Fire related to storage and shutdown




Scenario Description: Equipment or structure fire when equipment left unattended after use.




Potential Causes:




        a.   ignition of nearby easily combustible materials




        b.   ignition of fuel vapor by an appliance pilot light (or similar open source of ignition)




        c.   ignition of dry debris on deck




        d.   ignition of dry debris in field




        e.   ignition of tarp or other cover over equipment






Scenario 6: Ignition misfire
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Scenario Description:  Engine malfunction which results in an ignitable mixture  of unburnt fuel and air in the
muffler.

Potential Causes:

        a.   misfire caused by partial failure in ignition system (single cylinder engines)

        b.   misfire caused by failure in ignition system, particularly complete failure of ignition for one cylinder
            (2 cylinder V-twin engines)

        c.   after-fire/backfire  caused by engine run-on after ignition shut-down due to failure of the  engine
            flywheel brake or carburetor fuel-cut solenoid

Scenario 7: Fire due to rich operation

Scenario Description: Fire due to operation with richer than designed A/F ratio in engine or catalyst.

Potential Causes:

        a.   fuel system degradation such as faulty carburetor, oil consumption or carburetor deposits

        b.   faulty or misapplied choke

        c.   air filter element mal-maintenance

        d.   debris blocks catalyst venturi

In addition, through the FMEAs, we assess the hazard patterns identified in Chapter 3 related to equipment fire and
explosion for an unspecified reason.

Chapter 3 laid  out the basic NHH technology, discussed the current safety standards affecting design, and analyzed
in-use safety experience. This chapter identifies the key scenarios to evaluate and the causal factors to consider in
this assessment.  We turn now to a description of the test methods used in the  EPA laboratory and field work for
NHH engines.
1 Docket EPA-HQ-OAR-2004-0008-0310.
2 Docket EPA-HQ-OAR-2004-0008-0311.
3 Docket EPA-HQ-OAR-2004-0008-0312.
4 Docket EPA-HQ-OAR-2004-0008-0313.
5 Docket EPA-HQ-OAR-2004-0008-0314.
6 Docket EPA-HQ-OAR-2004-0008-0315.
7 Docket EPA-HQ-OAR-2004-0008-0316.
8 Docket EPA-HQ-OAR-2004-0008-0317.
9 Docket EPA-HQ-OAR-2004-0008-0318.
10 Docket EPA-HQ-OAR-2004-0008-0319.
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5.      NHH  Test  Program
This chapter describes EPA's laboratory and field testing of Class  I and Class II engines and equipment.  We
describe the engines selected for testing, the engine's emissions control systems, and the test methodology used to
assess safety of prototype Phase 3 engines compared to current Phase 2 product.
A.
ENGINE SELECTION
We selected a total of nineteen nonhandheld SI engines for laboratory and field testing in this study.  Twelve of the
engines were Class I engines and were evenly split between side-valve and OHV engine designs from four different
engine families.  Eight of the  engines were Class II engines, all OHV engine designs from three different engine
families.  General specifications for the Class I and Class II engines that were tested are provided in Tables 5-1 and
5-2.  The engines were obtained by purchasing residential lawn mowers and lawn tractors from retail stores in SE
Michigan.

The two  Class I side-valve engine families selected were certified to U.S. Federal Phase 2  Emission Standards,
without the use of emissions credit, as well as California Air Resources Board (CARB) Tier 2 Emission Standards.
Together these two engine  families represented  approximately 50% of all gasoline-Si Class I side-valve engine
sales, and they also represented 75% of gasoline-Si Class I  side-valve engines certified to Phase 2 for the 2004
model year.

The two  Class I OHV engine families selected for testing were also certified to the Phase 2 emission standards.
Together these two engine families represented approximately 46% of all gasoline-Si Class I OHV engine sales, and
approximately 50% of Class I,  OHV engines certified to Phase 2 for the 2004 model year.

Table 5-1:  Summary of Class I engine and equipment specifications.   All  of the engines tested were from
residential walk-behind lawn mower applications.
Engine ID numbers
(grouped by engine
family)
Emissions Standard (as
determined from
"emissions tag")
Advertised Power (h.p.)
Maximum Brake Power
(b.h.p)
Governed Speed @ 75%-
10% of maximum brake
torque (rpm)
Engine Displacement
(liters)
Valve Arrangement
Equipment Used for
Field Testing
243, 244, 245
Federal Phase 2,
CARB Tier 2
5.5
3.2-3.7
2700 - 2900
0.16
OHV
Self-propelled walk-
behind lawn mower,
configured for
mulching
241,255
Federal Phase 2, CARB
Tier 2
6.75
4.3-4.5
2800-3100
0.19
OHV
Not field tested -
obtained from self-
propelled walk-behind
lawn mowers
258
Federal Phase 2, CARB
Tier 2
6.0
3.0
3160-3260
0.19
Side-valve
Not field tested -
obtained from a self-
propelled walk-behind
lawn mower
236, 246, 248, 249,
259
Federal Phase 2,
CARB Tier 2
6.0
2.9-3.0
2700-2900
0.20
Side-valve
Self-propelled walk-
behind lawn mower,
configured for
mulching
                                                  33

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Two of the three Class II engine families  selected for testing were  both OHV designs,  and together represent
approximately 24% of the gasoline-Si Class II Phase 2 engine sales for the 2004 model year.  The third engine
family (engines 254 and 256) is a new design that has superseded one of the other Class II engine families tested
(engines 232 and 233) in high-volume consumer lawn and garden applications.

Table 5-2:  Summary of Class II engine specifications.  All of the  engines tested were from residential lawn tractor
applications.
Engine ID numbers (grouped
by engine family)
Emissions Standard
(transcribed from "emissions
tag")
Advertised Power (h.p.)
Maximum Brake Power
(b.h.p) @ 3060 rpm
Governed Speed (rpm) @
75%-10% of maximum
brake torque
Engine Displacement (liters)
Valve Arrangement
Equipment Used for Field
Testing
231,251,252,253
Federal Phase 2,
CARB Tier 2
18.0
12.8
2900-3100
0.5
OHV
Residential lawn
tractor w/manual
transmission
232,233
Federal Phase 2,
CARB Tier 2
17.5
12.4
2900-3150
0.49
OHV
Residential lawn
tractor w/manual
transmission
254,256
Federal Phase 2,
CARB Tier 2
20
11.8
3150-3350
0.6
OHV
Residential lawn
tractor w/hydrostatic
drive
B.
ENGINE MODIFICATIONS
This section describes the advanced emission control systems developed for the engines in section A.  Note that
brief descriptions of tested configurations are also included within the tabulated emissions results in Appendix B.

Class I - 10 g/kW-hr systems

EPA conducted a literature search of existing catalyst-muffler designs for Class I engines.  Three basic designs
covered under four separate patents  showed  promise for application to Class  I Phase 2  engines. 1,2,3,4  These
designs share a number of common features, including:

       Compact design, being virtually the same size as some standard mufflers available for this engine

       Use of a passive exhaust venturi or exhaust ejector for introduction of secondary air

       Exhaust pulse dampening located upstream of the venturi

       Relatively small substrate volume

One of the catalyst-muffler designs1 was already in mass production by an OEM for use on European walk-behind
lawn mowers (Figure 5-1).  EPA purchased several of these units and conducted  a preliminary engineering and
chemical analysis.  This  particular design used a simple, stamped venturi for passive secondary air entrainment and
a small (approximately 20 cc or 1.2 in3) cordierite monolith with 400 cell/square-inch (cpsi) construction common
                                                   34

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in automotive applications.  The catalyst substrate was retained with a common automotive-type matting material.
PGM loading was approximately 30 g/ft3 with a Pt:Pd:Rh ratio of approximately 5:0:1.

Following initial analysis of the  OEM  European catalyst-muffler, it was determined that an increase in catalyst
volume might be  needed to provide  sub-10  g/kW-hr  HC+NOx  emissions at high  hours after  taking into
consideration an expected degree  of catalyst  oil poisoning and degradation of engine-out emissions.  Initial
prototype samples were fabricated by lengthening the muffler by 20 mm and doubling the substrate volume within
the production European catalyst-muffler  (Figure 5-2).  Although  increasing substrate volume in this manner
increases exhaust backpressure, for the engine family that this catalyst muffler was tested with there was virtually
identical peak power output at wide-open-throttle (WOT) at  the A-Cycle test  speed (3060 rpm) for both the
modified catalyst-muffler and  the  OEM muffler.  Similar results  were achieved with other catalyst muffler
configurations that tested with other engines.  Thus the backpressure increase that resulted from the use of catalysts
within the exhaust  systems  was not sufficient to impact power output.  This may have been in part due to the
relatively small  catalyst volumes tested, the  geometry of the substrates  (generally  much lower cell density than
automotive substrates, and also generally "shorter-fatter" geometries), and the exhaust restriction of the substrates
relative to that of other parts of the exhaust system.
     2-stage baffle immediately
     downstream of exhaust port
  20 cc, 400 cpsi cordiente catalyst
  substrate with automotive matting
Venturi air inlets
                                                                                 Center divider
Figure 5-1: Details of an OEM catalyst-muffler from a European walk-behind lawn mower application.
                                                    35

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 Catalyst-muffler   reconfigured
 with  a second 20 cc  substrate
 (40 cc total), repositioned inlet
 and  modified  internal  baffles.
 This   is  the  unit  tested  with
 engine 241.
 Catalyst-muffler   reconfigured
 with  a second 20 cc substrate
 (40 cc total).  This is similar to
 the  configuration  tested  with
 engine 258.
 OEM European Catalyst-muffler
Figure 5-2: Catalyst-muffler from Figure 5-1 (bottom) modified with additional catalyst volume (center) and with
modifications to the inlet and internal baffles to allow use with engine 241 (top).
                                            36

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The lengthened European catalyst-muffler was further modified by changing the exhaust inlet to allow its use on an
additional engine type (see Figure  5-2).  Additional  catalysts with different formulation and construction were
obtained from major North American catalyst suppliers (Figure 5-3). Catalyst substrates tested included:

    1.  34 cc, 100 cpsi metal monoliths;

    2.  44 cc, 200 cpsi metal monoliths;

    3.  metal-mesh substrates;

    4.  22 cc 200 cpsi metal monolith with a 20 mm dia. X 73 mm long tubular pre-catalystc; and

    5.  the aforementioned 400 cpsi cordierite monoliths,  doubled to provide approximately 40 cc catalyst volume
        (Figure 5-2).

Ceramic monoliths have been used successfully in OEM applications in Europe, and have proven durable provide
appropriate matting and support for the  substrate is  provided within the catalyst muffler design.  Metal monoliths
are more resistant to shock than ceramic monoliths, and may be easier to package into  catalyst mufflers for some
applications, but are generally more  expensive. Metal mesh substrates approach the cost of ceramic monoliths,  and
have acceptable durability  due to recent improvements in substrate packaging and washcoat adhesion.  All three
substrate types were tested because they represent the range of types that EPA expects to be used to comply with the
California Tier 3 and the expected Federal Phase 3 standards for different applications.

Most of the prototype catalyst-mufflers contained catalyst substrates with different construction and PGM loading in
the OEM European catalyst-muffler  housing. Some designs also incorporated additional heat-shielding or shrouding
(see Figure 5-4).  One prototype catalyst-muffler, tested with engine 243, was completely fabricated from scratch
using a tubular venturi and a general layout  similar to previous  designs (Figure 5-5).3,4 An additional catalyst-
muffler for engine 249 was tested without the use of secondary air and was fit entirely within the standard OEM
muffler.

The tubular pre-catalysts were installed upstream of  the  secondary-air-venturi, with a 22  cc  200 cpsi monolith
installed downstream of the venturi (Engines 243 and 255). The catalyst-muffler tested with engine 255 is shown in
Figure 5-6.

The PGM loadings on the monolithic substrates ranged from 30 g/ft3 to 50 g/ft3.  Generally, higher loadings were
used with smaller substrate volumes to provide  a  similar overall level of PGM surface area within a smaller
packaging volume.  The loading ratio of 5:0:1  (Pt:Pd:Rh) as used with the production catalyst-muffler was the most
common, but loading ratios ranging  from 4:0:1 to 0.33:3.66:1 and one Rh-only only were also tested. The specific
loading of any particular catalyst tested and its relationship to particular data results was considered proprietary, but
general trends in emissions versus PGM loading and  loading ratio will be discussed within the results section.

When selecting catalyst secondary air configurations  to test with each engine,  the primary design  target was to
achieve less than  10 g/kW-hr HC+NOx emissions at the 125 hour useful life level because this is the most common
for residential walk-behind lawn mowers.  A maximum  of 7.0 g/kW-hr HC+NOx target was  set  for  low-hour
emissions performance for the Class I residential lawn mower engines to allow for engine and catalyst degradation
over the 125-hour useful life requirements for these engines.   Secondary design targets included minimization of
CO oxidation at  moderate to  high  load conditions (e.g., A-cycle modes  1 and  2) and exhaust system surface
temperatures comparable to those of current Phase 2 OEM systems.

The OEM versions of engines  243, 244 and 245 were equipped with mufflers enclosed in shrouds that directed air
flow across the surface of the mufflers for additional cooling of the exhaust system. The catalyst-muffler systems
developed for engines 243, 244, and 245 were equipped with shrouds providing a similar function, but with the air-
outlet of the shroud relocated in order to provide improved air flow over the outer surface of the catalyst-muffler.
! A tube with a single, perforated channel in which all of the internal surfaces are washcoated.
                                                    37

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These engines also were equipped with an exhaust ejector over the exhaust outlet of the catalyst-mufflers to both
cool the exiting exhaust gases and to provide for additional heat rejection from the surface of the shroud. A similar
shroud and ejector system was tested with engine 249.
Figure 5-3: Some of the catalyst substrate types evaluated by EPA with Class I and Class II engines included (from
left to right)  100 cpsi metal monoliths (in 50 mm and 33 mm diameters); 200 cpsi metal monolith; catalyzed tube
pre-catalysts (in 20 mm and 25 mm diameters); 400 cpsi coridierite (square-oval and round) and metal-mesh. The
50 mm diameter catalyst on the far left was used with Class II engine test configurations. The remaining catalysts
were tested with Class I engines.
Figure 5-4: Engine 236 with catalyst-muffler installed on dynamometer test stand at the U.S. EPA National Vehicle
and Fuel Emissions Laboratory (NVFEL). The muffler was derived from a production European catalyst-muffler.
It was modified to allow  installation onto  a different engine type, and a 44 cc metal monolith catalyst was
substituted for the original ceramic monolith.  A small heat shield was added to prevent heating of the intake
manifold.  The catalyst-muffler configurations for engines 246 and 249 were similar, but with different catalyst
substrates and PGM loadings.
                                                    38

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    Modified muffler
         shroud
OEM muffler
   shroud
OEM exhaust
    outlet
Figure 5-5: Engine 243 (left) equipped with a catalyst-muffler, passive venturi-secondary-air, muffler air shroud
and exhaust ejector compared to a similar engine (right) with the OEM muffler and muffler air shroud.
                Approximate location of 22cc main catalyst
    20mm dia. tube pre-catalvst

Figure 5-6:  Catalyst-muffler (left) and OEM muffler (right) tested with engine 255.
                                                 39

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Class II - 3.5 g/kW-hr HC+NOx system

Engines 231 and 232 were fitted with an ECU and components originally developed for the Asian motor-scooters
and small-displacement motorcycles. The fueling logic was speed-throttle-based with barometric pressure (BP) and
MAP correction capability. The OEM ignition system and mechanical speed governing were maintained.

The fuel  system consisted of an electronic fuel pump, external regulator, and small fuel injector.   The fuel pump
has a flow capacity of 2.5 grams per second at 250 kPa, which was the regulator's pressure setting. The fuel pumps
used were also designed with power consumption minimized to 1 amp.  Engine 231 used an in-line fuel pump and
engine 232 used an in-tank fuel pump. The ECU controlled the fuel pump with a pulse-width-modulated low side
drive.  The injectors used were a two-hole design with 12 Degree spray cone, and has a static flow of 1.4 grams per
second at the 250 kPa regulated fuel pressure.

The  sensors for the ECU were minimized to a throttle position sensor (TPS), air charge temperature sensor, oil
temperature sensor, ECU board-mounted MAP sensor,  and crankshaft variable reluctance sensor for a two-tooth
crankshaft target.  The throttle position sensor (TPS) required a zero-return spring force to avoid interference with
operation of the engine's mechanical governor.  Initially a springless linear potentiometer mounted on the governor
linkage primary control arm was used for TPS.  As development progressed, this unit was replaced with a TPS
sensor from an automotive electronic throttle control module.

Catalyst formulations  and the air-to-fuel ratio calibration of the open-loop electronic  fuel injection (EFI) system
were selected in a manner that prioritized NOx reduction and HC oxidation over CO  oxidation.  The  catalyst-
mufflers  were selected  for further testing  by first screening  six different catalysts with varying washcoating
formulations, substrate volume and substrate construction.  Specific PGM loadings, loading ratios,  and catalyst
construction for the catalysts used in  this study were proprietary, but in general loadings were between 50 and 70
g/ft3,  and loading ratios varied  from 0:5:1 to 5:0:1.  Both 200 cpsi and 400 cpsi metal-foil monolithic catalyst
substrates were tested. Catalyst volume varied from approximately 50% to 55% of the engine displacement.  A
typical catalyst-muffler is shown in Figure 5-7.

Details of the installation of modified components as installed on a lawn tractor chassis are shown in Figure 5-8.
The engine air shrouding was extended and  the routing of cooling air through the chassis of the lawn tractors was
changed  to route  the  cooling air from the engine fan,  downstream of the engine, over the catalyst-muffler and
exiting either to the side or the front of the lawn tractor. The resulting forced air cooling reduced exhaust system
temperatures and also prevented debris build-up in the areas adjacent to the exhaust system components.
                                                   40

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Figure 5-7:  The photos on the left show the layout of the 3-chamber OEM Nelson lawn tractor muffler.  The
mufflers used with the other Class II lawn tractor engines were very similar except for the inlet-pipe configuration.
OEM mufflers were sectioned and a catalyst monolith was installed between the upper and lower chambers.  The
outlet was relocated to facilitate use with an exhaust ejector, and the inlet was flanged to allow use of the catalyst-
muffler in different chassis configurations and to provide the additional clearance necessary for testing the catalyst-
muffler while the  engine was installed on  the  dynamometer.   The  catalyst mufflers  for the  8.0 g/kW-hr
configurations fit entirely within the OEM muffler (upper right and center right).  The catalyst-mufflers fabricated
for the 3.5 g/kW-hr configurations  (example, lower right) had a cylindrical section that extended above the main
body of the muffler to allow space  for additional catalyst volume, and the third chamber was relocated to the top
half of the muffler.  Use of an oval monolith would have allowed packaging within the OEM muffler space, but an
appropriate-size oval monolith was not available at the time of testing.
                                                    41

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                                                                 ECU with
                                                               integral MAP
                                                                  sensor
                                                               "hrottle-body
                                                                 injection
   Exhaust
    ejector
    outlet
   Approximate
location of catalyst
    and muffler
Extension of engine
air- shroud to direct
  air flow towards
  muffler location
Figure 5-8:  Engine 232 installed in a lawn tractor chassis, showing details of the engine and chassis modifications.
The exhaust ejector extends for nearly the entire width of the cavity in which the muffler is housed.
                                       42

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Class II - 8.0 g/kW-hr HC+NOx systems

The  tested configurations of engines 253 and 254 used OEM carburetors and air-to-fuel ratio  calibration.  No
changes were made to the base Phase 2 configuration of the engine other than those necessary to install the catalyst-
mufflers.  Four different catalysts were initially tested with varying PGM loading, loading ratio, substrate volume
and substrate construction, and two were selected for operation in the field. Specific PGM loadings, loading ratios,
and catalyst construction for the catalysts used in this study were proprietary, but in general loadings were between
30 and 40 g/ft3,   loading ratios were approximately 5:0:1, and both 200 cpsi metal-foil and 400 cpsi  ceramic
monolithic catalyst substrates were tested.  Availability of appropriately sized and coated  substrates had more
impact on choice  of substrate material since performance was comparable between the two substrate types at this
level of emissions control.   The  catalyst volumes varied from  approximately 25%  to  40% of the engine
displacement.  Photographs of the catalyst-muffler configurations for engines 253 and 254 are shown in Figures 5-9
and 5-10.
Figure 5-9:  Engine 253 undergoing dynamometer testing with catalyst-muffler installed.  The addition of a single
250cc 400 cpsi ceramic monolith into the OEM muffler and minor physical modifications to the exhaust-muffler
were the only changes made to this Class II, Phase 2 engine.  The exhaust-lambda sensor mounted into the exhaust
pipe was used for laboratory measurement purposes only.
                                                    43

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                                                                       Exhaust
                                                                    ejector outlet
  Exhaust
ejector inlet
Figure 5-10:  Engine 254 undergoing dynamometer testing with catalyst-muffler installed (left) and installed in a
lawn tractor chassis (right).  The addition of two 79cc, 100 cpsi metal-monolith catalysts into the OEM muffler and
minor modifications of the exhaust-muffler were the only changes made to this Class II, Phase 2 engine.
                                               44

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C.      INFRARED THERMAL IMAGING

The  primary experimental method used for comparison of exhaust system, engine, and  equipment surface
temperatures during laboratory and field testing was via infrared (IR) thermal imaging.5,6,7 IR thermal imaging is
based on principles originally  developed for target finding and surveillance by the U.S. Department of Defense.  IR
still images  in the laboratory  were obtained using an "IR Snapshot" IR  imager.  Full motion IR imaging  in the
laboratory and in the field was obtained using an "IR Flexcam T" infrared imager.  Both IR imagers correct the IR
radiance from any single point on the target surface in a manner that a captures precise, accurate representation of
the true temperature at that location. The following assumptions are necessary to allow this sort of analysis:

    1.   The IR absorption of  the air path between the target and the instrument is negligible, and

    2.   No  IR energy is transmitted through the target from sources behind the target.

In order to correct for reflection of the ambient background, it was necessary for the operator of the imager to input
the background temperature.  This was monitored in the laboratory and in the field using J-type thermocouples. It
should be noted that during laboratory testing EPA-NVFEL test cells are held at a nearly constant background
temperature  of 25 C  1 C.

The operator of the imager also provided inputs for the targets estimated  emissivity.  All the primary temperature
targets (Mufflers/Catalysts) were painted with a high temperature flat-black paint with a dull matte finish. This was
used to even out the emissivity over the surface of the object as well as to increase the value of the emissivity of the
object.  An  emissivity of 0.9 was used for this project.  To check the validity of the  emissivity assumptions, a
comparison  of the surface temperature measured with the IR imager was made to a known surface temperature
measured with a J-type thermocouple.  The temperatures were within 1% of agreement.

The IR imagers have the following general specifications:

       They use microbolometer detectors that require no cryogenic cooling.

       The detector elements are square and are located in a rectangular grid.

       The optical path of  the  camera includes an appropriate band-pass filter for  the temperature range of
        interest.

       The IR Snapshot Camera  has a NIST traceable calibration from 10 C to 1200 C with accuracy of 2 C or
        2% of reading.

       The IR FlexCam has a NIST traceable calibration from 0 C to  600 C with accuracy of 2 C or 2% of
        reading.

       The lenses for both cameras are made from germanium and are anti-reflective coated for high transmission
        in the temperature range of choice.

Both imagers were calibrated  using NIST traceable temperature standards prior to the beginning of the IR thermal
imaging tests and at the  end  of the test program.  No change to the calibration  curve  of either instrument was
necessary between the first and second set of calibrations.  Calibration results are provided in Appendix A.
                                                   45

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D.
LABORATORY TEST PROCEDURES
Operation over the Federal A-Cvcle

U.S. Federal Phase 2 A-cycle test (table 5-3) was used to gather emissions data and to provide a broad range of
engine operational conditions under which exhaust  system surface temperatures could be  measured using the
infrared thermal imaging equipment.8   The engine dynamometer test cell was kept a temperature of 25 C  1 C,
with an absolute humidity of 75 grains-H2O/lbm-dry-air.  Tests were conducted using a 20 kW (maximum) Edy-
current dynamometer.

IR still images were used during laboratory testing to allow more precise determination of peak temperatures and to
allow further flexibility within the temperature analyses than was possible with the full-motion-video IR imaging.

Some of the engines tested were equipped with a user-selectable governor speed setting.  For these engines the
speed setting was kept in the 100% position for A-cycle modes 2, 3, 4, and 5. The user-selectable governor speed
setting was set to 0% (low-speed idle) for mode 6.

Some of the  engines had no provision for user adjustment of  the  governor speed.  For these engines,  engine
operation occurred with  the engine governor controlling engine speed for modes 2, 3, 4,  5  and 6 with no
modifications or adjustments to engine governor operation. Mode 6 was run as a high-speed-idle condition.

In all cases, mode 1 of the A-cycle was obtained via bypassing the governor and operating the engine with a fixed
wide-open-throttle (WOT) and the dynamometer control set to the A-speed (3060 rpm).  Torque control provided a
coefficient of variance of 1 % or less in measured torque at WOT.

At each of the 6 steady-state modes of the A-cycle test, IR images were acquired following stabilization of cylinder
head temperature to a value of approximately:

                                          AT/At < 1 C/minute
where AT is the change in temperature measured with a K-type thermocouple embedded within a sparkplug gasked
for cylinder head temperature measurement, and At is the measured time interval.  Depending on the engine tested,
stabilization required between five and ten minutes in A-cycle Mode 1 and approximately five to six minutes for
Modes 2 through 6.

             Table 5-3: EPA A-Cycle Intermediate Speed Steady-State Engine Dynamometer Test
EPA A-cycle Mode
Engine Speed (rpm)
Torque
Cycle Weighting Factor
1
3060
100%
(@WOT)
9%
2
100%
governed
75%
20%
3
100%
governed
50%
29%
4
100%
governed
25%
30%
5
100%
governed
10%
7%
6
0%
governed
(low idle)
0
5%
Notes:
The engine speed governor was disabled for Mode 1, and the engine was operated at WOT with the
dynamometer in speed-control mode set to 3060 rpm. Modes 2-5 were operated with the engine speed
governor set to its 100% position and with the dynamometer in torque-control mode, with percent torque
based on the average Mode 1 value. Mode 6 was a no-load, low idle test point for both Class II engines, and
for engines 243, 244, and 245. Mode 6 was a no-load, high-idle test point for the remaining engines since
these were not equipped with a user-selectable speed setting for the engine governor.
                                                  46

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The limiting factor in the uncertainty of the IR surface temperature measurements was the accuracy ( 2% of point)
of the thermal imagers rather than test to test variability, thus single  tests  were conducted for each tested
configurations.  Catalyst-muffler and OEM muffler configurations for each engine were conducted within one test
day.

Hot Soak Testing

Part way through the test program, EPA began conducting hot soak tests to compare the rate of cooling of catalyst-
muffler equipped engines  to that of engines equipped with OEM mufflers.   Hot soaks are timed measurements
which are  made  following the  engine shut-down  after sustained  operation.  Laboratory hot soak tests  were
conducted following sustained, temperature stabilized operation at 100% load at WOT conditions (A-cycle Mode 1)
and following sustained, temperature stabilized operation at 50% load (A-cycle Mode 3).  Hot soak tests were also
conducted in the field following sustained grass cutting operations  (see the  section on "Field Operation" in this
chapter).  The 100% load point represented a worst case test with the highest obtainable exhaust system surface
temperatures.  The tested  engines  were equipped  with engine speed governors that could  only sustain WOT
momentarily  during normal operation.  The 50% load point was more representative of temperatures achieved
during moderate to heavy grass cutting conditions, and resulted in comparable surface temperatures to temperatures
measured during field testing.  For either the  100% or 50% load operational point, the engine was operated until
stable cylinder head and oil temperature conditions were achieved.  Stabilization required approximately six to eight
minutes of operation for the WOT  condition and approximately five to six minutes for the 50%  load condition,
depending on the engine. The ignition to the engine was then turned off and a timer was started. Infrared thermal
"still"  images were taken initially at 30 and 60 seconds following engine shut-down and at 1-minute intervals
thereafter.  Manufacturer's recommendations within  equipment owner's  manuals for equipment  using engine-
mounted fuel tanks (e.g., walk-behind lawn mowers) typically recommended waiting 2-minutes after engine shut-
down before  opening the cap of the fuel tank.  Thus peak surface temperatures 2-minutes after engine shut-down
were compared to the auto-ignition temperature of regular-grade gasoline  (approximately 250 C),  particularly for
the hot-soak  tests from the 50% load point and for tests of Class I engines that used fuel tanks mounted to the
engine. The  manufacturer's recommendations for lawn tractor refueling did not stipulate a specific waiting time
prior  to refueling.   The 2-minute period appeared to adequately represent  common usage of residential lawn
equipment, so this point during the hot soak period was also used for comparison of the  Class II engine and lawn
tractor configurations.

After-fire Testing

Two engine manufacturers identified after-fire due to engine run-on following a shut-down under high inertial load
to be a potential safety issue.  After-fire can occur when an engine is turning a high inertial load (e.g., a generator).
If the ignition is turned off, and there is no means  to  physically  stop engine rotation, then the inertial load will
temporarily keep the engine spinning. The mechanical governor will pull the carburetor throttle wide open, which
will both reduce engine braking and  can allow a full air-fuel charge to enter the engine. Because the ignition is shut
off, the full air-fuel charge exits the exhaust valve and enters the muffler.  The air-fuel charge  can ignite on hot
surfaces and  an "after-fire" flame can propagate through  the muffler and exit  the muffler or tailpipe.  Proper
engineering design typically prevents run-on after-fire  from occurring. Most Class I and Class II engines used in
high-inertia applications are equipped with either

    1.  a flywheel brake to rapidly stop the engine from spinning (within 3 seconds or less), or

    2.  a fuel cut solenoid that interrupts fuel flow  from the float bowl to the carburetor venturi, thus preventing
        fuel from flowing into the intake port and out the exhaust port after the ignition is turned off.

Run-on after-fire was encountered with carbureted, catalyst-equipped automobile and light-truck engines in the
1970s and 1980s, particularly with manual transmission vehicles coasting down long grades. One way that the issue
was addressed for these applications was to build  simple  flame  arresting properties into  the mufflers.9  Flame
arresting designs route  the exhaust gases through  channels,  passages and/or perforated  metal baffles that  are
                                                    47

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designed to absorb heat from the gases and thus extinguish a flame front. Flame arresting properties can be directly
incorporated into the sound attenuating baffles within the muffler.

Engine 241 was used for after-fire testing.  The after fire testing replicated conditions of engine run-on due to an
inertial load on an engine after the ignition is shut off. Testing occurred at near the end of the regulatory useful life
for the engine (125  hours) following dynamometer aging of the engine and catalyst-muffler. This particular engine
was tested with a standard OEM "shallow-box" style muffler with a central baffle-plate perpendicular to the muffler
inlet that divided the muffler approximately in half, similar to the OEM muffler shown on the right half of Figure 5-
6. This engine and OEM muffler was chosen because it had relatively high exhaust port temperatures and because it
demonstrated a consistent tendency for after-fire immediately following engine shut-down during WOT hot-soak
tests that were conducted.  The engine was also tested with a  catalyst-muffler with venturi secondary air and 40 cc
cordierite monolith catalyst similar to the  one pictured at the top of Figure  5-2. Flame arresting properties were
incorporated into the two-stage baffle  located upstream of the secondary air venturi.

The engine was operated at the 100% load, WOT condition on an Eddy-current dynamometer until stable cylinder
head  and oil  temperature conditions were achieved.   The  WOT  condition was  chosen to attain the highest
achievable exhaust  gas temperatures  and exhaust system surface temperatures. The engine's flywheel brake was
fixed into a disengaged position. The engine ignition was shut-off and the dynamometer load was simultaneously
dropped to zero. The engine continued to  spin due to the inertia of the dynamometer for approximately 7 seconds
before stopping completely.  This allowed  air and fuel to be drawn through the engine and into the exhaust system
without combustion in the engines combustion chamber.  The condition simulated shut-down with a high inertial
load and with failure of a fuel-cut solenoid  (typically used with generator sets  and lawn tractors to prevent after-fire)
or failure of a flywheel brake (used with all walk-behind lawn mowers for blade safety and to prevent after-fire).
Note  that federal  regulations  require  cutting blades  of walk-behind  mowers  to  stop within 3-seconds  of
disengagement of the blade  control, and 1- to 2-seconds is typical. 10 There  is currently no federal requirement
regarding blade-stopping time  for ride-on  lawn equipment.  There is an ANSI recommendation of 5 seconds for
blade stopping following disengagement of the blade control. 11

Digital video  of the after-fire tests was acquired to allow direct comparison of the OEM and catalyst-muffler
configurations. The test was repeated four times for the OEM muffler configuration.  Immediately following the
OEM muffler testing, the test was repeated  four times using the catalyst muffler.

Misfire Testing

Engine 255 was used for testing under conditions  of partial  ignition misfire.  An optical encoder providing 360
counts per engine revolution (one crank-angle-degree resolution) was installed onto the engine crankshaft output. A
laboratory controller temporarily grounded the ignition coil cut-off circuit based on input from the optical encoder
and the degree of misfire desired.  Initially, encoder data was acquired for 360  counts per revolution at a particular
engine operating condition, and a count of up to  1000 engine combustion cycles (2000 engine revolutions) was
initiated. When the ignition coil circuit was grounded, a complete 720 crank angle degrees (CAD) (or two complete
crankshaft revolutions) of ignition misfire would occur. This alleviated the need to track top dead center (TDC) and
spark timing.  The series of 1000 cycles could be continuously looped to allow  continuous operation at  a particular
percentage of ignition misfire.  Misfire could be made in equal intervals, so two misfires in 1000 cycles could occur
at cycles 500 and 1000.  Similarly, three misfires could occur following 333, 666, and 999 cycles. Other misfire
interval combinations were also evaluated.  The cycle count of 1000 was chosen arbitrarily and could be adjusted to
other values to check the effect of duration between misfires or to allow a higher rate  of misfire resolution.  The
final configuration used during testing utilized random number generation to  randomly select the specific cycles on
which misfire  would occur, while still allowing selection of the total percentage of misfire events. For example,
during prove-out of the misfire generation, the system was configured to cause  3% of the ignition firings to misfire
over 100 complete engine cycles and the random number generator provided misfire occurrences at cycles  12, 25,
89.

The next step  was to determine a reasonable operating condition (speed and load) for operating the engine under
partial misfire. An AC motoring dynamometer was used to map the load  provided by the cutting blade during
engine operation over a range  of typical engine speeds.  This essentially provided a torque curve analogous to a
                                                   48

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"propeller curve" for the conditions under which the cutting blade was spinning but not cutting grass.  The cutting
blade torque curve generated was thus established as the minimum torque point for engine operation.  The engine
was  operated  with engine speed controlled by the engine  governor, and misfire was initially induced during
operation on the dynamometer along the generated cutting blade torque curve.  Operation of the engine beyond 25%
ignition misfire resulted in extremely erratic engine operation and vibration and premature failure of the coupling
between the engine and the dynamometer. When operated at the 25% misfire condition, the erratic engine operation
would be immediately noticeable to the operator, causing engine stumbling, audible misfire  and backfire,  and
greatly  reduced ability  for the engine pick up load.   Sustained operation at 25% misfire was chosen as the
operational point for analysis  of exhaust system surface  temperatures.   Even this operational point should be
considered a conservative  estimate of a maximum misfire level since grass cutting operations and the power-take-
off for the wheel drive system would require more engine torque output than the cutting blade torque curve used
during testing, which was approximately equivalent to torque of the 25% load A-cycle mode 4 test point at the
speed encountered during misfire.

The engine was tested with the OEM muffler and the catalyst-muffler shown in figure 5-6. Following initiation of
sustained 25% misfire and stabilization of exhaust gas temperatures measured at the exhaust port, IR thermal images
were  taken of both  the  OEM muffler and  catalyst-muffler  configurations  to allow comparison of  surface
temperatures.

Simulated Rich Operation

Engine  255 was also used for simulated  rich operation. A carburetor was modified by changing the main jet to
provide an air-to-fuel ratio number approximately  1.0 to 1.5 units richer than the standard carburetor jetting.  This
air-to-fuel ratio was consistent with test results obtained from a similar engine previously tested by EPA (engine
#1514) that returned from field operations running excessively rich.  The rich operation was found to be due to a
float-valve that was partially contaminated with debris. 12  The engine was tested in this condition over all 6 modes
of the EPA A-cycle and with both an OEM muffler and with the same catalyst-muffler configuration used for the
misfire testing.

E.      FIELD OPERATION

Field operation was conducted to:

    1.      Obtain operational experience with both OEM and catalyst-equipped engine configurations

    2.      Provide an accelerated means of accumulating engine  hours to assess the emissions of both OEM
            Phase 2 and catalyst-equipped engines at either mid-life or near the end of useful life

    3.      Provide a means to assess surface temperatures of lawn care equipment during grass cutting operations
            with the engines installed on equipment chassis

Installation into a chassis was particularly  important for the IR thermal imaging analysis  of the lawn tractor
applications.  The chassis included heat  shielding and the ejectors used with the catalyst-muffler configurations
were installed onto the chassis. Cooling air-flow downstream of the engine was also routed through the chassis and
over the catalyst-mufflers  to improve heat rejection. These subsystems could not be adequately duplicated on the
engine dynamometer.

The engines were initially run for at least three hours either on the dynamometer, or on the mower-decks while
cutting grass. An additional two to seven hours of dynamometer run-time  followed this.  Emissions were monitored
during dynamometer testing until stabilized (-10% coefficient  of variance in brake-specific HC+NOx for three
repeated measurements), which typically required between five and ten hours of total operation from the new
condition, depending on the engine. The final three repeated measurements were taken as the "low hour" emission
baseline.
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The engines were then installed onto standard walk-behind lawn mowers. For the initial stages of field operations, a
field test apparatus was constructed that could pull up to nine walk-behind mower decks simultaneously through
large  fields in Southeast Michigan using a  garden tractor (Figures  5-11 and  5-12)  to  allow a more rapid
accumulation of hours of operation in the field cutting grass. This was done primarily to accelerate the operation of
a large  number of Class I,  Phase 2 lawn-mowers to generate high-hour emissions results for the purposes of
generating emissions inventory data. Emissions results from the initial stages of field operation can be found in the
Docket to the Nonroad SI Engine Phase 3 rule. 13  The apparatus was equipped with hydraulics that lifted the front
of each mower up when turning around to simulate similar turn maneuvers used during typical operation.

Subsequent stages of field operations, which included all of the Class I and Class II engines for which field data is
reported in this study, were conducted in South Central Texas during the Spring of 2005  (Class II only, Figure 5-
13), in Southwest Tennessee  during the fall of 2005 (Class I and Class II, Figure 5-14), and in  Florida in early 2006.
In these stages both lawn mowers and lawn tractors were used, and they were operated by individual operators
instead of using the field test apparatus.  Mowing was conducted with the lawn mowers and lawn tractors in an
echelon formation in large fields to prevent debris from contacting adjacent equipment.  Lawn mowers and lawn
tractors were also segregated to operate in different sections of each field. A total of six walk-behind lawn mowers
were used in grass cutting operations until they reached approximately  110 hours of operation.  Of the six lawn
mowers, three used side-valve engines equipped with catalyst-mufflers, two used OHV engines equipped with
catalyst-mufflers, and one used  a side-valve engine equipped with an OEM  muffler.  The two lawn  mowers
equipped with OHV engines  and catalyst-mufflers were also equipped with air shroud designs that directed air from
the engine cooling fan that exited from the engine cylinder over the outer surface of the catalyst-muffler in a manner
similar to the OEM air shroud design used with these particular  lawn mowers.   Three of the  catalyst-muffler
equipped  lawn mowers (both units with the OHV engines and one with the side-valve engine) were additionally
equipped with exhaust ejectors to both reduce the temperatures of the exhaust gases leaving the catalyst-muffler and
to improve  heat rejection from muffler and/or air  shroud  surfaces.   Both lawn tractors  were  equipped with
modifications to engine air shrouding and with exhaust ejectors (see Figure 5.8).

During field operation, up to  eight hours of engine run-time per day was possible. Large, level fields were cut.  The
run sequence each day was as follows:

1.      Each day started by checking the lubricating oil (and adding if necessary) and topping off the fuel tanks.

2.      The engines were then started and grass cutting operations commenced. During a workday, engines were
only shut down for refueling or poor weather or cutting conditions. Cutting operations ranged from 2 hours to 9
hours per  day, depending on weather.

3.      During refueling, oil levels were monitored, and engine oil was added if necessary.  Oil consumption was
monitored during the Tennessee field tests.

4.      At the end of each full day of operation, debris was cleaned from the mower decks. During the initial stage
of field testing (southeast Michigan),  compressed air was used to  clean the mower decks  and intake air filters.
During the later stages of field  operation, mowing decks were brushed clean and air filters were not  serviced
between normal maintenance intervals unless a  loss of engine performance was noticed by the operator. If air filter
service was required between service intervals due to visible blockage, it typically involved removing the intake air
filter and brushing accumulated debris from the  filter prior to reinstallation (engines 243, 244, and 245 only).

5.      Major  maintenance  consisted of changing the  lubricating oil (using manufacturer-specified lubricants)d,
air-filters, and spark-plugs at the manufacturers-specified intervals.   When intervals were specified by season
instead of hour level, 25-hours of operation was used as one season.

Field operation continued for a total of approximately 110 hours for the Class I engines and 240 hours for the Class
II engines. Afterwards, the engines were removed from the  lawn mowers or lawn tractors for dynamometer testing.
d Lubricants were SAE 30 API SL or  SAE 10w30 API SM (depending on application).  Manufacturer's API
specifications were API SF or better.
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Figure 5-11:  Field test apparatus with lawn mowers cutting grass in Southeast Michigan, late summer 2004.  The
apparatus was equipped hydraulic rams to lift the front of each mower to simulate turns at 10-meter intervals.  The
mower decks were set to a cutting height of three inches while cutting grass that was approximately five to six
inches in length.
Figure 5-12: The lawn mowers were stopped for refueling, debris clean-off, and basic checks each hour. This took
approximately  30 minutes, so the mowers were cycled between one hour on and half an hour off with a maximum
of eight hours  of actual mower running time per day, depending on weather.  Regular (87 octane) unleaded pump
gasoline was supplied to the work site using portable plastic gasoline cans with a trigger-nozzle, but no automatic
shut off.
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Figure 5-13:  Lawn tractor cutting grass in Central Texas in the spring of 2005.  Regular (87 octane) unleaded
pump-gasoline was supplied to  the  work  site  using portable plastic gasoline  cans with pour spouts.   Cutting
conditions were relatively dry with a high amount of debris.  Grass length varied from approximately five inches to
approximately 18 inches.  Mower decks were set to a cutting height of approximately three inches.
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Figure 5-14:  Lawn mower and Lawn tractor cutting grass in Southeast Tennessee in the fall of 2005. Regular (87
octane) unleaded pump-gasoline was supplied to the work-sight using portable plastic gasoline cans with pour
spouts (same fuel cans as in Texas - see Figure 11).  Conditions were cool and wet with a large amount of debris.
Grass length varied from approximately eight inches to approximately 18 inches. Mower decks were set to a cutting
height of approximately  three inches.   Both wet and dry cutting conditions were encountered.  Dry  cutting
conditions were accompanied with high levels of debris.
Figure 5-15:  Lawn mower and Lawn tractor cutting grass in Florida in early 2006. Regular (87 octane) unleaded
pump-gasoline was supplied to the work-sight using portable plastic gasoline cans with pour spouts.  Conditions
were hot and dry with tall try grass and a large amount of debris.  Grass length varied from approximately five
inches to approximately twelve inches.  Mower decks were set to a cutting height of approximately three inches.
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Acquisition of IR Thermal Images in the Field

Both still images and full-motion video infrared imaging was used to collect surface temperature data during grass
cutting operations in the field in Southwest Tennessee and Florida. Full motion video infrared imaging was used to
allow comparison of OEM and catalyst-equipped lawn tractors  and lawn mowers while cutting grass in large
(approximately 200-acre), level fields. The video IR imager was mounted onto a tripod and the cutting paths of the
equipment were arranged such that one piece of equipment passed into the range of view for the imager.  The
operator of the imager then tracked the equipment  for approximately 20 linear feet.  Approximately halfway
through, the equipment stopped for 5 seconds directly perpendicular to the imager at a position marked onto the turf
surface to temporarily allow a higher resolution, more  precise IR image for each pass in front of the imager.  Passes
were taken from both sides of the lawn tractors, and from the exhaust-muffler side of the lawn mowers.

Both full motion video and still  imaging was used to  measure surface temperatures during timed  hot soaks
following sustained (approximately 30-45 minutes) grass cutting with both the lawn tractors and the lawn mowers.
Both full motion video and still imaging were also used to measure turf surface temperatures during extended idling
of lawn tractors.   Initial  measurements conducted during equipment set-up that showed  that Turf surface
temperatures underneath and in front of the lawn tractor stabilized after approximately five minutes of idling with
the engine speed setting adjusted to "high". Brief IR  measurements of turf surface temperatures following 5 to 30
minutes of idling showed no significant difference versus just five  minutes of idling, thus the final measurements of
turf surface temperatures were taken for approximately two minutes of idling following an initial five minutes of
idle for turf surface temperature stabilization.
1 P.A. Sandefur, W.M. Kindness, "Catalytic Converter Having a Venturi Formed From Two Stamped Components",
U.S. Patent No. 5,548,955, 1996.
2 G.J. Gracyalny, P.A. Sandefur, "Multi-Pass Catalytic Converter", U.S. Patent No. 5,732,555, 1998.
3 Y. Yamaki, H. Kaneko, K. Nakazato, "Engine Exhaust Apparatus", U.S. Patent No. 5,431,013, 1994.
4 A. Shiki, M. Nakano, H. Nakazima, "Muffler with Catalyst for  Internal Combustion Engine", U.S. Patent No.
4,579,194, 1986.
5  V. Vavilov,  V. Demin,  "Infrared thermographic inspection of operating smokestacks", Infrared Physics &
Technology, Volume 43, Issues 3-5 , June 2002, Pages 229-232.
6 R. Monti, G. P. Russo, "Non-intrusive methods for temperature measurements in liquid zones in microgravity
environments", Institute of Aerodynamics ", Acta Astronautica, Volume  11, Issue 9 , September 1984, Pages 543-
551.
7 H. Wiggenhauser, "Active IR-applications in civil engineering", Infrared Physics & Technology, Volume  43,
Issues 3-5 , June 2002, Pages 233-238.
8 Title 40, U.S. Code of Federal Regulations, Part 90, Subpart E, Appendix A.
9 S. Mizusawa, "Silencer for and Internal Combustion Engine", U.S. Patent No. 4,124,091, 1978.
10 Title 16, U.S. Code of Federal Regulations, Part 1205.
11 ANSI B71.1-2003, "American National Standard for Consumer Turf Care Equipment - Walk-Behind Mowers
and Ride-On Machines with Mowers - Safety Specifications".
12 "Control of Emissions From Nonroad Spark-Ignition Engines, Vessels, and Equipment Document", Docket ID
"EPA-HQ-OAR-2004-0008-0089", tests 1514-4, 1514-5 and 1514-6.
13 "Control of Emissions From Nonroad Spark-Ignition Engines, Vessels, and Equipment Document", Docket ID
"EPA-HQ-OAR-2004-0008-0089".
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6.      Test  ResultsComparison  between EPA's  Phase  3  Prototypes
        and Current Engine Systems
In this chapter we will discuss the results of laboratory and field testing of the Class I and Class II engines described
in Chapter 5, tables 5-1 and 5-2, respectively.

A.      EMISSIONS RESULTS

A summary of the exhaust emissions results for the tested engine configurations over the EPA A-cycle may be
found in Appendix B. Emissions levels of all of the catalyst-configured systems tested were consistent with the
California Tier 3 and the expected Federal Phase 3  emission standards.  In many cases, HC+NOx emissions were
well below the expected Phase 3 standards. An increase in exhaust back-pressure was expected with the addition of
catalyst-mufflers to the engines, but engine power output and load response was comparable to  that of the engines
using OEM mufflers.

B.      LABORATORY TEST RESULTS

Surface temperature measurements by infrared thermal imaging - Class I Side-valve Engines

Engine 258:

Figure 6-1 shows infrared thermal images for A-cycle modes 1, 3 and 5 taken during laboratory testing of engine
258 with a catalyst-muffler and with an OEM muffler following approximately 10 hours of engine break-in and
catalyst "degreening".6  The catalyst-muffler used was the European catalyst-muffler with the stamped secondary-
air-venturi, modified to increase the catalyst substrate volume  to approximately 40 cc (2-20 cc 400 cpsi ceramic
monoliths, similar to  the "middle" unit in Figure 5-2) as described in Chapter 5.  The peak temperatures on the
catalyst-muffler were near the exhaust outlet. The through-bolts attaching the muffler to the engine and one of the
welds between the outer and inner halves of the catalyst-muffler were also at  similar temperatures to the outlet.
This particular weld was a result of modifications  made to  the muffler to increase catalyst volume.  Production
mufflers typically use a folded seam rather than a  continuous weld to join stamped halves together, and folded
seams tend to hold in less heat.

The peak temperatures for the OEM muffler were at the muffler through-bolts and the lower half of the outside
surface of the muffler, immediately downstream of where the exhaust expands through the muffler baffle.  The
OEM muffler peak temperatures were significantly hotter than those of the catalyst-muffler at all six of the A-cycle
test modes, which covered the entire operational range of the engine. The heat-affected surface  area above 350 C
covers a larger area of the OEM muffler at high load than was the case for the catalyst-muffler.  While cooler
temperatures of the catalyst-muffler versus the OEM muffler initially seem counterintuitive, the catalyst-muffler has
a number of design elements that allow it to reject heat more effectively than the OEM muffler, including:

    1.   The catalyst-muffler routes the exhaust gases through three stages of baffles (two pre-catalyst, one  post-
        catalyst) vs. a single stage baffle for the OEM muffler.

    2.   The catalyst-muffler has approximately double the external surface area of the OEM muffler to reject heat
        over.

    3.   The catalyst-muffler has a longer internal path (including one flow reversal) to reject heat through.

    4.   Approximately 25% of the catalyst-muffler surface  area is located directly in the cooling air-flow of the
        engine fan immediately downstream of the  cylinder fins.  Very little cooling air reaches the OEM muffler
        due to its positioning well forward of where much of the cooling air exhausts from the engine.
e Catalyst degreening involves operation of a catalyst in engine exhaust long enough for an initial degree of thermal
sintering of PGM to occur.  This was performed for emissions testing purposes only.
                                                  55

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Engine 236

Figure 6-2 shows infrared thermal images for A-cycle modes 1, 3 and 5 taken during laboratory testing of engine
236 following approximately 10  hours  of engine break-in and catalyst "degreening".   The catalyst-muffler was
similar in construction to the one used with engine 258 except that the catalyst used a 200  cpsi, 44 cc metal
monolith with a tri-metallic washcoating formulation, and the inlet location was changed to allow fitment to engine
236 since this engine is from a different engine family than engine 258.

This engine  had peak OEM-muffler temperatures that were 50 to 60 degrees higher than that of engine 258.  As a
result, both the catalyst-muffler and OEM muffler surface temperatures were higher for engine 236 than what was
observed for engine 258.  Comparing the catalyst-muffler in figure 6-2 to  that in figure 6-1,  the section of the
catalyst-muffler containing the catalyst substrate was considerably hotter than that in figure 6-1, in part due to lower
air-flow rate from the cooling fan and higher cooling air temperatures for engine 236 relative to engine 258.  The
OEM cooling fan was integral to the flywheel and used six constant cross section flat-paddle-type blades. There is
substantial potential to reduce catalyst-muffler surface temperatures for engine 236 via use of a higher efficiency,
higher volume cooling fan and  by paying close attention to the routing of cooling air-flow relative to the muffler
position.

As with engine 258, the peak surface temperatures with catalyst-muffler were significantly  cooler than those of the
OEM muffler at each of the A-cycle test points. The hottest areas of the catalyst-muffler were the portion of the
muffler that contained the catalyst substrate (the area center-right of the images) and the continuous weld running
along the top  of the  catalyst-muffler.  The hottest area of the OEM muffler was on the outer surface directly
opposite from the exhaust port outlet. The heat-affected  surface area above  350 C was comparable for the OEM
muffler and the catalyst-muffler.
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                  Catalyst-muffler,
                venturi secondary air
            100% Load - Wide Open Throttle
                                         -600.0


                                         -500


                                         -400

                                         -300 *'


                                         -200


                                         -100

                                         -25.0
          Maximum surface temperature: 471 C

                  50% Load - Mode 3
                                          600.0
          Maximum surface temperature: 351 C

                  10% Load-Mode 5
                                          600.0
          Maximum surface temperature: 332 C
         OEM Muffler

  100% Load - Wide Open Throttle
Maximum surface temperature: 511 C

        50% Load - Mode 3
                                                                                             600.0
Maximum surface temperature: 412 C

        10% Load-Mode 5
                                                                                             600.0
Maximum surface temperature: 397 C
Figure 6-1: Infrared thermal images showing the surface temperatures of exhaust system components for side-valve
engine 258 at low hours, equipped with a catalyst-muffler (left) and an OEM muffler (right) for modes 1, 3 and 5 of
the A-cycle.
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                 Catalyst-muffler,
               venturi secondary air
            100% Load - Wide Open Throttle
                                     -600.0

                                     -500

                                     -400

                                     -300 "C

                                     -200

                                     -100

                                     -25.0
        Maximum surface temperature:  494 C

                50% Load - Mode 3
                                      100
                                      25 u
        Maximum surface temperature:  420 C

                 10% Load-Mode 5
                                      100
                                      25.0
        Maximum surface temperature:  433 C
           OEM Muffler


    100% Load - Wide Open Throttle
                             -600.0

                             -500

                             -400

                             -300 *C

                             -200

                             -100

                             -25.0
Maximum surface temperature: 579 C

        50% Load - Mode 3
Maximum surface temperature: 493 C

        10% Load-Mode 5
                             -600.0


                             -500


                             -400


                             -300 (


                             -200


                             -100

                             -25.0
Maximum surface temperature: 497 C
Figure 6-2: Infrared thermal images showing the surface temperatures of exhaust system components for side-valve
engine 236 at low hours, equipped with a catalyst-muffler (left) and an OEM muffler (right) for modes  1, 3 and 5 of
the A-cycle.
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Infrared thermal imaging - Class IOHV Engines

In some respects, Class I OHV engines present more of a design challenge with respect to exhaust component heat
rejection than their side-valve counterparts. Peak exhaust gas temperatures measured at the muffler inlet can be 50-
100 C higher at some operating conditions when compared to side-valve engines used in similar walk-behind lawn
mower applications.  In some cases, OEM muffler configurations tested incorporated shrouds around the muffler to
enhance heat rejection via forced convection using cooling air from the engine cooling fan (engines 243 and 244).
Other OEM muffler designs for OHV engines were generally similar to those used with side-valve engines (engines
241, 255).  The shrouded designs maintained a minimum clearance between the muffler and the shroud to prevent
debris accumulation, similar to the clearances used to prevent debris accumulation within the engine shrouding of
the cylinder and cylinder-head.  The catalyst-muffler configurations tested by EPA with engines 243  and 244
incorporated similar shrouding, and in one case (engine 243) used a modified OEM air-shroud.

Engine 241

Figure 6-3 shows infrared thermal images for A-cycle modes 1, 3 and 5 acquired during laboratory testing of engine
241 following approximately 110 hours of dynamometer aging (near the end of useful life).  The catalyst-muffler
used was similar to that used with engine 258 (40 cc, 400 cpsi ceramic monolith, top of figure 5-2). The muffler
baffles and muffler inlet were reconfigured, and the muffler did not use through-bolts exposed to the exhaust flow.
No modifications were made to the stamped secondary-air venturi.  The exhaust gas temperatures for this OHV
engine family were typically higher than those observed for side-valve engines (e.g., engine 258).   Peak surface
temperatures for the catalyst-muffler occurred on the outer muffler shell, immediately downstream of the catalyst
substrate, and on the weld along the lower parting seam of the muffler shell.  Peak surface temperatures for the
OEM muffler occurred along the outer-most surface  of the muffler shell and near the stub-pipe exhaust outlet.  Peak
surface temperatures for the catalyst-muffler were cooler than the OEM muffler for the 100% load,  WOT condition,
and were comparable to the OEM muffler over the remaining steady-state operating conditions of the A-cycle.  The
OEM muffler's highest surface temperatures generally covered a larger surface area of the outer muffler shell than
was the case for the catalyst-muffler.

Hot soak tests  conducted from the 100% load WOT condition show the catalyst-muffler cooler than the OEM
muffler for the first 30 seconds following shutdown (figure 6-4).  At one minute following shutdown from WOT,
the temperature decay of the  catalyst-muffler decreased due to conductive heat transfer from the internal surfaces to
the outer surfaces of the catalyst-muffler.  Thus at 30 seconds after shutdown from WOT, the catalyst-muffler peak
temperatures were  approximately the  same temperature as the OEM muffler rather than cooler, and at one minute
following shutdown, the catalyst-muffler peak  temperatures were approximately  80 C  higher than the OEM
muffler. After approximately two minutes following shutdown from the WOT condition, peak temperatures for the
catalyst-muffler were again comparable to the OEM muffler (figures 6-4 and 6-5).

During hot-soak tests from the 50% load point  (mode 3), surface temperatures  of the catalyst-muffler and OEM
muffler were comparable throughout the hot-soak period (figures 6-6 and 6-7).  The initial hot-soak temperatures
obtained following sustained 50% load operation  were also  more comparable  to exhaust system  peak surface
temperatures measured field operation.  After approximately 2-minutes following shut-down from 50% load, peak
temperatures of both the OEM muffler and the  catalyst-muffler were below 250 C, which is approximately the
auto-ignition temperature of gasoline.  This corresponded well to the manufacturer's recommendations within the
Owner's Manual for this engine that the operator wait two minutes following shut-down before removing the cap to
the fuel tank for refueling.

Engine 255

Figure 6-8  shows  infrared thermal images for A-cycle modes 1, 3,  and 5  acquired during laboratory testing of
engine 255 with a catalyst-muffler and with an OEM muffler following approximately 10 hours of engine break-in
and catalyst "degreening".  The catalyst-muffler used was the same unit shown in figure 5-6. Although engine 255
is  from the same  engine family as engine 241, the catalyst-muffler has several  key differences.  In  order to
simultaneously  enhance emission control performance and heat rejection, part of the catalyst volume was relocated
upstream of the secondary-air-venturi by mounting a catalyzed-tube pre-catalyst in the short length of exhaust pipe
                                                   59

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between the exhaust port and the entrance to the muffler body.  The catalyst substrate size was reduced, the cell
density was halved, and a metal monolith construction was substituted for the cordierite monoliths used with engine
241. A tri-metallic washcoating formulation was used, although PGM loading was similar to that used with engine
241 on a per-unit of catalyst volume basis.  The increased catalyst efficiency of this catalyst-muffler configuration
allowed a reduction in secondary-air entrainment.  Two  of the four air inlet holes in the stamped venturi  were
blocked to reduce the volume of secondary-air flow drawn by the stamped venturi.  In the end, the  level of
HC+NOx emissions control for the catalyst-muffler tested with engine 255 was approximately  equivalent to the
system tested with engine 241, but with approximately 50% less secondary air flow, and an overall reduction in total
catalyst volume and PGM.  CO oxidation at low operational hours was reduced from approximately 50%  over the
A-cycle to approximately 15%.

Peak surface temperatures  for the catalyst-muffler were in the  area where the exhaust flow  turns 180  degrees,
between the catalyst outlet and the muffler outlet.  Peak surface temperatures for the OEM muffler were on the
outer-surface near where the exhaust expands through the muffler baffles. The peak surface temperatures of the
catalyst-muffler were approximately 30 to 60 degrees cooler than the OEM muffler for all six modes of the A-cycle
test and were also reduced  relative to the catalyst-muffler tested with engine 241.  The heat-affected surface area
above 350 C for the catalyst-muffler was comparable to that of the OEM muffler.

Engine 244

Figure 6-9 shows infrared  thermal images  for A-cycle modes 1,  3, and  5 acquired during  laboratory testing of
engine 244 with a catalyst-muffler and with an OEM muffler following approximately 10 hours of engine break-in
and catalyst "degreening".  The catalyst-muffler used was similar to that used with engine 258,  but with a different
catalyst (44 cc, 200 cpsi metal monolith, tri-metallic  washcoating formulation).  The muffler baffles and muffler
inlet were reconfigured, and the muffler did not use through-bolts exposed to the exhaust flow.  A steel shroud was
fabricated to  route air-flow over the catalyst-muffler in a manner  similar  to that of the OEM  muffler and shroud
used with this engine. An exhaust ejector was incorporated into the catalyst-muffler shroud design to cool the
muffler outlet (the hottest part on the OEM muffler configuration)  and to provide additional cooling to the exhaust
gases  exiting the catalyst-muffler.  The  use of the ejector dropped the peak temperature  of exposed surfaces by
approximately 200 C relative to  the OEM configuration over the six modes of the A-cycle test. Exposed  surfaces
were below the auto-ignition point of gasoline (-250 C) at all of the tested conditions, including WOT. The tested
catalyst-muffler configuration maintained 100-200 C cooler exposed peak surface temperatures for the entire five
minute timed hot-soak period for hot soaks from both the WOT (see Figures 6-10 and 6-11)  and 50% load (see
Figures 6-12 and 6-13) conditions when compared to the OEM configuration.  The peak temperatures of the shroud
used with the catalyst-muffler increased slightly during the first minute following engine  shut-down, and then
decreased throughout the remainder of the timed soak period.

Engine 243

The tests conducted  with  engine 244  were repeated with a  nearly identical  engine   (engine 243) that also
incorporated  further improvements in the design of the catalyst-muffler, air shrouding and exhaust ejector.  A
completely different muffler design was used which included a new concentric tube venturi.  During development,
secondary-air flow was progressively  reduced to minimize  CO while maintaining HC+NOx control above  40%
efficiency over the A-cycle.  The size reduction of the muffler enabled  by the improvements allowed use of a
modified version of the OEM muffler shroud. The exhaust ejector was lengthened approximately 25% to  increase
the draw of air  through the ejector.  The changes resulted in reduced CO oxidation and a further 20 to 40 C
reduction in  external surface temperatures  relative to the catalyst-muffler and shroud configuration tested  with
engine 244 (figure 6-14).  Peak temperatures of exposed surfaces were  below 200 C for all  operating points,
including the region near the exhaust outlet from the ejector.   During the hot soak from the WOT condition,  peak
surface temperatures were similar to the  catalyst-muffler tested with  engine 244 and approximately 200 C cooler
than peak temperatures with the OEM system (figures 6-15 and 6-16). Peak temperatures during hot-soak from the
50% load condition were 20-40 C cooler than  the earlier catalyst-muffler configuration, and approximately  100-
300 C cooler than the OEM system (figures 6-17 and 6-18).
                                                   60

-------
                 Catalyst-muffler,
               venturi secondary air
            100% Load - Wide Open Throttle
                                     rGOO.O
                                      25 i
        Maximum surface temperature:  447 C

                 50% Load - Mode 3
                                      -600.0


                                      -500


                                      r400


                                      -300 C


                                      r200


                                      -100

                                      -25.0
        Maximum surface temperature:  362 C

                 10% Load-Mode 5
                                      100
                                      25.0
        Maximum surface temperature:  296 C
           OEM Muffler


    100% Load - Wide Open Throttle
                             - 600.0

                             r 500

                             ''- 400
                             -200

                             Moo

                             -25.0
Maximum surface temperature: 480 C

        50% Load - Mode 3 _
                              -600.0

                              L500

                              -400

                              -300 T

                              -200

                              -100

                              -25.0
Maximum surface temperature: 371 C

        10% Load -Mode 5
                             -600.0

                             -500

                             -400

                             -300 C

                             -200

                             -100

                             -25.0
Maximum surface temperature: 300 C
Figure 6-3:  Infrared thermal images showing the surface temperatures of exhaust system components for OHV
engine 241 at high hours, equipped with a catalyst-muffler (left) and an OEM muffler (right) for modes 1, 3 and 5
of the A-cycle.
                                                  61

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           Modified Catalyst-muffler
                                     100
                                     25.0
       Maximum surface temperature: 423 C

                                    -600.0
       Maximum surface temperature:  396 C
                                     1 oo
                                     2GO
       Maximum surface temperature:  384 C

                                    r 600.0
                                     100
                                     :ri LI
      Maximum surface temperature:  324 C
                                                  O-seconds
                                                  30-seconds
                                                   1-minute
                                                  2-minutes
                             OEM Muffler _
                                                 -600.0


                                                 H500


                                                 -400

                                                 -300 'f


                                                 -200


                                                 -100

                                                 -25.0
                   Maximum surface temperature:  485 C

                                                .r 600.0
                   Maximum surface temperature:  418 C
                                                 -100

                                                 -25.0
                   Maximum surface temperature:  301 C

                                                 -600.0

                                                 -500

                                                 -400

                                                 -300 (

                                                 -200

                                                 -100

                                                 -25.0
                   Maximum surface temperature:  301 C
Figure 6-4:  Infrared thermal images showing the
241 during a hot-soak period immediately after enj
cycle mode  1).
surface temperatures of exhaust system components for engine
;ine shutdown from sustained operation at WOT, 100% load (A-
                                                     62

-------
           Modified Catalyst-muffler
                                      100

                                      25.0
       Maximum surface temperature: 265 C
                                      [600.0


                                      500


                                     -400

                                     -300 T


                                     -200
                                   I
100
                                      250
       Maximum surface temperature: 219C
                                                   3-minutes
             4-minutes
                                         OEM Muffler
                                                                                                   100
                                                             25.0
                               Maximum surface temperature: 258 C
                                                           B-BOO.O
-500


-400


-300


-200


-100

-25.0
                               Maximum surface temperature: 218 C
Figure 6-5:  Continuation of the hot-soak shown in figure 6-4.
                                                      63

-------
           Modified Catalyst-muffler
                                    mrSOO.O
        Maximum surface temperature: 351 C
                                    L25.0
        Maximum surface temperature: 325 C

                                     -600.0

                                     -500

                                     -400

                                     -300 '

                                     -200

                                     -100
                                     -25.0
        Maximum surface temperature: 290 C

                                     -eoo.o

                                     -500

                                     -400

                                     -300 '

                                     -200

                                     -100
                                     -25.0
        Maximum surface temperature: 247 C
                                                   0-seconds
                                                  30-seconds
1-minute
2-minutes
                           OEM Muffler
                                                                                                 -SOO.O
                  Maximum surface temperature: 360 C
                                              t-25.0
                  Maximum surface temperature: 318 C

                                               -soo.o

                                               -500

                                               -400
                  Maximum surface temperature: 288 C
                                               -100
                                               -25.0
                  Maximum surface temperature: 242 C
Figure 6-6:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
241 during a hot-soak period immediately after engine shutdown from sustained operation at 50% load (A-cycle
mode 3).
                                                     64

-------
    Modified Catalyst-muffler
                             -600.0

                             -500

                             -400

                             -300 T

                             -200

                             -100
                             -25.0
Maximum surface temperature: 206 C

                             -soo.o

                             -500

                             -400

                             -300 T

                             -200

                             -100
                             -25.0
Maximum surface temperature: 176 C
                                                 3-minutes
                                                 4-minutes
                                                                           OEM Muffler
                                                                Maximum surface temperature: 207 C
                                                                                              100
                                                                                              250
                                                                Maximum surface temperature: 173 C
Figure 6-7: Continuation of the hot-soak shown in figure 6-6.
                                                   65

-------
                  Catalyst-muffler,
                venturi secondary air
             100% Load - Wide Open Throttle
                                         r 600.0


                                         -500


                                         -400


                                         -300  '


                                         -200


                                         -100

                                         -25.0
          Maximum surface temperature: 440 C

                  50% Load - Mode 3
                                         ^600.0


                                         -500


                                         -400


                                         -300  ''


                                         -200


                                         -100

                                         -25.0
          Maximum surface temperature: 310 C

                  10% Load-Mode 5
                                         -600.0


                                         L500


                                         -400


                                         - 300  ''


                                         -200


                                         -100

                                         -25.0
          Maximum surface temperature: 248C
          OEM Muffler

   100% Load - Wide Open Throttle
                               -600.0


                               -500


                               -400


                               -300  '


                               i-200


                               -100

                               -25.0
Maximum surface temperature: 470 C

        50% Load - Mode 3
                               r 600.0


                               -500


                               L400


                               -300  '


                               -200


                               r100

                               -25.0
Maximum surface temperature: 360 C

        10% Load-Mode 5
                               ^600.0


                               -500


                               -400


                               -300  '


                               r200


                               ^100

                               :-25.0
Maximum surface temperature: 296 C
Figure 6-8:  Infrared thermal images showing the surface temperatures of exhaust system components for OHV
engine 255 at low hours, equipped with a catalyst-muffler (left) and an OEM muffler (right) for modes 1, 3 and 5 of
the A-cycle.
                                                     66

-------
                 Catalyst-muffler,
               venturi secondary air
            100% Load - Wide Open Throttle
                                     r600.0
                                      25.0
        Maximum surface temperature: 230 C

                 50% Load - Mode 3
                                      100
                                      25.0
        Maximum surface temperature:  102 C

                 10% Load-Mode 5
                                      100
                                      25.0
        Maximum surface temperature:  161 C
           OEM Muffler


    100% Load - Wide Open Throttle
                             rGOO.O

                             i- 500

                             1-400
                             :-2oo

                             MOO
                             -25.0
Maximum surface temperature: 551 C

        50% Load - Mode 3
                                                                                         100
                                                                                         25 LI
Maximum surface temperature: 421 C
        10% Load-Mode 5
                           I
                                                                                         100
                                                                                         25.0
Maximum surface temperature: 363 C
Figure 6-9:  Infrared thermal images showing the surface temperatures of exhaust system components for OHV
engine 244 at high hours, equipped with a catalyst-muffler (left) and an OEM muffler (right) for modes 1, 3 and 5
of the A-cycle.  The OEM muffler configuration was equipped with a full shroud that directed air-flow over the
muffler. This configuration was largely reproduced for the catalyst-muffler. An exhaust-ejector was also added for
improved shroud and exhaust-gas cooling (dark blue rectangular area).
                                                  67

-------
           Modified Catalyst-muffler
                                   -600.0
       Maximum surface temperature: 228 C
                                    25.0
       Maximum surface temperature: 234 C

                                   r600.0


                                   I- 500
       Maximum surface temperature: 240 C
                                    25.0
       Maximum surface temperature: 215 C
                                                 0-seconds
                                                 30-seconds
                                                  1-minute
                                                 2-minutes
          OEM Muffler
Maximum surface temperature:  526 C
                                                                                               100
Maximum surface temperature:  527 C
Maximum surface temperature:  483 C
                                                                                               25.0
Maximum surface temperature:  418 C
Figure 6-10:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
244 during a hot-soak period immediately after engine shutdown from sustained operation at WOT,  100% load (A-
cycle mode 1).
                                                    68

-------
          Modified Catalyst-muffler
                                 r 600.0
     Maximum surface temperature: 196 C
                                  100

                                  250
     Maximum surface temperature: 180 C


                                 r600.0


                                 i-500
                                  26 0
     Maximum surface temperature: 164 C
                                               3-minutes
                                               4-minutes
                                               5-mmutes
          OEM Muffler
Maximum surface temperature: 363 C
Maximum surface temperature:  319C
                                                                                          100
                                                                                          25.0
Maximum surface temperature:  280 C
Figure 6-11: Continuation of the hot-soak shown in figure 6-10.
                                                 69

-------
           Modified Catalyst-muffler
                                    -600.0
       Maximum surface temperature: 168 C
                                    25.0
       Maximum surface temperature: 173 C

                                    [600.0

                                    500
                                    100
                                    25.0
       Maximum surface temperature: 176 C

                                    - 600.0
                                    100
                                    Jb.O
       Maximum surface temperature: 169 C
                                                  0-seconds
                                                 30-seconds
                                                  1-minute
                                                  2-minutes
          OEM Muffler
                             100
                             25.0
Maximum surface temperature: 411 C

                            r 600.0

                            -500
                             100
                             25.0
Maximum surface temperature: 389 C
Maximum surface temperature: 357 C
                                                                                                100
Maximum surface temperature: 321 C
Figure 6-12:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
244 during a hot-soak period immediately after engine shutdown from sustained operation at 50% load (A-cycle
mode 3).
                                                     70

-------
          Modified Catalyst-muffler
     Maximum surface temperature: 158  C
     Maximum surface temperature: 148 C
                                 100
                                 25.0
     Maximum surface temperature: 135 C
                                              3-minutes
                                              4-minutes
                                              5-minutes
          OEM Muffler
Maximum surface temperature: 284 C
Maximum surface temperature: 251 C
Maximum surface temperature: 224 C
Figure 6-13:  Continuation of the hot-soak shown in figure 6-12.
                                                71

-------
                 Catalyst-muffler,
               venturi secondary air
            100% Load - Wide Open Throttle
                                     r 600.0

                                     1-500

                                     1-400

                                     i-300 *C

                                     j-200

                                     -100

                                     -25.0
        Maximum surface temperature:  184 C

                50% Load - Mode 3
                                      100
                                      25.0
        Maximum surface temperature:  125 C

                 10% Load-Mode 5
                                      100
                                      25.0
        Maximum surface temperature:  101 C
           OEM Muffler


    100% Load - Wide Open Throttle
                             rGOO.O

                             i- 500

                             j-400
                             :-2oo

                             j-100

                             -25.0
Maximum surface temperature: 551 C

        50% Load - Mode 3
                                                                                         100
                                                                                         25 LI
Maximum surface temperature: 421 C
        10% Load-Mode 5
                            I
                                                                                         100
                                                                                         25.0
Maximum surface temperature: 363 C
Figure 6-14:  Infrared thermal images showing the surface temperatures of exhaust system components for OHV
engine 243 at high hours, equipped with a catalyst-muffler (left) compared to an engine from the same engine
family (engine 244) equipped with an OEM muffler (right) for modes 1, 3 and 5 of the A-cycle.  In this case, the
catalyst-muffler used  a concentric tube venturi with an annular exhaust inlet.  The OEM muffler configuration was
equipped with a full shroud that directed air-flow over the muffler.  This configuration was largely reproduced for
the catalyst-muffler via modifications to  the OEM shroud. An exhaust-ejector was also added for improved shroud
and exhaust-gas cooling.
                                                  72

-------
           Modified Catalyst-muffler
                                    100

                                    25.0
       Maximum surface temperature:  182C

                                   -600.0

                                   -500
       Maximum surface temperature:  164 C
       Maximum surface temperature:  177C
                                   -100
       Maximum surface temperature:  168 C
                                                 0-seconds
                                                 30-seconds
                                                  1-minute
                                                 2-minutes
          OEM Muffler
Maximum surface temperature:  526 C
                                                                                               100
Maximum surface temperature:  527 C
Maximum surface temperature:  483 C
                                                                                               25.0
Maximum surface temperature:  418 C
Figure 6-15:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
243  (left) and engine  244 (right) during a hot-soak period  immediately after engine shutdown from sustained
operation at WOT, 100% load (A-cycle mode 1).
                                                    73

-------
          Modified Catalyst-muffler
     Maximum surface temperature:  168 C
                                 t25.0
      Maximum surface temperature: 183C
     Maximum surface temperature:  162 C
                                  100
     Maximum surface temperature:  155 C
                                              3-minutes
                                              4-minutes
                                              5-mmutes
                                              6-minutes
          OEM Muffler
Maximum surface temperature: 363 C
Maximum surface temperature: 319C
Maximum surface temperature: 280 C
Maximum surface temperature: 248 C
Figure 6-16:  Continuation of the hot-soak shown in figure 6-15.
                                                 74

-------
           Modified Catalyst-muffler
                                    100
                                    25.0
       Maximum surface temperature: 115 C

                                   -600.0

                                   -500
       Maximum surface temperature: 120 C
       Maximum surface temperature: 1 1 1 C
                                    -100
       Maximum surface temperature: 1 1 1 C
                                                  0-seconds
                                                 30-seconds
                                                  1-minute
                                                  2-minutes
          OEM Muffler
                             100
                             25.0
Maximum surface temperature: 411 C

                            r 600.0

                            -500
                             100
                             25.0
Maximum surface temperature: 389 C
Maximum surface temperature: 357 C
                                                                                                100
Maximum surface temperature: 321 C
Figure 6-17:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
243 (left) and 244 (right) during a hot-soak period immediately after engine shutdown from sustained operation at
50% load (A-cycle mode 3).
                                                    75

-------
          Modified Catalyst-muffler
     Maximum surface temperature: 132  C
                                 t25.0
     Maximum surface temperature: 112 C
                                  100
                                  25.0
     Maximum surface temperature: 113 C
                                               3-minutes
                                               4-minutes
                                               5-minutes
          OEM Muffler
Maximum surface temperature: 284 C
Maximum surface temperature: 251 C
Maximum surface temperature:  224 C
Figure 6-18: Continuation of the hot-soak shown in figure 6-17.
                                                 76

-------
Infrared thermal imaging - Class IIOHV Engines

Infrared thermal images are shown for three of the Class II lawn tractor engine types tested by EPA.  It should be
noted that the routing of cooling air through the lawn tractor chassis is important for both engine and exhaust system
cooling.  Also, for the catalyst-equipped configurations, the routing of cooling air through the chassis was modified
to enhance cooling of exhaust system surfaces.  Forced cooling of this  type could not be adequately replicated
during engine dynamometer testing, so the test results presented should be  seen as worst case with respect to surface
temperatures.  Please  refer to the field test results to see comparisons of engines and exhaust configurations as
installed in the lawn tractor chassis.

Engine 231

Figure 6-19 shows infrared thermal images for A-cycle modes 1, 3 and 5  taken during laboratory testing of engine
231 equipped with a catalyst-muffler and EFI compared to an OEM configuration following approximately 10 hours
of engine break-in and catalyst  "degreening" and an additional 10 hours of operation accumulated during engine
management system development. The catalyst-muffler used was similar to  the one pictured in the lower right of
figure 5-7. The peak temperatures for the catalyst-muffler were on the surfaces of the head-pipe and on the surfaces
adjacent to a series of baffles located in the lower half of the muffler. The peak temperatures of the OEM muffler
were on the surfaces of the head-pipe and on the upper half of the muffler,  immediately upstream of the first muffler
baffle.  Comparable peak temperatures were found for both the catalyst-muffler and the OEM muffler for all six
steady-state operating  modes of the A-cycle.  Surface temperatures for both configurations were approximately 100
C higher than what was measured for the Class I configurations.

Engine 251

Figure 6-20 shows infrared thermal images for A-cycle modes 1, 3 and 5  taken during laboratory testing of engine
251 equipped with a catalyst-muffler and an OEM muffler.  Engine 251 was from the same engine family as engine
231.  The catalyst-muffler used was similar to the one shown in the middle-right of figure 5-7, but with the outlet on
the bottom of the muffler.  Peak surface temperatures for both the catalyst-muffler and the OEM muffler were on
the head-pipe and  the region  of the muffler immediately  downstream of the  head-pipe.   Comparable peak
temperatures were found for both the catalyst-muffler and the OEM muffler for all six modes of the A-cycle.

Hot soak tests were conducted with this engine from the 50% load condition (see figure 6-21 to 6-23).  The cooling
of the catalyst-muffler, as indicated by peak surface temperatures, lagged  approximately one minute behind that of
the OEM muffler, probably due  to the increased mass of the catalyst-muffler in comparison with the OEM muffler.
The time required for surface temperatures to cool to 250 C was approximately six minutes for the catalyst-muffler
and five minutes for the OEM muffler.

Engine 254

Figure 6-24 shows infrared thermal images for A-cycle modes 1, 3 and 5  taken during laboratory testing of engine
254 equipped with a catalyst-muffler and an OEM muffler.  The catalyst-muffler used on engine 254 differed from
the catalyst muffler used on engine 251 in several ways.  The head-pipe used a double-wall construction to reduce
its temperature.  The overall substrate volume was reduced and divided into 2 parallel substrates to reduce exhaust
back-pressure. Additionally, 100 cpsi metal-monolith construction was used instead of 200 cpsi, reducing cost and
further reducing exhaust back-pressure.  Peak temperatures were comparable between the catalyst-muffler and the
OEM muffler systems for all six modes of  the A-cycle.  The  double-wall construction reduced peak surface
temperatures  of the head-pipe used  with the catalyst-muffler by approximately 150 C  at moderate to high-load
conditions. Similar double-wall construction could also be applied to other parts of the exhaust system to reduce
peak temperatures in specific locations.

During hot soak  testing on  engine  254 from sustained operation at WOT, cooling of the  catalyst-muffler was
comparable to the OEM muffler for the  first 60 seconds, and then lagged behind the OEM system by one to two
minutes for the remainder of the timed hot soak test (see Figures 6-25 to 6-27). During the hot-soak tests from the
50% load condition, the catalyst-muffler peak temperatures over the first  60  seconds cooled off faster than for the
                                                   77

-------
OEM muffler.  From approximately two minutes after shut-down to the end of the soak test, the cooling of catalyst-
muffler peak surface temperatures lagged approximately one to two minutes behind those of the OEM muffler,
similar to the WOT hot-soak conditions (see figures 6-28 and 6-29).
        EFI w-catalyst, Engine 231
100% Load - Wide Open Throttle - Mode 1
                             t-600.0


                              -500


                              -400

                              -300  


                              -200


                              -100

                              -25.0
   Maximum surface temperature:  558 C

           50% Load - Mode 3
                              c- 600.0


                              -500


                              r400

                              -300  C


                              -200


                              r100

                              -25.0
   Maximum surface temperature:  512 C

           10% Load - Mode 5
                              -600.0


                              -500


                              i-400

                              -300 *C


                              -200


                              -100

                              ^25.0
   Maximum surface temperature:  482 C
                                                             OEM Configuration, Engine 231
                                                       100% Load - Wide Open Throttle - Mode 1
                                                                                     r 600.0
                                                                                      -500


                                                                                      r400


                                                                                      -300


                                                                                      -200
c
                                                                                      -100
                                                                                     L25.0
                                                          Maximum surface temperature: 613 C

                                                                  50% Load - Mode 3
                                                                                     c- 600.0


                                                                                      -500


                                                                                      -400

                                                                                      -300 C


                                                                                      -200


                                                                                      -100

                                                                                      -25.0
                                                          Maximum surface temperature: 542 C

                                                                  10% Load - Mode 5
                                                                                      -600.0


                                                                                      -500


                                                                                      -400

                                                                                      i-300 C


                                                                                      -200


                                                                                      hon

                                                                                      -25.0
                                                          Maximum surface temperature: 470 C
Figure 6-19:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
231 at low hours, equipped with a open-loop EFI and a high-efficiency catalyst-muffler (left) and an OEM muffler
(right).
                                                  78

-------
      OEM Carburetor w-catalyst, Engine 251
     100% Load - Wide Open Throttle - Mode 1
                                       r600.0
                                       1-500


                                       -400


                                       -300


                                       L200


                                       -100

                                       -25.0
       Maximum surface temperature:  591.7 C

                50% Load - Mode 3
                                ^600.0


                                -500


                                -400

                                i-300  C


                                -200


                                -100

                                -25.0
Maximum surface temperature:  529.7 C

         10% Load - Mode 5
                                -600.0


                                -500


                                -400

                                :- soo


                                -200


                                .-100

                                -25.0
       Maximum surface temperature:  445.5 C
     OEM Configuration, Engine 251
100% Load - Wide Open Throttle - Mode 1
                                  T 600.0
                                  r500


                                  -400


                                  i-300


                                  r200


                                  rlOO

                                  -25.0
                                                                                       T:
  Maximum surface temperature: 599.3 C

           50% Load - Mode 3
                                                                                         ^600.0


                                                                                         -500


                                                                                         L400


                                                                                         -300


                                                                                         r200


                                                                                         -100

                                                                                         -25.0
                                       'C
                                                          Maximum surface temperature: 538.9 C

                                                                   10% Load - Mode 5
                                                                                         p600.0


                                                                                         -500


                                                                                         -400


                                                                                         i-300 '


                                                                                         -200


                                                                                         -100

                                                                                         -25.0
  Maximum surface temperature: 449.7 C
Figure 6-20:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
251 at low hours, equipped with catalyst-muffler (left) and an OEM muffler (right). Both configurations used the
OEM carburetor.
                                                  79

-------
    OEM Carburetor w-catalyst, Engine 251

                                      -600.0

                                      -500

                                      L400

                                      -300  '

                                      -200

                                      -100

                                      -25.0
    Maximum surface temperature:  520.4 C
                                      -500
                                      -400
                                      -300
                                          *C
                                      -200
                                      -100
                                      -25.0
    Maximum surface temperature:  521.1 C

                                     r 600.0


                                      500


                                      r400


                                      L300 *'


                                      -200


                                      -100

                                      -25.0
    Maximum surface temperature:  489.4 C
O-seconds
                                                30-seconds
 1-minute
                 OEM Configuration, Engine 251
                                               -600.0
                                               -500
                                               -400
                                               -300
                                                    C
                                               -200
                                               -100
                                               -25.0
              Maximum surface temperature: 534.1 C

                                               -600.0


                                               r500


                                               -400


                                               -300  '


                                               -200


                                               -100

                                               -25.0
              Maximum surface temperature: 484.9 C

                                               -600.0
                                                100
                                                25.0
              Maximum surface temperature: 430.0 C
Figure 6-21:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
251 during a hot-soak period immediately after engine shutdown from sustained operation at 50% load (A-cycle
mode 3).
                                                   80

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    OEM Carburetor w-catalyst, Engine 251

                                      r- 600.0

                                      -500

                                      -400

                                      -300  '

                                      -200

                                      -100
                                      -25.0
    Maximum surface temperature: 415.7 C

                                      -600.0

                                      i-5QO

                                      r400

                                      -300  >

                                      -200

                                      -100
                                      -25.0
    Maximum surface temperature: 358.7 C

                                     mr 600.0

                                       500

                                      r400

                                      L300  *'

                                      -200

                                      -100
                                      -25.0
    Maximum surface temperature: 316.6 C
2-minutes
3-minutes
4-minutes
                 OEM Configuration, Engine 251
                                                -600.0
                                                -500
                                                -400
                                                -300
                                                     C
                                                -200
                                                -100
                                                -25.0
Maximum surface temperature:  356.2 C

                                  -600.0

                                  -500

                                  -400

                                  -300

                                  -200

                                  -100
                                  -25.0
                                                     "C
Maximum surface temperature:  313.3 C

                               '   -600.0

                                 -500

                                 -400

                                 1-300
                                                     C
                                                ^200
                                              I
                                   100
                                                 25.0
              Maximum surface temperature:  278.7 C
Figure 6-22: Continuation of the hot-soak shown in figure 6-21.
                                                    81

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    OEM Carburetor w-catalyst, Engine 251

                                      -600.0

                                      -500

                                      -400

                                      -300  '

                                      -200

                                      -100
                                      -25.0
    Maximum surface temperature:  286.3 C

                                      -600.0

                                      -500

                                      r400

                                      ^300  ''

                                      H200

                                      -100
                                      -25.0
    Maximum surface temperature:  258.2 C

                                     ^600.0

                                      r500

                                      -400

                                      -300 '

                                      r200

                                      -100
                                      -25.0
     Maximum surface temperature: 234.5C
5-mmutes
6-minutes
7-minutes
                 OEM Configuration, Engine 251
                                                (600.0



                                                -400
                                               I- 300
                                                    C
                               I
                                                loo
                                                25.0
Maximum surface temperature: 249.4 C

                                  600.0

                                  -500

                                  -400

                                  -300  '

                                  -200

                                  -100
                                  -25.0
Maximum surface temperature: 223.0 C

                               '   -600.0

                                  -500

                                  -400

                                  -300 *'

                                  -200

                                  -100
                                  -25.0
              Maximum surface temperature: 201.8 C
Figure 6-23: Continuation of the hot-soak shown in figures 6-21 and 6-22.
                                                   82

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      OEM Carburetor w-catalyst, Engine 254
     100% Load - Wide Open Throttle - Mode 1
                                     -700.0
       Maximum surface temperature: 651 C
      Maximum head-pipe temperature: 420 C

               50% Load - Mode 3
       Maximum surface temperature: 612 C
      Maximum head-pipe temperature: 483 C
               10% Load - Mode 5
                                     r 700.0

                                     -600

                                     -500

                                     -400  i(

                                     -300

                                     :200

                                     :100

                                     -25.0
       Maximum surface temperature: 587 C
      Maximum head-pipe temperature: 561 C
     OEM Configuration, Engine 254
100% Load - Wide Open Throttle - Mode 1
                                 -700.0
   Maximum surface temperature: 651 C
  Maximum head-pipe temperature:  586 C
           50% Load - Mode 3
   Maximum surface temperature: 610 C
  Maximum head-pipe temperature: 610 C
           10% Load - Mode 5
                                                                                       700.0
                                                                                       25.0
   Maximum surface temperature: 577 C
  Maximum head-pipe temperature:  577 C
Figure 6-24:  Infrared thermal images showing the surface temperatures of exhaust system components for engine
254 at low hours, equipped with catalyst-muffler (left) and an OEM muffler (right). Both configurations used the
OEM carburetor.
                                                83

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    OEM Carburetor w-catalyst, Engine 254
                                    -mo
       Maximum surface temperature: 649 C
       Maximum surface temperature: 648 C
       Maximum surface temperature: 584 C
                                                0-seconds
                                                30-seconds
                                                 1-minute
OEM Configuration, Engine 254
                             -700,0
Maximum surface temperature: 636 C
Maximum surface temperature: 636 C
                                                                                                   *C
Maximum surface temperature: 585 C
6-25:  Infrared thermal images showing the surface temperatures of exhaust system components for engine 254
during a hot-soak period immediately after engine shutdown from sustained operation at 100% load, WOT (A-cycle
mode 1).
                                                   84

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    OEM Carburetor w-catalyst, Engine 254
                                      -700.0
       Maximum surface temperature: 494 C
       Maximum surface temperature: 437 C
                                            T
                                       -100
                                      t-25.0
       Maximum surface temperature: 384 C
                                                  2-minutes
                                                  3-minutes
                                                  4-minutes
OEM Configuration, Engine 254
                                                                                                    100

                                                                                                    25.0
Maximum surface temperature: 446 C
Maximum surface temperature: 356 C
                                100

                                25.0
Maximum surface temperature: 298 C
6-26: Continuation of the hot-soak shown in figure 6-25.
                                                     85

-------
    OEM Carburetor w-catalyst, Engine 254
                                      -700.0
       Maximum surface temperature: 340 C
       Maximum surface temperature: 292 C
                                            T
                                       -100
                                       t-25.0
       Maximum surface temperature: 260 C
                                                  5-minutes
                                                  6-minutes
                                                  7-minutes
OEM Configuration, Engine 254
                                                                                                    100

                                                                                                    25.0
Maximum surface temperature: 251 C
Maximum surface temperature: 215 C
                                700.0

                                600

                                500

                                400

                                300

                                200

                                100

                                25.0
                                                                                                        T:
Maximum surface temperature: 187 C
6-27: Continuation of the hot-soak shown in figures 6-25 and 6-26.
                                                     86

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    OEM Carburetor w-catalyst, Engine 254
                                     -700.0
       Maximum surface temperature: 620 C
       Maximum surface temperature: 520 C
                                      -100
                                      t-25.0
       Maximum surface temperature: 479 C
                                                 0-seconds
                                                30-seconds
                                                 1-minute
OEM Configuration, Engine 254
                                                                                                  100

                                                                                                  25.0
Maximum surface temperature: 600 C
Maximum surface temperature: 592 C
                                100

                                25.0
Maximum surface temperature: 493 C
6-28:  Infrared thermal images showing the surface temperatures of exhaust system components for engine 254
during a hot-soak period immediately after engine shutdown from sustained operation at 50% load (A-cycle mode
3).
                                                    87

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    OEM Carburetor w-catalyst, Engine 254
                                     100

                                     25.0
       Maximum surface temperature: 424 C
       Maximum surface temperature: 375 C
       Maximum surface temperature: 334 C
       Maximum surface temperature: 298 C
                                                  2-minutes
                                                  3-minutes
                                                  4-minutes
                                                  5-minutes
OEM Configuration, Engine 254
                             -700.0
Maximum surface temperature: 375 C
Maximum surface temperature: 302 C
Maximum surface temperature: 254 C
                              100
                              25.0
Maximum surface temperature: 215 C
6-29: Continuation of the hot-soak shown in figure 6-28.

-------
Muffler outlet temperatures - Class I and Class II Engines
Exhaust gas outlet temperatures measured for each of the 6-modes of the A-cycle tests  are shown  in
Figure 6-30 for representative examples of Class I side-valve, Class I OHV, and Class II OHV engine for
both OEM muffler and catalyst-muffler configurations.  The exhaust outlet temperatures for the Class I
catalyst-mufflers were comparable or cooler in comparison with the Class I OEM mufflers.   The Class II
catalyst-muffler exhaust outlet temperatures were 30-40 C higher than the OEM muffler. When mounted
in  the  lawn tractor chassis, all of the Class II engines  tested in the field were equipped  with  exhaust
ejectors that significantly lowered the exhaust gas temperatures at the outlet via mixing with  ambient air.
   600
--T Exh Out, 258 w/OEM Muffler
--T Exh Out, 258 w/Catalyst
-A-  T Exh Out, 244 w/OEM Muffler
--T Exh Out, 244 w/Catalyst
-&-T Exh Out, 251 w/OEM Muffler
-e-T Exh Out, 251 w/Catalyst
 LU
                                  23456
                                                  A-Cycle Mode#
Figure 6-30: Exhaust gas outlet temperatures measured during engine dynamometer testing over the 6 steady-state
modes of the A-cycle test for representative Class I side-valve  (258) and OHV (244) engines and for a Class II
engine (251). Note that the dashed lines are for OEM muffler configurations, and the solid lines are for catalyst-
muffler configurations.
Run-on after-fire testing

A digital image from one of the tests is presented in Figure 6-31.  A full comparison of the OEM muffler and the
catalyst-muffler configurations tested under the same test conditions will require viewing of digital video acquired
during testing.  Digital video files may be accessed for viewing via the Phase 3 Nonroad SI Engine Docket and also
from the DVD attached to this study.1 The test conditions are described in Chapter 5.

After-fire was evident for engine 241 for each of the four tests of the high-inertia shut-down conditions tested with
the OEM muffler.  This can be seen quite dramatically in digital videos. In many cases, a flash of flame exited the
tailpipe during after-fire (Figure  6-31).  In all cases, a series of a sharp "bangs" in the audio track of the videos are
evident, sounding  similar to a fire-cracker.  The force of the after-fire can be seen in the resulting recoil of the
exhaust collection cone mounted downstream of the tailpipe.  It should be  noted  that  the collection cone was
mounted to an approximately 25-Ib base located approximately 3  feet below the collection cone.

The tests were repeated four times with the catalyst-muffler, but after-fire was not evident for the four repeats of the
high-inertia shut-down conditions.  While the catalyst muffler was adapted from an OEM design, the two-stage
inner baffling differed somewhat in its physical layout (a 3/4" diameter perforated tube followed by  a perforated
plate, with 0.125"  perforations)  and surface area to prevent flame propagation.  A degree of flow restriction was
also added near the muffler exit through the use of a serviceable OEM spark arresting screen.
                                                 89

-------
Figure 6-31:  Digital image taken of engine 241 during after-fire testing with OEM muffler.  A 6" or longer after-
fire flame was observed extending from the tailpipe  into the exhaust collection  cone, accompanied by a sharp
"bang" similar to a firecracker.  Repeated testing of engine 241 under the same conditions with a catalyst-muffler
did not result in after-fire.

Ignition misfire testing

Audible engine misfire, increased engine vibration, and erratic torque output were observed while operating engine
255 at the 25% misfire condition.  The misfire condition is clearly visible within the torque, speed, and HC data (see
Figures 6-32 and 6-33) and in digital video taken of engine operation during misfire.  Digital video files showing
engine operation during operation at the 25% misfire  condition may be accessed for viewing within the Phase 3
Nonroad SI Docket and from the DVD attached to this study1.

Infrared thermal images comparing the tested catalyst-muffler and OEM muffler  configurations are presented in
Figures 6-34 and 6-35.  The peak temperatures of the catalyst-muffler were approximately 60 C cooler than the
OEM muffler prior to the onset  of ignition misfire. After 30 seconds of operation at 25% random ignition misfire,
the OEM muffler peak temperatures were unchanged and the catalyst-muffler peak temperatures had increased to
approximately the same temperature as the OEM muffler.  As misfire progressed, the  OEM muffler began to cool
and the catalyst  muffler temperatures continued to increase.  Temperatures for both configurations stabilized
between three and five minutes  of operation.  After five minutes of misfire, the catalyst-muffler had approximately
130 C higher peak  surface temperatures than the OEM muffler at the same condition (see Figure 6-34).   The
stabilized temperatures  of the  catalyst-muffler  undergoing 25% random misfire  were comparable to the  OEM
muffler operating normally  at  a  50% load condition (Figure 6-8).   The temperature increase was due to the
exothermic reaction of partially  burned fuel components over the catalyst substrate. The catalyst-muffler used with
engine 255 included  a number of design elements to limit the exothermic reaction  during misfire. These included
dividing the catalyst volume upstream and downstream of the secondary, reducing the amount of secondary air, and
choosing a formulation for the upstream pre-catalyst that favored net-rich HC reactions appeared.  The design
appeared to be moderately successful at limiting the exotherm since peak temperatures stabilized to less than 400 C
after approximately three minutes of misfire.

Additional testing was conducted to determine if air-shrouding similar to that used with engines 243 and 244 would
be effective at reducing the peak temperatures of exposed surfaces to temperatures below the corresponding peak
temperatures obtained with the OEM muffler configuration (see Figure 6-35).  With the  shroud in place,  peak
temperatures during misfire testing were reduced  substantially, and remained at least  50 C cooler than the OEM
                                                   90

-------
configuration.  Peak temperatures of the shrouded catalyst muffler were relatively constant throughout the five
minutes of misfire. The surface temperature of the shroud adjacent to location of the catalyst within the exhaust
system and the surface temperature of the exhaust ejector outlet increased from approximately 100 C prior to the
onset of misfire to stabilized temperatures of approximately 180 C after five minutes of ignition misfire.
   320
   300
   280
   260
   240
-5 220
200
180
160
140
120
100
 80
 60
 40
 20
- Engine Speed (rpm)
 HC (ppmC)
- Muffler Inlet T fC)
-Torque (Ib-ft)
                                                               25%
                                                              Misfire"
                                                                                          45
                                                                                          40
                                                                                             35
                                                                                             30
                                                                                             50
                                                                                             25
                                                                                             20
                                                                                             15  O
                                                                                             10
                                                                                             5
                                             789
                                              Time (Minutes)
                                                               10
                                                                      11
                                                                            12
                                                                                  13
                                                                                        14
Figure 6-32:  Operational data with engine 255 and OEM muffler showing initial temperature stabilization followed
by approximately five minutes of operation with 25% random ignition misfire.  Note that HC concentrations are
from dilute-CVS measurements.
320

300
 280
O
 260
Q.
3 240
\
^ 220
^ 200
i, 180
~O ..,,
d) 160
HI
5> 14
c 120
c 100
80
60 -
40
20
C
u











/
I


-\







~^
/^
/
1
1



/v^
-VV^V^^^-



1 2






i-  ^
^^ HC (001110
 Muffler Inlet T(C
^Torque (Ib-

25%


'^.^^^,,,r~~<^r,'~-~-



3 4







K
)





AO-W^^xA-r^W



5 6


n|n


v^







Aft
vffY


c
7



(







1

Mil III i*1 rt lll' I'll 1
l\lp|| 'Klpf ^r" V'Hlf
I 1
 .  '

8 9 1


vvi/i|v"




"^~~ -^   "





.ii
l||yv






^y \











T



1


1










i
1


/'



E











n






45

40



30

25
20

15
10

5


                                             Time (minutes)
Figure 6-33:  Operational data with engine  255 and  catalyst-muffler showing initial temperature  stabilization
followed  by approximately  five  minutes  of operation with 25% random ignition misfire.   Note  that HC
concentrations are from dilute-CVS measurements.
                                                    91

-------
Engine 255 with Catalyst-Muffler
    & Venturi Secondary Air
                               -600.0


                               -500


                               -400


                               -300  '


                               -200


                               -100

                               -25.0
Maximum surface temperature:  256 C

                              ^600.0


                               -500


                               - 400


                               -300


                               -200


                               -100

                               -25.0
Maximum surface temperature:  318C

                               -600.0


                               r5QQ


                               - 400


                               -300  '


                               -200


                               -100
                                           T
                                      U25.0
       Maximum surface temperature:  382 C
                                                 0-seconds
                                                 30-seconds
                                                 5-minutes
                                                                   Engine 255 with OEM Muffler
                                                                                                  600.0
                                                                                                 -500
                                                                                                  200
                                                                                                  100
                                                                                                  25.0
                                                                  Maximum surface temperature: 321 C
                                                                                                  600.0
                                                                                                  100
                                                                                                  25.0
                                                                  Maximum surface temperature: 322 C
                                                                                                  600.0
                                                           Maximum surface temperature: 251 C
Figure 6-34:  Infrared thermal images showing the surface temperatures of exhaust system components for OHV
engine 255 at low hours equipped with a catalyst-muffler (left) and an OEM muffler (right).  The images were taken
immediately before (top) and after 30  seconds (middle) and five minutes (bottom)  of continuous operation at a
condition of 25% random misfire and the minimum torque  measured for the lawn mower blade for this application
at 2900 rpm (approximately 25% load or A-cycle mode 4).
                                                    92

-------
Engine 255 with Catalyst-Muffler
    & Venturi Secondary Air
                               -600.0


                               -500


                               -400


                               -300  '


                               -200


                               -100

                               -25.0
Maximum surface temperature:  204 C

                              ^600.0


                               -500


                               - 400


                               -300


                               -200


                               -100

                               -25.0
Maximum surface temperature:  185 C

                               -600.0


                               r5QQ


                               - 400


                               -300  '


                               -200


                               -100
                                           T
                                      U25.0
       Maximum surface temperature:  197C
                                                 0-seconds
                                                 30-seconds
                                                 5-minutes
                                                                   Engine 255 with OEM Muffler
                                                                                                  600.0
                                                                                                 -500
                                                                                                  200
                                                                                                  100
                                                                                                  25.0
                                                                  Maximum surface temperature: 321 C
                                                                                                  600.0
                                                                                                  100
                                                                                                  25.0
                                                                  Maximum surface temperature: 322 C
                                                                                                  600.0
                                                           Maximum surface temperature:  251 C
Figure 6-35:  Infrared thermal images showing the surface temperatures of exhaust system components for OHV
engine 255 at low hours equipped with a catalyst-muffler and air shroud (left) and an OEM muffler (right).  The
images were taken immediately before (top) and after 30 seconds (middle) and five minutes (bottom) of continuous
operation at a condition of 25% random misfire and the minimum torque measured for the lawn mower blade for
this application at 2900 rpm (approximately 25% load or A-cycle mode 4).
                                                    93

-------
Rich Operation

The 1.0 to 1.5 change in air-to-fuel ratio was achievable for A-cycle modes 1-4 via changes to the main carburetor
jet. During mode 5, the main jet change resulted in a change of 0.7 air-to-fuel ratio, and no change for mode 6.
Figure 6-36 shows a comparison between the air-to-fuel ratio achieved with the OEM carburetor main jet and the
modified carburetor on engine 255.  Engine-out CO emissions increased in modes  1  to 4  of the A-cycle by
approximately 40 to 50%.  Engine-out HC emission were approximately doubled.  Power at WOT increased by
approximately 6%.

Thermal imaging results for operation over modes 1,  3  and 5 of the A-cycle are shown in 6-36.  Peak surface
temperatures were comparable between the catalyst-muffler and OEM configurations over all six modes of the A-
cycle.  Surface temperatures for the catalyst muffler were virtually unchanged relative to  the tests conducted with
the OEM carburetor jetting. Although higher concentrations of CO and HC reactants were available in the exhaust,
the richer operation also limited  the amount of oxygen  available in the exhaust, which limited the  exothermic
oxidation reactions of the CO and HC over the catalyst.   The richer carburetor jetting reduced the peak surface
temperatures of the OEM muffler by approximately 30 to 40 C, or to approximately the same peak temperatures as
those of the catalyst-muffler.
  15:1
  14:1
OEM Carburetor

Main jet modified for rich operation
                                                  A-Cycle Mode #

Figure 6-36:  A comparison of air-to-fuel ratio for the first five modes of the A-cycle test.
                                                   94

-------
         Engine 255 with Catalyst-Muffler
             & Venturi Secondary Air
            100% Load - Wide Open Throttle
                                        600.0
                                         100

                                         25.0
        Maximum surface temperature:  433 C

                50% Load - Mode 3 _
                                         600.0
                                        200


                                        100

                                        25.0
        Maximum surface temperature:  317C

                 10% Load-Mode 5	
                                        600.0
                                            c
                                         m
                                         100
                                        25.0
        Maximum surface temperature:  244 C
   Engine 255 with OEM Muffler

    100% Load - Wide Open Throttle
                                                                                          -600.0
                                                                                          -500
                                                                                          -400
                                                                                          -300
                                                                                          -200
                                                                                          -100
                                -25.0
Maximum surface temperature: 450 C

        50% Load - Mode 3
                                                                                           600.0
                                 100
                                 25.0
Maximum surface temperature: 320 C

        10% Load-Mode 5
                                                                                           600.0
                                 200
                                                                                           100
                                                                                           25.0
Maximum surface temperature: 246 C
Figure 6-37:  Infrared thermal images showing the surface temperatures of exhaust system components for OHV
engine 255 at low hours equipped with a catalyst-muffler (left) and an OEM muffler (right) for modes 1, 3 and 5 of
the A-cycle with the carburetor main-jet modified to provide 1-1.5 richer air-to-fuel ratio than the OEM jetting.
                                                  95

-------
c.
FIELD TESTING RESULTS
During the course of field testing, over 1200 individual refueling events were carried out on six walk-behind lawn
mowers and four lawn tractors without incident.  Of these, four of the lawn mowers and two of the lawn tractors
were equipped with catalyst-mufflers and accounted for over 700 of the refueling events. Auxiliary fuel cans were
kept in close proximity to grass cutting operations and thus refueling typically occurred less than two minutes after
engine shut-down.

During field operations in Tennessee, four of the lawn mowers (all with the same engine  type) had unacceptable
levels of debris accumulation in the area of the engine cooling shroud immediately above the cylinder head and on
top of the engine cylinder and required frequent maintenance. The issue was related to the design of the cooling fan
and the fan air-intake  and caused maintenance issues with both the OEM and catalyst-equipped configurations of
this engine family. The other two engines from a different engine family that were used during field testing (244,
245) did not have any appreciable debris accumulation within the OEM engine shroud. These two engines used a
small perforated screen attached to the top of the cooling fan to prevent debris above a certain size from entering the
cooling fan and engine shroud.  Engines 244 and 245 also used a  cooling fan with significantly  higher flow  (30
curved fan vanes versus  six flat-paddle type vanes).  Engines 246, 248, and 249 were retrofitted with screens near
the inlet to the cooling fan and no further debris accumulation problems were encountered (see Figure 6-38).
                             Excessive
                               debris
                           accumulation
                                    Engine 245
                                    cooling fan
                                    w/perforated
                                      disc inlet
Figure 6-38:  Engines 246, 248, 249 and 259 had problems with excessive debris build-up underneath the engine
cooling shroud (top, engine 259 shown).  Engine 245 had negligible debris build-up on engine and catalyst-muffler
surfaces,  even after 110 hours of field operation (bottom left).  Note the perforated disc attached to the top of the
cooling fan that prevented debris ingestion with engine 245.  An exterrnal screen was added near engine fan's air-
intake on engines 246, 248 and 249 to eliminate ingestion of large debris by the engine cooling fan (bottom right).
                                                   96

-------
During hundreds of hours of grass cutting operations there was no discernable difference in operation attributable to
the use of catalyst-mufflers with the lawn mowers or the lawn tractors.  All of the lawn mowers were operated to
approximately 100 to 110 hours (within 15-25 hours of the end of useful life).  The lawn tractors were operated to
approximately 240 hours (within 10 hours of the end of useful life for engines 231 and 252 and to within 10 hours
of mid-life for engines 232 and 233).

Surface Temperature Measurements by Infrared Thermal Imaging Taken During Grass Cutting Operations

Full motion video infrared thermal images were used to allow surface temperature measurement with the equipment
under load during grass cutting operations. Observations drawn from the videos will be presented in this section. A
full comparison of IR video  images from the OEM muffler and the catalyst-muffler configurations tested during
field operations will  require  viewing of digital video data acquired during testing. Digital video files may be
accessed for viewing via the Phase 3 Nonroad SI Engine Docket and also via the DVD attached to this study.1 The
IR thermal images were acquired at ambient conditions of 18.5 C (65 F), 80% relative humidity and little to no
wind for the testing in Tenneessee.  The IR thermal images were acquired at ambient conditions of 30 C (86 F)  ,
46% relative humidity with light 5 to 10 mph winds. The impact of the wind was not readily apparent in the surface
temperature measurements from the equipment, but effect of wind can clearly be  seen on the turf surfaces for the IR
video  images taken during idling. The grass cutting conditions can be seen in Figures 5-14 and 5-15.

Class  I Lawn Mowers

The lawn mower equipped  with engine 259 and an OEM muffler was operating with  surface temperatures
exceeding 360 C during cutting of moderate to heavy grass. The lawn mowers equipped with engines 244 and 245
and catalyst-mufflers  were operating with surface temperatures of approximately 120 C and 150 C, respectively,
during grass cutting in approximately the same location. The lawn mowers equipped with engines 246 and 248 and
catalyst mufflers operated with surface  temperatures of approximately 280 C.  The lawn mower equipped with
engine 249 and a catalyst-muffler operated with surface  temperatures of approximately 130  C.  In all cases, the
surface temperatures of the lawn mowers equipped with catalyst-muffler configurations were significantly less than
the lawn mower equipped with engine  259 and the OEM muffler.  The sub-200 C temperatures achieved with
engines 244, 245, and 249 are due to the use of air shrouding and forced-air cooling  around the  muffler and due to
the use of ejector cooling of the  exhaust gases and the outer surface of the air shroud.  The lower surface
temperatures of the catalyst-mufflers used with engine 244 and 249 relative to that used with engine 245 may have
been  due to the reduced use of platinum  within their catalyst washcoating formulations.  Engine 249  used a
rhodium-only  formulation and engine 244 used a  formulation that was  predominantly palladium with a small
amount of platinum and rhodium.  The  best combination of emissions control and lower surface temperatures for
these applications appeared to be achievable using a trimetallic washcoating formulation of approximately 30 g/ft3 -
40 g/ft3 PGM that were predominantly palladium with smaller, roughly equivalent  amounts of platinum and
rhodium. The rhodium-only catalyst was also comparably effective at achieving low surface temperatures and was
capable of similar emission  control performance to the palladium-rich trimetallic formulations at much lower
loading levels  (i.e., only slightly higher total PGM cost).  The rhodium-only catalyst was also the only catalyst in
this testing capable of reaching EPA's HC+NOx emission targets without the use of passive secondary air. The lack
of secondary air  and reduced CO oxidation for engine 249 may have also  contributed to its relatively low surface
temperatures during grass cutting.

Class  II Lawn Tractors - 3.5 g/kW-hr systems

The lawn tractor equipped with engine 252, which was an OEM muffler and induction system configuration, had
exposed surface  temperatures of approximately  150 C as viewed  from  both  sides of the  tractor when cutting
moderate to heavy grass.  Note that the view of the exhaust outlet of the muffler was obscured by the OEM touch
guard over the exhaust system.  The lawn tractor equipped with engine 231, which had the EFI system and catalyst-
muffler, had exposed  surface temperatures of approximately  110 C. Note that the exhaust outlet housed within the
exhaust ejector was in clear view of the IR Equipment. This temperature  was not recorded as an external surface
temperature.
                                                   97

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The lawn tractor equipped with engine 233, which was an OEM muffler and induction system configuration, had
exposed surface temperatures of approximately 220 C to 280  C.  The lawn tractor equipped with engine 232,
which had the EFI system and catalyst-muffler, had exposed surface temperatures of approximately 200 C.

In the case of both engine families, exposed surfaces were cooler for the catalyst-muffler equipped engines.  This
differed somewhat from the laboratory results, in part due to the more effective cooling of the catalyst-mufflers as
installed  in the chassis due to the re-routing of cooling  air through the chassis  and the addition of the exhaust
ejectors.

Class II Lawn Tractors - 8.0 g/kW-hr systems

The lawn tractor equipped with engine 251, which used an OEM muffler, had exposed surface  temperatures of
approximately 200 C as viewed from both sides of the tractor when cutting moderate to heavy grass, with peaks as
high as 300 to 365 C. The lawn tractor equipped with engine 253, which had the catalyst-muffler, had exposed
surface temperatures of approximately 115 to 130 C, with peaks of 160 to 190 C.

The lawn tractor equipped with engine 256, which used an OEM muffler, had exposed surface  temperatures of
approximately  180 C to 230 C with peak temperatures of 290 to 320 C.  The lawn tractor equipped with engine
254, which had the catalyst-muffler, also had exposed surface temperatures of approximately  180 to 230 C and
peak temperatures of 290 to 320 C.

In the case of both engine families, exposed surfaces were ether comparable (engine 254) or cooler (engine 253) for
the catalyst-muffler equipped engines.  This differed somewhat from the  laboratory results, in part due to the more
effective  cooling of the catalyst-mufflers as installed in the chassis due to the re-routing of cooling air through the
chassis and the addition of the exhaust ejectors.

Results of Hot-Soak Tests Conducted in the Field

Results of the hot soak tests conducted after approximately  30 to 45 minutes of grass  cutting are presented in
Figures 6-39 and 6-40 for the lawn mowers and lawn tractors, respectively, for data taken in Tennessee in the fall of
2005 and in Figures 6-41 and 6-42, respectively, for data taken in Florida in early 2006.

Tennessee Tests

At the two minute nominal refueling point following engine  shut-down, two  of the lawn mowers equipped with
catalyst mufflers (engines 246 and 248)  had comparable surface peak  surface temperatures to the lawn  mower
equipped with the OEM muffler (engine 259). Two of the catalyst-muffler equipped lawn mowers (engines 244 and
249) were significantly cooler than the lawn mower equipped with the OEM muffler.  The temperature decrease
with time was more pronounced with the OEM configuration (259). Temperatures for all tested configurations were
comparable at approximately five to six minutes following engine shut-down. Trends in soak temperatures relative
to muffler shrouding and catalyst precious metal composition were similar to those observed during grass cutting.
Catalyst washcoating formulations with higher palladium or rhodium content in place of platinum higher content
tended to start the soak period with lower temperatures.  Catalyst-mufflers using air shrouds and exhaust ejectors
also tended to start the soak period with lower temperatures.

Florida Tests

At the two minute nominal refueling point following engine shut-down,  all of the catalyst-muffler equipped lawn
mower and lawn tractor configurations had lower peak surface temperatures than the OEM muffler configurations.
                                                   98

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    280
                                                                                244 w/catalvst
                                                                                245 w/catalvst
                                                                                246 w/catalvst
                                                                                248 w/catalvst
                                                                                249 w/catalvst
                                                                                259 OEM muffler
        0:00     1:00     2:00     3:00    4:00    5:00     6:00
                                                Time (min.:sec.)
7:00
8:00
9:00    10:00
Figure 6-39:  A comparison of peak surface temperatures for six lawn mowers measured using infrared thermal
imaging during hot-soak tests immediately following engine shut-down after approximately 30 minutes of grass-
cutting.  At the nominal two  minute refueling point,  peak temperatures of the catalyst-muffler equipped lawn
mowers were either comparable to (246, 248) or below (245, 244, 249) the lawn mower equipped with an OEM
muffler (259).  This data was acquired in SW Tennessee.


Both of the lawn tractors equipped with EFI and catalyst-mufflers (engines 231 and 232) were cooler than the OEM
lawn tractors (engines 233  and 252) at the nominal two minute refueling point after engine shut-down.  Surface
temperatures for both EFI and catalyst-muffler configurations were at or below 100 C for the entire soak period
following engine shut-down. Surface temperatures for the lawn tractor equipped with engine 231 decreased slower
than the lawn tractors equipped with engines 232, 233 and 252.  Surface temperatures  were  comparable for the
configurations with engines 232, 233 and 252 at approximately five to six minutes following engine shut-down.

Engine 231 had higher cylinder head and oil temperatures than engines 232 and 233 (but less than engine 252) and
231 also had somewhat less cooling capacity  from the engine fan than engines 232 and 233. It is possible that the
higher chassis and engine temperatures of lawn tractor equipped with engine 231 combined with the increased mass
of the catalyst-muffler reduced the rate of heat transfer from the exhaust system following shut-down.
                                                  99

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                                                                231 w/EFI&Catalyst
                                                             232 w/EFI&Catalyst

                                                             233 OEM Configuration
                                                             252 OEM Confiauration
         0:00     1:00    2:00     3:00     4:00    5:00    6:00
                                               Time (min.:sec)
7:00     8:00
9:00    10:00
Figure 6-40:  A comparison of peak surface temperatures for four lawn tractors measured using infrared thermal
imaging during hot-soak tests immediately following engine shut-down after approximately 30-minutes  of grass-
cutting.  At the nominal 2-minute refueling point, peak surface temperatures for the lawn tractors equipped with EFI
and catalyst mufflers were comparable to (231) or significantly cooler than (232) the OEM configurations (233,
252).  Note that engines 232 and 233 are both from one engine family, and that engines 231 and 251 are both from
another engine family (refer to table 5-2). This data was acquired in SW Tennessee.
                                                 100

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    o
    s
                                                                             244 w/uatalyst
                                                                             245 w/OEM Muffler
          0:00      1:00       2:00       3:00      4:00       5:00

                                                Time (min.:sec.)
6:00
7:00
8:00
Figure 6-41:  A comparison of peak surface temperatures for two lawn mowers measured using infrared thermal
imaging during hot-soak tests immediately following engine shut-down after approximately 30 minutes of grass-
cutting. This was a repeat of hot-soak testing for engines 244 and 245 at a higher ambient temperature (30  C vs.
18.5 C),  and with engine 245  using  an OEM muffler.  At  the nominal  two minute refueling point, peak
temperatures of the catalyst-muffler equipped lawn mower (engine 244) was below that the lawn mower equipped
with an OEM muffler (engine 245). The range  of surface temperatures encountered were approximately  60 C
higher than those measured at  lower ambient temperature conditions  (Figure 6-39).  This data was  acquired in
Florida.
                                                  101

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   o
                                               253 w/Catalyst
                                               251 w/OEM Muffler
                                               254 w/Catalyst
                                               256 w/OEM Muffler
        20
          0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
                                                Time (min.:sec.)
Figure 6-42:  A comparison of peak surface temperatures for four lawn tractors measured using infrared thermal
imaging during hot-soak tests immediately following engine shut-down after approximately 30-minutes of grass-
cutting. At the nominal 2-minute refueling point, peak surface temperatures for the lawn tractors equipped with
catalyst mufflers (engines 251 and 256) were significantly cooler than the OEM muffler configurations (engines 251
and 256).  Note that engines 251  and 253 are both from one engine family, and that engines 254 and 256 are both
from another engine family (refer to table 5-2). This data was acquired in Florida.
                                                  102

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 Idle Testing

The turf surface temperatures for the catalyst-muffler equipped lawn tractors were either comparable (engine 254)
or reduced (engine 253) relative to the turf surface temperatures measured during idling of the lawn tractors with the
OEM mufflers (engines 251 and 256).  The variation in turf temperatures was due entirely to wind gusts. Wind
breaks were improvised on two  sides of the lawn tractors, but light wind gusts were  observed to cause an
approximately  10 C to 20 C oscillation in peak turf temperatures measured for engines 254 and 256. Wind was
relatively calm during the measurements with engines 251 and 253, which  reduced the variability in peak turf
temperatures to approximately 5 C to 10 C.  Note that engines 251 and 253 are both from one engine family, and
that engines 254 and 256 are both from another engine family (refer to  table 5-2).  This data was acquired in
Florida.
       120
       100
    r  so
    
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7.      Design  and Process Failure  Mode  and Effects Analyses (FMEA)
        to Assess NHH Incremental Safety Risk

A.      BACKGROUND

In addition to the laboratory and field  work described in previous chapters, EPA contracted with Southwest
Research Institute of San Antonio, Texas to conduct design and process Failure Mode and Effects Analyses.  The
full text of the SwRI report is contained in an Appendix to this study.

An FMEA is an engineering analysis tool to help engineers and other professional staff on the FMEA team to
identify and manage risk. In an FMEA, potential failure modes, causes of failure, and failure effects are identified.
The primary purpose of the FMEA is to identify those causes of failure modes with the greatest potential for adverse
effect both in terms of frequency of occurrence of the cause of the failure and in the severity of the consequences of
the failure.  Within an FMEA the multiplicative product of the numerical values assigned to the frequency of
occurrence of the causal mechanism and  severity of the effect of the failure is referred to as risk probability. This
risk probability is used by  the FMEA team to rank problems for potential action to reduce or eliminate the  causal
factors. The focus of the FMEA is on identifying and prioritizing the causal factors for the failure modes, because
the causal factors are the elements that a manufacturer can consider in order to reduce the adverse effects that might
result from a failure mode. While data is employed to the greatest degree possible, ultimately the process depends
on the professional judgment by members of the FMEA team.

Risk and risk probability are not the same. In traditional safety analysis, risk usually refers to the likelihood of the
occurrence of a hazardous outcome. The  occurrence of a hazardous outcome in a given event is much less than the
occurrence of the event itself (e.g., most trip and fall events do not lead to broken bones). In this context, the risk
probability is not the risk that an actual hazardous outcome will  occur in a given event, but is a tool to rank the
relative risk of events based on the frequency of the causal factor leading to a failure mode and the severity of the
potential effect of the failure.  The frequency used to determine risk probability is the estimate of the frequency of
the potential cause of the failure mode not the frequency of the potential effect(s) if the failure mode were to  occur.
For example, one failure mode that was evaluated is  backfiring from the  engine. One factor that could cause
backfire would be a richer fuel mixture.  A richer mixture does not always lead to backfire, if it did then there is
always an increased risk of fire or burn.  The FMEA analysis looks at the probability that the causal factor, (the
richer fuel mixture), would occur, and the severity of the outcome if the richer fuel mixture did lead to backfire and
a fire or burn. The analysis does not try to determine the likelihood that richer fuel mixture will in fact lead to fire
or burn, instead, the analyses basically assumes the  worst case - the backfire does occur and leads to a fire or burn.
The analysis looks at various failure modes from this worst case  perspective, in order to rank the highest priority
issues to address. Thus, for FMEA purposes the risk probability associated with richer fuel mixture may be the same
for all potential outcomes of a richer fuel  mixture because the probability of the causal factor of richer fuel mixture
occurring is the same. However, the hazardous outcome of a fire or burn occurring is clearly not the same as the
probability that a richer fuel mixture will occur. Determining hazard risk is beyond the scope of a design or process
FMEA.
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B.  THE WORK CONDUCTED BY SwRI

In doing this work for EPA,  SwRI  used the basic FMEA approach contained in SAE Standard J1739.1  This
approach requires the FMEA team to identify and characterize the systems and subsystems involved and then for
each subsystem list:

        1.   The item/function being analyzed

        2.   The potential cause(s)/mechanism(s) of the failure (both primary and contributing, as appropriate)

        3.   The potential failure mode

        4.   The potential effect(s) of the failure

        5.   The classification of the effect

        6.   The severity of the failure mode

        7.   The frequency of occurrence of the potential cause(s)/mechanism(s)

        8.   Risk Probability Number (RPN) [( 6)x(7)]


SAE J1739 provides detailed and helpful guidance to the team on how to set-up and conduct the FMEA. However,
the FMEA is a tool and is often tailored by an FMEA team to help better meet project needs. In this case, looking at
the incremental risk question raised by EPA required SwRI to make adaptations  in the way they applied the SAE
protocol. These are described in the full text of the SwRI  report attached to this study.

This FMEA covered equipment using Class I and Class II engines. For  Class I engines, the equipment identified
was a typical walk-behind lawnmower (WBM). For Class II, the equipment identified was a ride-on lawnmower
(ROM). Two different types of FMEAs were prepared. The first was design FMEAs for both the WBM and ROM.
The  second were three process  FMEAs  covering refueling, maintenance, and  shutdown and  storage of the
equipment.

These FMEAs were conducted to  identify and assess potential differences in risk probability between engines and
equipment  meeting EPA Phase 2 emission standards  and properly  designed  engines and equipment  meeting
potential EPA Phase  3 emission  standards. For Phase  2 Class I and II powered-equipment, SwRI used typical
currently produced  equipment/engines.  Obviously, production Phase 3  equipment  is  not  available.   The
characteristics of properly designed Phase 3 equipment/engine as considered by SwRI are presented in Table 7-1.
                                                  105

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Table 7-1. Projected Phase 3 Engine Characteristics
Item No.
1
2
3
4
5
6
7
8
9
10
Class I Lawnmower Engine
Application of catalyst (moderate activity 30-50%)
designed to minimize CO oxidation, maximize
NOX reduction, with low HC oxidation efficiency
at high exhaust-flow-rates and high HC oxidation
efficiency at low-exhaust flowrates. This design is
expected to minimize catalyst exotherm.
Cooling and shrouding of engine and muffler to
minimize surface temperatures. Use of heat
shielding and/or air-gap insulated exhaust
components to minimize surface temperatures.
Design flow patl^affles through the mufflers to
incorporate flame arresting design features, to
improve heat rejection to muffler surfaces and to
spread heat rejection over a large surface area of
the muffler. This will reduce the incidence of
backfire and reduce localized hot spots.
Different catalyst substrates (ceramic, metal
monolith, hot tube, metal mesh) can be
successfully used.
The use of air ejectors to cool exhaust gases at the
muffler outlet and to improve cooling of heat
shielding.
Use of a small amount of passive supplemental air
to improve exhaust chemistry at light load, but
designed so bulk exhaust remains rich of
stoichiometry at all conditions, and flow-limited at
high exhaust flowrates. This design minimizes
risk of excessive catalyst exotherm.
Use of fuel filter and/or improved design needle
and seat in carburetor to minimize problems
caused by fuel debris.
Improved intake manifold design to reduce intake
manifold leaks.
Cooling system designed to reduce the
accumulation of debris, including the use of a
mesh or screen on cooling fan inlet, when lacking
in current design.
Improved ignition system design to be more
reliable and durable than on Phase 2.
Class II Ride-on Mower Engine
Application of catalyst (moderate activity 30-50%)
designed to minimize CO oxidation, maximize
NOX reduction, with low HC oxidation efficiency
at high exhaust flowrates and high HC oxidation
efficiency at low-exhaust flowrates. This design is
expected to minimize catalyst exotherm.
Cooling and shrouding of engine and muffler to
minimize surface temperatures. Use of heat
shielding and/or air-gap insulated exhaust
components to minimize surface temperatures.
Design flow patl^affles through the mufflers to
incorporate flame arresting design features, to
improve heat rejection to muffler surfaces and to
spread heat rejection over a large surface area of
the muffler. This will reduce the incidence of
backfire and reduce localized hot spots.
Different catalyst substrates (ceramic, metal
monolith, hot tube, mesh) can be successfully
used.
The use of air ejectors to cool exhaust gases at the
muffler outlet and to improve cooling of heat
shielding.
Use of carburetor recalibration to improve exhaust
chemistry at light load conditions.
Improved air/fuel ratio control through tighter
manufacturing tolerances to minimize variation.
No anticipated design changes.
Cooling system designed to reduce the
accumulation of debris.
Improved ignition system design to be more
reliable and durable than on Phase 2.
                      106

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                       Table 7-1. Projected Phase 3 Engine Characteristics (continued)
11
12
13
14
15
16
17
18
Improved component design and manufacturing
processes to reduce air-fuel ratio production
variability to stabilize engine performance and
emissions.
Locate fuel tanks away from heat sources.
Use of carburetors with appropriate idle circuits,
float-bowl vent, and automatic choke or improved
primer bulb. This will improve fuel system
reliability.
Locate the exhaust port away from the
carburetor/fuel line to minimize carburetor
heating.
Improved exhaust system design and materials for
better durability and reliability.
Improved muffler/catalyst/equipment design since
currently, the muffler designs do not incorporate
catalysts.
Evaporative emission controls: hoses, tank, cap,
and evaporative emission control system.
As Needed: non-contact, bi-metal thermal switch
to disable ignition system to shut engine down in
event of excessive temperature.
Component changes are not expected. Improved
manufacturing processes to reduce air-fuel ratio
production variability to stabilize engine
performance and emissions.
Locate fuel tanks away from heat sources.
Use of carburetors with appropriate idle circuits,
float-bowl vent, and automatic choke. This will
improve fuel system reliability.
No anticipated design changes.
No anticipated design changes.
Improved muffler/catalyst/equipment design since
currently, the muffler designs do not incorporate
catalysts.
Evaporative emission controls: hoses, tank, cap,
and evaporative emission control system.
As Needed: non-contact, bi-metal thermal switch
to disable ignition system to shut engine down in
event of excessive temperature. Manufacturers
will need to consider the potential trade-off of
disengaging engine power on ride-on equipment if
were to occur on a slope.
C.  DESIGN FMEA

The design FMEAs looked at the subsystems/components likely to be modified for compliance with potential Phase
3 exhaust and evaporative  emission control  requirements  and those affected by the  modification.  Twelve
systems/subsystems were evaluated for both the WBM (Class I) and the ROM (Class II). This broad approach was
deemed essential because of the technical interdependency among these systems in creating power and the potential
interactions among these systems in failure mode situations. The twelve subsystems evaluated included:

        1.   intake air filter

        2.   carburetor system

        3.   governor

        4.   intake manifold, port, valve, and seals

        5.   block, power head

        6.   exhaust valve and seal

        7.   exhaust manifold, muffler, muffler shroud, and gasket

        8.   supplemental air (venturi)

        9.   catalyst

        10.  cooling system
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        11. ignition system

        12. fuel tank and line
The design FMEAs were structured and conducted in the following manner: (The reader may find it useful to refer
to the template in Figure 7-1.)
Figure 7-1: Sample FMEA Tern]


Item



Potential
Cause
(Contributing)



Potential
Cause
(Primary)



Potential
Failure
Modes



Potential
Effect(s) of
Failure



Classificatio
n
of Effect



Sev
Ph
2


jlate.

Occur
Ph2



RPN
Ph
2



RPN
Ph3



Sev
Ph
3



Occur
Ph3


RPN
Delta
(Ph2
vs. Ph
3)



Notes


First the system and function were identified. Next, for each item identified, each cell of the columns of the FMEA
was completed.  This relied heavily on Swill's understanding of small engines, combustion, fuels, and  how the
primary and contributing causes can translate into potential failure modes. The failure modes of the subsystem were
often identified as a potential cause (primary or contributing) of a potential failure mode of other engine system.

Once the potential failure modes were identified, the team  ranked the estimated occurrence rate.  Then the team
identified the potential effects (usually more than one) and  ranked their individual severity. Information from the
CPSC  databases discussed in Chapter 4 was instrumental in linking potential failure modes  and effects. The
rankings for the severity of the failure mode and the frequency of occurrence of potential cause were drawn from
the tables (shown below) which were taken from the SwRI report.  For the severity classification any failure mode
involving a potential burn or fire was ranked as a 9 or 10, respectively, while an increase in the risk of fire or burn
was ranked as a 9.  The final steps in the FMEA process were to assign the effect to one of four classes (safety,
regulatory compliance, performance, other) and to calculate the risk probability number for each row by multiplying
the occurrence and severity values. The entire process was completed for each of the twelve subsystems for the
WBM Phase 2, WBM Phase 3, ROM Phase 2, and ROM Phase 3 equipment. Calculating the delta RPN shown in
the template required  a subtraction of the RPN value for the Phase 2 and Phase 3 analysis for each item.  The full
results for these four design FMEAs are in the attached SwRI reports.
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                               Table 7-2: Severity Ranking Scale
Ranking
	
10
9
8
7
6
5
4
3
2
1
Effect
Hazardous
Serious
Extreme
Major
Significant
Moderate
Minor
Slight
Very Slight
None
Severity of Effect - Customer
Hazardous effect. Safety Related. Regulatory non-
compliant
Potential hazardous effect. Able to stop without mishap.
Regulatory compliance in jeopardy.
Item inoperable, but safe. Customer very dissatisfied
Performance severely affected, but functional and safe.
Customer dissatisfied
Performance degraded, but operable and safe. Customer
experiences discomfort
Performance moderately affected. Fault on non-vital
requires repair. Customer experiences some
dissatisfaction
Minor effect on performance. Fault does not require
repair. Non-vital fault always noticed. Customer
experiences minor nuisance.
Slight effect on performance. Non-vital fault noticed most
of the time. Customer slightly annoyed.
Very slight effect on performance. Non-vital fault may be
noticed. Customer is not annoyed.
No effect.
                        Table 7-3: Occurrence Ranking Scale.
Ranking
10
9
8
7
6
5
4
3
2
1
Probability
Almost Certain
Very High
High
Moderately High
Medium
Low
Slight
Very Slight
Remote
Almost Impossible
Likely Failure Rates
Greater than / Equal to 1 in 2
1 in 3
1 in 8
1 in 20
1 in 80
1 in 400
1 in 2000
1 in 10,000
1 in 50,000
<1 in 500,000
Note 1:  For the Design FMEA the Occurrence Ranking is related to the design life of the equipment.
Note 2:  For the Process FMEA the Occurrence Ranking is related to a one-year operation period.

D.  PROCESS FMEA

As discussed in Chapter 4, input received from various  sources and the CPSC databases revealed three processes
which to some degree lead to problems in-use.  The process FMEAs conducted by SwRI addressed refueling,
equipment shut down and storage, and maintenance (equipment cleaning, oil/filter change, spark plug change, blade
sharpening, and drive belt replacement). While some of the information and results from the design FMEA would
carry across to  the process FMEAs (e.g., air filter problems), a key difference between the analyses of these
activities in the design and process FMEAs is the introduction of the operator as  a factor. Otherwise, the process
FMEAs were conducted very much like the design FMEAs, with heavy reliance on the SwRI technical expertise
and inputs gleaned from the CPSC databases.


E.  FMEA RESULTS

The purpose of the FMEAs was  to identify and assess change in engines, equipment, and operation that could
potentially impact safety when moving from Phase 2 compliant product to Phase 3 compliant product. To meet this
                                                 109

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objective there were two further steps necessary to put the FMEA results in a format useful for this study.  The first
is related to the "Classification of Effect" column.  Above we indicated that the study divided all of the potential
effects into one of four categories; of those four, only safety is relevant here.  Second, as was presented above, the
analysis should be presented in a format that shows incremental RPN differences between Phase 2 and Phase 3
product.  The differences between the outcomes of the  Phase 2 and Phase 3 design and process FMEAs are
instructive in characterizing potential safety concerns in each category and identifying potential incremental safety
risks. This  is possible  because  the  delta RPN number is indicative of the incremental change in risk  from the
engineering perspective. From the viewpoint of a designer, a positive delta RPN would indicate a directional
reduction in the incremental risk, a zero value would represents essentially  no incremental change, and a negative
delta RPN would suggest a directional increase in risk.  Tables 7-4 to 7-8, shown below, present the design and
process FMEA results for the safety-related items from the attached SwRI report.

F.   DISCUSSION OF DESIGN FMEAs FOR CLASSES I AND II

A review of the analyses presented in Tables 7-4 and 7-5  clearly indicates that for both the WBM (Class I) and
ROM (Class II)  FMEAs, the overall FMEAs are comparable for Phase 2 and the Phase 3 compliant equipment.
Table 7-4 presents the safety-related items of the FMEA for WBMs. In the WBM (Class I engine) FMEA, SwRI
identified 24 failure modes with the potential for an impact on safety. In comparing the Phase 3 and Phase 2 RPNs,
11 indicated a positive RPN delta and thus the potential for a directional improvement in safety, while one  indicated
a negative RPN delta and thus  the  potential for a directional degradation  in safety, and 12 indicated no overall
change in RPN. Similarly, Table 7-5 presents the safety-related items of the FMEA for ROMs. In the ROM (Class II
engine) FMEA, SwRI identified 25 failure modes with the potential for an incremental safety effect.  In comparing
the Phase 3 and Phase 2 RPNs, 8 indicated a positive RPN delta and thus the potential for a directional improvement
in safety, while one indicated a negative RPN delta and thus the potential for a directional degradation in safety, and
16 indicated no overall change in RPN.

Chapter 4 identified  seven scenarios for evaluation,  and indeed the FMEAs also identified many of the potential
causes listed in Chapter 4 as potential failure modes.  The FMEA outcomes for these items will be discussed further
in Chapter 8.

There was one hazard pattern identified in the CPSC IPII database  where the cause was unknown. In Chapter 3 this
is identified as "Unspecified: For reasons unspecified, the running lawn mower catches fire/explodes."  With no
detail, it is  not wise  to speculate on the specific cause(s) of these events.  While these types of incidents are not
directly addressed in the FMEA a review of the FMEA tables and the details on incidents of this nature may provide
some perspective. Major engine malfunction is addressed in the Class I and Class II FMEAs with the conclusion
that there is no  change in risk probability number.  Also, fuel line and fuel tank leak or failure is assessed in the
Class I and  Class II  design FMEAs with the general conclusion that the possibility that some manufacturers  may
move fuel tanks to address fuel evaporative emission controls could at least directionally reduce the risk probability
number for Phase 3 versus Phase 2 equipment.  In addition, the Class I and Class II FMEAs indicate a lower risk
probability  number for debris fires for a properly designed Phase  3 system  compared to a current Phase 2 system.
Thus, based on this  assessment, to the degree that these types of potential causes lead to fire in operation, EPA
believes that in an overall sense there will not be an increase in this type of fire for a properly designed Phase 3
system.

The design FMEAs looked at the subsystems/components likely to be modified for compliance with potential Phase
3 exhaust  and  evaporative emission  control  requirements and those affected  by the modification.  Twelve
systems/subsystems were evaluated for both the WBM (Class I) and the ROM (Class II). This broad approach was
deemed essential because of the technical interdependency among these systems in creating power and the potential
interactions among these systems in failure mode situations.  The potential effect of failure modes on the catalyzed
muffler performance  was considered in each item evaluated. No system or subsystem was considered in isolation.

Considering this systems view and the interactions among the subsystems it is worthwhile to discuss the issue of
enleanment, an increase in the intake A/F ratio above the design value.  This can occur because of an increase in
the available air or a decrease in the available fuel, and is usually a result of a failure of a component or subsystem
upstream of the exhaust manifold.  Concerns have been expressed that enleanment on an engine with a catalyzed
                                                   110

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muffler could lead to fire and burn risk because the activity of the catalyst would enhance CO oxidation in the
presence of the extra air. However, increased oxidation also occurs in a non-catalyst muffler because the muffler
acts like a thermal reactor.

Even without potential failures exhaust system surface temperatures are above the levels needed for contact burns to
occur. With enleanment the surface temperatures would still be above the temperatures needed for thermal burns to
occur. The FMEA identified three potential failure modes related to leaner mixtures, including situations where the
air filter, the  carburetor, or the intake air manifold failed to function as designed. For all three potential failure
modes even with the potential for hotter exhaust gas, hotter exhaust system surface temperatures, and/or hotter
engine surface temperatures, the  RPN related to fire and burn risk is zero or improved for Phase 3 compared to
Phase 2.

The Phase 3 catalyzed system incorporates improvements which will reduce the surface temperature exposed to the
user.  The improvements include  cooling air from the fan directed over the muffler and the heat shield designed to
cover the entire muffler  and  direct that cooling air around the muffler and out designated areas  for maximum
muffler cooling.  Therefore, increased temperatures resulting from differing exhaust conditions would not result in a
significant increased temperature to the user over that  of  a Phase 2 system experiencing  the  same exhaust
conditions.

Process FMEAs

SwRI also performed process  FMEAs on the WBM and the ROM to assess potential failure modes and effects for
three of the most common events in the life cycle of the engine and equipment. These included refueling, shutdown
and storage,  and maintenance. A review of the information provided by CPSC  indicates current in-use safety
problems in all three areas.

First, with regard to refueling, in Table 7-6, SwRI identified 25 aspects of the operation with potential impacts on
safety. Of these, 12 involved the actual dispensing of fuel from a gas can into the equipment tank. SwRFs analysis
indicated no change in RPN for Phase 2 and Phase 3 equipment for any of the 25 events involving refueling.

The second process FMEA (Table 7-7) involved shutdown and storage of equipment  after use. The  IPII data  base
provided by CPSC included a number of situations where, for various reasons, equipment stored either outdoors or
indoors after use led to a grass or  structure fire. In most cases the causes were not clear, but were presumably related
to grass/leaf debris or combustible material coming into contact with hot surfaces or the ignition of fuel  vapor by
sources not related to  the mower unit.  SwRI identified 15  items with potential safety implications related to
shutdown and storage.  In none of these did the FMEA indicate any differences in RPN between Phase 2 and Phase
3 equipment.

The  third process  FMEA (Table 7-8) involved different aspects of common  maintenance practices including
cleaning equipment, changing the oil/filter, changing the spark plug, sharpening the cutting blade, and replacing the
drive belt. Of the 16 different items identified, SwRI identified five in which the RPN improved slightly. In each of
these, the potential for fuel spillage on the operator or on hot surfaces during  maintenance would be reduced
because of tank and cap changes brought on by potential EPA fuel evaporative emission control requirements.

G.  CONCLUSION

The RPN values are the output from the FMEA which the engineer would use to  rank and prioritize actions which
might be taken to reduce potential risk. Since EPA is most interested in assessing the incremental risk of going from
Phase 2 to Phase 3, the delta RPN as presented in the SwRI analyses is instructive in understanding how design and
performance changes on the engines/equipment might affect in-use fire and burn risk.

When comparing the delta RPN results for the Phase 2 WBM and Phase 3 WBM design FMEAs and comparing the
delta RPN results for the Phase 2 ROM and Phase 3 ROM design FMEAs the engineer would conclude that the
Phase 3 equipment does not present an increase in risk of fire and burn relative to Phase 2. The FMEAs for  both
WBMs and ROMs give comparable and in  some cases directionally positive results.  The engineer's decisions on
                                                   111

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ranking and prioritizing risks to address would not be significantly different for a properly designed Phase 3 system
compared to a current Phase 2 system.

An inspection of the RPN delta columns in Tables 7-4 to 7-8 shows only modest changes.  The vast majority of
RPN deltas were positive or zero for the  safety classification indicating either a directional improvement  or no
change in risk. This indicates that from the FMEA perspective, the potential causes identified in the seven scenarios
in Chapter 4 would not be worse for a properly designed Phase 3 system and some would be better.

This analysis includes a catalyzed muffler in the Phase 3 systems. Since a Phase 2 system does not have a catalyzed
muffler, the potential exists to identify failure modes related to the inclusion of the catalyst in the muffler.  In the
Phase 3 WBM and ROM FMEAs, the  catalyzed muffler was considered in every item evaluated.  In the beginning
of this chapter EPA discussed that the rationale for selecting twelve subsystems in the WBM and ROM FMEAs,
was to ensure that the analyses captured the technical interdependency  among these subsystems in creating power
and the potential interactions among these systems in failure mode situations.  That is to say, problems in air intake,
ignition, carburetion, fuel storage etc all had  the potential to manifest themselves as causal effects for fire or burn
problems related to the catalyzed muffler. However, of the approximately  twenty five items evaluated in both the
WBM and  ROM design FMEAs where the catalyst was considered in each item, the analyses identified only  one
type failure mode which led to a negative delta RPN. The vast majority  had a positive or zero delta RPN leading to
the conclusion catalyst-equipped WBMs and catalyst-equipped ROMs can be implemented without an increase in
risk of fire or burn.

The one item with a negative delta RPN in both the Class I and Class II design FMEAs was related to either an
incorrect or improperly installed catalyst in the muffler where there was not one in the Phase 2 system. In this case,
the FMEA  performed its intended function  - to identify for the designer  potential failure modes and effects to allow
for an appropriate response as necessary. In this case the severity was rated a 10 based on burn or fire concerns  and
the frequency of the  failure was rated as a 2 (remote)  by SwRI. The chance of this occurring truly seems remote
since catalyst geometries will by definition partially eliminate mistakes (the wrong catalyst won't fit  in the  space
allocated)  and  there  are  very tight  finite  limits  on catalyst  wash  coating which would limit the severity.
Conceptually, this potential problem is similar to one not identified in the Phase 2 FMEAs, that being the mis-
installation of the muffler or an incorrect muffler.  In this case there would be potential problems  related to
backpressure or changes in cooling air flow which could affect fire and burn risk. No such problems were identified
in the CPSC  databases. Nonetheless, if the FMEA team decided to address this concern for Phase 3 engines there
are a number of approaches including QA/QC processes to address potential catalyst vendor or installation problems
or improved heat shielding. Thus, EPA does not see this potential failure mode  as creating an in-use risk.
1  SAE J1739, "Potential Failure Mode and Effects Analysis in Design (Design FMEA) and Potential Failure Mode
and  Effects Analysis in Manufacturing and Assembly  Processes  (Process FMEA)  and Effects Analysis for
Machinery (Machinery FMEA)", SAE International, August 2002.
                                                   112

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                                                     Table 7-4: Class I Safety FMEA Items
Class I Safety FMEA Items

Ref. Item
No.

1


2



3




4




5


Item

Intake Air
Filter


Intake Air
Filter



Carburetor
System




Carburetor
System




Carburetor
System


Potential Cause
(Contributing)
Degradation or
element, wrong
filter or dirty or
Prefilter not oiled
Degradation or
element, wrong
filter or dirty or
missing filter.
Prefilter not oiled
 f I

jets in production
1 h'l'h
ii
Float breaks,
debris in float
jets in production,
choke stuck
production
variability

....
needle valve stuck
open, or cracked
primer bulb


Cause
(Primary)

richer
mixture


leaner
mixture



leaner
mixture




richer
mixture


leakage of
fuel to
mower deck,
air filter or
elsewhere
(i.e. out of air
filter)

Potential
Failure Modes

backfire


hotter exhaust


Higher
temperature in
engine and
catalyst



backfire




fuel ignites


Effect(s) of
Failure

fire or burn


fire or burn



fire or burn




fire or burn




fire or burn


Classification
of Effect

1_Safety


1_Safety



1_Safety




1_Safety




1_Safety


Sev
Ph2

10


10



10




10




10


Occur
Ph2

3


3



4




5




2


RPN
Ph2

30


30



40




50




20


RPN
Ph3

20


30



40




40




20


Sev
Ph3

10


10



10




10




10


Occur
Ph3

2


3



4




4




2


RPN Delta (Ph
2 vs Ph 3)

10


0



0




10




0


Notes
In this scenario, the backfire is of such intensity that it can
cause a fire or burn. EPA demonstrated that the backfire
incidence was significantly reduced with the addition of a
properly designed catalyzed muffler system. That fact drives
a reduction in the Occurrence ranking.
The rankings are the same with or without a catalyst because
there will be no increase in burn risk with the application of a
properly designed catalyst. The effect could be mitigated by
the presence of a thermal switch.

The rankings are the same with or without a catalyst. Any
effect that the catalyst might have on temperature level is
offset by the expected improvements in air cooling of the
manifold system on Phase 3 products. If the change in
temperature is significant the effect could be mitigated by the
presence of a thermal switch.

In this scenario, the backfire is of such intensity that it can
cause a fire or burn. EPA demonstrated that the backfire
incidence was significantly reduced with the addition of a
properly designed catalyzed muffler system. That fact drives
a reduction in the Occurrence ranking.



The rankings are the same with or without a catalyst because
exposed muffler temperatures are nominally equivalent. Fuel
can be ignited by hot surfaces or the ignition system.

                                                               113

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Class I Safety FMEA Items
Ref. Item
No.


6



7


8


9



10






11



Item


Carburetor
System



Governor


Intake
Manifold


Block



Block






Exhaust
Manifold



Potential Cause
(Contributing)

gasket failure, or
needle valve stuck
open, or cracked
primer bulb




None
Crack or leak in
manifold


Higher thermal
load



Higher thermal
load








None

Potential
Cause
(Primary)
leakage of
fuel to
air filter or
(i.e. out of air
filter)

Malfunction-
ing governor


leaner
mixture


higher
engine
temperatures



higher
engine
temperatures


loosening of
muffler,
manifold or
failed gasket
(gasket is
less common
on Class I
vertical shaft
engines)
Potential
Failure Modes


fuel puddles



open governor
causes engine
overspee
Engine,
system and
catalyst run
hotter
Engine failure

component
seizure,
broken valve
or spring,
excess wear)
Engine failure
(internal
component
seizure,
broken valve
or spring,
excess wear)



exhaust leak



Potential
Effect(s) of
Failure


fire or burn


catastrophic
failure (potential
injury due to
flying parts)

fire or burn


catastrophic
failure (potential
injury due to
flying parts)



fire or burn






fire or burn



Classification
of Effect


1_Safety



1_Safety


1_Safety


1_Safety



1_Safety






1_Safety



Sev
Ph2


10



9


10


9



10






10



Occur
Ph2


4



2


9


4



4






6



RPN
Ph2


40



18


90


36



40






60



RPN
Ph3


40



18


40


36



40






40



Sev
Ph3


10



9


10


9



10






10



Occur
Ph3


4



2


4


4



4






4



RPN Delta (Ph
2 vs Ph 3)


0



0


50


0



0






20



Notes

The rankings are the same with or without a catalyst because
exposed muffler surfaces have been shown to be nominally
equivalent in Phase 2 (no catalyst) and Phase 3 (catalyzed)
prototype systems.


Engine failure caused by overspeed. The rankings are the
same with or without a catalyst.

The lower occurrence for Phase 3 is due to the expected
improvement of the manifold system for Phase 3 products.
The effect could be mitigated by the presence of a thermal
switch.


Engine failure caused by excessive temperatures. The
rankings are the same with or without a catalyst. The effect
could be mitigated by the presence of a thermal switch.



Engine failure can result in contact with hot metal or fluids.
The rankings are the same with or without a catalyst. The
effect could be mitigated by the presence of a thermal switch.





The lower Phase 3 occurrence is due to the Phase 3 improved
exhaust system design.



                                                   114

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Class I Safety FMEA Items
Ref. Item
No.

12


13

14


15

16




17



18
Item

Exhaust
Manifold


Exhaust
Manifold

Catalyst


Cooling
System

Cooling
System




System



Ignition
System
Potential Cause
(Contributing)

Debris
accumulation




None
Manufacturing,
supplier or
problem


None


None



None


plug wire, failed
coil, loose
flywheel, magneto
Potential
Cause
(Primary)
reduction in
cooling and
increased
temperatures
removal or
mechanical
failure of the
shroud
incorrect or
improperly
catalyst

system
shroud failed
plugging of
cooling
passages
due to debris
plug bad,
short in plug
wire, failed
coil, loose
flywheel,
magneto,
module
failure

loss of spark
Potential
Failure Modes

debris
adjacent to


loss of muffler
shroud

excessive
catalyst
performance
loss of cooling
to engine block
and muffler
system

reduction of
engine cooling



weak or
intermittent
spark (misfire)



backfire
(misfire)
Potential
Effect(s) of
Failure

fire


fire or burn

fire or burn


burn risk

burn risk



muffler or
temperatures
and increased
burn risk


fire or burn
Classification
of Effect

1_Safety


1_Safety

1 Safety


1_Safety

1_Safety




1_Safety



1_Safety
Sev
Ph2

10


10

1


9

9




9



10
Occur
Ph2

3


3

1


2

5




5



6
RPN
Ph2

30


30

1


18

45




45



60
RPN
Ph3

20


20

20


18

36




27



40
Sev
Ph3

10


10

10


9

9




9



10
Occur
Ph3

2


2

2


2

4




3



4
RPN Delta (Ph
2 vs Ph 3)

10


10

-19


0

9




18



20
Notes
The lower occurrence for the Phase 3 is due to the
improvement of the air ducting for cooling and control of
debris accumulation. In addition, fan inlet screens are
expected on all Phase 3 engines. The failure mode could be
mitigated by the presence of a thermal switch.

The lower occurrence for the Phase 3 is due to the
improvement of the air ducting for cooling and shroud design.

The Phase 2 ranking is low by definition, since Phase 2 does
not have a catalyst. For Phase 3, the severity ranks high due
to the potential safety impact. The effect could be mitigated
by the presence of a thermal switch.

The rankings are the same with or without a catalyst. The
effect could be mitigated by the presence of a thermal switch.
By definition of the Phase 3 product, the improved design
features for Phase 3 results in a slight reduction in
Occurrence. The effect could be mitigated by the presence of
a thermal switch.


The lower occurrence for the Phase 3 is due to the improved
ignition system for Phase 3 products. The effect could be
mitigated by the presence of a thermal switch.


In this scenario, the backfire is of such intensity that it can
cause a fire or burn. EPA demonstrated that the backfire
incidence was significantly reduced with the addition of a
properly designed catalyzed muffler system. That fact drives
a reduction in the Occurrence ranking.
                                                   115

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Class I Safety FMEA Items

Ref. Item
No.

19


20


21


22


23


24


Item

Fuel Tank


Fuel Tank


Fuel Tank


Fuel Tank


Fuel Tank


Fuel Tank


Potential Cause
(Contributing)



None


None


NfgTP muffler or
catalyst
temperatures near
fuel lines
High muffler or
catalyst
temperatures near
fuel lines
High muffler or
catalyst
temperatures near
fuel lines

Cause
(Primary)

leak of tank
or line


leak of tank
or line


leak of tank
or line


fuel tank or
line melted


fuel tank or
line melted


fuel tank or
line melted


Potential
Failure Modes

fuel puddles


fuel puddles


fuel leaks on
hot component


fuel puddles


fuel puddles


fuel leaks on
hot component


Effect(s) of
Failure

fire or burn


operator fuel
exposure


fire or burn


fire or burn


operator fuel
exposure


fire or burn


Classification
of Effect

1_Safety


1_Safety


1_Safety


1_Safety


1_Safety


1_Safety


Sev
Ph2

10


9


10


10


9


10


Occur
Ph2

5


5


4


3


3


2


RPN
Ph2

50


45


40


30


27


20


RPN
Ph3

40


36


30


20


18


20


Sev
Ph3

10


9


10


10


9


10


Occur
Ph3

4


4


3


2


2


2


RPN Delta (Ph
2 vs Ph 3)

10


9


10


10


9


0


Notes
By definition of the Phase 3 product, the improved design
features for Phase 3 is expected to result in a slight reduction
in Occurrence. The evaporative emission controls will
reduce leak occurrence
By definition of the Phase 3 product, the improved design
features for Phase 3 is expected to result in a slight reduction
in Occurrence. The evaporative emission controls will
reduce leak occurrence
By definition of the Phase 3 product, the improved design
features for Phase 3 is expected to result in a slight reduction
in Occurrence. The evaporative emission controls will
reduce leak occurrence
By definition of the Phase 3 product, the improved design
features for Phase 3 is expected to result in a slight reduction
in Occurrence. The evaporative emission controls will
reduce leak occurrence
By definition of the Phase 3 product, the improved design
features for Phase 3 is expected to result in a slight reduction
in Occurrence. The evaporative emission controls will
reduce leak occurrence

The rankings are the same with or without a catalyst. The
exposed muffler temperatures are nominally equivalent.

                                                   116

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                                                  Table 7-5: Class II Safety FMEA Items
Class II Safety FMEA Items

Ref. No.



1





2










3










Item



Intake Air Filter





Intake Air Filter










Carburetor
System










Potential Cause
(Contributing)

Degradation or
tear of filter
element, wrong
filter or dirty or
missing filter.

Degradation or
tear of filter
element, wrong
filter or dirty or
missing filter.
Restriction in
fuel passages,
wrong jets in
production, or
choke stuck
open, or
production
variability. Fuel
injection system
fuel pump or
fuel pressure
regu a or
filter or injector
restriction.
Injector wiring
connection
degraded.
MAP, ECM, or
O2 sensor
failure.
Potential
Cause
(Primary)



richer mixture





leaner mixture










leaner mixture









Potential
Failure
Modes



backfire





hotter
exhaust









higher
temperature
in engine and
Catalyst









Potential Effect(s) of
Failure



fire or burn





fire or burn










fire or burn










Classification
of Effect



1_Safety





1_Safety










1_Safety










Sev
Ph2



10





10










10










Occur
Ph2



2





3










3










RPN
Ph2



20





30










30










RPN
Ph3

Sev
Ph3



20





30










30











10





10










10










Occur
Ph3



2





3










3










RPN Delta
(Ph 2 vs Ph 3)



0





0










0










Note
In this scenario, the backfire is of such intensity that it can
cause a fire or burn. EPA demonstrated that the backfire
incidence was significantly reduced with the addition of a
properly designed catalyzed muffler system. The occurrence
is held the same for Phase 2 and 3 in this case since Class II,
Phase 2 products are already judged to have a relatively low
occurrence of backfire due to intake filter issues.
The rankings are the same with or without a catalyst because
there will be no increase in fire or burn risk with the
application of a properly designed catalyst. The effect could
be mitigated by the presence of a thermal switch.








The rankings are the same with or without a catalyst. Any
effect that the catalyst might have on temperature level is
offset by the expected improvements in air cooling of the
manifold system on Phase 3 products. If the change in
temperature is significant the effect could be mitigated by the
presence of a thermal switch.







                                                               117

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Class II Safety FMEA Items
Ref. No.






4








5

6




7



Item






Carburetor
System








Carburetor
System

Carburetor
System




S
v



Potential Cause
(Contributing)
Float breaks,
debris in float
needle, or
wrong jets in
production,
choke stuck
closed, or
production
variability. Fuel
injection fuel
system fuel
pressure
regulator
failure. Fuel
injector stuck
open. MAP,
ECM, O2
sensor failure.
gasket failure,
or needle valve
stuck open, or
fuel pump /
regulator leak
gasket failure,
or needle valve
stuck open, or
fuel pump /
regulator leak
ECM failure,
solenoid return
spring
breakage
causes fuel
cutoff solenoid
open failure
Potential
Cause
(Primary)






richer mixture







leakage of fuel
to mower
deck, air filter
or elsewhere
filter)
leakage of fuel
to mower
deck, air filter
or elsewhere
(i.e. out of air
filter)


fuel flow into
and from
engine


Potential
Failure
Modes






backfire








fuel ignites

fuel puddles




fuel puddles



Potential Effect(s) of
Failure






fire or burn








fire or burn

fire or burn




fire or burn



Classification
of Effect






1_Safety








1_Safety

1_Safety




1_Safety



Sev
Ph2






10








10

10




10



Occur
Ph2






4








2

3




4



RPN
Ph2






40








20

30




40



RPN
Ph3






30








20

30




40



Sev
Ph3






10








10

10




10



Occur
Ph3






3








2

3




4



RPN Delta
(Ph 2 vs Ph 3)






10








0

0




0



Note






In this scenario, the backfire is of such intensity that it can
cause a fire or burn. EPA demonstrated that the backfire
incidence was significantly reduced with the addition of a
properly designed catalyzed muffler system. That fact drives
a reduction in the Occurrence ranking.







The rankings are the same with or without a catalyst because
exposed muffler temperatures are nominally equivalent. Fuel
can be ignited by hot surfaces or the ignition system.

The rankings are the same with or without a catalyst because
exposed muffler surfaces have been shown to be nominally
equivalent in Phase 2 (no catalyst) and Phase 3 (catalyzed)
prototype systems.



The rankings are the same with or without a catalyst.



                                                     118

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Class II Safety FMEA Items
Ref. No.

8


9



10




11




12



13


14

Item

Governor


Intake Manifold



Intake Manifold




Block




Block



Exhaust
Manifold


Exhaust
Manifold

Potential Cause
(Contributing)

None


Crack or leak in
manifold


Intake manifold
leak causes
MAP to read
higher pressure



Higher thermal
load




Higher thermal
load



None


Debris
accumulation

Potential
Cause
(Primary)

malfunctioning
governor


leaner mixture



richer mixture




higher engine
temperatures




higher engine
temperatures


cracked
muffler,
manifold or
failed gasket
reduction in
engine cooling
/ increased
muffler
temperatures
Potential
Failure
Modes
open
governor
causes
engine
overs peed
engine,
exhaust
system and
catalyst run
hotter


backfire


engine failure
(internal
component
seizure,
broken valve
or spring,
excess wear)
engine failure
(internal
component
seizure,
broken valve
or spring,
excess wear)

exhaust leak


ignition of
debris
adjacent to

Potential Effect(s) of
Failure

catastrophic failure
(potential injury due
to flying parts)


fire or burn



fire or burn




catastrophic failure
(potential injury due
to flying parts)




fire or burn



fire or burn


fire

Classification
of Effect

1_Safety


1_Safety



1_Safety




1_Safety




1_Safety



1_Safety


1_Safety

Sev
Ph2

9


10



10




9




10



10


10

Occur
Ph2

2


4



3




3




3



4


3

RPN
Ph2

18


40



30




27




30



40


30

RPN
Ph3

18


40



30




27




30



30


20

Sev
Ph3

9


10



10




9




10



10


10

Occur
Ph3

2


4



3




3




3



3


2

RPN Delta
(Ph 2 vs Ph 3)

0


0



0




0




0



10


10

Note

Engine failure caused by overspeed. The rankings are the
same with or without a catalyst.


The rankings are the same with or without a catalyst. The
effect could be mitigated by the presence of a thermal switch.

The failure relates to fuel Injected engines. EPA
demonstrated that the backfire impact was reduced with the
addition of a properly designed catalyzed muffler system for
Class I. However, since the design quality of the Class II
equipment mufflers is very good on Phase 2, the impact of
adding the catalyst is minimal.


Engine failure caused by excessive temperatures. The
rankings are the same with or without a catalyst. The effect
could be mitigated by the presence of a thermal switch.




Engine failure can result in contact with hot metal or fluids.
The rankings are the same with or without a catalyst. The
effect could be mitigated by the presence of a thermal switch.



The lower Phase 3 occurrence is due to the Phase 3
definition of improved exhaust system design.


The lower occurrence for the Phase 3 is due to the
improvement of the air ducting for cooling and control of
debris accumulation.

                                                     119

-------
Class II Safety FMEA Items

Ref. No.

15


16
17

18



19





20



21

22

23

Item

Exhaust


Catalyst
Cooling
System

Cooling
System



Ignition System





Ignition System



Fuel Tank

Fuel Tank

Fuel Tank

Potential Cause
(Contributing)

None

Manufacturing,
installation
problem
None

None



None



bad plug, short
in plug wire,
failed coil, loose
flywheel,
magneto

None

None

Equipment tip
over, material
failure,
component
failure

Cause
(Primary)
removal or
mechanical
failure
incorrect or
installed
catalyst
plugging of
cooling
passages due
to debris
cooling system
shroud failed
plug bad, short
in plug wire,

failed coil,
loose flywheel,

ignition
module failure


loss of spark



leak of tank or
line

leak of tank or

leak of tank or
line

Failure
Modes
loss of
muffler
shroud
increased
catalyst
performance
reduction of
engine
coo ing
loss of
cooling
weak or
intermittent

spark, or loss
of ignition in

cylinders
(misfire)



(misfire)


fuel puddles,
or sprays

fuel puddles,

fuel contacts
hot
component

Potential Effect(s) of
Failure

fire or burn


fire or burn
burn risk

burn risk



catalyst
temperatures and
increased burn risk




fire or burn



fire or burn

operator fuel

fire or burn

Classification
of Effect

1 Safety


1_Safety
1_Safety

1_Safety



1_Safety





1 Safety



1_Safety

1 Safety

1_Safety

Sev
Ph2

10


1
9

9



9





10



10

9

10

Occur
Ph2

3


1
4

2



3





4



3

3

3

RPN
Ph2

30


1
36

18



27





40



30

27

30

RPN
Ph3

20


20
27

18



27





30



20

18

20

Sev
Ph3

10


10
9

9



9





10



10

9

10

Occur
Ph3

2


2
3

2



3





3



2

2

2

RPN Delta
(Ph 2 vs Ph 3)

10


-19
9

0



0





10



10

9

10

Note
The lower occurrence for the Phase 3 is due to the
improvement of the air ducting design for cooling and shroud
design.
The Phase 2 ranking is low by definition, since Phase 2 does
not have a catalyst. For Phase 3, the severity ranks high due
to the potential safety impact. The effect could be mitigated
by the presence of a thermal switch.
The rankings are the same with or without a catalyst. The
effect could be mitigated by the presence of a thermal switch.

The rankings are the same with or without a catalyst. The
effect could be mitigated by the presence of a thermal switch.



The rankings are the same with or without a catalyst. The
effect could be mitigated by the presence of a thermal switch.



In this scenario, the backfire is of such intensity that it can
cause a fire or burn. EPA demonstrated that the backfire
incidence was significantly reduced with the addition of a
properly designed catalyzed muffler system. That fact drives
a reduction in the Occurrence ranking.
By definition of the Phase 3 product, the improved design
features for Phase 3 is expected to result in a slight reduction
in Occurrence. The evaporative emission controls will
reduce leak occurrence
The rankings are the same with or without a catalyst.

By definition of the Phase 3 product, the improved design
features for Phase 3 is expected to result in a slight reduction
in Occurrence. The evaporative emission controls will
reduce leak occurrence
                                                     120

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Class II Safety FMEA Items
Ref. No.

24


25


26
Item

Fuel Tank


Fuel Tank


Fuel Tank
Potential Cause
(Contributing)
High muffler or
catalyst
temperatures
near fuel tank
High muffler or
catalyst
temperatures
near fuel tank
High muffler or
catalyst
temperatures
near fuel tank
Potential
Cause
(Primary)

fuel tank or
line melted


fuel tank or
line melted


fuel tank or
line melted
Potential
Failure
Modes

fuel puddles
or sprays


fuel puddles
or sprays


hot
component
Potential Effect(s) of
Failure

fire or burn


operator fuel
exposure


fire or burn
Classification
of Effect

1_Safety


1_Safety


1_Safety
Sev
Ph2

10


9


10
Occur
Ph2

2


2


2
RPN
Ph2

20


18


20
RPN
Ph3

20


18


20
Sev
Ph3

10


9


10
Occur
Ph3

2


2


2
RPN Delta
(Ph 2 vs Ph 3)

0


0


0
Note

The rankings are the same with or without a catalyst.


The rankings are the same with or without a catalyst.


The rankings are the same with or without a catalyst.
                                                     121

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                                   Table 7-6: Refueling Process FMEA
Refueling Process FMEA
Ref. Item
No.

1


2

3

4

5


6


7




8


9

Process Function

Shut off engine


Open mower cap

Open mower cap

Open mower cap

Remove fuel can


Remove fuel can
cap


Remove fuel can
cap









Potential Cause
(Primary)

failed to shut engine
off


overpressure of fuel
tank

overpressure of fuel
tank

overpressure of fuel
tank

operator behavior

hot fuel and high
pressure(high
temperature storage,
heating from sunlight)
hot fuel and high
pressure(high
temperature storage,
heating from sunlight)



operator behavior


operator behavior

Potential
Failure Modes

engine
running




spillage (hot
fuel, full tank,
pressurized
tank - i.e. vent
blocked)



Fail to open





fuel spray
upon opening
cap/vent






Potential Effect(s) of
Failure

risk of refueling while
engine running and a
potential of a fire or burn


operator contact w/ fuel

spillage onto hot
surfaces and a potential
of a fire or burn

fire

fuel spillage


operator contact w/ fuel


spillage




spillage


vapor released from can

Classification
of Effect

1_Safety


1_Safety

1_Safety

1_Safety

1_Safety


1_Safety


1_Safety




1 Safety


1 Safety

Sev

9


9

9

10

9


9


9




9


9

Occur

2


2

2

2

4


2


2




4


4

R.P.N.

18


18

18

20

36


18


18




36


36

Notes
No difference between Phase 2 and
Phase 3 expected. Thermal images
indicate that at idle operation the
maximum surface temperatures are
comparable for Phase 2 and Phase 3
designs.
A safety concern, but no significant
difference between Phase 2 and Phase
3 expected. (Phase 3 tank venting
could be a slight improvement)
A safety concern, but no significant
difference between Phase 2 and Phase
3 expected. (Phase 3 tank venting
could be a slight improvement)
A safety concern, but no significant
difference between Phase 2 and Phase
3 expected. (Phase 3 tank venting
could be a slight improvement)
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.

A safety concern, but no difference
between Phase 2 and Phase 3
expected.



A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
                                               122

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Refueling Process FMEA
Ref. Item
No.
10
11



12


13

14

15



16
17

18

19

20

Process Function
pick up can and
pour
pick up can and
pour



pick up can and
pour


pick up can and

pick up can and

pick up can and



pick up can and
pour
pick up can and
pour

pick up can and

pick up can and

pick up can and

Potential Cause
(Primary)
fuel spill
fuel spill



fuel spill


fuel spill

fuel spill

fuel spill



fuel spill
material failure

engine running

engine running

static charge

Potential
Failure Modes
fuel puddle on
equipment
fuel spill into
fan inlet



cowling and
makes contact
with a hot

component
spill on
operator
and/or
bystander


spillage on
surrounding
areas
gas can
cracks


refuel while
running

spark

Potential Effect(s) of
Failure
fuel fire
fuel fire



fuel fire


fuel exposure

fuel fire and burn

fuel fire and burn



creates combustible
material
fuel spill and potential of
fire or burn

spill fuel

fuel vapor ignites

fire or explosion

Classification
of Effect
1_Safety
1_Safety



1_Safety


1_Safety

1 Safety

1 Safety



1_Safety
1_Safety

1 Safety

1 Safety

1 Safety

Sev
10
10



10


9

10

10



9
9

9

10

10

Occur
4
4



4


4

4

4



4
3

2

2

2

R.P.N.
40
40



40


36

40

40



36
27

18

20

20

Notes
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but effectively no
difference between Phase 2 and Phase
3 expected. Thermal imaging cross-
validation studies indicated that "...the
application of a catalyst to a small
gasoline engine does not increase, and
can actually lower, exhaust system
surface temperatures..."
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.


A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
                                        123

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Refueling Process FMEA
Ref. Item
No.
21
22
23
24
25
Process Function
pick up can and
pour
Recap the Mower
Tank
Recap the Mower
Tank
Restart
Restart
Potential Cause
(Primary)
gas cap on can is not
secure
failure to recap mower
tank
failure to recap mower
tank
fuel on the equipment
fuel or debris left on
the equipment
Potential
Failure Modes
spillage on
surrounding
areas
fuel spillage or
vapor release
onto
equipment or
operator
during
operation
ignition
component
failure
hot surfaces
ignites
Potential Effect(s) of
Failure
fire or burn
fire
fuel exposure
fire or burn
fire or burn
Classification
of Effect
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
Sev
10
10
9
10
10
Occur
2
3
3
2
2
R.P.N.
20
30
27
20
20
Notes
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
A safety concern, but no difference
between Phase 2 and Phase 3
expected.
                                        124

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                             Table 7-7: Shutdown and Storage Process FMEA
Shutdown and Storage Process FMEA
Ref. Item
No.
1

2
3
4

5

6


7

8



9


10

Process Function
Engine Shut Down

Engine Shut Down
Engine Shut Down
Engine Shut Down

Engine Shut Down

Equipment Storage


Equipment Storage

Equipment Storage



Equipment Storage


Equipment Storage

Potential Cause
(Primary)
ignition cut off and
engine brake fail (and
engine does not shut

engine won't stop and
operator goes for help
engine won't stop and
operator goes for help
engine won't stop and
operator pulls plug

engine won't stop and
operator pulls plug
wire
cover with tarp while
engine hot (any
material)


cover with tarp while
engine hot (any
material)

garage or shed when


store in or near
garage or shed when
engine hot


garage or shed when

Potential
Failure Modes
engine left
running, and
operator may
pull plug wire
to stop
untended
operation
risk of fuel
ignition due to
high voltage
spark
operator
contacts hot
component

tarp ignites

equipment
ignites
combustible
material
water heater
pilot light
gasoline vapor
from leak, spill
or refueling
Spilled fuel or
debris on
mower deck
ignites
Potential Effect(s) of
Failure
high surface
temperatures, and risk
of fuel ignition from high
voltage spark and risk
of shock
bystander gets injured
by burn
debris fire
fire or burn

burn

fire ignites adjacent
materials


fire damages equipment

structural fire



structural fire


Equipment or structural
fire

Classification
of Effect
1_Safety

1_Safety
1_Safety
1_Safety

1_Safety

1_Safety


1_Safety

1_Safety



1_Safety


1_Safety

Sev
9

10
10
10

10

10


10

10



10


10

Occur
2

2
2
2

2

2


2

1



1


1

R.P.N.
18

20
20
20

20

20


20

10



10


10

Notes
No difference between Phase 2 and Phase
3 expected

No difference between Phase 2 and Phase
3 expected
No difference between Phase 2 and Phase
3 expected
No difference between Phase 2 and Phase
3 expected

No difference between Phase 2 and Phase

Tarp ignites and fire could spread. No
impact due to addition of a catalyst.


Tarp ignites and fire could spread. No
impact due to addition of a catalyst.
Surrounding material could ignite. No
impact due to addition of a catalyst. Data
available does not support a higher
occurrence ranking.

Gas vapor could ignite. No impact due to
addition of a catalyst. Data available does
not support a higher occurrence ranking.

Debris on the mower deck could ignite. No
impact due to addition of a catalyst. Data
available does not support a higher
occurrence ranking.
                                            125

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Shutdown and Storage Process FMEA
Ref. Item
No.
11
12
13
14
15
Process Function
Equipment Storage
Equipment Storage
Equipment Storage
Equipment Storage
Equipment Storage
Potential Cause
(Primary)
store in or near
garage or shed when
engine hot
park equipment on
combustible debris
park equipment on
combustible debris
park equipment on
combustible debris
park equipment on
combustible debris
Potential
Failure Modes
operator
and/or
bystander
contacts hot
component
debris ignites
Potential Effect(s) of
Failure
burn
debris fire
structural fire
bystander gets injured
by burn
fire damages equipment
Classification
of Effect
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
Sev
10
10
10
10
10
Occur
2
2
2
2
2
R.P.N.
20
20
20
20
20
Notes
No impact due to addition of a catalyst.
Surrounding material could ignite. No
impact due to addition of a catalyst.
Surrounding material could ignite. No
impact due to addition of a catalyst.
No impact due to addition of a catalyst.
Surrounding material could ignite. No
impact due to addition of a catalyst.
                                     126

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                                 Table 7-8: Maintenance Process FMEA
Maintenance Process FMEA
Ref. Item
No.
1
2
3
4
5
6
7
8
9
10
11
12
Process Function
Cleaning Equipment
Cleaning Equipment
Cleaning Equipment
Change Oil / Filter
Change Oil / Filter
Change Oil / Filter
Change Oil / Filter
Change Air Filter
Change Spark Plug
Change Spark Plug
Sharpen Blade
Sharpen Blade
Potential Cause
(Primary)
Tip equipment to clean
underneath
Tip equipment to clean
underneath
maintenance or
cleaning while the
equipment is hot
Improper maintenance
maintenance or
cleaning while the
equipment is hot
Tip equipment for
maintenance
Tip equipment for
maintenance
maintenance or
cleaning while the
equipment is hot
maintenance or
cleaning while the
equipment is hot
testing for spark
tipping equipment for
blade access
tipping equipment for
blade access
Potential Failure
Modes
spill fuel or oil
contact with hot
part
spill oil
contact with hot
part
spill fuel or oil
contact with hot
part
contact with hot
part
spark ignites fuel
equipment falls
spill fuel or oil
Potential Effect(s) of
Failure
fire
operator exposure to
fuel or oil
burn
operator exposure to
oil
burn
fire
operator exposure to
fuel or oil
burn
burn
fire
personnel injury
fire
Classification of
Effect
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
1_Safety
Sev
10
9
10
9
10
10
9
10
10
10
10
10
Occur
8
8
6
9
6
8
8
6
6
3
5
8
R.P.N.
80
72
60
81
60
80
72
60
60
30
50
80
Notes
Vapor control requirements will
reduce occurrence with Phase 3
product to 7 and the RPN to 70.
Vapor control requirements will
reduce occurrence with Phase 3
product to 7 and the RPN to 63.
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
Vapor control requirements will
reduce occurrence with Phase 3
product to 7 and the RPN to 70.
Vapor control requirements will
reduce occurrence with Phase 3
product to 7 and the RPN to 63.
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
Vapor control requirements will
reduce occurrence with Phase 3
product to 7 and the RPN to 70.
                                                                                           127

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Maintenance Process FMEA
Ref. Item
No.
13
14
15
16
Process Function
Sharpen Blade
Replace Drive Belt
Replace Drive Belt
Replace Drive Belt
Potential Cause
(Primary)
Improper reassembly
wrong belt installed
belt installed
incorrectly
maintenance or
cleaning while the
equipment is hot
Potential Failure
Modes
spill fuel or oil
belt slips or does
not engage
belt slips or does
not engage
contact with hot
part
Potential Effect(s) of
Failure
personnel injury
belt fire / debris fire
belt fire / debris fire
burn
Classification of
Effect
1_Safety
1_Safety
1_Safety
1_Safety
Sev
10
10
10
10
Occur
1
4
3
6
R.P.N.
10
40
30
60
Notes
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
No difference between Phase 2
and Phase 3 expected
                                                                              128

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129

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8.      Conclusions - Impact of Phase 3  Exhaust Standards  on  Class  I
        and Class II  NHH Engines

In this chapter, EPA draws conclusions based upon:

     1.  the results of laboratory testing conducted with EPA prototypes of engines with Phase 3 exhaust emissions
        control systems,

     2.  the results of laboratory testing conducted with current Phase 2 engines, and

     3.  the results of the FMEA for each of the key scenarios used to evaluate the incremental risk associated with
        advanced emission control technology for NHH engines and equipment.

     In all cases, based on the data presented in this report, EPA concludes that the catalyst-based Phase 3 standard
     under consideration poses no incremental increase in the risk of fire or burn for Class I and Class II NHH
     engines.

SCENARIO 1: CONTACT BURNS

Scenario Description: Thermal burns due to inadvertent contact with hot surface on engine or equipment.

Potential Causes:

    a.   muffler surface temperature increases due to debris inhibiting flow of cooling air

    b.   higher temperatures on mower deck or around muffler due to higher radiant heat load  from muffler or
        engine

    c.   muffler temperature increase due to air-to-fuel ratio enleanment caused by calibration drift over time, fuel
        system problems or air filter element mal-maintenance

    d.   exhaust gas leaks increase surface temperatures

Conclusions Based on EPA Testing of Phase 2 engines and Phase 3  Prototypes:

    a.   Muffler surface temperature increases due to debris inhibiting flow of cooling air. Engines equipped with
        catalyst-mufflers showed no greater propensity to trap debris than those equipped with OEM mufflers,
        even during operation in high-debris environments in the  field. Both laboratory and field testing showed
        that properly designed catalyst-mufflers could achieve comparable, or even  cooler, surface temperatures
        relative to today's OEM muffler designs.  EPA did find evidence of cooling air being blocked by debris
        during field testing  for some engine designs, regardless of exhaust system configuration (see figure 6-36).
        A partially blocked cooling system could potentially limit the amount of cooling air available for forced
        convective cooling of the exhaust system, and this could occur whether or not the engine is equipped with
        a catalyst. Engines  244 and 245 in Class I and all of the Class II engines tested were designed with coarse
        screens on the inlet to the cooling fan.  Engines with properly designed cooling fan air-inlet  screens had
        minimal or no issues regarding debris  ingestion and blockages within the engine cooling system.  Debris
        build-up on muffler surfaces did not occur on engines equipped with air-shrouding for muffler or catalyst-
        muffler cooling.  Properly designed systems were capable of grass cutting operations to near the end of
        useful life with minimal build-up of debris either within the cooling system or on exhaust system surfaces
        (engines 231, 232,  233, 244, 245, 251).   These grass cutting operations included high-debris conditions
        that led to nearly complete blockage of the cooling systems on engines 246, 248, 249 and 259.  Retrofitting
        the engines with a screen near the air-inlet to the cooling fan resolved the debris-blockage issue.
                                                                                                   130

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b.  Higher temperatures on mower deck or around muffler due to higher radiant heat load from muffler or
    engine:  EPA laboratory testing and field testing clearly indicate that comparable, or even cooler, surface
    temperatures can be achieved for properly designed catalyst-mufflers relative to today's OEM mufflers
    (see Chapter 6).  Most Phase 2-compliant engines already have sufficient cooling-air capacity to manage
    heat rejection  from properly designed catalyst-mufflers, and cooling system designs will be carried or
    improved for Phase 3 engines. Proper catalyst design for minimizing heat load includes the use of catalyst
    designs that minimize of CO oxidation through careful selection of catalyst size, washcoating composition
    and  PGM loading.  Comparisons of surface temperatures between OEM muffler  and catalyst-muffler
    configurations for a broad range of engine families and operational conditions are presented within Chapter
    6.

c.  Muffler temperature increase due to air-to-fuel ratio enleanment caused by calibration drift over time, fuel
    system problems or air filter element mal-maintenance'.  Conditions of richer and leaner air-to-fuel ratios,
    as well as little to no change in air-to-fuel ratio,  have been observed on the engines EPA has tested as they
    have accumulated hours, and can occur whether the engine is equipped with a catalyst-muffler or with
    current OEM muffler designs. Leaner air-to-fuel ratios tend to lead to increased exhaust gas temperatures.
    While exhaust  temperatures would increase regardless of the presence of a catalyst, the  concern  is that
    excessive exhaust system  surface temperatures would occur if the engine operated near or lean of
    stoichiometry due to the increased availability of oxygen in the exhaust for CO oxidation over the catalyst.

    The  only induction system problem that EPA has observed as a consistent cause of lean operation at high
    hours has been a  failure of the seal between the carburetor and intake manifold with one particular family
    of Class  I engine. This particular engine family uses a plastic, tubular intake manifold design without a
    manifold flange onto which the carburetor can directly mount.  Instead, the carburetor seals to the manifold
    tube by deforming an O-ring located between the carburetor, a carburetor support, and the tube.  With this
    design, a flat-spot often wears onto the O-ring over time due to engine vibration and insufficient support of
    the weight of the  carburetor, resulting in an air leak  into the induction system that bypasses the carburetor
    and  causes lean operation.  This was a common occurrence during field aging of lawn mower engines in
    southeast Michigan with three out of four engines from the same  engine family as engine 258 having an
    intake manifold O-ring failure and subsequent induction leak with lean operation.  Some of the engines that
    had  intake-manifold gasket failures in the field were tested by  EPA,  and then sent to an independent
    laboratory for tear-down and inspection.  The engines were at or close to catastrophic mechanical  failure
    (complete inoperability), and in one case the engine could not be started and run on the dynamometer for
    testing.  These engines had:

         1.   Greatly reduced power output (up to 40% lower)

         2.   Very poor load pickup

         3.   Failed head gaskets

         4.   Cylinder head temperatures exceeding 300 C and oil temperatures of 180 to 200 C at high loads

         5.   Greatly increased oil consumption, due to cylinder bore distortion and loss of oil viscosity at high
            temperatures

         6.   Visible smoke coming from the exhaust (see Figure 8-1)

    In the event  of an  induction system failure resulting  in  a severe  manifold  air leak  and lean-of-
    stoichiometric  operation, an increased catalyst exotherm would occur as long as the catalyst is active. Net
    lean operation with an air-cooled engine at above  moderate load conditions would also result in  engine
    damage,  and would likely  result in deactivation of the  catalyst from both thermal sintering and  oil-
    poisoning.   In extreme cases, lean operation and high oil consumption may lead to substrate failure or
    plugging of the monolith which may result in engine  inoperability.
                                                                                                  131

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    Figure 8-1:  Smoke plume at idle from Class I engine with failed intake manifold and head gasket.
    Use of a proper intake manifold design with positive sealing through a flat intake manifold flange, along
    with proper mechanical support of the mass of the carburetor minimizes the likelihood of lean-drift of the
    air-to-fuel ratio over time.   Other engine families tested by EPA that used  more typical flat-flange-
    mounting systems on their intake manifolds or, in some cases, direct mounting of a side-draft carburetor to
    the intake port with no manifold, together with robust carburetor support did not exhibit any significant
    trend towards lean operation at high hours.

    Catalyst deactivation is an emissions compliance issue, engine manufacturers will need to use robust intake
    manifold designs and carburetor supports in order to comply with the Phase 3  emissions regulations to the
    end of the engines'  useful life.  Such designs should reduce or eliminate the occurrence of lean air-to-fuel
    ratio drift, and should improve both the  safety and the durability of Phase 3 engines relative to today's
    Phase 1 and Phase 2 engines.  Another alternative for walk-behind lawn mowers would be to entirely
    prevent operation of a malfunctioning engine via the use of a low cost (<$1.00), serf-resetting bimetal-disk
    thermal switch to shut down the engine's ignition system if a pre-set temperature is exceeded.   Bimetal
    devices are already  commonly used on Class I lawn mower engines to provide automatic choke activation,
    and  are  non-contact devices that  are mounted  directly  behind  the muffler to  sense  exhaust heat.
    Noncontact bimetal shut-off switches are used in a wide variety of consumer products, including portable
    hair-driers, irons, battery-electric lawn mowers, home water heaters and clothes driers.

    The impact of air filter mal-maintenance  on emissions and air-to-fuel ratio has been significantly reduced
    since the advent of the Phase 2 emission standards in the US. The majority of carburetors used with Phase
    2 engines are equipped with float bowl venting that provides compensation for air-filter mal-maintenance.
    Thus changes in carburetor air-inlet restriction are already largely compensated for by design.

d.   Exhaust system leaks:  The hypothesis is that an exhaust leak would allow significant air entrainment into
    the exhaust system upstream of the  catalyst, leading  to increased CO oxidation  and increased catalyst-
    muffler surface temperatures. The layout of existing Class I and Class II exhaust systems would  make the
    occurrence of this phenomenon extremely unlikely. The relatively close coupled exhaust systems used by
    Class I and Class II engines along with the exhaust restriction imposed by the muffler and catalyst would
    cause exhaust leaks out of the exhaust system, but would limit ambient air leakage into the exhaust system
    to a negligible level since the pressure  pulsations in the exhaust are entirely or nearly entirely at a higher
    pressure than ambient.

    Controlled "leakage" of air into exhaust systems is used as a method of providing secondary air for exhaust
    catalyst systems.  Examples include  the  stamped venturi used by European catalyst-mufflers on Class I
    engines (see figure 5-1) and the check-valve pulse-air systems used with some  motorcycle catalyst systems
    and used by automobiles in the 1980s  and early 1990s. It is highly unlikely that an exhaust leak would
    occur in a manner that would produce  the exact shape and exhaust flow restriction necessary for venturi
    induction of air into the exhaust.
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        Pulse-air systems rely on exhaust gas pulsation to just below ambient pressure to draw air into the exhaust
        through a check-valve.  Such systems rely on the fact that exhaust traveling through a long pipe has inertia
        and the flow is compressible.  Between exhaust valve  events, the inertia of the exhaust gases can create
        temporary conditions at which the exhaust gases are below ambient pressure, allowing ambient air to be
        entrained into the  exhaust  system.  While the  pulse-air phenomenon has been used  successfully with
        catalyst systems in numerous automotive and motorcycle applications,  attempts to apply pulse-air systems
        to Class I and Class II engines have not been successful.  Class I  lawn mower mufflers are most often
        mounted directly to the exhaust port, although some are mounted up to 4-inches downstream of the exhaust
        port.  Class II  lawn tractor mufflers are mounted approximately 8-inches to  2-feet downstream of the
        exhaust port. EPA attempted to apply check-valve pulse air systems to both Class I and Class II engines
        during early development of exhaust catalyst systems  in support of the  Phase  3 rule.  With such close
        coupling of the exhaust system, the inertia of the  exhaust gases traveling from the exhaust port and the
        exhaust system upstream of the catalyst-muffler resulted in exhaust pressure that did not fall below ambient
        pressure between exhaust valve closing and opening events, and thus there was no net change in exhaust
        stoichiometry.  Similarly, EPA expects that leakage in these  systems would obey physics and result  in
        exhaust gases traveling from the higher pressures found within the exhaust system to the lower pressures
        found in the ambient without any significant amount of air moving in the opposite direction.

Temperatures above the human skin burn threshold exist with current production OEM mufflers under a broad
range of normal operating conditions. Proper design and layout  of the exhaust system can minimize occurrences  of
touch-burns regardless of whether or not the exhaust system incorporates a catalyst or if a system fault occurs. EPA
demonstrated similar or cooler operating temperatures for properly-designed catalyst-mufflers compared to today's
OEM mufflers (see  Chapter 6).  Catalyst-mufflers equipped with air shrouds and exhaust ejectors in some cases
resulted in systems that were significantly cooler than many current OEM muffler designs.
                                                                                                     133

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Conclusions Based on FMEA of Burn Safety

The  potential  for  increased temperature which  could increase thermal burns was assessed in various engine
subsystems and processes within the FMEA. In the FMEA protocol, if the effect of the potential failure was burn or
increased burn risk the item was given a severity classification of 9. There were 58 items in the  5 FMEAs which
indicated burn or increased burn risk as the potential effect of failure. As can be seen in Table 8-1 below, there was
not a significant change in risk probability for burns in going from a Phase 2 engine to a properly designed Phase 3
system. Overall, 17 items in the five FMEAs indicated the potential for a  small improvement in risk probability,
two indicated the potential for a small degradation, and 39 indicated no change.

Table 8-1: Burns Safety FMEA Summary - Incremental Change from Phase 2 to Phase 3
FMEA Type
Design
Class I:
Class II:
Process
Refueling:
Shutdown/Storage :
Maintenance:
Number of Items with
Burn as the Potential
Effect of Failure
Number with
Potential
Improvement
Number with
No Change
Number with
Potential
Degradation*

19
21
10
7
8
13
1
1

8
5
5
0
0
0
8
5
5
0
0
0
* These two items are discussed in Chapter 7, section G.

SCENARIO 2:  DEBRIS FIRE

Scenario Description: Grass and leaf debris on engine/ equipment

Potential Causes

    a.   muffler surface temperature increases due to debris inhibiting flow of cooling air, debris trapped in tight
        areas blocks air flow, dries out and heats up

    b.   higher temperatures on mower deck or around muffler due to  higher radiant heat load from muffler or
        engine

    c.   muffler temperature increase due to air-to-fuel ratio enleanment caused by calibration drift over time, fuel
        system problems or air filter element mal-maintenance

    d.   exhaust gas leaks increase surface temperatures

    e.   misfueling: use of highly oxygenated fuel such as E85

Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:

    a.   Muffler temperature increases due  to debris inhibiting flow of cooling air, debris trapped in tight areas
        blocks air flow,  dries out and heats up:  As mentioned in the  previous section on touch burns, engines
        equipped with properly-designed catalyst-mufflers  have no greater propensity to trap  debris than those
        equipped with OEM  mufflers,  and have successfully operated to  full useful  life in the field  under
        conditions that included high-debris environments.  Both laboratory and field testing have shown that
        properly designed catalyst-mufflers can achieve comparable, or even  cooler, surface temperatures relative
        to today's OEM  muffler designs. The combination of air shrouding and the use of exhaust ejectors can be
        expected to provide  significant improvements in prevention of debris build-up and debris ignition by
        lowering surface temperatures, lowering exhaust gas outlet temperatures, and improving debris clearance
        over hot exhaust system surfaces.
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    b.  Higher temperatures on mower deck or around muffler due to higher radiant heat load from muffler or
        engine or exhaust system leaks'.  As mentioned in the previous  section on touch burns, EPA laboratory
        testing and field testing  clearly indicates that comparable, or even cooler, surface temperatures  can be
        achieved for properly designed  catalyst-mufflers relative to today's  OEM mufflers (see Chapter  6).
        Systems using forced-air cooling  and exhaust ejectors will actually radiate significantly less onto  mower
        deck surfaces than many existing OEM muffler systems.

    c.  Muffler temperature increase due  to air-to-fuel ratio enleanment caused by calibration drift over time, air
        filter element mal-maintenance, or exhaust system leaks: As mentioned in the previous section on touch
        burns,  air-to-fuel ratio drift can be  largely eliminated via moderate improvements to induction  system
        designs.  Such improvements will be necessary in order to comply with Phase 3 emission standards at full
        useful  life, and  will result in improvements to both engine durability and  safety.  A  low-cost bimetal
        ignition cut-off switch could also  be used for walk-behind lawn mower applications to prevent excessive
        exhaust system surface temperatures in the event of a system failure causing excessively lean operation.

    d.  Exhaust gas leaks increase surface temperatures: As mentioned in the previous section on touch burns,
        the exhaust backpressure and layout of Class I and Class II exhaust systems will result in leaks of exhaust
        gases out of the  system, but not  air into the system.  Thus exhaust leakage cannot appreciably  change
        exhaust stoichiometry, increase CO oxidation, or increase catalyst-muffler temperatures.

    e.  Misfueling: use of highly oxygenated fuel such  as E85:  Misfueling a Phase 3 Class I or Class II engine
        with E85 would most likely result in an engine incapable of starting. While E85 is not yet widely available
        in the  U.S., its use is increasing  in centrally fueled  fleets.  The air-to-fuel of ratio of an engine with a
        similar carburetor calibration to today's Phase 2 engines would be beyond the lean-flammability limit for
        sustaining E85 combustion if the tank were completely filled with E85. Misfueling with a lesser amount of
        E85 would result in anything from no effect at all to lean-misfire or inoperability depending on the ratio
        with which it is blended with gasoline.  A significant degree of lean  misfire would rapidly deactivate the
        catalyst, posing emissions compliance issues but not  necessarily safety issues.  The carburetor calibration
        of Phase 3 engines would likely follow current Phase 2 design practice and would allow engine operation
        on up  to 10% ethanol  in a gasoline blend.  Misfueling  beyond 10% ethanol  would result in leaner than
        normal exhaust  stoichiometry, but  would  not necessarily  result in higher exhaust gas  temperatures.
        Ethanol has a lower net heat of combustion than gasoline, which effectively would "de-rate" engine power
        output. Ethanol also can evaporatively cool the intake charge. Both effects would contribute to lowering
        combustion and exhaust temperatures.

Temperatures capable of causing debris ignition occur under normal operating conditions with current production
OEM mufflers. Proper design and layout of the exhaust system are necessary to minimize occurrences of debris
ignition regardless of whether or not the  exhaust system incorporates a catalyst.  EPA demonstrated similar or
cooler operating  temperatures for  properly-designed  catalyst-mufflers  compared to  today's OEM mufflers.
Catalyst-mufflers  equipped with air-shrouds and exhaust ejectors in some cases resulted in systems  that were
significantly cooler than  many  current OEM muffler designs, and such designs would be expected to decrease,
rather than increase, the incidence ignition of debris. Current OEM designs and EPA testing have demonstrated that
air-shrouding and forced-air cooling can be incorporated into the exhaust system designs in a manner that not only
results in negligible accumulation of debris on hot exhaust system surfaces, but can even assist with clearing debris
from hot exhaust system  surfaces  if proper attention is paid to cooling air velocity and maintaining sufficient gaps
within the shrouding around  the exhaust system. Testing  results for extended  idling  under  dry, high  debris
conditions show that turf surface temperatures rapidly stabilize (under five minutes) and also demonstrate that turf
surface temperatures under and adjacent to lawn tractors equipped with catalyst-muffler can be comparable, or even
cooler than, turf surface temperatures underneath and adjacent to current lawn tractors equipped with OEM mufflers
(see Chapter 6).

Conclusions Based onFMEA of Debris Fire Safety

The potential for increased temperature which could exacerbate the possibility for debris fires was identified as a
potential effect of failure in the Class I and Class II engine  subsystems  and the  refueling and storage/shutdown
                                                                                                       135

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process FMEAs. In the FMEA protocol, if the effect of the potential failure was fire or increased fire risk the item
was given a severity classification of 10 or 9, respectively. There were 23 items in the four FMEAs which indicated
fire or increased fire risk related to debris as the potential effect of failure (e.g., not related to fuel or backfire). As
can be seen in Table  10-2, below, there were not significant changes in risk probability for debris fires in going
from current Phase 2  engines to a properly designed Phase 3 system. Overall, seven items in the four FMEAs
indicated the potential for a small improvement in the risk  probability,  two indicated the potential for a small
degradation, and 14 indicated no change.

Table 8-2:  Debris Fire Safety FMEA Summary - Incremental Change from Phase 2 to Phase 3
FMEA Type



Design
Class I:
Class II:
Process
Refueling:
Shutdown/Storage :
Number of Items with
Debris Fire as the
Potential Effect of
Failure
Number with
Potential
Improvement

Number with
No Change


Number with
Potential
Degradation*


8
8
4
o
5
3
4
1
1

1
6
0
0
1
6
0
0
* These two items are the same as indicated for contact burn since the potential effect was fire or burn. These two
items are discussed in Chapter 7, section G.
SCENARIO 3 FUEL LEAK

Scenario Description: Fires due to fuel leaks on hot surfaces

Potential Causes:

    a.   faulty fuel tank

    b.   faulty fuel line or connection

    c.   tip-over during maintenance

    d.   tip over in operation

    e.   faulty carburetor

    f.   heat affects fuel tank or fuel line integrity



Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:

The faults encountered due to fuel leakage can potentially occur with equal frequency for engines equipped with
current OEM muffler designs or with catalyst-mufflers.  As indicated above, EPA's testing has shown that properly
designed catalyst-muffler systems can achieve comparable, or even cooler, surface temperatures relative to today's
OEM muffler designs.   Additionally, proper catalyst-muffler thermal management as demonstrated in EPA's test
program will result in no significant increase in heat load on fuel system components. Surface temperatures above
the auto-ignition temperature for gasoline occur during normal  operation for engines equipped with both  OEM
mufflers and engines  equipped with catalyst-mufflers;  thus, an equal potential  exists for ignition of fuel on hot
surfaces if a leak or spillage  occurs.    Because the Phase  3 regulations address evaporative and running loss
                                                                                                      136

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emissions, EPA expects that the frequency and severity of fuel leakage and fuel-related fires will be reduced relative
to today's Phase 1 and Phase 2 equipment.  Compliance with Phase 3 standards will require improvements in tank
materials, fuel line materials and fuel line connections, and will reduce the likelihood of failure and/or leakage.
Running loss controls on lawn tractors  will likely require replacement of front-mounted (engine  compartment
mounted) fuel tanks with rear-mounted fuel tanks, moving both refueling operations and spillage in the event of
turn-over into a location that is further away from hot engine components. Phase 3 compliant venting systems also
include cap designs which have the propensity to reduce  fuel loss in the event of tipping of equipment either
inadvertently or during maintenance.  Fuel  leakage  during maintenance and  storage can also be limited to the
quantity of fuel in the  carburetor float-bowl by equipping lawn mowers and lawn tractors with inexpensive, positive
fuel cut-off valves. Fuel cut-off valves are frequently used in consumer lawn-care products.

Conclusions Based on FMEA of Fuel Spills or Leaks

The potential for increased fuel leaks or spills from equipment creating a fire risk was identified as a potential effect
of failure in the Class I and Class II engine subsystems and the maintenance process FMEA. In the FMEA protocol,
if the effect of the potential failure was fire or increased fire risk the item was given a severity classification of 10 or
9, respectively. There  were 16 items in the three FMEAs which indicated fire or increased fire risk related to fuel
spill or leak from equipment as the potential effect of failure. As can be seen in Table 8-3, below, there were modest
positive changes in risk probability for fuel  spill or leak related fires in going from current Phase 2 engines to a
properly designed Phase 3 system.  Overall, eight items in the three FMEAs  indicated the potential for a small
improvement in risk probability, none indicated the potential for degradation, and eight indicated no change.  The
positive  changes  were related  to  improved  fuel tank designs  related  to  fuel  evaporative emission control
requirements.

Table 8-3:  Fuel Leak or Spill Safety FMEA Summary - Incremental Change from Phase 2 to Phase 3
FMEA Type



Design
Class I:
Class II:
Process
Maintenance:
Number of Items with
Fuel-Related Fire as
the Potential Effect of
Failure
Number with
Potential
Improvement

Number with
No Change


Number with
Potential
Degradation


6
7
o
J
2
4
5
0
0

o
J
o
J
0
0
                                                                                                      137

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SCENARIO 4: REFUELING-RELATED

Scenario Description: Fires related to spilled fuel or refueling vapor

Potential Causes:

    a.   fuel spilled on hot surfaces

    b.   spilled fuel evaporates or refueling vapors lead to fire indoors

Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:

EPA field test hot-soak data showed that at the manufacturer's specified minimum two minute refueling point after
engine  shutdown,  exhaust  system surface temperatures for properly designed catalyst-muffler systems were
comparable or cooler than current OEM mufflers.  The field tests also showed that exposed surface temperatures
rapidly decayed to below the autoignition temperature for gasoline after engine shut-down for all of the lawn tractor
and lawn mower configurations tested (see Chapter 6).

Based on CPSC NEISS cases for the five year period of 2000-2004, there was an estimated yearly average of 3,814
emergency room treated thermal burn injuries associated with lawn mowers.  Refueling activities accounted for
approximately 7%  of these injuries. EPA estimates that approximately 1.5 billion refueling events occur per year
for lawn and garden equipment.   While CPSC NEISS  cases involved fires from refueling events, the  relative
infrequency of refueling fires in comparison with the very large number of refueling events demonstrates that fires
from refueling of lawn and garden equipment are relatively infrequent.  The surface temperature data indicates that
the relative infrequency of refueling fires with this equipment is probably due  to surface temperatures rapidly
decreasing to below the minimum gasoline surface ignition temperature  of approximately 280 "C.1  This rapid
decrease in surface temperatures  is  comparable  equivalent between Phase 2  and expected Phase 3  system
configurations (see Chapter 6, section C).

Refueling  of lawn  mowers  or lawn  tractors  in enclosed areas is hazardous  and recommendations against this
practice are included  in equipment owner's  manuals.  EPA's field and laboratory  data  showed  that properly
designed catalyst-muffler systems can achieve comparable, or even cooler, surface temperatures relative to today's
OEM muffler designs.  While refueling in an enclosed area is certainly inadvisable under any circumstances, such
misuse with a Phase 3 lawn mower  or lawn  tractor would not pose  any additional fire  risk beyond the already
considerable risk of this practice with current Phase 1 and Phase 2 equipment.

The required changes to fuel systems that will be necessary for compliance with Phase 3 permeation and  running
loss emissions standards will also reduce the potential for refueling fires for lawn tractors.  Relocation of fuel tanks
from the engine compartment to the rear of lawn tractors will greatly  reduce the likelihood of spilled fuel coming
into contact with hot engine surfaces.

Conclusions Based onFMEA of Refueling-Related Safety

The potential for refueling-related fires where the equipment was involved was identified as a potential effect of
failure in  the refueling process FMEA (see Table 7-6). There were 11 items in the FMEA which  indicated fire
related to  refueling as the potential effect of failure. As can be seen in Table 8-4 below, while fuel evaporative
emission controls present the possibility for  improvement, overall there was no change in risk probability for
refueling-related fires in going from current Phase 2 engines to a properly designed Phase 3 system.
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Table 8-4: Refueling Related Safety FMEA Summary - Incremental Change from Phase 2 to Phase 3
FMEA Type
Process
Refueling:
Number of Items with
Refueling-Related Fire
as the Potential Effect
of Failure
Number with
Potential
Improvement
Number with
No Change
Number with
Potential
Degradation

11
0
11
0
SCENARIO 5: STORAGE AND SHUTDOWN

Scenario Description: Equipment or structure fire when equipment left unattended after use.

Potential Causes:

    a.   ignition of nearby easily combustible materials

    b.   ignition of fuel vapor by pilot light

    c.   ignition of dry debris on deck

    d.   ignition of dry debris in field (lawn tractors)

    e.   ignition of tarp or other cover thrown over equipment

Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:

Surface temperatures during hot soak conditions following engine shut-down were comparable between equipment
tested by EPA with catalyst-mufflers  and with OEM mufflers (see Chapter 6).  Conditions certainly exist under
which combustible materials can be ignited if the equipment is misused, mal-maintained, or stored improperly. The
relative frequency of incidences of this sort should be no different for Phase 3 lawn mowers and lawn tractors than
is the case for current Phase 1 and Phase 2 equipment.  Throwing a tarp over a recently run lawn mower can result
in ignition of the tarp regardless of whether or not the lawn mower is equipped with a catalyst-muffler.

While  it is certainly inadvisable  to store  lawn tractors  and lawn mowers in enclosures with open  flames (e.g.,
storage of equipment in an attached garage near a water heater or furnace), the frequency of ignition of fuel vapor
by pilot lights should be reduced with Phase 3 equipment relative Phase  1 and Phase 2 equipment. This is due to the
reduction in volatile organic compound concentrations in the immediate vicinity of the equipment through the use of
evaporative emissions controls that comply with the Phase 3 emission standards.

Conclusions Based on FMEA of Shutdown and Storage Safety

The potential for  ignition of fuel or other adjacent materials  was assessed  in the shutdown and storage process
FMEA. There were 10 items in the FMEA which  indicated fire or increased  fire risk related to shutdown and
storage (see Table 7-7) as the potential effect of failure. As can be seen in Table 8-5 below, there were no changes
in risk probability for storage  and shutdown related fires in  going from current Phase 2 engines to  a properly
designed Phase 3  system. This is the case because the hot surface cool down profiles for Phase 2 equipment and
properly designed Phase 3 equipment are comparable.
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Table 8-5:  Shutdown and Storage FMEA Safety Summary - Incremental Change from Phase 2 to Phase 3
FMEA Type
Process
Shutdown/Storage :
Number of Items with
Shutdown/Storage Fire
as the Potential Effect
of Failure
Number with
Potential
Improvement
Number with
No Change
Number with
Potential
Degradation

10
0
10
0
SCENARIO 6: IGNITION MISFIRE

Scenario Description: Engine malfunction which results in an ignitable mixture of unburnt fuel and air  in the
muffler.

Potential Causes:

    a.   misfire caused by partial failure in ignition system (single cylinder engines)

    b.   misfire caused by failure in ignition system, particularly complete failure of ignition for one cylinder (2
        cylinder V-twin engines)

    c.   after-fire/backfire caused by engine  run on after ignition shut-down due to failure of the engine flywheel
        brake or carburetor fuel-cut solenoid

Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:

Ignition misfire can rapidly result in catalyst deactivation. Because of this,  EPA predicts that ignition system
improvements that include use of higher output ignition coils and higher-quality ignition wires will be necessary to
ensure compliance with the Phase  3 emission standards.  These improvements will  decrease  the  incidence of
ignition misfire relative to Class  1 and Class 2 equipment.  Still, of the potential failure modes that can  occur,
ignition misfire is the condition of most concern with regards to the use of catalyst-mufflers with Class I lawn
mowers and Class II lawn tractors.  This is the only condition that has been identified that provides both excess fuel
and excess air simultaneously to exhaust system internal surfaces in a proportion that can support combustion.

    a.   Single-cylinder engine misfire: The  design approach taken by EPA to  address ignition misfire with engine
        255  was to divide  the catalyst volume between locations  upstream and  downstream  of secondary air
        entrainment ("pre-catalyst" and "main catalyst").  These changes improved catalyst efficiency relative to
        total catalyst volume, and allowed  a reduction in the amount  of secondary air used.   The reduction in
        secondary air reduced  CO oxidation and reduced surface temperatures during  normal operation.  This
        resulted in surface temperatures below that of the OEM muffler during normal operation,  and allowed
        further engineering  margin for a temperature increase to occur with  the catalyst-muffler during misfire.
        The pre-catalyst was also optimized for relatively  rich operation (similar to 2-stroke catalyst applications)
        and reduced HC emissions upstream of the entrainment of secondary air both during normal operation and
        during misfire.  This allowed the use of a smaller main catalyst downstream of the secondary air. During
        misfire, the smaller, space-velocity limited main catalyst was overwhelmed with reactants, thus reducing
        heat rejection from the  main catalyst during misfire.  A moderate but  manageable increase in temperature
        was  observed for this system, and surface temperatures during misfire were still within 60 C of normal
        operating temperatures  with the standard muffler.  Use of air-shrouding, forced-air cooling of the exhaust
        and use of an exhaust ejector was more than sufficient to counter the impact of misfire on catalyst-muffler
        surface temperatures.    An alternative approach  would be to use a low cost, serf-resetting bimetal-disk
        thermal switch to shut down the engine's ignition system if high temperatures are encountered near exhaust
        system surfaces due to a partial ignition system failure.
                                                                                                      140

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    b.  V-twin ignition misfire:  Conditions exist under which lawn tractors equipped with V-twin engines can
        operate with one cylinder's ignition system completely deactivated and operate in a manner in which the
        failure may not be immediately apparent to  the operator of the equipment.   This is potentially a more
        hazardous condition than could occur with ignition misfire from a single cylinder engine since a full air
        and fuel charge from the deactivated engine cylinder can mix with the hot exhaust gases from the active
        engine cylinder and impinge on hot surfaces within the muffler. A similar degree of misfire with a single
        cylinder engine would result in engine  stalling. One solution would be to divide the exhaust system such
        that there is one small catalyst  substrate for each of the two  cylinders of the V-twin.  This could be
        accomplished with two catalyst mufflers, or with a single catalyst muffler with completely separate flow-
        paths for each cylinder.  In the case of full ignition misfire on  one cylinder, the exhaust gases would
        rapidly cool to below the light-off temperature for HC over the catalyst for the section of the catalyst-
        muffler fed by non-firing cylinder.

    c.  After fire caused by engine run-on after shutdown:  EPA testing demonstrated that a properly designed
        catalyst-muffler can reduce the incidence of after-fire during run-on relative  to a current  OEM muffler
        system (see Chapter 6). Design principles for preventing after-fire flame propagation in mufflers are well
        understood, and can be incorporated into a muffler's baffles and internal passages, and  can be combined
        with spark arresting at the muffler outlet.

Conclusions Based on FMEA of Ignition Misfire

The potential for an increase  in misfire-related phenomena to cause an increase in fires  or burns was assessed as a
potential effect of failure in the Class I and Class II engine subsystems.  In the FMEA protocol, if the effect of the
potential failure was burn, fire or increased fire risk the item was given a severity classification of 9 or 10. There
were four items in the two FMEAs which listed fire or increased burn risk related to misfire as the potential failure
mode. As can be seen  in Table 8-6, below, there were modest positive changes in risk probability for misfire in
going from current Phase 2 engines to a properly designed Phase 3 system.  Overall, three items in the two FMEAs
indicated the potential for a small improvement, none  indicated the potential for degradation, and one indicated no
change.   The positive changes were  related to the expected improvements in the ignition system for a properly
designed Phase 3  system.

Table 8-6: Misfire Safety FMEA Summary - Incremental Change from Phase 2 to Phase 3
FMEA Type
Design
Class I:
Class II:
Number of Items with
Misfire Potential
Failure Mode
Number with
Potential
Improvement
Number with
No Change
Number with
Potential
Degradation

2
2
2
1
0
1
0
0
                                                                                                       141

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 SCENARIO 7: RICH OPERATION

Scenario Description: Fire due to operation with richer than designed air-to-fuel ratio in engine or catalyst.

Potential Causes:

    a.   fuel system degradation such as faulty carburetor, oil consumption or carburetor deposits

    b.   faulty or misapplied choke

    c.   ignition system failure

    d.   air filter element mal-maintenance

    e.   debris blocks catalyst venturi

Conclusions Based on EPA Testing of Phase 2 engines and Phase 3 Prototypes:

Based on EPA testing, the impact of richer air-to-fuel ratios appears to be minimal with respect to exhaust surface
temperatures (figure 6-35) on both OEM muffler and properly  designed catalyst-muffler systems.  This is  not
surprising since during rich operation, exhaust gas oxygen concentrations are low and thus CO oxidation is reduced.
Extremely rich air-to-fuel  ratios could cause after-fire in the muffler at some conditions.  This was not observed in
EPA testing at rich air-to-fuel  ratio conditions for either the OEM muffler or the catalyst-muffler, or in earlier tests
of an engine with a malfunctioning carburetor float valve (engine  #1514)10.  EPA's work with run-on after-fire
suggests that with proper design, flame-arresting can be easily incorporated into catalyst-muffler designs to reduce
the incidence of after-fire for catalyst-mufflers relative to current OEM mufflers. Overly rich air-to-fuel ratios pose
an emissions compliance issue by increasing engine-wear and engine-out emission degradation over time and by
reducing catalyst efficiency by partial deactivation of the  catalyst through coking of catalyst surfaces.  In order to
comply with Phase 3 regulations at engine full useful life, it is expected that manufacturers will eliminate the use of
manual chokes and switch to the use of either automatic chokes or priming bulbs. This has largely occurred already
with Phase 2 Class I engines.

    a.   Fuel system degradation:  This  would be an emissions compliance  issue,  but would not result in  any
        difference in safety for Phase 3 equipment relative to existing Phase 1 and Phase  2 equipment.

    b.   Faulty or misapplied choke:  The resulting overly-rich air-to-fuel ratios pose an emissions compliance
        issue by increasing engine-wear and engine-out emission degradation over time, and by reducing catalyst
        efficiency by  partial  deactivation of the catalyst  through the coking  of catalyst surfaces, but would  not
        result in any  differences in safety for Phase 3  equipment relative to existing Phase 1 and  Phase 2
        equipment. In order  to comply with Phase  3  regulations  at engine  full useful life, it is expected that
        manufactures will eliminate the use of manual chokes and switch to the use of either automatic chokes or
        priming bulbs.  This has largely occurred already with Phase 2 Class I engines.

    c.   Ignition system failure:  Ignition system failure is not related to rich operation. As such, it is covered
        separately under scenario 6.

    d.   Air filter element mal-maintenance: The impact of air-filter mal-maintenance on emissions  and air-to-fuel
        ratio has been significantly reduced since the advent of the Phase 2 emission standards. The majority of
        carburetors used with Phase 2 engines are equipped with float bowl venting that provides compensation for
        a degree air-filter mal-maintenance.  Thus changes in carburetor air-inlet restriction are already largely
        compensated for by design. Extreme blockage of the air filter element resulting in rich operation would
        increase exhaust emissions, but based on EPA test results would not result in any difference in safety for
        Phase 3 equipment relative to existing Phase 1 and Phase 2 equipment.
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    e.   Debris blocks catalyst venturi:  The impact of debris blockage of catalyst venturi would be increased
        emissions and reduced heat rejection at some conditions.  While this would pose an emissions compliance
        issue, EPA would not expect any safety-related impact from venturi air-inlet blockage. The venturi of the
        European catalyst-muffler design (figure 5-1) is located in a low-debris area in its OEM application.  The
        venturi inlet was similarly located in low debris locations in EPA's applications of this basic design to two
        different engine families used with four of the engines in the field operations in  southwest Tennessee
        (engines 244, 245, 246, and 248).  These systems were operated to near the end of useful life and  none
        experienced any significant degree of venturi blockage.

Conclusions Based on FMEA of Rich Operation

Rich operation was identified as a potential safety concern by one organization. Within the Class I  and  Class II
design FMEAs there were  only  five situations identified where a rich mixture could  potentially create  a safety
problem.  In each case, the potential  effect of the failure was backfire.  To some  degree these problems are
redundant with misfire as discussed above.  Rich operation can lead to  other potential failure effects  such  hard
starting, general  degradation of performance, or emissions increases but in no other scenario was there a potential
safety issue identified.

Table 8-7: Backfire Safety FMEA Summary - Incremental Change from Phase 2 to Phase 3
FMEA Type


Design
Class I:
Class II:
Number of Items with Backfire
Potential Failure Mode

Number with
Potential
Improvement
Number
with No
Change
Number with Potential
Degradation


2
3
2
1
0
2
0
0
  American Petroleum Institute, "Ignition Risk of Hydrocarbon Vapors by Hot Surfaces in Open Air", Table 3:
Open Air Ignition Tests Under Normal Wind and Convection Current Conditions, API Publication #2216, January
1991.
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9.  Safety  Analysis of Small SI Engine Evaporative Emissions Control
Technologies

A.      CURRENT TECHNOLOGY

Fuel Evaporative Emissions

EPA intends to propose standards for evaporative emission control requirements for NHH and HH equipment.
Evaporative emissions refer to gasoline vapor lost to the atmosphere from a number of mechanisms including:

    1.   permeation: These emissions occur when fuel vapor works its way through the material used in the fuel
        system. Permeation occurs most commonly through plastic fuel tanks and rubber fuel hoses.

    2.   diurnal: These emissions result from temperature changes throughout the day. As the day gets warmer, the
        fuel temperature increases and the fuel evaporates into the atmosphere.  This is sometimes referred to as
        breathing losses.

    3.   diffusion:  These emissions result from vapor exiting through a vent path to the atmosphere regardless of
        changes in temperature. This occurs due to the vapor concentration gradient between vapor in the tank or
        hose and the outside atmosphere.

    4.   running loss: These emissions are similar to diurnal emissions except that the heating of the fuel is caused
        by engine operation.

    5.   refueling:  These emissions occur when vapors displaced from the fuel tank escape when fuel is dispensed
        into the tank.

    6.   hot  soak:   These emissions occur from hot fuel cooling after engine shutdown. Traditionally they can
        emanate from the fuel tank or the carburetor.

    7.   spillage: These emissions occur when fuel is spilled by the user during refueling events.

The following sections  describe the current technological designs for NHH and HH equipment that will be impacted
by the potential Phase 3 evaporative emissions standards.

NHH Equipment

NHH  equipment refers generally to gasoline-powered equipment that does not require operator support for its
operation.  It can be free standing, such as a pressure  washer or generator, or wheel-based, such as a walk-behind
lawnmower,  a  ride-on  mower, or a cultivator. We are considering fuel tank and fuel hose permeation standards,
diffusion, and running loss control requirements for NHH equipment.

Fuel tanks for NHH equipment are often mounted on or near the engine.  Due to the small  size of the tanks and
equipment, and to aid in stability in typical Class  I applications,  the fuel tanks are  often mounted directly on the
engines.  Tank volumes are normally < 0.5 gallon and are made of either metal or high density polyethylene
(HDPE). Class I applications normally have only one fuel tank. For Class II equipment, it is more common for fuel
tanks to be mounted near the engine on the chassis as opposed to directly on the engine.  For example, some ride-on
mowers mount the  fuel tank in the engine compartment. For  equipment with rear-mounted engines it is not
uncommon to have  the  fuel tank in the rear as well. Tank volumes are  normally > 1.5 gallons and it is common to
have two higher capacity (>  5 gallon) dual tanks on larger commercial equipment.   Class II equipment tanks are
normally made of injection or blow-molded HDPE or rotomolded cross link polyethylene (XLPE).
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Generally, the fuel  systems  on Class I and Class II equipment have no rollover valves or other mechanisms to
prevent fuel from spilling on the engine or equipment when the equipment is tipped on its side or turned over.
Some tanks use tortuous venting paths in the fuel caps, which also restrict fuel flow, but others simply use holes in
the fuel caps for venting which would also allow fuel to spill out of the tanks at higher flow rates.  Fuel tank caps
are primarily made of plastic and typically do not have  a tether to prevent loss of the cap. Running loss emissions
from fuel tank heating during operation are typically vented through the fuel cap.

NHH equipment uses a variety of fuel hose constructions.  They may be extruded rubber hose meeting SAE J30R7
requirements or they may use a multi-layer hose such as would meet SAE J30R9. Typical materials used are nitrile
rubber, and in some cases, fluoroelastomers.

HH Equipment

HH equipment refers  generally to gasoline-powered tools that are supported by the user during operation.  This
category includes chainsaws, string trimmers,  leaf blowers, and other similar equipment.  EPA is considering fuel
hose and fuel tank permeation standards and diffusion control requirements for HH equipment.

Fuel tanks on HH equipment are typically molded out of either nylon or polyethylene. Most of these tanks are < 0.5
gallons in capacity and in some cases much less. With some equipment, instead of a tank being attached as part of
the overall equipment assembly, the fuel tank is structurally integrated into the body of the equipment. This design
approach is used in common applications such as chainsaws, hedge trimmers, and brush cutters.  This construction
helps to provide structural strength to the equipment and results in the fuel tank being molded out of the same
material as the rest of the body.  In these cases, nylon is typically used due to the favorable heat resistance and
stiffness characteristics it offers. The fuel tanks used in HH equipment may either be vented to the atmosphere or
they may be sealed.  Manufacturers  often seal the fuel tanks to prevent spillage during use.  This is especially
common on tools such as chainsaws where the equipment is regularly turned over during normal use.

HH equipment uses a variety of fuel hose constructions. They may be extruded rubber hose or may be molded into
custom forms.  Typical materials used  are nitrile  rubber, polyurethane, polyvinyl chloride, and in some cases,
fluoroelastomers. According to the Outdoor Power Equipment Institute, the vast majority  of HH equipment has
total fuel hose lengths of less than 15 cm.

B. CURRENT SAFETY STANDARDS

The current safety standards for NHH equipment are discussed in Chapter 3. At this point there are no mandatory or
general industry consensus standards related to  safety practices or standards  for fuel tanks or fuel hoses used in
NHH or HH equipment.  One exception to this is UL 1602 which does present guidelines for the construction of
gasoline-powered edgers.

Although industry wide standards are not used, extensive product qualification and durability testing is performed.
According to industry sources, manufacturers typically soak tanks at an elevated temperature on various fuels to test
for fuel compatibility.  In addition, most manufacturers  perform impact tests on their fuel tanks.  Impact tests vary
by manufacturer and can be performed using drop testing, pendulum swung hammers, or sharp point impact. Other
procedures that manufacturers have stated that they use for evaluating fuel tank durability include pressure tests and
vibration tests.
Most NHH equipment use hose meeting SAE J30 R7 standards.  As discussed below, these standards include a long
list of durability tests.  One engine and equipment manufacturer that does not use hose labeled as SAE J30 R7 stated
that they use similar pliability and durability tests as are in the SAE recommended practice. In addition, they test for
abrasion resistance and the minimum load required for pulling the hose off of a fitting. They stated that they use the
hose pull of load specified in ANSI B71.3.   Although this standard is intended for snow throwers, the pull off
requirement can be applied to other applications.
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HH equipment manufacturers typically use fuel hoses made of polyurethane, nitrile rubber, or polyvinyl chloride.
For edgers, the hose  must meet a number of durability requirements according to UL 1602.  These durability
requirements include  ultraviolet light exposure, dry  heat aging,  fuel resistance, and low temperature flexibility.
Industry sources have stated that they also perform heat resistance testing and pull off testing on this hose and use
the same  fuel hose for the rest of their  equipment.  HH equipment manufacturers also use molded nitrile or
fluoroelastomer hoses on some of their equipment. Industry sources stated that they perform a number of durability
tests on these hoses  as well which include  fuel resistance, a pull off load requirement,  heat  resistance, cold
temperature flexibility, and vibration resistance.

ASTM also provides guidance for hose durability testing. ASTM D1149 provides test procedures for determining
cracking in the hose that may occur from ozone exposure.  ASTM D471  describes test procedures for determining
the resistance of rubber products to a number of test fuels. ASTM D380 references these test methods and describes
several additional durability tests for fuel hose. These additional tests include tensile strength, elongation, adhesion,
pressure tests, low temperature exposure, tension, and hot air aging. One  equipment manufacturer specifically
stated that they use these test procedures. In addition,  all of these ASTM test methods are referenced in SAE J30.

In addition to the above testing, manufacturers often operate the equipment in the field for extended periods of time
to evaluate durability.  Among other things, these  evaluations give manufacturers the ability  to evaluate the
performance of the fuel tanks, hose,  and connections.   The use of these durability tests can affect safety in that
manufacturers are able to look for defects that may lead to fuel leaks in the field.

Industry sources have also stated  that they test for fuel  overflow on their NHH equipment.  These sources have
referenced ANSI standards  B17.1 for lawnmowers, B17.3  for  snow throwers, and B17.4  for commercial turf
equipment.  These standards basically require that there be a shield or other method to prevent any fuel  overfill
during refueling from  spilling onto an ignition source such as the muffler or non-insulated electrical wire.
C. IN-USE SAFETY EXPERIENCE

As discussed in earlier chapters, assessing incremental risk requires an understanding of the problems and in-use
safety experience with current products. For this analysis we used data from CPSC's website regarding NHH and
HH  equipment.  The CPSC website publishes Recalls and Product Safety  News,  where  manufacturers, in
cooperation with CPSC, voluntarily recall products that pose a safety hazard to consumers. Recall notices published
during the period of January 2000 to December 2004 were reviewed. Our analysis focused only on incidences that
were relevant to the fuel systems that may be affected by potential Phase 3 emission standards.

NHH Equipment

The  in-use safety discussion for NHH equipment in Chapter 3  includes issues related to potential evaporative
emission control technology.  During the period of January 2000 to December 2004, there were a total of 22 lawn
mowers or lawn mower engines recalls due to safety issues related to thermal burn injuries. These 22 recall notices
affected approximately 850,000 lawn mower units. In the same time period, CPSC reported 11 recalls for fuel tank
leaks and five recalls for fuel line leaks.  Chapter 3 presents CPSC Injury/Potential Injury Incident File and In-
Depth Investigations  related to lawn mower fuel leak incidents.

HH Equipment

In reviewing the CPSC Recall website, EPA reviewed recalls related to gasoline-powered HH equipment such as
blowers, trimmers, edgers,  chainsaws,  augers, and brush cutters.  From 2000 to 2004,  EPA identified 11 recalls
categorized as fire/burn hazards. Of these 11 recall actions, three were associated with potential fuel leakage from
hoses, seven were associated with potential fuel leakage from tanks, and one was related to flames in the engine
exhaust.  These 11 recall actions included more than 80 percent of the HH equipment recalled in that time period.

EPA recognizes that  a list of voluntary recalls does not provide details on injuries associated with fires and burns.
However, as shown  with NHH equipment  in Chapter 3,  recall notices do provide  a good indication of what the
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safety issues are for a given class of equipment. Based on this, our analysis of incremental risk should focus on fire
and burn hazards related to fuel leaks and spills arising from the use of technology to control fuel hose or fuel tank
permeation emissions.

D. EMISSION CONTROL SYSTEM DESIGN AND SAFETY

NHH Equipment

We are considering evaporative emission standards for Small SI engines in the Class I and Class II subcategories.
These standards include the control of the permeation of fuel vapors through nonmetallic fuel system components,
such as rubber fuel hoses and plastic fuel tanks, and the  control of fuel vapor vented out of the fuel system.  This
section discusses the various evaporative emission control approaches under consideration and what impacts these
control strategies may have on safety. When evaluating potential safety impacts of evaporative emission control, we
considered primarily the chance of a fuel hose or  fuel tank liquid leak or a combustible fuel vapor reaching an
ignition source, such as a hot exhaust  system, when the engine is in use.  Thus component durability is a key issue.

Fuel hoses

Most NHH equipment uses rubber hose for delivering gasoline from the fuel tank to the engine. The typical fuel
hose construction is a nitrile rubber hose with a protective cover for abrasion resistance.   To meet the fuel hose
permeation standards under consideration, manufacturers would be able to use this hose construction except that an
additional barrier layer would need to be added to minimize permeation fuel through the hose material. A typical
barrier material would  likely be a fluoroelastomer  or fluoroplastic material.  Barrier hose constructions are used
widely in automotive applications and even on some Class II engines. The lines used today typically meet SAE and
ASTM standards; in most  cases fuel  hose meeting the SAE J30R7 is used.  In addition, manufacturers  commonly
specify minimum  loads to pull  their fuel  hose off of the connecting  barbs.   One  example of a published
recommended minimum pull off load  is 10 Ibs specified in ANSI B71.3.

Fuel hose under the SAE J30 R7 rating must pass a number of tests designed to measure the durability of the hose.
These  tests include  a burst pressure, tensile strength and elongation,  dry  heat resistance, oil resistance, ozone
resistance, kink resistance, and several fuel exposure  tests.  The fuel resistance tests include repeating most of the
above tests after soaking the hose with both ASTM fuel Cf and a test fuel made up of 85 percent ASTM fuel D
blended with 15 percent ethanol. In addition, to test for "sour fuel" resistance, the hose is tested for tensile strength
and elongation after being exposed to a test fuel made up of ASTM Fuel B and sufficient t-butyl hydroperoxide to
achieve a specified peroxide level.  Finally, the hose is tested for permeation on ASTM fuel C. In addition, the SAE
requirements  include an adhesion test which sets  a minimum load required to separate the tube from the protective
cover

EPA's fuel hose permeation requirements must be met using EPA test procedures. However, past testing indicates
that many hoses meeting the  SAE J30 R9, R11A,  or R12  requirements will meet EPA permeation requirements.
Hoses meeting R9 or better specifications would also have to meet all other durability requirements associated with
the SAE J30 standard as described in  the preceding paragraph.  Barrier hoses constructed  today are generally higher
quality hose that also have better temperature resistance than non-barrier hose. For instance, SAE J30 R9 hose must
meet a dry heat resistance test based on 150C heat aging compared to 125C for R7 hose.  According to one hose
manufacturer, heat resistance is primarily a function of the cover material rather than the permeation barrier material
itself. This should directionally address current concerns related to fuel lines droping under radiant load.

Furthermore,  the barrier materials are  made of rubber compounds that are resistant to permeation by gasoline,
including ethanol blends and oxidized ("sour") gasoline. This fuel resistance not only  protects against chemical
attack, but also limits swelling due to the permeation of fuel.  By limiting the swelling and  contracting  (drying)
cycles and chemical attacks that may cause the hose to become brittle, the hose may resist cracking as well.  Finally,
the barrier layers are thin and are  not expected to lead to any significant differences  in hose flexibility or ability to
retain connections  within the fuel system. Based on the rigorous nature of the SAE testing requirements and the
f These ASTM fuels are blends of isooctane/toluene: B=70%/30%, C=50%/50%, D=60%/40%.
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essentially universal use of hoses meeting SAE specification in NHH applications, we expect no increase in fuel
hose leaks associated with the use of low permeation fuel hose relative to current fuel hose. The hose which would
be used is commercially available today.

Fuel tanks

Fuel tanks  on NHH equipment are usually constructed of HDPE through a blow molding or injection molding
process. There are still a few models, some with very high sales, using metal tanks.   Some  of the larger NHH
equipment, such as commercial turf care equipment, uses fuel  tanks constructed  of XLPE.  XLPE  is thermoset
which means that that a reaction takes place in the plastic during molding (at an  engineered temperature) which
creates the cross-link structure.  HDPE and XLPE have poor fuel permeation resistance characteristics while metal
tanks do not permeate. There are several technological approaches that can be used to reduce gasoline permeation
through plastic fuel tanks (HDPE and XLPE).  These approaches include surface treatments, barrier constructions,
and alternative materials.

Surface treatments, such as fluorination and sulfonation, could be used to meet the standard that EPA is considering.
These treatments are performed as a secondary step after the fuel  tank is molded;  both create a  thin layer on the
inner or outer surfaces of the fuel tank that acts as a barrier to permeation.  In fluorination, a barrier is created on
both the inner and outer surfaces while in sulfonation, it is created only on the inner surface.  These treatments do
not materially change the construction of the fuel tank and are not expected to affect the durability of the fuel tanks
because the barrier is not thicker than 20 microns thick and does  not affect the tank  wall material which is typically
3-6 mm thick.  These approaches are both used to meet the  current California gasoline permeation standards for
portable fuel cans.

Multi-layer fuel tank constructions which create a barrier to permeation have been used in automotive applications
for many years. The most common approach is to mold a thin layer of ethyl vinyl alcohol (EVOH) inside a HDPE
shell. This approach is commonly used  in high production volume, blow-molded  fuel tanks but  could be  used in
lower production volumes through a molding process known as thermoforming.  Another approach available for
blow-molded fuel tanks is to blend a small amount of EVOH  directly into the HDPE. During molding, the EVOH
creates non-continuous overlapping barrier platelets which restrict permeation.  For each of these  technologies, the
barrier material is only a small percentage of the total makeup  of the fuel tank.  In addition, adhesion layers are used
between the barrier and the HDPE shell to prevent the layers from pulling apart. These  technologies have the
advantage of having been in use for many years and having been demonstrated in automotive and other applications
with no safety issues.  Automotive manufacturers require the fuel  tanks to  meet wide range of durability tests on
these fuel tanks including fuel exposure, flame tests, and low temperature drop impact tests.

Rotationally molded XLPE tanks would use one of several techniques to reduce permeation. In the first technique
nylon, which has good permeability properties, is applied as an inner shell inside the fuel tank. The manufacturer
has demonstrated that the nylon has an excellent bond with the XLPE.: As a result  of this bond and the strength of
the nylon, this construction offers strong resistance to impact.  Testing at Imanna  Laboratory, Inc. showed that a
tank of this construction met the United States Coast Guard (USCG) durability requirements described in chapter 10
which include impact testing and flame resistance.2 Another new approach for XLPE tanks is to coat the tank with
a low permeation epoxy in a secondary step after molding.   This approach does  not change the basic fuel tank
construction but only adds an outer layer similar  in thickness as a coat of paint.  A third approach  for reducing
permeation would be  to  rotomold the  fuel tanks out of lower  permeation materials such as nylons, acetal
copolymers, or thermoplastic polyesters.  Materials  manufacturers  have been working for years on engineered
plastics that are compatible with the molding processes and design requirements of today's fuel tanks.

In the case where manufacturers make any changes to their fuel tanks, such as materials or geometry, they  must
evaluate the effect of these changes on their product.  There are no standard procedures for evaluating the safety
characteristics of these fuel tanks. Each vendor  or manufacturer has developed  their own tests to  ensure
performance.  Examples of these durability  tests  include impact testing, temperature testing, and fuel exposure
testing.  It should be noted that EPA's permeation test procedures (contained in 40  CFR 1051.515) incorporate test
requirements which will help to ensure the in-use  integrity of these tanks.  Current requirements  include extended
time of fuel soak in a 10  percent ethanol/gasoline blend,  slosh testing, pressure-vacuum cycling, and prolonged
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exposure to ultraviolet light. Because there are not set industry standards for durability testing of fuel tanks, it may
be helpful to consider additional tests which could address emissions durability such as high and low temperature
cycling.

In none of these three  approaches (surface treatment, barrier construction, and alternative materials) would EPA
expect there to be an adverse incremental impact on safety.  Surface treatments and barrier construction are used in
portable and installed fuel tanks today.  The choice of proper materials and construction durability is important and
we believe that the manufacturer specific test procedures and production audits and EPA requirements are sufficient
to ensure that there will be no increase in the types of fuel leaks that lead to fire and burn risk in use. There is also
the potential for at  least a directional improvement in safety  in  Phase 3 standards  associated with reducing
permeation of fuel vapor from the equipment in a closed space such as a shed or garage.

Running Loss

We are also considering several approaches to reducing the evaporative emissions associated with direct venting of
fuel  vapors  from the fuel tank.  We focus primarily on running loss venting emissions.  When  equipment is
operating, the fuel is heated by the engine, the exhaust system, and possibly the hydraulic system.  We  are
considering two primary approaches to controlling running loss venting emissions.

First, the equipment could be designed to minimize heat reaching the fuel tank.  This  could be achieved through
heat shielding, changing from metal to plastic tanks, or by relocating the fuel tank further from heat sources. In the
case of Class I equipment, the fuel tank could be moved away from the muffler to the opposite side  of the engine
block. On Class II  equipment,  there would be more room on the  equipment to move the tank away from heat
sources such as the engine or exhaust system.  Overall, EPA expects this would be the preferred approach since it
would be the least expensive way to comply with the test procedures and emissions standards under consideration.
If the fuel tank is moved away from heat sources, the likelihood  of fuel spilling on a hot surface during refueling
would also be reduced.  Heat shielding and changing tank material would  also reduce heat getting to the fuel.
Changing from metal to plastic tanks where practical would also substantially reduce running loss emissions and the
overall hot surface area.

The  second approach to controlling running loss emissions would be to route the vapor to the engine intake to be
burned by the engine.  A restriction would need to  be  placed in the vent line to the engine to keep  the  engine
manifold vacuum from drawing too  much vapor from the  fuel tank.  This restriction could be in the form of a
limited flow  orifice  or a valve.  This would have the additional benefit of acting as a rollover valve since  the
limiting orifice or valve restricting vapor flow would  inhibit fuel flow from the tank if the equipment was inverted.
Even without moving the fuel tank, the equipment could be designed to prevent fuel spillage during refueling from
reaching hot surfaces that could ignite the fuel. As discussed above,  some manufacturers design their equipment to
prevent fuel overfill from reaching these hot surfaces consistent with ANSI B71.1, B71.3, and B71.4.

To control diffusion-related venting emissions, manufacturers could make use of fuel caps with no venting or with
venting through a tortuous path.  These caps, which are used in some applications today, would reduce fuel spillage
when the equipment is turned over or even due to sloshing in the fuel tank.  The chance of a fuel cap being lost
could be reduced with a tether which could reduce the chance of fuel spillage due to open or improperly plugged fill
necks. We would expect to accomplish this type of control as part of our running loss control requirements.

Conclusion

NHH equipment is capable  of achieving reductions in fuel tank  permeation, fuel hose permeation, and fuel tank
vapor venting emissions without an adverse incremental impact on safety.

For fuel hoses and fuel tanks the applicable consensus standards, manufacturer specific test procedures and EPA
requirements are sufficient to ensure that there will be no increase  in the types of fuel leaks that lead to fire and burn
risk in use. The running loss control program being considered by EPA will create requirements that will reduce risk
of fire in use.  Moving fuel tanks away from heat sources, improving cap designs to limit leakage on tip over, and
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requiring a tethered cap will all help to eliminate conditions which lead to in-use problems related to fuel leaks and
spillage.

Furthermore, reductions in permeation emissions and the techniques for reducing running loss emissions are likely
to have a salutary impact on the overall safety  of NHH systems. The  evaporative emission standards under
consideration would  lead to significant reductions in fuel vapor emitted  to the atmosphere.   This  is especially
important in closed spaces because evaporative emissions occur regardless of whether the equipment is operated
(i.e. a piece of equipment stored in a shed with fuel in the tank continues to permeate and vent fuel vapor into the
shed); such controls could prevent vapor concentrations in closed spaces from becoming high enough for the vapor
to reach a flammable mixture.   Exposing the fuel  tank  to less  heat may also reduce  post shutdown hot soak
emissions from the tank.

HH Equipment

We are considering fuel hose and fuel  tank permeation emission standards for HH  equipment.   The standards and
test procedures would be similar to those discussed above for NHH engines.

Fuel Hose

For the most part there are  no significant differences in the fuel hose related safety issues for NHH and HH engines
and equipment. Although somewhat different constructions are used today,  manufacturers perform many durability
tests on HH hose as well.  These tests are described above. HH equipment manufacturers can make use of the same
low permeation hose  materials and constructions described above for NHH equipment. These low permeation hose
constructions use a fluoroelastomer or fluoroplastic material as a barrier.  Alternatively, the entire fuel hose could be
molded from a fluoroelastomer.

In some  applications, molded fuel hoses are used rather than simple extruded fuel hose.  These fuel hoses are
typically either molded out of  nitrile rubber or a fluoroelastomer.   Fluoroelastomers  are  essentially  rubber
impregnated with fluorine which  results in good fuel permeation resistance.  Manufacturers of equipment that may
be used in cold weather have stated that they must use  nitrile rubber because the fluorelastomer material may
become brittle at very low temperatures. While they have presented data supporting this claim, it was based on a
fluoroelastomer without a low temperature additive package. Fluoroelastomers used in automotive applications use
low temperature additive packages and are designed for strength at temperatures as low as -40C.  In addition, at
least one snowmobile manufacturer has recently begun using a low temperature fluoroelastomer for its fuel system
seals. Fuel hose meeting SAE and ASTM standards is available today which meets a widespread set of safety and
durability requirements.

Manufacturers have claimed that barrier hoses are stiffer and may not hold on to hose connections as well as nitrile
rubber hose. The barriers used in low permeation hose are thin and, in our evaluation, barrier hose is not noticeably
different in stiffness than nitrile hose and fits well over typical hose barbs used today.  If a manufacturer felt it was
necessary, there is a wide range of fuel  hose clamps available today.

Manufacturers have indicated that they  would perform durability testing on any new hose constructions they were to
use.   These tests are described  above.  In addition, manufacturers  have stated  that they  would  test the low
permeation hose on their equipment under field testing.   Based on these practices and the properties  of the low
permeation materials  discussed above,  the low permeation fuel hose requirements being considered by EPA would
not lead to an increase in fuel leaks or risk of fire or burn in use.

Fuel Tanks

Most fuel tanks on HH equipment are made of HDPE.   EPA expects emission reductions would be achieved
through the  surface treatments or barrier technologies identified  for NHH equipment and that the in-use safety
experience would be similar.  The surface treatments described  above were fluorination and sulfonation.  The
barrier treatments described above included a thin EVOH barrier layer within  a HDPE shell and non-continuous
barrier platelets created by blending the EVOH into the HDPE prior to molding.  As discussed  above, the  surface
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treatments do not change the construction of the fuel tank but only put a microscopic barrier on the outer surface.
The barrier technologies only make up a small fraction of the total material of the fuel tank and have been long
demonstrated in automotive and other applications.

Manufacturers of equipment with structurally integrated fuel tanks have stated that they must use nylon because of
its structural qualities.  An additional advantage  of  nylon is that it has lower permeation  rates than HDPE.
However, on test fuel containing ethanol, the permeation rate through nylon fuel tanks is still slightly higher than
the permeation  standard  under consideration.    Under  the  program  we are  considering, EPA  expects that
manufacturers using nylon in their structurally integrated tanks will be able to continue to do so. Thus, EPA expects
there will be no change and thus no  increase in risk.

Conclusion

HH equipment is capable of achieving reductions  in fuel tank permeation and fuel  hose permeation without  an
adverse  incremental impact  on safety.  For fuel hoses  and fuel tanks the applicable consensus standards,
manufacturer specific test procedures and EPA requirements are sufficient to ensure that there will be no increase in
the types of fuel  leaks that lead to fire and burn risk in use. The evaporative emission standards under consideration
would lead to significant reductions in fuel vapor emitted to the atmosphere. This is especially important  in closed
spaces because evaporative emissions occur regardless of whether the equipment is operated; such controls could
prevent vapor concentrations in closed spaces from becoming high enough for the  vapor to reach a flammable
mixture.

E. CONCLUSION

EPA has reviewed the  fuel hose and fuel tank characteristics for NHH and HH equipment and evaluated control
technology which could be used to reduce evaporative emissions from these two subcategories.  This equipment is
capable of achieving reductions in fuel tank and fuel hose permeation without an adverse incremental impact  on
safety. For fuel hoses and fuel tanks, the applicable consensus standards, manufacturer specific test procedures and
EPA requirements are sufficient to ensure that there will be no increase in the types of fuel leaks that lead to fire and
burn risk in use.   Instead, these standards will reduce vapor emissions both during operation and in storage.  That
reduction, coupled with some expected equipment redesign, is expected to lead to reductions in the risk of fire or
burn without affecting  component durability.  Additionally, the running loss control program being considered by
EPA for NHH equipment will lead to changes that are expected to  reduce risk of fire in use. Moving fuel tanks
away  from heat  sources, improving cap designs to  limit leakage on tip over, and requiring a tethered cap will  all
help to eliminate conditions which lead to in-use  problems related to fuel leaks and spillage.  Therefore,  EPA
believes that the application of emission control  technology to reduce  evaporative emissions from these two
subcategories will not lead to an increase in incremental risk of fires or burns and in some cases is likely to at least
directionally reduce such risks.
1   O'Brien, G., Partridge, R., Clay, B., "New Materials and Multi-Layer Rotomolding Technology  for Higher
Barrier Performance Rotomolded Tanks," Atofina Chemicals, 2004, Docket EPA-HQ-OAR-2004-0008-0044.
2  Partridge, R., "Petro-Seal for Ultra-low Fuel Permeation; Evaporative EPA Emissions from Boat Fuel Systems,"
Arkema, Presentation at the 2004 International Boatbuilders' Exhibition and Conference, October 25, 2004, Docket
EPA-HQ-OAR-2004-0008-0252.
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10. Safety Analysis for Marine  SI
This section gives an overview of Marine SI engines and vessels that may be impacted by further exhaust and
evaporative emission control requirements. It also provides the technical basis and analysis for our assessment of
the incremental impact on safety of potential marine SI exhaust and fuel evaporative emission standards

A. CURRENT TECHNOLOGY
Marine Engines

Marine SI engines are typically grouped into the following categories:

    1.   Outboards (OB).  These  are engines mounted  on the stern of a boat with the entire  engine  and drive
        assembly external to the hull.  Outboards range in power from less than 2 horsepower (hp) to more than
        250 hp.  More than half of the Outboards sold in the US are less than 50 hp.

    2.   Personal watercraft (PWC). These vessels are  generally intended for 1-3 riders where the riders sit (or
        stand) on top of the vessel with their legs straddling it. Examples of PWC include Jet skis, Wave runners
        and Sea Doo watercraft. Traditional PWC sold today are all above 50 hp, but some lower power specialty
        applications, such as motorized surfboards, fall into this category as well.

    3.   Sterndrives and  Inboards (SD/I).   These engines are typically built by adding  marine  components to
        automotive engine blocks and range in power from about 130 hp to  more than 1000 hp.  A stern drive
        engine (also known as an inboard/outboard) is mounted in the stern of the boat and has a direct drive
        through the hull similar to an outboard drive. An inboard engine is generally mounted in the center or rear
        of the vessel and the engine is linked to the propeller by a drive shaft.

    4.   Marine auxiliary engines. These are small engines used on boats for auxiliary power.  Although they are
        currently categorized  as Class I  NHH engines (and in  some  cases Class II NHH engines), they have
        features that are unique to marine applications.   Specifically, they make use of their environment to water-
        cool the engine and water-jacket the exhaust.

This study focuses on engines less than 50 hp. For this reason we only include OB, PWC, and marine generator sets
in the following discussion.

To meet existing emission standards, OB and PWC manufacturers are converting much of their product mix from
traditional crankcase scavenged carbureted two-stroke engines to either four-stroke engines or two-stroke direct
injection engines.  Smaller four-stroke engines (<25  hp) are  anticipated to continue to  use carburetion; however,
electronic fuel injection is becoming popular on larger engines.

PWCs have  a fuel tank integrated into the vessel/engine structure and all is sold as a unit. OB engines are self
contained power units but typically do  not have an attached fuel tank.  Either a portable fuel tank is used with the
engine (mostly for smaller engines) or the engine is connected to a fuel tank in the vessel that  is permanently
installed by the boat builder.

As stated above, engines used in marine generator sets are water cooled with water-jacketed exhaust. The purpose
of the water-jacketing is  to maintain low  surface temperatures to minimize exhaust system temperatures.  These
engines are often packaged in small compartments on boats and could overheat if they relied solely on ambient air
for the  cooling  system.   Two engine manufacturers   currently dominate  this niche  market.  Recently, both
manufacturers have introduced models  with electronic fuel injection  and catalysts in the exhaust system and have
stated their intentions to convert to catalyzed engines in the near future. Catalyst technology has been driven by the
desire to reduce  carbon monoxide emissions.  Known carbon monoxide poisonings have been disproportionately
high among boats with generators compared to other vessels.
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Marine Vessel Fuel Systems

The marine vessels under consideration here include those powered by OB and PWC engines. The marine industry
has both mandatory and voluntary standards for boat construction (discussed below) which include requirements for
fuel system components such as fuel hoses and fuel tanks.

Vessels powered with OB engines use both portable and installed tanks. Portable marine fuel tanks, which are used
primarily with small OB engines, are normally 5-6 gallons. They are normally designed of blow-molded HDPE.
They are designed with a quick connect fitting for the fuel hose which closes and seals the system when not in use.
Outboard vessels with installed fuel tanks primarily use roto-molded XLPE fuel tanks.  However, fuel tanks made
of aluminum or fiberglass are also used, primarily on larger vessels.  These tanks range in capacity from 12 gallons
to well over 100 gallons. Outboard vessels with installed tanks generally follow the recommended industry practice
of venting the fuel tank though a hose which extends to the outside of the hull.  Thus diurnal emissions  are
uncontrolled.

Fuel tanks used on PWC are  installed by the vessel manufacturer.  They range in size  from 4-18 gallons  and are
usually constructed of blow-molded HDPE. Fuel  tanks on PWC are sealed with pressure relief valves so there are
low diurnal emissions. The purpose of sealing the fuel tank is to prevent fuel spillage into the water during use.

Fuel hoses include those carrying liquid fuel as well as those carrying fuel vapor. OB engines employ fuel hoses on
the engine and come with a fuel hose to be connected to the portable or the installed fuel tank. For those OB  engines
with installed fuel tanks, there is a fuel fill hose  through which gasoline enters the fuel tank and another smaller
diameter hose used to vent the fuel tank. Fuel hose is generally constructed of polyvinyl chloride or nitrile rubber
with an abrasion-resistant cover and often a braid or wire reinforcement.  The fuel, vent, and fill neck hoses  can
range from only a few feet in length to dozens of feet in length depending on the size of the vessel, the location of
the fuel tank and engine,  and the location of the  tank vents and fill  caps. For portable fuel tanks, the  hose is
generally about 6 feet in length and includes quick connections at both ends and a rubber primer bulb in the middle.
Portable fuel tanks vent through a fuel cap mounted directly on the fuel tank so there is no vent hose.

PWC come with a fully installed fuel system. The  fuel hoses include those used to route fuel to the engine as well as
those used to draw fuel from the installed fuel tank.  These tanks are normally top fill so there is no appreciable fuel
fill neck involved.

B. IN-USE SAFETY EXPERIENCE

As discussed in earlier chapters,  assessing incremental risk requires an understanding of the problems and in-use
safety experience with current products.  For this  analysis we used data available on the USCG website for marine
vessels. Presented below are  incidences that are relevant to the engine/equipment subsystems that may be affected
by our emission standards.
Marine Engines and Vessels

The  USCG website (www.uscgboating.org)  includes  boating  statistics  developed from  the  recreational  boat
numbering and casualty reporting systems.  The most recent publication on these statistics is "Boating Statistics -
2004" which includes a five year summary of boating accidents.  The table 10-1 presents boating accidents related
to fuel fires.
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                      Table 10-1: Coast Guard Five Year Summary of Fuel Related Fires
Type of Accident
Fire or Explosion of Fuel



Year
2004
2003
2002
2001
2000
Incidences
162
142
160
153
183
Fatalities
4
7
4
2
2
Injuries
158
68
82
73
93
The  above statistics  only  include incidences  that are reported to USCG under 33 CFR  173.55.  Because  this
regulation places minimum thresholds on property  damage  or treatment requirements,  incidences may  go
unreported.  Additionally, the USCG report does not provide any more detail on the causes of the fuel related fires.
Even looking into the incidence reports, details are  not generally given on  the source of the fuel or fuel vapor
leading to the fire or explosion.  In many of the incidence reports the operator stated that they had just started their
engine when the fire started. Recommended  practice is to run a blower to remove fuel vapor from the engine
compartment prior to starting the engine.  The purpose of this is to remove fuel vapor that could be a fire hazard.
This fuel vapor may come from fuel spillage, leaks in the fuel system, and/or permeation through plastic tanks  and
rubber hoses.

C. CURRENT SAFETY STANDARDS

The marine industry is regulated for safety primarily by USCG.  In addition, USCG standards are supplemented by
voluntary standards created by the American Boat and Yacht Council (ABYC) Reference is also made to SAE  and
Underwriters Laboratories tests and standards.   These standards  cover a wide range of boating safety issues which
include engine installations and fuel system requirements. All of the technologies being considered for controlling
exhaust and evaporative emissions from marine engines are covered by these safety requirements. These include:

        33 CFR 183  Subparts J  and K
        ABYC H-2, H-24, H-25, P-l, and TH-23
        UL 1102 and 1185
        SAEJ1527andJ2046

Marine Engines
The  primary safety  issues related to exhaust emission controls  pertain to maximum exhaust system surface
temperatures, the risk of exhaust system leaks (i.e. carbon monoxide) into the vessel, and the risk of flammable
gasoline  vapor mixtures around an engine.   As discussed above, marine engines used in recreational vessels
typically have water-jacketed exhaust to minimize the temperature of exposed surfaces.

USCG safety requirements for boats and associated equipment are contained in 33 CFR 183.  Subpart J deals
specifically with fuel systems on boats and includes specifications for fuel pumps and carburetors on the engine.
The scope of Subpart J includes all gasoline propulsion and auxiliary marine engines, excluding outboards. These
regulations state that the fuel pump must be on the engine or within 12 inches of the engine and that it must not leak
fuel even if the diaphragm fails.  These regulations also limit the amount that a carburetor may leak under several
specified conditions and require anti-siphon valves and fuel shut off valves under specific conditions.  The purpose
of these requirements is to minimize the risk of fuel spilling into the boat.  In addition 46 CFR part 58 includes
installation requirements for gasoline marine engines.   These installation requirements include backfire flame
control, drip collectors for carburetors, cooling or insulation for the  exhaust system, and  safe exhaust  pipe
installations.  These regulations do not apply  to OB engines because they are not considered to be permanently
installed.  Supplemental recommended practice for electric fuel transfer pumps is included in ABYC H-24 which
specifies delivery hose length, outlet pressure, and when the pump may be energized.

The only USCG safety standards that directly apply to OB engines are in 33 CFR 183, Subpart L.  These standards
require that outboards capable of a minimum  specified thrust must be equipped with a device to prevent the OB
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from being started in gear.  USCG has not promulgated further safety standards for OB engines primarily because
the need has not been demonstrated for further regulation.

USCG standards for ventilation of vapors from boats with gasoline engines (auxiliary or propulsion) are contained
in 33 CFR 183, Subpart K.  Subpart K requires that each compartment containing a gasoline engine be open to the
atmosphere or be vented by a blower system. Where a powered ventilation system is required, USCG requires a
label stating "Warninggasoline  vapors can explode.  Before starting engine, operate blower for 4 minutes and
check engine compartment bilge for gasoline vapors." These ventilation requirements are supplemented by ABYC
H-2 which also requires compartments with non-metallic fuel tanks to be vented to atmosphere.

ABYC P-l states that all surfaces on the exhaust system on permanently installed marine engines that may come
into contact with persons or gear must be at or below 200F or have protective guards, jacketing, or covers.

ABYC also details recommended practices for minimizing the risk of CO exposure on boats. These recommended
practices are described in ABYC TH-23 which is a technical report intended for design, construction, and testing
criteria to identify and minimize the presence of CO around a boat with a gasoline propulsion or auxiliary marine
engine.

Marine Vessel Fuel Systems

The primary  safety  issue regarding marine  fuel systems is to prevent fuel from leaking into the boat.  USCG
requirements for marine fuel systems are located in 33  CFR 183, Subpart J.  Subpart J deals specifically with fuel
systems on boats and contains durability and other design requirements for fuel tanks and fuel hoses.  It should be
noted that Subpart J applies to all boats that have gasoline engines (propulsion and/or auxiliary), except for OB
engines.  However, ABYC H-24 supplements 33 CFR 183 and extends these practices to all boats with gasoline fuel
systems, including OB engines. Some smaller boats do  not have installed gasoline fuel systems. Operators of these
boats use OB engines attached to portable fuel tanks which are covered by ABYC H-25. Specifications for marine
fuel hoses and fuel tanks are discussed below.

Fuel Hoses

Both 33 CFR  183 and ABYC H-24  reference SAE J1527 for the proper design of marine fuel hoses.  The USCG
regulations and SAE recommended practice distinguishes between  Type A and Type B fuel hose. Type A fuel hose
normally contains liquid fuel while Type B hose normally contains  no liquid fuel. Both hose types are subject to the
21/2 minute flame test under 33  CFR  183, Subpart J; however, Type B  hose has a more relaxed permeation
requirement.. In addition, both types  of hose  must still be self extinguishing within 60 seconds when burned. SAE J
1527 includes several other durability tests including  abrasion resistance, burst pressure,  vacuum collapse, cold
temperature flexibility, tensile strength and elongation,  oil  resistance, ozone resistance,  and fuel resistance tests on
ASTM fuel C and a test fuel containing 85 percent ASTM fuel C and 15 percent methanol.  The fuel resistance tests
state that the  hose  must meet maximum tensile  change, elongation change, and volume changes after being
immersed in the  test fuels.  Also, SAE J1527 specifies  maximum allowable permeation rates on the two test fuels.
Finally, this recommended practice includes an adhesion test which sets a minimum load required to separate the
tube from the protective cover.

PWC  manufacturers generally use an alternative recommended practice provided under SAE J2046 for their fuel
system designs.  This  recommended practice includes tests and limits for tensile strength and elongation,  dry heat
resistance, ozone resistance, oil heat resistance, burst pressure, vacuum collapse, cold  temperature flexibility, and
resistance to ASTM fuel C. This fuel resistance includes immersing the hose in fuel and testing the tensile change,
elongation change, and volume change.  Also, a permeation limit is set for ASTM fuel  C.  In addition, SAE J2046
contains an adhesion test which sets  a minimum load for separating the tube and cover.  Finally, this recommended
practice includes a 21/2 minute flame test for the entire fuel system.

For fuel hose used with portable fuel tanks, UL 1185 recommends that fuel hose meet the USCG Type A or Type B
standards discussed above.
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Fuel Tanks

33 CFR 183 Subpart J includes several specifications and durability tests for marine fuel tanks which are installed in
vessels with gasoline propulsion or auxiliary engines, excluding OB engines. These fuel tank specifications include
prohibited materials, labeling requirements, and a limit on the pressure in the fuel tank of 80 percent of the pressure
marked on the label that the tank can withstand without leaking (at least 3 psi). The fuel tanks must pass several
durability tests without leaking. These durability tests include a static pressure test, a shock test, a pressure impulse
test (25,000 cycles from 0-3 psi), a slosh test (500,000 cycles  15 from level), and a 2!/2 minute fire test.

ABYC H-24 supplements 33 CFR 183 and extends these practices to all gasoline powered boats with installed fuel
tanks, including those using OB engines.  One notable addition is that ABYC H-24 requires  a 5/8"  ID vent hose to
prevent pressure from building up  in the fuel tank.  Additional requirements are contained in UL 1102 which
references ASTM H-24 and 33 CFR 183, Subpart J.  These additional requirements include shock testing of fittings,
a static pressure test, and requirements for gaskets to be tested for fuel and oil resistance and atmospheric aging.

ABYC H-25 defines recommended practices for  the design of portable marine fuel tanks.  These specifications
include requirements for color (red), UV  inhibitors, mechanical  strength from -18C to 60C, labeling, and vent
openings that can be closed so that they are liquid and vapor tight. This recommended practice includes several
durability tests  as well.  These durability  tests include a low temperature drop test, exposure to a test fuel of 85
percent ASTM fuel C blended with  15 percent methanol, and an expansion and contraction test. UL 1185 includes
additional requirements including standards for fittings and accessories integral to the portable fuel tank such as the
fuel hose and the quick connect fittings. Additional tests for the fuel tank include vibration, durability of vent and
fill closures, fitting impact, permeation, light and water exposure,  and a fire test.  In addition there are requirements
for gaskets  to be tested for fuel and oil resistance and atmospheric  aging.

D. EMISSION CONTROL SYSTEM DESIGN

Marine Engines

We expect to propose emission standards for OB and PWC that will require significant upgrades in fuel systems and
calibration.  These standards are expected to  eliminate carbureted two-stroke engines from the market.  These 2-
stroke engines have short-circuiting losses in the  cylinder due to the intake and exhaust valves being open at the
same time.  As  a result, 25 percent or more of the fuel passes through the engine unburned.  Over the past decade,
manufacturers have introduced lower emitting four-stroke or direct-injection two-stroke engines across their entire
product lines.  We anticipate that further  emission controls will  result in manufacturers discontinuing their older
carbureted two-stroke engine lines and  selling only their cleaner four-stroke or direct-injection two-stroke designs.
We do not expect that the potential exhaust emission standards would require after-treatment technology for control
of exhaust emissions.  We are not anticipating the use of new technology to meet the exhaust emissions standards
but only the expanded use of current cleaner technologies.

Marine Auxiliary Engines

These are small engines used on boats  for auxiliary power, in most cases for electric power generation. Although
they are currently categorized as Class INHH  engines (and in some cases Class IINHH engines), they have features
that are unique  to marine applications.  Specifically, they make use of their environment to water-cool the  engine
and water-jacket the exhaust.  Marine auxiliary engine manufacturers have aggressively pursued the development of
advanced emission control technology for these products  in response to market place concerns. These systems use
catalytic converters inside of a water-jacketed system and electronic feedback controls to give optimum air to fuel
ratio. This emission control approach allows for very low exhaust emission levels relative to current NHH HC+NOx
and CO emission standards.

Marine Vessels

We have already proposed  evaporative emission standards for vessels powered  by Marine  SI engines that are
similar in scope to those discussed above  for nonhandheld land-based engines.  These  include fuel hose and fuel
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tank permeation control. Also, while we are not proposing standards for controlling vessel running loss emissions,
we have already proposed standards requiring the control of diurnal emissions.

Fuel Hose

Most marine vessels using SI engines use polyvinyl chloride or nitrile rubber hose to deliver gasoline from the fuel
tank to the engine.  To meet the fuel hose permeation standards under consideration, manufacturers would be able to
use the current basic type of hose construction except that an additional barrier layer would need to be added to the
construction.  A typical barrier material would likely be a fluoroelastomer or fluoroplastic material.  Current fuel
lines used in marine applications meet USCG and ABYC standards for flame resistance and durability as well as
requirements for fuel system fittings and clamps.   The barrier layers needed to control permeation are thin and are
not expected to lead to any significant differences in hose flexibility or ability to retain connections within the fuel
system. The hose which could be used is commercially available today.

Fuel tanks

Marine fuel tanks include portable tanks constructed of HDPE and installed  fuel tanks made of XLPE, aluminum,
and fiberglass.  Portable fuel tanks made of HDPE are used  in PWCs and with lower horsepower OB engines.
Aluminum, fiberglass,  and XLPE are used  in installed tanks in vessels using higher horsepower OB engines.
HDPE, XLPE,  and fiberglass  have poor permeation resistance  characteristics.   Fuel does  not permeate through
aluminum tanks. As was the case with NHH engines and equipment, there are several technological approaches that
can be used to reduce gasoline permeation through plastic fuel tanks. These approaches include surface treatments,
barrier constructions, and alternative materials.

Surface treatments, such as fluorination and sulfonation, do not materially change the  construction of the fuel tank.
These treatments are performed as a secondary step after the fuel tank is molded and create a thin layer on the
surfaces of the fuel tank that  acts as a barrier to permeation.  In fluorination a barrier is created on both the inner and
outer surfaces while in sulfonation it is created only on the inner surface. These treatments do not materially change
the construction of the fuel tank and are not expected to affect the durability of the fuel tank because the barrier is
less than 20 microns thick. Surface treatments are  used to meet the California gasoline permeation standards for
portable fuel cans.

Multi-layer fuel tank constructions which create a barrier to  permeation have been used in automotive applications
for many years. The most common approach is to mold a thin layer of ethyl  vinyl alcohol (EVOH) inside a HDPE
shell.  This approach is commonly used in high production volume, blow-molded fuel tanks and can be used in
lower production volumes through a  molding process known as thermoforming.  Another approach available for
blow-molded fuel tanks is to create a non-continuous barrier by blending a small amount of EVOH directly into the
HDPE.  During molding, the EVOH  creates overlapping barrier platelets which restrict permeation.  For each of
these technologies, the barrier material is only a  small percentage of the  total makeup of the fuel tank. Non-
continuous barriers can reduce permeation by more than 85 percent while continuous barriers can achieve more than
a 99 percent reduction in permeation.  These technologies have the advantage of having been in use for many years
and  having been applied  in various applications. Automotive  manufacturers  require these  fuel  tanks to meet
durability specifications similar to those required by the US Coast Guard.

Rotationally molded XLPE tanks would be able to make use  of barrier technologies. In one technique nylon, which
has good permeability properties, is applied as an inner shell inside the fuel  tank.  The manufacturer has
demonstrated that the nylon has an excellent bond with the XLPE.1  As a result of this bond  and the strength of the
nylon, this  construction offers strong resistance to  impact.  Testing at IMANNA labs  showed that a tank of this
construction met the USCG  durability requirements in 33 CFR 183, Subpart J which includes impact testing and
flame resistance.2 As a result of this bond and the strength of the nylon, the construction meets the USCG impact
and flame resistance requirements discussed above.  In addition,  emission testing  has  shown good permeation
control performance compared to baseline. Another new approach for XLPE tanks is to  coat the tank with a low
permeation epoxy  in a secondary step after molding.3   This  approach does  not  change the basic  fuel tank
construction but only adds an outer layer similar in thickness as a coat of paint. In addition, an intumescent additive
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has been developed which can be added to the epoxy coating for additional flame resistance. Emission testing on
this technology has also shown good emission control performance.

Fiberglass fuel tanks can meet low permeation requirements through the use of a nanocomposite barrier layer.  This
barrier layer is composed of fiberglass impregnated with microscopic fibers of treated volcanic ash.  A company
named ECSI has developed this technology for use in marine fuel tanks.  Through testing, ECSI has demonstrated
this technology to  meet  USCG and  ABYC standards  for fuel system mechanical  strength requirements.4  In
addition, emission testing has shown good emission control performance.

Diurnal Emissions Control

As was discussed in the beginning of Chapter 9, diurnal emissions occur when the rising ambient temperature heats
the fuel inside the fuel tank and displaces the fuel vapors created through fuel tank vents.  In the cases where these
venting emissions are high, a combustible fuel vapor concentration could occur if the  vapor is vented into an
enclosed space such as the confines a vessel.  In addition, fuel vapor vents create a path for fuel to spill out of the
fuel system during refueling or when fuel sloshing occurs.

The simplest approach to controlling diurnal emissions is simply to close  the tank vent. Under this scenario, when
the  tank heats up, pressure would  build in the fuel tank, but no fuel vapor would be vented to the atmosphere.
Pressure would be limited with a pressure relief valve that would open at higher pressures.  In addition, a vacuum
relief valve would be needed to prevent a vacuum in the fuel tank which could restrict fuel delivery to the engine
and cause the engine to stall.  This is really only an option for smaller tanks where the potential for significant
geometric shape deformation under pressure is small. Portable marine fuel tanks are designed to be sealed when not
in use, and PWC use sealed fuel tanks (with pressure relief valves) to prevent spillage during operation.  Leakage
from these tanks is normally not into a  confined space such as a vessel bilge.

Another well developed approach to controlling diurnal emissions has been used in automobiles for over 30 years.
In this approach a plastic canister containing activated  carbon is placed in the vent line.  This carbon canister
collects fuel vapor vented from the fuel tank as it breathes during the day.  The canister could then be either actively
or passively purged. Active purging refers to drawing the vapor to the engine to be burned.  Passive purging refers
to removing gasoline vapor stored on the activated carbon through the air  naturally drawn into the fuel tank through
the  vent line during  cooling periods.  Canister  systems  represent  a  simple technology that has long  been
demonstrated in various applications without safety issues.5
E. ASSESSMENT OF SAFETY IMPACT OF NEW EMISSION STANDARDS

New Exhaust Emission Standards for OB/PWC

Because we are not anticipating the use of new technology to meet the exhaust emissions  standards, we do not
believe that further emission  control will result in an incremental safety risks relative to the current mix of
technology.   Current 4-stroke and 2-strke direct injection technologies are more  sophisticated than the older
carbureted two-stroke design and have been used for nearly a decade.  Although there were some early technical
issues  with two-stroke direct injection  engines, these issues have  been  largely  resolved  though significant
engineering efforts.  As a result of these engineering efforts, the  newer 4-stroke and  2-stroke direct injection
technologies are actually more reliable than older designs. In addition, they are more fuel efficient which allows for
greater range and, arguably a lower chance of running out of fuel.  These improvements in reliability and range
would be expected to improve safety issues related to being  stranded at sea.

New Exhaust Emission Standards for Marine Auxiliary Generators

Manufacturers of marine auxiliary engines are leading the way  in new  exhaust emission control technology in the
marine sector. Even with catalysts packaged in the exhaust manifold, these engines have low surface temperatures
because the exhaust manifolds containing the catalysts are water-jacketed with surface water drawn and returned to
the ambient source to cool the exhaust system.  With water  jacket cooling EPA does not anticipate any heat-related
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problems or increase in fire due to catalysts. In addition, these systems are electronically controlled with feedback
systems that can be used to detect problems with the engine before they become problematic.  Finally, a safety
benefit is  achieved by the very large reduction in CO emissions from these engines.  This reduction in CO will
benefit not only the boat operators but swimmers and other individuals in the vicinity of the boat.

Fuel Hose Permeation Standards

Low permeation fuel hose subject to the USCG requirements would still need to meet the requirements specified in
SAE J1527 and discussed above.  In fact, one manufacturer is selling barrier fuel hose today that meets the USCG
requirements and is used by several boat builders.  This hose meets the permeation requirements we are considering.
This hose construction is similar to baseline hose constructions except that a barrier layer is added. In the same
way, manufacturers of PWC and portable fuel tanks, would still be expected to comply with SAE J2046  and UL
1185 respectively.  To meet the fuel hose permeation standards under consideration, manufacturers would be able to
use the existing hose constructions except that an additional barrier layer would need to be added to minimize
permeation fuel through the hose material.

Low permeation fuel hose will have no negative implications for safety and may have  some benefits.  The addition
of a barrier layer would not require a change in the general construction of the hose. In addition, barrier materials
are made of compounds that are resistant to permeation by gasoline, including ethanol blends and oxidized ("sour")
gasoline.  This fuel resistance not only protects against  chemical attack, but also limits  swelling due to the
permeation of fuel. By limiting the swelling and contracting (drying) cycles and chemical attacks that may cause
the hose to  eventually become brittle, the hose may better resist cracking as well. The barrier hose may reduce
concentrations of fuel vapor in confined spaces where the fuel hoses are routed such as the engine compartment,
vessel bilge, or other areas in the hull where the fuel tank may be located.

This lower concentration could help prevent a flammable mixture of fuel vapor from forming within the confines  of
the vessel.  It should be noted that low permeation fuel hose is available today and is used by many boat builders.

Fuel system fittings and clamps are also covered by the USCG and ABYC standards.  These specifications require
the fittings to  have a bead, flare, or other grooves to help prevent the hose from pulling off the fittings.  Clamps
must be corrosion resistant, not cut the hose, and resist one pound tensile force.  In addition, all fittings, joints, and
connections must be easily accessible for inspection and maintenance. With any changes in hose constructions, boat
builders would still need to design their connections to meet these requirements.  As some boat builders are using
low permeation fuel hose today, they are also using corresponding fittings and clamps.
                                                                                                      159

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Fuel Tank Permeation Standards

In any situation where a manufacturer makes changes to fuel tanks, such as materials or geometry, they must
evaluate the potential safety effects of these changes.  Under current industry practices new fuel tank designs are
durability tested under the USCG requirements and ABYC and UL recommended practice described above.  These
tests include pressure impulse, fuel and oil exposure, atmospheric aging, slosh, shock, and flame resistance.

The techniques suggested above would also meet the USCG and ABYC durability requirements including the flame
test

We expect that the use of low permeation fuel tanks will have no negative implications for safety and may have
some benefits.  Permeation barriers could  minimize  permeation of the fuel into the tank walls  and reduce any
negative effects of fuel exposure. In addition, low permeation fuel tanks would lead to reduced concentrations of
fuel vapor  in confined spaces in the vessel hull where the fuel tank is located; a lower fuel vapor concentration
means a reduced risk of fire. The choice of proper materials and construction durability is also important.

Under our current permeation requirements for recreational vehicles, we require durability testing as part of the fuel
tank permeation test procedure.  Prior to the permeation test, the fuel tank is filled with gasoline containing 10%
ethanol and soaked for 20 weeks at 285C. In addition, the fuel tank is subject to a pressure vacuum test made up
of 10,000 cycles from -0.5 to 2.0 psi, a slosh test made up 1 million cycles where the tank is rocked 15, and a 240
hour UV exposure test.  Although these tests are intended to  help ensure  the long term  effectiveness of the
permeation control technology, they also inherently assess the durability of the fuel tank as well.

Fuel Tank Diurnal Emission Control Standards

Portable fuel tanks are currently designed to be pressurized through a manual control valve on the vent. The use of
a sealed tank with vacuum relief would not add to the pressure experienced by the fuel tank and therefore offer no
incremental safety risk. The vacuum relief valve could offer a safety benefit in that it could prevent occurrences of
engine stalling that may occur if the operator  were to forget to open the manual valve prior to starting the engine.
PWC fuel tanks are already using sealed fuel systems with pressure relief valves.  We expect that this design would
meet the emission control requirements under consideration.

Carbon canisters do  not present an incremental risk to safety for marine vessel use.  These canisters are passive
systems in  the vent line and create nothing more than nominal backpressure on the  tank. The use of the carbon
canister can have positive safety implications. First, the carbon  will collect vapor from the fuel  tank which will
result in less gasoline vapor which can infiltrate the engine and bilge areas on the boat.  Second, the design of the
diurnal control system will include a mechanism to prevent fuel from entering the vent hose during refueling. This
mechanism could be as simple as a small orifice between the fuel tank and the canister that would be sized to limit
fuel from entering the vent  hose during refueling but be large enough to prevent a restriction on vapor flow during
diurnal breathing. For an average fuel tank, this orifice would be on the order of 1mm in diameter.  This could help
reduce fuel spillage that sometimes occurs today from the vent line during refueling.  Because the fuel tank would
need to vent through the canister to achieve the emission reductions,  the fuel cap would need to form a vapor tight
seal.  Four boat manufacturers installed carbon canisters last summer on a total of fourteen boats as part of a
demonstration project. At the  end of the summer, all of the canisters were still operating properly and no safety
incidences were reported.6
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F. CONCLUSION

EPA reviewed the characteristics of marine engines less than 50 horsepower and evaluated the emission control
technologies used  to  reduce exhaust emissions from  these engines.   EPA  also  reviewed the fuel  system
characteristics for marine vessels using these engines and evaluated emission control technologies which could be
used to reduce fuel evaporative emissions from these two subcategories. Marine engines including marine auxiliary
engines  must meet USCG standards  related  to  safety.   In addition,  it is industry practice to meet  ABYC
requirements. There are thousands of 4-stroke and 2-stroke direct injection engines in the fleet today which would
meet the exhaust emission standards being considered by EPA. Based on the fact that the technology needed to
meet the standards we are considering is already in use in both OB and PWC engines, EPA does not believe that the
technology needed to meet new standards would result in an increase of risk of fire and burn to consumers in use.

With regard to fuel hoses, fuel tanks, and  diurnal controls, there are  rigorous USCG, ABYC, UL,  and  SAE
standards which manufacturers will continue to meet for fuel system components.  In addition, USCG and others
would be able to expand their requirements in response to new fuel systems designs  if they saw the  need to do so.
Furthermore, the EPA permeation certification  requirements related to emissions durability will add an additional
layer of assurance. Low permeation fuel hoses are used safely today in many marine vessels.  Low permeation fuel
tanks and diurnal emission controls have been demonstrated in various applications  for many years without an
increase in safety risk.

Furthermore, a properly designed fuel system with fuel tank and fuel hose permeation controls and diurnal emission
controls would reduce the fuel vapor  in the boat, thereby  reducing the opportunities for fuel related fires.  In
addition, using improved low permeation materials coupled with designs  meeting USCG and ABYC requirements
should reduce  the  risk of  fuel leaks  into the vessel. EPA believes that the  application of emission  control
technologies on marine engines and vessels for meeting the proposed evaporative emissions standards would not
lead to an increase in incremental risk of fires or burns.
1   O'Brien, G., Partridge,  R., Clay, B., "New Materials and Multi-Layer Rotomolding Technology for Higher
Barrier Performance Rotomolded Tanks," Atofina Chemicals, 2004, Docket EPA-HQ-OAR-2004-0008-0044.
2  Partridge, R., "Petro-Seal for Ultra-low Fuel Permeation; Evaporative EPA Emissions from Boat Fuel Systems,"
Arkema, Presentation at the 2004 International Boatbuilders' Exhibition and Conference, October 25, 2004, Docket
EPA-HQ-OAR-2004-0008-0252.
3   Bauman, B., "Advances in Plastic Fuel Tanks," Fluoro-Seal International, Presentation at the 2004 International
Boatbuilders' Exhibition and Conference, October 25, 2004 Docket EPA-HQ-OAR-2004-0008-0036.
4     Chambers, I, "Marine  Fuel Containment...  A  Permanent Solution," Engineered  Composite Structures,
Presentation at the 2004 International Boatbuilders' Exhibition and Conference, October 25, 2004 Docket EPA-HQ-
OAR-2004-0008-0037.
5  "Stopping Vehicle Fires & Reducing Evaporative Emissions: The Need to Control Gasoline & Alcohol Blend
Volatility," Center for Auto Safety, March 1988, Docket EPA-HQ-OAR-2004-0008-0330.
6   Tschantz, M., "Summer Test Program Carbon Analysis," Meadwestvaco Corporation, Presentation at the 2005
International Boatbuilders' Exhibition and Conference, October 20, 2005 Docket EPA-HQ-OAR-2004-0008-0290.
                                                                                                   161

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Appendix A- Basic principles  of Infrared  thermal  imaging1
IR TEMPERATURE BASICS

Temperature is a measure of the thermal energy  contained by an object; the degree of hotness or coldness of an
object is measurable by a number of means and is defined by temperature scales. Temperature, in turn, determines
the direction of net heat flow between two objects.

There are three modes of heat transfer, conduction, convection and radiation.  All heat is transferred by means of
one or another of these three modes, infrared thermography is most closely associated with radiative heat transfer,
but it is essential to understand all three in order to comprehend the significance of IR Thermograms.

CONDUCTIVE HEAT TRANSFER

Conductive heat transfer is the transfer of heat in stationary media. It is the only mode of heat flow in solids, but
can also take place in liquids and gases.  It occurs as  a result of atomic vibrations and (in solids) and molecular
collisions (in liquids).  Whereby energy is moved, one  molecule at a time, from higher temperature  sites to lower
temperature sites.

CONVECTIVE HEAT TRANSFER

Convective heat flow takes place in a moving medium and is almost always associated with transfers between a
solid and a moving fluid (such as air). Free convection takes place when the temperature differences necessary for
heat transfer produce density changes in the fluid and the warmer fluid rises as a result  of increased buoyancy.
Forced convection takes place when an external driving force, such as a cooling fan, moves the fluid.

RADIATIVE HEAT TRANSFER

Radiative heat transfer is unlike the other two modes in  several respects:

       It can propagate through a vacuum

       It occurs by electromagnetic emission and absorption.

       It occurs at the speed of light and behaves in a  manner similar to light

While conductive and convective  heat transferred between  points  is  linearly proportional to the temperature
difference between them, the energy  radiated from a  surface is proportional to the fourth power of its absolute
temperature.  The radiant thermal energy is transferred between two surfaces is proportional to the third power of
the temperature difference between the surfaces.

Thermal infrared radiation leaving  a  surface is called radiant exitance  or radiosity.  It can be emitted from the
surface,  reflected off a surface, or transmitted through a surface.  The  total radiosity is equal to the  sum of the
emitted component, reflected component and the transmitted component.  The surface temperature, however, is only
related to the emitted component.

The  measurement of thermal infrared radiation is  the basis for  non-contact  temperature measurement and IR
thermography. Like light energy, thermal radiation is  a photonic phenomenon that occurs in the  electromagnetic
spectrum.  While light energy takes place in the visible portion of the spectrum, radiative heat transfer takes place in
the infrared portion of the spectrum.

All target surfaces warmer than absolute zero radiate  energy in the  infrared spectrum.  Very hot targets radiate
visibly as well. IR thermal imagers measure and display images of this infrared radiated energy.
                                                                                                   162

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From the point of view of IR radiation characteristics, there are three types of target  surfaces;  blackbodies,
graybodies and non-graybodies (also called spectral bodies).  A black body radiator is defined as "a theoretical
surface having unit emissivity at all wavelengths and absorbing all radiant energy impinging upon it" Emissivity is
defined as the ratio of radiant energy emitted from a surface to the energy emitted from a blackbody surface at the
same temperature. Although blackbody radiators are theoretical and do not exist in practice, the surface of most
solid objects are graybodies, that is, surfaces with emissivities that are fairly constant with wavelength.

Total radiosity available to a measuring device from a target surface has three components: emitted energy, reflected
energy and energy transmitted through the target surface.  If the target is a blackbody emitter, it has an emissivity
equal to one, and it will reflect and transmit no energy. If the target is a graybody emitter,  then it will resemble a
black body in spectral distribution, but since its emissivity is less than one, it may also  reflect and/or transmit
energy.  If the target is a non-graybody emitter, it may also emit, reflect and transmit energy.  Since only the emitted
component is related to temperature of the target surface it becomes apparent that a significant  step in making IR
temperature measurements is eliminating or compensating for the other two components.

Infrared radiation from the target passes through some transmitting medium on its way to the  infrared instrument.  If
the medium is a vacuum then there is no loss of energy, but most infrared measurements are mad through air.  The
effect of atmospheric gases can be ignored for short distances, such as a few meters.

HOW THE IR FLEXCAM T AND IR SNAPSHOT CAMERA'S CONVERT RADIANCE TO TEMPERATURE

The IR Flexcam T and IR Snapshot imagers correct the infrared radiance from any single point on the target surface,
so as to  approach the  true temperature measurements at that location.  To  do this,  it first assumes that the IR
absorption of the air path between the target and the instrument is negligible.  It also assumes that there is no IR
energy transmitted through the target from sources behind the target.  In order to correct for reflection of the
ambient background it  requires the operator to input the background temperature. Note that the EPA-NVFEL test
cells are held at a temperature of 25C +/- 1C.

The operator also inputs the  targets  estimated  emissivity.   All the targets  of interest (Mufflers/Catalysts/Heat
Shields) have been painted with a high temperature flat-black paint which has a very dull matte finish.   This is used
to even out the emissivity of the  object over the surface as well as to increase the value of the emissivity of the
object.   An emissivity  of 0.9  was used for  this  project.  To  check the validity of the emissivity  assumptions, a
comparison of the surface temperature measured with the IR imager was made to a known surface  temperature
measured with a thermocouple.  The temperatures were within 1% of agreement.

The IR imagers used for EPA's test program have the following general specifications.  They use microbolometer
detectors that require no cryogenic cooling.  The  detector elements are square  and are located in  a rectangular grid.
The optical path of the camera  includes an appropriate band-pass filter for the temperature range of interest.  The IR
Snapshot Camera has a NIST traceable calibration from IOC to 1200C with accuracy of 2C  or 2% of reading.  The
IR FlexCam has a NIST traceable calibration from OC to 600C with accuracy of 2C or 2% of reading. The lenses
for both cameras  are made from germanium  and are anti-reflective coated for high transmission  in the temperature
range of choice.

The calibration of both the IR Flexcam and IR Snapshot was repeated on January 11, 2006. Both imagers were
within  the  manufacturer's  accuracy specifications, thus neither imager required calibration  adjustment.   The
calibration results are presented in Tables A-l and A-2.
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Table A-l:  Summary of results for the validation of temperature calibrations for the "FlexCamT" and "FLIR"
imagers.  Both imagers were adjusted to account for the emissivity of the temperature targets and an ambient
temperature of 25C.
                                 EPA IR Flexcam T
                                 Point Temperature
                                        4.6
                                        99.1
                                       351.8
                                       590.1
Table A-2:  Summary of results for the validation of temperature calibration for the EPA "IR Snapshot" imager.
Emissivity of
Temperature
Target
0.98
0.93
0.97
0.93
Target
Temperature
(C)
5
100
350
600
Briggs & Stratton FLIR
Point Average
Temperature Temperature
4.9
102
350
602
v ^>
5.6
101.6
351.5
601.6
Emissivity of
Temperature
Target
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
Target
Temperature
(C)
5
20
37
50
75
100
240
300
350
600
700
800
900
1000
1100
1200
Average
Temperature
(C)
3.51
19.57
36.44
49.19
74.18
98.99
239.8
301.85
350.88
594.65
694.06
793.47
901.97
986.42
1091.14
1192.84
1  Adapted from the IR Flexcam T and IR Snapshot Operating Manuals, Infrared Solutions Inc., Plymouth, MN,
2004.
                                                                                                  164

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Appendix B: Emissions Results
             Table B-l: Emissions summary - Class I OHV engines at low (10-20) hours.
Engine
241
241
255
255
2982
2982
243
243
244
244
245
245
Tested
Configuration
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-
muffler*, venturi
air
OEM
Catalyst-muffler,
venturi air**
OEM
Catalyst-muffler,
venturi air"*
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-muffler,
venturi air
HC+NOx
(g/kW-hr)
10.6 0.5
3.9 0.2
11.2
5.0
8.4 0.5
4.9 0.3
13.4 0.9
71
11.0
7.2
10.9
5.6
NOx
(g/kW-hr)
3.0 0.3
1.45 0.2
3.2
0.7
4.4 0.4
2.8 0.2
4.6 0.3
1.8 0.2
1.8
1.1
2.4
0.6
HC
(g/kW-hr)
7.6 0.3
2.5 0.3
8.0
4.3
4.0 0.3
2.2 0.3
91
51
9.2
6.1
8.5
5.0
CO
(g/kW-hr)
313 29
138 46
340
288
161  15
85 10
351 13
334 50
517
433
472
381
Notes:
Engines 241, 255, and 2982 are from the same engine family.
Engines 243, 244, and 245 are from the same engine family
*Tubular pre-catalyst, 22cc 200 cpsi metal monolith downstream of stamped secondary-air venturi
**35 cc, 100 cpsi metal monolith, stamped secondary -air venturi.
*** Reduced substrate volume, tubular venturi.
Stamped Venturis used were based on the OEM design.
"" values represent 95% confidence intervals for a 2-sided t-test, for 3 to 4 replicate measurements.
                                                                            165

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       Table B-2:  Emissions summary - Class I side-valve engines at low (10-20) hours.
Engine
6820
258
258
236
236
246
246
248
248
249
249
Tested
Configuration
OEM
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-muffler,
(no secondary
air)*
HC+NOx
(g/kW-hr)
10.8 0.5
10.5
6.7
15.2 .2
4.9 0.6
12.4
5.6
12.0
4.6
11.3
6.3
NOx
(g/kW-hr)
2.2 0.2
2.5
1.2
3.0 0.8
0.90 0.05
1.8
0.8
3.0
0.8
3.0
0.9
HC
(g/kW-hr)
8.7 0.6
8.1
5.5
12.1 0.8
4.0 0.7
10.6
4.8
9.0
3.8
8.3
5.4
CO
(g/kW-hr)
458 45
487
380
380 38
218 62
490
333
403
294
413
351
Notes:
Engines 6820 and 258 were from the same engine family, and used identical catalyst muffler designs.
Engines 236, 246, and 249 were from the same engine family.
Stamped Venturis used were based on the OEM design.
"" values represent 95% confidence intervals for a 2-sided t-test, for 3 to 4 replicate measurements.
The catalyst-muffler for engine 6820 was not available until just prior to the initiation of field aging - emissions
measurements at low-hours were not conducted.
*Rh-only catalyst
Table B-3:  Emissions summary - Class IOHV and side-valve engine tested at high (>110) hours.
Engine
241 (OHV)
241
2982 (OHV)
2982
6820 (side-
valve)
6820
Tested
Configuration
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-muffler,
venturi air
OEM
Catalyst-muffler,
venturi air
HC+NOx
(g/kW-hr)
13.4 0.6
6.6 0.2
10.2 0.4
7.0 0.4
15.4 0.4
9.4 0.7
NOx
(g/kW-hr)
5.2 0.4
3.2 0.2
6.1 0.4
4.5 0.3
2.6 0.5
2.8 1
HC
(g/kW-hr)
8.1 0.6
3.40.1
4.1 0.2
2.5 0.2
13 1
6.6 0.8
CO
(g/kW-hr)
266 9
180 4
148 6
85 6
380  42
168 19
Notes:
"" values represent 95% confidence intervals for a 2-sided t-test, for 3 to 4 replicate measurements.
                                                                                             166

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                Table B-4: Emissions summary - Class II OHV engines at low (10-40) hours.
Engine
231
231
231
251
251
252
253
253
232
232
232
233
Tested
Configuration
OEM
EFI
EFI, catalyst-
muffler
OEM
catalyst muffler
OEM
OEM
catalyst muffler
OEM
EFI
EFI, catalyst-
muffler
OEM
HC+NOx
(g/kW-hr)
7.0 1
6.9
1.8 0.4
9.2
3.1 0.3
9.1 0.8
6.9 0.4
4.5 0.1
8.5 0.5
8.0 0.3
2.2 0.1
8.1 0.7
NOx
(g/kW-hr)
3.0 0.6
3.0
0.6 0.2
5.9
0.9 0.6
7.3 0.8
3.00.1
0.29 0.01
2.25 0.08
4.4 0.3
0.8 0.2
2.2 0.3
HC
(g/kW-hr)
41
3.8
1.3 0.5
o o
J.J
2.8 0.4
1.8 0.2
4.0 0.5
4.2 0.1
6.2 0.5
3.7 0.6
1.4 0.2
6.0 0.4
CO
(g/kW-hr)
333 60
308
120  29
228
245  93
188 33
380 23
529 11
475  29
274  42
154 27
459  24

Table B-5:  Pre- and Post-catalyst emissions for a Carbureted 400cc Class II engine after 50, 300, and 500 hours of
                                               operation.
Engine
142
142
142
142
142
142
Tested
Configuration
OEM
Catalyst
OEM
Catalyst
OEM
Catalyst
Accumulated
Hours of
Engine
Operation
50
50
300
300
500
500
HC+NOx
(g/kW-hr)
6.56 0.03
2.5 0.6
7.27 0.18
3.5 0.04
9.8 0.1
2.8 0.7
NOx
(g/kW-hr)
2.8 0.1
0.12 0.06
3.60 0.08
0.367 
0.002
6.4 0.2
0.7 0.2
HC
(g/kW-hr)
3.74 0.07
2.3 0.6
3.70.1
3. 15 0.04
3.40.1
2.1 0.5
CO
(g/kW-hr)
300 15
282  47
238 4
263 9
165 7
170  26
Notes:
The catalyst tested with engine 142 is a duplicate of the unit tested within the catalyst-muffler of engine 253.
                                                                                                    167

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Appendix C - FMEA of Small SI Equipment and Engines
                                                   168

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