EPA-650/4-75-024-e
Environmental Monitoring Series
FOR QUALITY ASSURANCE PROGRAMS
FOR MOBILE SOURCE EMISSIONS
MEASUREMENT SYSTEMS:
PHASE III, LIGHT-DUTY DIESEL-POWERED VEHICLES -
QUALITY ASSURANCE GUIDELINES
U.S. Environmental Protection Agency
Office of Research and Development
Washington, D. C. 20460
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GUIDELINE DISTRIBUTION RECORD
EPA-650/4-75-024-e "Guidelines for Quality Assurance Programs for
Mobile Source Emissions Measurement Systems: Phase III, Light-Duty
Diesel-Powered Vehicles - Quality Assurance Guidelines"
The series of documents, "Guidelines for Quality Assurance Programs for
Mobile Source Emissions Measurement Systems," have been prepared and issued in a
revisable document-controlled format so that any future revisions or additions
may be distributed to the Guideline users. Individual copy numbers have
been assigned to each volume of the series. These numbers appear on this record
sheet and on the title page of each document. The user of these documents must
complete the "Distribution Record Card" and return it in the pre-addressed
envelope to the address shown below so that automatic distribution for future
revisions may be made directly to the user. Also, notice of any reassignment
of the documents by number and title to other individuals (by name, address,
and copy number) should be sent to the same address.
U.S. Environmental Protection Agency
Office of Mobile Source Air Pollution Control
2565 Plymouth Road
Ann Arbor, Michigan 48105
ATTN: Quality Assurance COPY No.
(cut along dotted line)
DISTRIBUTION RECORD CARD
Guideline
User Date
Last Name First Middle Initial
Title
Address
to Send
Future Street
Revisions btreet
and
Additions
City State Zip Code
If address is a firm (fill in)
Firm
I have received copy No. of EPA-650/4-75-024-e "Guidelines for Quality
Assurance Programs for Mobile Source Emissions Measurement Systems:
Phase III, Light-Duty Diesel-Powered Vehicles - Quality Assurance
Guidelines"
Please send me any revisions and additions of this volume.
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EPA-650/4-75-024-e
GUIDELINES
FOR QUALITY ASSURANCE PROGRAMS
FOR MOBILE SOURCE EMISSIONS
MEASUREMENT SYSTEMS:
PHASE III, LIGHT-DUTY DIESEL-POWERED VEHICLES -
QUALITY ASSURANCE GUIDELINES
by
Harold Wimette, Rod Pilkington, and Tom Kelly
Olson Laboratories, Inc.
421 East Cerritos Avenue
Anaheim, California 92805 '
Contract No. 68-02-1740
ROAP No. 26BGC
Program Element No. 1HA327
EPA Project Officers:
R. C. Rhodes
Quality Assurance and Environmental Monitoring Laboratory
Research Triangle Park, North Carolina 27711
and
C. Don Paulsell
Office of Program Management
Ann Arbor, Michigan 48105
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Mobile Source Air Pollution Control
and
Office of Research and Development
Washington, D. C. 20460
June 1975
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EPA REVIEW NOTICE
This volume has been prepared by Olson Laboratories , Incorporated
consistent with the Environmental Protection Agency Quality Assurance
principles and concepts and with the Environmental Protection Agency Mobile-
Source Testing Practices at Ann Arbor, Michigan.
The guidelines and procedures are generally applicable to mobile
source testing operations and are intended for use by those engaged in such
measurement programs
It is requested that recipients and users of this document submit any
comments and suggestions to the Project Officers.
Mention of trade names or commercial products does not constitute
Environmental Protection Agency endorsement or recommendation for use.
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environ-
mental Protection Agency, have been grouped into series. These broad
categories were established to facilitate further development and applica-
tion of environmental technology. Elimination of traditional grouping was
consciously planned to foster technology transfer and maximum interface
in related fields. These series are:
1. ENVIRONMENTAL HEALTH EFFECTS RESEARCH
2. ENVIRONMENTAL PROTECTION TECHNOLOGY
3. ECOLOGICAL RESEARCH
4. ENVIRONMENTAL MONITORING
5. SOCIOECONOMIC ENVIRONMENTAL STUDIES
6. SCIENTIFIC AND TECHNICAL ASSESSMENT REPORTS
9. MISCELLANEOUS
This report has been assigned to the ENVIRONMENTAL MONITORING
series. This series describes research conducted to develop new or
improved methods and instrumentation for the identification and quanti-
fication of environmental pollutants at the lowest conceivably significant
concentrations. It also includes studies to determine the ambient concen-
trations of pollutants in the environment and/or the variance of pollutants
us a Junction of time or meteorological factors.
This document is available to the public for sale through the National
Technical Information Service, Springfield, Virginia 22161.
Publication No. EPA-650/4-75-024-e
11
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FOREWORD
All mobile source testing facilities have some elements
(activities) of a quality assurance system built into their routine
testing operations. These activities may not have been identified
and/or integrated into a formal quality assurance program. It is the
objective of these guidelines to provide guidance to both (1) facilities
which desire to organize an integrated quality assurance program, and
(2) facilities which may have already organized towards an integrated
quality assurance program, but may desire to review their program as a
result of the recommendations and suggestions included in these guide-
lines. The extent of implementation will depend upon the requirements
of each individual test facility.
iii
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EXECUTIVE SUMMARY
Quality assurance guidelines for diesel-powered light duty
mobile source emission measurements are quite similar to those pre-
viously reported for gasoline-powered vehicles EPA-650/4-75-024-a
"Guidelines For Quality Assurance Programs For Mobile Source Emission
Measurement Systems," Phase I, Light Duty Gasoline-Powered Vehicles,
June 1975. The testing of a diesel vehicle requires certain modifica-
tions of the gasoline procedure for the determination of hydrocarbons.
Basically, these differences involve elimination of the evaporative
emission requirement, modification of the vehicle preconditioning and
introduction of a heated flame ionization instrument to continuously
monitor the hydrocarbon emissions. Quality requirements for these
special modifications as well as the detailed test procedures used by
the EPA, are presented in this document.
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TABLE OF CONTENTS
Page
FOREWORD iii
EXECUTIVE SUMMARY v
Section
1 INTRODUCTION 1-1
1.1 Objective and Scope of Guidelines 1-1
1.2 Formation of Quality Assurance Guidelines 1-2
1.2.1 Section 1 Introduction 1-2
1.2.2 Section 2 Organizing for Quality 1-3
1.2.3 Section 3 Measurement System Analysis 1-3
1.2.4 Section 4 Guidelines for Performance,
Audits and Maintenance Procedures 1-3
1.2.5 Section 5 Quality Assurance Guidelines for
Documentation of the Measurement System 1-3
1.2.6 Section 6 Application of Statistical Quality
Assurance Methods to the Emission
Test System 1-3
1.2.7 Section 7 Analysis of Variability in the
Measurement of Emissions from Light Duty
Diesel Engines 1-3
1.2.8 Section 8 Quality Assurance System
(On Site) Survey 1-3
1.2.9 Appendices 1-3
2 ORGANIZING FOR QUALITY 2-1
2.1 Operations Management 2-1
2.1.1 Quality Assurance Management . 2-1
2.1.2 Emission Test Facility Management 2-1
3 MEASUREMENT SYSTEM ANALYSIS 3-1
3.1 Applicable Federal Register Procedures 3-1
3.2 Elements of a Measurement System for Light Duty
Diesel Engine Emission Measurement 3-2
3.2.1 Evaporative Emiission Measurement 3-2
3.2.2. Exhaust Emission Measurement 3-3
4 GUIDELINES FOR PERFORMANCE AUDITS AND MAINTENANCE
PROCEDURES 4-1
5 QUALITY ASSURANCE GUIDELINES FOR DOCUMENTATION OF THE
MEASUREMENT SYSTEM 5-1
VI1
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APPLICATION OF STATISTICAL QUALITY ASSURANCE METHODS
7
7.1
7.2
7.2.1
7.2.2
7.3
8
9
TO THE EMISSION TEST SYSTEM
ANALYSIS OF VARIABILITY IN THE MEASUREMENT OF
EMISSIONS FROM LIGHT DUTY DIESEL ENGINES
Variables Associated with the Measurement of
Variables Associated with the Measurement of
Analysis of Variables Associated With Measurement
Variation Assciated with the Equipment and Test
Procedures Used in the Measurement System ....
Measurement of Variability in Emission
QUALITY ASSURANCE SYSTEM SURVEY
REFERENCES
6-1
7-1
7-1
7-1
7-2
7-2
7-3
8-1
9-1
Appendices
A, B,
and C
Refer to Phase I Report
viii
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LIST OF FIGURES
Figure No. Page
3-1 Elements of a Measurement System for Light Duty
Diesel Vehicle Emissions 3-2
LIST OF TABLES
Table No. Page
4-1 Federal Register Specifications Light Duty Diesel
Powered Vehicle 4-2
7-1 Average 1975 Light Duty Emission and Fuel Economy
Results 7-4
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Section: 1(LD)
Revision: 0
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Page 1 of 3
Section 1
INTRODUCTION
The quality assurance staff of the EPA Quality Assurance and
Environment Monitoring Laboratory, Research Triangle Park, North Carolina
is responsible for the administration of a quality assurance program for
air measurement systems, resulting from the implementation of the Clean
Air Act. Standards for the emissions from light and heavy duty mobile
sources have been promulgated, and procedures published for the measure-
ment of their emissions and certification. Quality assurance guidelines,
however, have not been previously specified for these mobile source
emission measurement testing procedures. Such quality assurance programs
are necessary to assure the integrity of the data resulting from these
tests. This report presents guidelines for quality assurance programs
for measurement systems used in mobile source testing according to the
applicable requirements of the Federal Register for the 1975 model-year.
The guidelines for the quality assurance program for mobile
source measurement systems are prepared in four phases.
o Phase I - For light duty gasoline-powered vehicles (cars
and trucks)
o Phase II - For heavy duty diesel engines
o Phase III - For light duty diesel-powered vehicles (cars
and trucks)
o Phase IV - For heavy duty gasoline engines
This document presents the guidelines for implementing a
quality assurance program for the measurement of emission from light
duty diesel vehicles (Phase III). Guidelines for the other phases are
reported in separate documents.
1.1 OBJECTIVE AND SCOPE OF GUIDELINES
These guidelines provide information on general quality methods
which may be used in emission testing. They were primarily designed for
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Section: 1 (LD)
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Date: June 1975
Page 2 of 3
use by management and supervisory personnel involved in the development
or operation of quality programs. Upper management may use the guide-
lines to evaluate the quality programs which presently exist within
their own laboratory or organization.
The measurement system for light duty diesel vehicles consist
of the testing, calibration and analytical requirements; the operational
and measurement procedures used; and the operational and measurement
data obtained. The primary objective of this program was to analyze
this system and apply the principles and techniques of modern quality
assurance systems to the total testing process to assure the validity
and reliability of the tests and the resulting test data.
Many of the guidelines and test procedures described in Phase I
of this program are directly applicable to the light duty diesel vehicle
emission measurement system. Consequently, the objective of this supple-
ment is to provide additional information and procedures required specif-
ically for light duty diesel emission tests.
1.2 FORMATION OF QUALITY ASSURANCE GUIDELINES
In order to identify those areas requiring special definition
for Phase III, the report for Phase I was reviewed along with the avail-
able information concerning light duty diesel emission test procedures,
to determine necessary revisions or modifications of the Phase I documents.
Sections and paragraphs requiring revision are numbered identically to
the original document to facilitate cross reference. Sections applicable
in their entirety are noted as such.
The quality assurance guidelines for light duty vehicle emis-
sion measurement systems are contained in Sections 1 through 8, with all
references appearing in Section 9. A summary of the contents of each
section follows.
1.2.1 Section 1 Introduction
A description of the background, objective and organization of
the guidelines.
1.2.2 Section 2 Organizing for Quality
A typical Quality Assurance Organization is presented. Quality
functions are identified and the various key elements of a quality
program are described.
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1.2.3 Section 3 Measurement System Analysis
A description of the measurement system defining the equip-
ment, test procedure specifications and tolerances, quality provisions
and other requirements necessary for emission testing of light duty
diesel vehicles.
1.2.4 Section 4 Guidelines for Performance Audits and Maintenance
Procedures
General guidelines are presented for performance inspection
and maintenance of instruments and equipment used in the measurement
systems. Preventive maintenance programs are described for increasing
the reliability and efficiency of the test equipment.
1.2.5 Section 5 Quality Assurance Guidelines for Documentation
of the Measurement System
Guidelines for the development of a documentation system are
presented with representative forms, a description of the manuals, data
recording, and failure analyses used by a quality assurance program.
1.2.6 Section 6 Application of Statistical Quality Assurance Methods
to the Emission Test System
Basic statistical techniques such as control charts, analysis
of variance and data validation as applied to a quality system are
described.
1.2.7 Section 7 Analysis of Variability in the Measurement
of Emissions from Light Duty Vehicles
Sources of variability are identified and, where possible,
quantified to show their effect on the data.
1.2.8 Section 8 Quality Assurance System (On Site) Survey
A procedure and survey form for conducting a quality assurance
survey of a laboratory performing light duty emission testing is presented.
1.2.9 Appendices
Statistical techniques and nomenclatures appear in Appendix A-l.
Appendix A-2 contains control chart multiplication factors. Appendices B-l
and B-2 include a glossary of terms and a list of abbreviations commonly
used in the measurement system. Appendix C of Volume 1 contains general
Quality Management Procedures (QMP) which define those functions identified
as being necessary in a quality program.
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Section: 2
Revision: 0
Date: June 1975
Page 1 of 1
Section 2
ORGANIZING FOR QUALITY
2.1 OPERATIONS MANAGEMENT
2.1.1 Quality Assurance Management
2.1.2 Emission Test Facility Management
Administrative procedures and Quality Assurance functions are
identical with those of EPA-650/4-75-024-a "Guidelines For Quality
Assurance Prgrams For Mobile Source Emission Measurement Systems,"
Phase I, Light Duty Gasoline-Powered Vehicles, June 1975.
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Section: 3(LD)
Revision: 0
Date: June 1975
Page 1 of 3
Section 3
MEASUREMENT SYSTEM ANALYSIS
3.1
APPLICABLE FEDERAL REGISTER PROCEDURES
The measurement system for light duty diesel emission measure-
ments are defined in the Federal Register, Volume 38, No. 151, dated
August 7, 1973 and Volume 39, No. 205, dated October 22, 1974. The
applicable paragraphs of the Federal Register are as follows:
Light Duty
Diesel Cars
85.101
85.102
85.103
85.176-1
85.175-7
85.175-9
85.175-10
85.175-11
85.175-12
85.175-13
85.175-14
85.175-15
85.175-16
85.175-17
85.175-18
85.175-19
85.175-20
85.175-21
85.175-22
85.175-23
Light Duty
Diesel Trucks
85.301
85.302
85.303
85.376-1
85.376-7
85.376-9
85.376-10
85.376-11
85.376-12
85.376-13
85.376-14
85.376-15
85.376-16
85.376-17
85.376-18
85.376-19
85.376-20
85.376-21
85.376-22
85.376-23
Title
General Applicability
Definitions
Abbreviations
Emission Standards for 1976
Model-Year Vehicles
Mileage Accumulation and Emission
Measurement
Test Procedures
Diesel Fuel Specifications
Vehicle Preconditioning
Dynamometer Driving Schedule
Dynamometer Procedure
Three-Speed Manual Transmission
Four-Speed and Five-Speed Manual
Transmission
Automatic Transmissions
Engine Starting and Re-Starting
Sampling and Analytical System
Information to be recorded
Analytical System Calibration
and Sample Handling
Dynamometer Test Run
Chart Reading
Calculations
13
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Section: 3 (LD)
Revision: 0
Date: June 1975
Page 2 of 3
3.2 ELEMENTS OF A MEASUREMENT SYSTEM FOR LIGHT DUTY VEHICLE
EMISSION MEASUREMENT
A requirement of a total quality assurance program is to
maintain control at all important stages of a process. In this measure-
ment system, an analytical process, it is necessary to first identify
its functional elements. In order to categorize these elements, the
measurement system has been divided into two basic operations:
o Vehicle Preparation
o Exhaust Emission Measurement
These two operations are further separated into the tasks or
elements requiring quality consideration in Figure 3-1.
Figure 3-1. ELEMENTS OF A MEASUREMENT SYSTEM FOR LIGHT DUTY DIESEL
VEHICLE EMISSIONS
FEDERAL TEST PROCEDURE
FOR
LIGHT DUTY DIESEL VEHICLES
VEHICLE PREPARATION
AND
PRECONDITIONING
o Receive vehicle
o Vehicle inspection
o Preparation
o Preconditioning
EXHAUST EMISSION
MEASUREMENTS
o Dyno warm-up
o Start-up procedure
o CVS sampling
o Analytical measurements
o Data reduction
3.2.1 Evaporative Emission Measurement
This procedure is not applicable to diesel vehicles.
14
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Section: 3(LD)
Revision: 0
Date: June 1975
Page 3 of 3
3.2.2 Exhaust Emission Measurement
A summary matrix of the vehicle preparation and exhaust emis-
sion measurement for light duty vehicles has been presented in Tables 3-2
and 3-4 in the report for Phase I. The emission test for the diesel
vehicle is identical to that for the gasoline vehicle, with the following
exceptions;
Preconditioning - AMA route is not required. Only a single
7.5-mile FTP cycle is run with a 12-hour soak period. This procedure is
detailed in Test Procedure No. 703-D (Volume II, Phase III).
Exhaust Analysis - Because of the low volatility of the unburned
fuel in the exhaust, a heated sampling system and FID detector are
required. The sample is analyzed and concentration integrated during
the complete FTP cycle. Details of this- procedure are given in Test
Procedure No. 707-D (Volume II, Phase III).
Specifications for the above procedural changes are listed in
Table 4-1. Applicable test procedures for the light duty diesel emission
measurement system are listed in the Table of Contents for Volume II of
this report.
15
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Section: 4
Revision: 0
Date: June 1975
Page 1 of 2
Section 4
GUIDELINES FOR PERFORMANCE AUDITS
AND MAINTENANCE PROCEDURES
The guidelines presented in this section are applicable to
both measurement systems. A listing of additional specifications for
light duty diesel testing are presented in the following supplement to
Table 4-1.
19
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Table 4-1. FEDERAL REGISTER SPECIFICATIONS
LIGHT DUTY DIESEL POWERED VEHICLES
Reference
Paragraph
85.175-10
85.376-10
Procedure or Equipment Description
Diesel Fuel Specification
Specification or Tolerance
Type 1-D and Type 2-D
Refer to referenced paragraph for complete
specifications (a) (b) .
13 o a w
d 01 » n>
o H- rt
ro H- o
o S5
f-l 0 *
It O
VD
-J
Ui
85.175-9
Vehicle Preconditioning
Fuel Temperature 68-86 F
Fill to "Tank Fuel Volume" (40 percent of nominal
tank volume).
Run single FTP cycle (7.5 miles) at ambient of
68-86°F
Soak - Min. of 12 hours 68-86°F
to
o
85.175-18(d) Exhaust gas continuous analytical system 1.
Heated continuous sample line, heated
filter and heated pump.
Heated Hydrocarbon Analyzer (HFID)
o Response time 90 percent full scale, 1 sec.
o Sample transport time, 4 seconds
o Chart record, chart recorder and analog
integrator with two read-outs or chart
recorder and on-line digital computer for
manual or electronic integration of
analyzer output signal during the three
operating phases of the test
85.175-20(b) Hydrocarbon Sample Handling
Set point 300-390°F ±10°F
20 minute warm-up, minimum for electronics,
stabilization point for heated components.
Start integrator for HC at start and end of bag
sampling.
Recorder chart may be integrated manually for
checking integrator or computer.
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Sections: 5(LD)
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Section 5
QUALITY ASSURANCE FOR
DOCUMENTATION OF THE MEASUREMENT SYSTEM
Section 6
APPLICATION OF STATISTICAL
QUALITY ASSURANCE METHODS TO THE EMISSION TEST SYSTEM
The above two sections are directly applicable to both measure-
ment systems. The general guidelines described for documentation and
statistical methods may be incorporated into a quality system for all
mobile source emission testing. When establishing a quality plan for a
particular mobile source testing facility, these two sections of the
Phase I report should be consulted for guidance in such areas as control
of procedural manuals, recording of results, processing and audit control
of emission data, initiating control charts and the implementation of
corrective action procedures.
25
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Section: 7(LD)
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Section 7
ANALYSIS OF VARIABILITY IN THE MEASUREMENT
OF EMISSIONS FROM LIGHT DUTY VEHICLES
Since a majority of the procedures and equipment utilized for
analysis of gasoline vehicle emissions are also used for the determina-
tion of exhaust emissions from diesel vehicles, the sources of variability
are quite similar for both measurement systems. Test variability has
been discussed in depth in the previous report and additional information
on test error analysis may be obtained from the following recently
published papers:
1. H. Klingenberg, M. Fock, K.H. Lies and L. Pazsitka, "A
Critical Study of the United States Exhaust Emission Certification Test-
Error Analysis for the Test Procedure." Presented at the 67th annual
meeting of the Air Pollution Control Association, Denver, Colorado; June
9-13, 1974.
2. M. Fock, K.H. Lies and L. Pazsitka, "Critical Study of
the United States Exhaust Emission Certification Test-Error and Probability
Analysis," presented at the Society of Automotive Engineers Meeting,
Houston, Texas; June 3-5, 1975; Paper No. 750678.
7.1 VARIABLES ASSOCIATED WITH THE MEASUREMENT OF EVAPORATIVE
EMISSIONS
Because of the low volatility of diesel fuel (IBP.330-390F),
evaporative emissions are not a significant contributing factor in the
emissions from diesel-powered vehicles. Consequently, portions of the
light duty procedure associated with this measurement are not performed
on diesel vehicles.
7.2 VARIABLES ASSOCIATED WITH THE MEASUREMENT OF EXHAUST EMISSIONS
The measurement of CO, C0_ and NO for both measurement systems
are identical and the associated sources ana magnitude of test error are
quite similar as illustrated by Figure 7-2 in the report for Phase I,
29
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Section: 7 (LD)
Revision: 0
Date: June 1975
Page 2 of 4
which compares test variability associated with different types of
control systems (gasoline) and the diesel engine. This data also shows
the value of using a lower range for measurement of CO, which is compat-
ible with the lower concentrations of CO emitted by diesel engines as
compared to gasoline-powered vehicles.
Hydrocarbons (HC) must be determined differently because of
their tendency to condense and form aerosols at ambient temperatures.
The diluted diesel exhaust is sampled continuously at a point
just prior to the heat exchanger of the constant volume sampler (CVS).
As this is the primary difference between the two measurement systems,
the following paragraphs will discuss variables associated with this
measurement.
7.2.1 Analysis of Variables Associated with Measurement and Reduction
of Data
The continuous hydrocarbon trace is integrated electronically
or manually for each portion of the Federal Test Procedure (FTP). An
average concentration is determined for each phase, and the data reduced
using the same formulas as for light duty gasoline emissions including a
measurement and correction for background hydrocarbons in the dilution
air bag sample.
Errors in determining the average concentration of hydrocarbons
will have a direct effect on the resultant mass value. In addition to
the sources of variability discussed in 7.2.1.3 of the Phase I Report,
the concentration of hydrocarbons will be affected by the accuracy of
the integrator and the response time (limited to 4 seconds) of the
heated flame ionization instrument, especially during the transient
modes of the cycle. These two particular sources of variability require
periodic verification by manual integration of the recorder trace and
response time. The response time is determined by the injection of a
tracer gas (propane) into the inlet of the CVS. The electronic inte-
grator could also be checked using the propane injections technique, by
correlation with a bag sample collected concurrently with the integrated
continuous sample.
7.2.2 Variation Associated with the Equipment and Test Procedures
Used in the Measurement System
The sample handling system for diesel exhaust measurement
requires a heated sample line, filter and FID detector. The prescribed
temperature is 300 to 390 F controlled within ±10°F of the set point.
This hydrocarbon sampling system has two unique sources of variability,
the temperatures of the sampling system and partial oxidation of the
30
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Section: 7 (LD)
Revision: 0
Date: June 1975
Page 3 of 4
hydrocarbons. These sources are interrelated and have been of great
concern in heavy duty testing, but have received little attention in
light duty testing. Although not mentioned in the Federal Test Proce-
dure, some form of optimization of response should govern the selection
of the temperature set point for the sampling system. This might be
achieved, for example, by varying the operation of a diesel engine at a
steady-state, equilibrium condition.
The diluted exhaust sample is taken at a point just prior to
the inlet to the heat exchanger of the CVS. The function of this heat
exchanger is to maintain a constant temperature at the CVS pump inlet.
A temperature of between 110 to 115 F is usually selected. To stabilize
the temperature of the mix, the heat exchanger must heat as well as cool
the exhaust, raising a rather obvious question. What happens to the
hydrocarbons during the cold portion (first 505 seconds) of the test
when the vehicle exhaust system, the inlet system of the CVS, and the
temperature of the exhaust air mix are all very close to ambient tempera—
tures? At the beginning of the test the exhaust hydrocarbons may absorb
on the surfaces and of course desorb from these same surfaces during the
"hot" portions of the test. This situation would, of course, give an
incorrect exhaust profile integration. The magnitude of this effect
remains to be determined.
The temperature of the sampling system must be uniform over
its entire length. Hot or cool spots can cause erroneous readings of
the exhaust hydrocarbons, such as low readings due to condensation
resulting from cool spots. A high concentration of oxygen is present in
the sample because the sample is diluted with air. Hot spots in the
sample lines can cause partial oxidation of the hydrocarbons. Oxygenated
hydrocarbons have a lower response coefficient for FID detection and
give an erroneously low reading. The severity of the oxidation process
would depend on the intensity of the "hot" spots and the response coeffi-
cients of the FID detector. When setting up a sampling system, the
sample temperatures should be determined at several points along the
system to assure that temperature uniformity does exist.
7.3 MEASUREMENT OF VARIABILITY IN EMISSION MEASUREMENT SYSTEMS
Variability of the measurement system is defined as the
inability to achieve identical test results from repeated tests on the
sajne vehicle without change to hardware or vehicle adjustment specifica-
tions. Variability exists in test results to varying degrees dependent
on the type of variability, test-to-test, cell-to-cell within a labora-
tory, or laboratory-to-laboratory. Several examples of actual correla-
tion data are given in the Phase I Report. In addition, data from an
31
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Section: 7(LD)
Revision: 0
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Page 4 of 4
interlaboratory correlation of four diesel vehicles are given in
Table 7-1. These emission values are given in metric units which may be
converted to the .familiar g/mile basis by multiplying by 1.609.
Table 7-1. AVERAGE 1975 LIGHT DUTY EMISSION
AND FUEL ECONOMY RESULTS
Emission
HC,g/km
CO,g/km
N0x,g/km
Fuel economy
km/1 Carbon
balance
Gravimetric
Reference:
Lab
EPA
SwRI
EPA
SwRI
EPA
SwRI
Nissan
Datsun
0.14
0.22
0.84
0.84
0.85
0.95
Mercedes
220D
0.18
0.15
0.69
0.66
1.02
0.75
Peugeot Opel
504D Rekord
2.07
1.22
2.52
1.47
0.68
0.62
0.24
0.24
0.75
0.61
0.80
0.82
EPA
SwRI
SwRI
11.9
10.6
10.2
11.9
12.1
11.1
9.8
11.3
10.0
10.1
11.1
10.2
K.J. Springer, R.C. Stahman "Emissions and Economy
of Four Diesel Cars." Presented at the SAE Automotive
Engineering Congress and Exposition, Detroit, Michigan;
February 24-28, 1975. Paper No. 750332.
Many of the precautions and checks mentioned in this section
are included in the Test Procedures (Volume II). Each test facility,
depending upon its experience and judgment, should carefully review this
section to determine if some or all of the additional precautions and
checks should be introduced into their operational test procedures as
routine or periodic checks.
32
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Sections: 8 (LD)
9 (LD)
Revision: 0
Date: June 1975
Page 1 of 1
Section 8
QUALITY ASSURANCE SYSTEM SURVEY
Refer to Phase I Report
Section 9
REFERENCES
Additional references for this document
were included in the text
APPENDICES A, B, AND C
Refer to Phase I Report
37
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