EPA-AA-SDSB-87-05
Technical Report
Safety Implications of Onboard Refueling
Vapor Recovery Systems
June 1987
FINAL REPORT
Technical Reports do not necessarily represent final EPA
decisions or positions. They are intended to present
technical analysis of issues using data which are
currently available. The purpose in the release of such
reports is to facilitate the exchange of technical
information and to inform the public of technical
developments which may form the basis for a final EPA
decision, position or regulatory action.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Sources
Office of Air and Radiation
U. S. Environmental Protection Agency
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EPA-AA-SDSB-87-05
Technical Report
Safety Implications of Onboard Refueling
Vapor Recovery Systems
June 1987
FINAL REPORT
Technical Reports do not necessarily represent final EPA
decisions or positions. They are intended to present
technical analysis of issues using data which are
currently available. The purpose in the release of such
reports is to facilitate the exchange of technical
information and to inform the public of technical
developments which may form the basis for a final EPA
decision, position or regulatory action.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Sources
Office of Air and Radiation
U. S. Environmental Protection Agency
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Table of Contents
Section Page
I. Executive Summary 3
II. Introduction 7
III. Onboard Control System Description 9
IV. Design Considerations for a Safe System 27
V. In-Use Fuel System Safety 50
VI. Cost and Leadtime Considerations 61
VII. Heavy-Duty Gasoline Vehicle Requirements 74
VIII. Conclusion 95
IX. References 97
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I. Executive Summary
The purpose of this technical report is to evaluate the
safety implications of requiring onboard refueling vapor
recovery systems on gasoline-powered passenger cars, light
trucks and heavy-duty vehicles. In thaf light, special
attention is given to the analysis of the design considerations
for a safe onboard system and the other measures necessary to
insure that the design considerations incorporated are capable
of providing a high level of in-use fuel system integrity.
Onboard refueling systems are in many ways similar to
present fuel tank evaporative emission systems. The emissions
emanate from the same location on the vehicle and the basic
technology used to control the two types of emissions is quite
similar. Many of the components are analogous, if not
essentially identical, and the configuration/layout of the
systems on the vehicle is also expected to be about the same.
In fact, these two systems and system functions are so similar
that many manufacturers will likely combine their onboard
refueling and fuel tank evaporative emission systems into one
integrated system which can serve both purposes. The fact that
these systems are similar and will be integrated has two
effects on the safety of onboard systems. First, many of the
approaches and techniques used to safely implement evaporative
emission control systems can also be applied to insure the safe
implementation of an integrated onboard refueling/evaporative
emission system. Second, any safety problems related to
integrated onboard/evaporative systems should be evaluated
incremental to present evaporative systems. Quite simply,
there is no need to add a whole new system to the vehicle.
Concerns over the potential safety implications of onboard
systems have, however, been raised. These concerns can be
grouped into four general areas. These include requirements to
pass the National Highway Traffic Safety Administration (NHTSA)
safety tests, the effects of tampering and system defects,
refueling operations, and in-use fuel system safety.
Concerns with the design requirements necessary to comply
with the NHTSA safety tests focused on the need to integrate an
onboard system into a vehicle in a manner which would provide
the crashworthiness and rollover protection demanded by Federal
Motor Vehicle Safety Standard (FMVSS) 301. EPA's analysis
indicates that crashworthiness for the key vapor lines and
other system components could be accomplished using many of the
same approaches and techniques now applied successfully to
evaporative emission systems. Further, the rollover protection
now provided for the fuel tank through the use of a limiting
orifice can be gained through the application of one of the
several rollover valve designs now available.
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Concerns have also been expressed that canister tampering
and component defects could lead to in-use safety problems.
While canister tampering is infrequent, the rate can be reduced
and the potential safety effects eliminated through proper
placement. Manufacturers are expected to consider " the safety
implications of tampering when evaluating canister location
options on the vehicle as they do now with evaporative control
system canisters. While the concern has been expressed that
defects in onboard system components could have safety
implications, no data or other bases have been found that
suggest onboard systems would influence the nature or frequency
of such occurrences as compared to those seen on current
evaporative emission systems. In fact, given the experience
gained by the manufacturers in safely implementing evaporative
controls, it is likely that an integrated onboard/evaporative
system could be implemented with no more (and perhaps less)
problems than present evaporative emissions systems.
Concerns over the safety of refueling operations are
centered on the potential to overpressurize the fuel system.
EPA's analysis finds that use of a liquid seal solves all
overpressure problems, and that if a mechanical seal is used a
simple pressure relief device can be used to eliminate any
overpressure concerns. As discussed in the analysis, a few
other less significant potential problems have very
straightforward engineering solutions.
Finally, while it is clear that onboard-equipped vehicles
can be designed to comply with FMVSS 301 requirements, there
has been concern expressed that fuel system integrity in-use
may decrease by some non-quantifiable amount because FMVSS 301
can't cover all potential accident situations and an onboard
system requires modifications and additions to the present
evaporative emission system. While no test procedure can cover
all potential situations, it does not necessarily follow that
system modifications or additions will cause an increase in
risk over present systems.
Both vehicle and fuel system safety are evaluated as an
integral part of the overall design and development process.
This involves multiple trade-offs, balances, and compromises
with other key design considerations. Given the need to
consider all key design criteria, manufacturers accept or
manage a certain amount of risk. Since the safety demands of
Federal standards such as FMVSS 301 must be incorporated into
vehicles/systems, these standards represent the minimum. In
many cases the level of safety achieved in-use goes beyond that
required by Federal standards, being driven by in-use liability
concerns.
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If a manufacturer perceives that the added risk mentioned
above may exist for one or more of its vehicle models, there
are ways to respond through direct measures or through keeping
the overall risk in-use at acceptable levels through other
design flexibilities. EPA's analysis identifies and describes
a number of these measures. Manufacturers can make vehicles
safer than they are now; an onboard requirement does not
increase the amount of risk a manufacturer need incur or
accept. Manufacturers are expected to integrate onboard
controls into their fuel systems without compromising safety.
Further, as part of overall risk management, implementing
onboard controls provides the opportunity to improve overall
fuel handling and fuel system safety. Refueling spills will be
reduced and flammable vapors will be trapped in the canister
instead of being vented out the fillpipe near the nozzle
operator where inadvertent ignition is possible. Also,
installing rollover valves could improve the safety for those
vehicles now using external fillpipe vent lines without
rollover valves. The positive seal provided by a rollover
valve is an improvement over the "controlled leak" rollover
protection currently provided by a limiting orifice. In
addition, implementing onboard systems could further enhance
safety by providing the opportunity to make other safety
related fuel systems changes which have been delayed for
economic or other reasons (e.g., changing from rear to side
fill). Finally, if a manufacturer chooses to use a collapsible
fuel bladder to control refueling emissions, this would
eliminate all of the potential concerns raised relative to the
canister based onboard system, and would provide improvements
in safety over the present fuel system.
Other key considerations include safety related costs and
the leadtime needed to implement onboard controls safely. This
analysis estimates that safety costs related to implementing
onboard systems will range from $4.50-$9.00 per vehicle. While
the cost estimates for the needed hardware, modifications and
fuel consumption impacts are reasonably accurate, there is some
uncertainty in the development and safety crash testing cost
estimates. However, safety related onboard costs are quite
insensitive to even large changes in the estimates for
development and safety certification.
In a general sense, EPA's estimates are supported by the
fact that the modifications needed for present vehicles to
insure fuel system safety in-use have been acquired relatively
inexpensively, and vehicles with evaporative emission systems
comply with FMVSS 301 today. Much of the groundwork needed to
implement an integrated onboard refueling/evaporative emission
control system safely has been completed and many of the same
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techniques and approaches can be used. The fact that
integrated systems will be used means that some costs incurred
to implement evaporative emissions systems safely will not
reoccur. EPA's analysis has adequately accounted for safety
costs in its estimate of the total onboard system cost. Safety
costs contribute about 25 percent of the $20 cost estimated for
a passenger car onboard system.
With regard to leadtime, given the magnitude of the task
and past experience with implementing evaporative emission and
fuel system integrity standards (FMVSS 301), this analysis
indicates that 24 months leadtime is adequate. However, EPA is
committed to providing the leadtime needed to implement onboard
controls safely and effectively, and is open to considering
additional leadtime or a short phase-in of controls to assist
manufacturers in dealing with problems on unique vehicle models.
Finally, the onboard systems which would be installed on
HDGVs are quite similar to those expected for passenger cars
and light trucks, even though the safety test requirements are
different for HDGVs. With the exception of school buses, the
fuel system integrity testing centers more on evaluation of
fuel tank integrity than vehicle crash testing. Nevertheless,
many of the concerns raised and addressed above regarding
onboard safety for lighter-weight vehicles also apply to HDGVs
and support the judgment that onboard systems can be applied
safely to this class of vehicles within the leadtime laid out
above and for a reasonable cost.
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II. Introduction
EPA has received several comments from the Motor Vehicle
Manufacturers Association, Automobile Importers of America (and
their member companies), and the Insurance Institute for
Highway Safety which have expressed various levels of concern
about the potential safety implications of onboard vapor
recovery systems.[1,2] Also, some preliminary comments
regarding onboard safety have been received from NHTSA's
technical staff.[3] The American Petroleum Institute (which
has independently developed several onboard-equipped vehicles)
and the Center for Auto Safety have expressed support for the
implementation of onboard vapor recovery systems.[4,5] The
purpose of this report is to discuss and analyze the safety
related concerns raised regarding onboard vapor recovery
systems.
Motor vehicle manufacturers face many difficult technical
decisions in the design and development of vehicle systems and
the integration of these systems into new vehicle models. The
difficulty of these decisions often arises from the fact that
this design, development and integration process requires the
simultaneous consideration of a number of key criteria. One of
the most important of these criteria, safety, is normally given
a high priority in the design and integration process.
However, the process also includes careful and prudent
consideration of the trade-offs necessary to deal with other
important criteria such as performance, • reliability, cost,
styling, and regulatory requirements such as fuel economy and
emissions. In each case, manufacturers must find the
appropriate balance of all the important criteria. Since the
design of emission control systems has the potential to affect
the overall safety of vehicles, EPA views safety as a primary
concern when evaluating the feasibility of an emission control
device.
EPA is presently evaluating the use of onboard vapor
recovery systems (onboard systems) as a means of controlling
refueling emissions. The potential safety implications of such
controls require special consideration, because implementing
onboard systems will involve some minor modifications of the
vehicle fuel system. While safety influences all aspects of
vehicle design, fuel system safety and integrity is a key
concern in the design and integration process.
In evaluating the safety implications of requiring onboard
controls, EPA has applied the philosophy that no increase in
overall risk should be caused or accepted, beyond that now
present with today's fuel/evaporative system. This applies to
both compliance with the applicable Federal safety standards
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and the in-use safety of vehicles equipped with onboard
systems. The following analysis will show that straight
forward engineering solutions are available for all of the
potential safety problems which have been identified, and that
while final choices regarding exact system designs lie with the
manufacturers, safe fuel system designs are achievable by all.
This analysis of onboard safety issues and the associated cost
and leadtime generally applies to any canister-based onboard
system design. Further, as will be discussed below, this
analysis indicates that it is quite possible that overall fuel
system safety improvements could accompany the implementation
of onboard controls.
The importance of evaluating the safety of onboard systems
is highlighted by the Clean Air Act (Section 202 (a) (6)) which
directs EPA to consult with the Department of Transportation
(DOT) before requiring the use of onboard vapor recovery
systems. This requirement is intended to insure that all
safety issues have been properly identified and addressed.
This report will also help to assist in the fulfillment of this
requirement.
As outlined below, the remainder of this report is divided
into five sections. The first section following this
introduction (Section III), provides a general description of
an onboard system to aid in the understanding of any related
safety issues. Section IV summarizes and provides EPA's
analysis of the comments received regarding the design of a
safe onboard system, and Section V discusses onboard effects on
in-use fuel system safety. Section VI discusses the effects
safety considerations have on other important factors such as
vehicle costs and leadtime. Heavy-duty gasoline-fueled
vehicles (HDGV) pose similar yet distinct onboard control
system safety issues, and Section VII addresses these
similarities and differences. The final section provides
conclusions.
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III. Onboard Control System Description
Before considering any safety issues, it is important to
have a clear understanding of onboard refueling vapor recovery
systems (onboard systems) and how they work. Likewise, before
considering the characteristics of the control system, it is
important to understand the nature of refueling emissions. The
purpose of this section is to provide the reader with both a
clear understanding of what refueling emissions are and how
onboard systems operate to control these emissions.
In many respects, onboard systems are similar to the
evaporative emission control systems now in use on most
gasoline-powered vehicles. In fact, it has been suggested that
onboard systems are more an extension or modification of
current evaporative emission systems than the implementation of
a new control technology. An explanation of the differences
and similarities between the two systems will provide a better
understanding of the incremental nature of onboard systems
relative to current evaporative systems, and will be useful in
assessing the design, cost, and leadtime implications of
implementing onboard controls safely, which are to be discussed
later in the report.
This section will first briefly describe evaporative
emissions and how they are currently controlled. Next,
refueling emissions will be discussed and similarities between
onboard systems and current evaporative emission systems will
be presented. The section will end with a discussion of the
differences between the two control systems.
A. Evaporative Emissions
Evaporative emissions emanate from two basic sources: the
fuel tank and the fuel metering system (either a carburetor or
fuel injectors). Evaporative emissions arising from the fuel
tank are primarily "diurnal" emissions while those from the
fuel metering system are termed "hot soak" emissions.* This
analysis is primarily concerned with fuel tank evaporative or
diurnal emissions since these emissions are currently
controlled using an approach similar to that envisioned for an
onboard system.
It should be noted that a small amount of hot soak
emissions come from the fuel tank; the fuel tank
evaporative control system would handle these as well as
the diurnal emissions.
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Diurnal evaporative emissions consist of gaseous
hydrocarbons that are displaced from the tank when fuel in the
tank is heated. Fuel heating can result from changes in
ambient temperature or during vehicle operation due to the
vehicle exhaust system and/or recirculation of fuel heated by
the engine. In either case, as fuel in the tank and vapor
above the fuel heat up, more of the liquid fuel evaporates, and
the vapor itself expands, thus causing hydrocarbon vapor to be
released into the atmosphere (unless captured by a control
system). Fuel volatility, size of the vapor space, initial
tank temperature, and the degree to which the tank is heated
can all impact the quantity of hydrocarbons emitted. Diurnal
emissions occur on at least a daily basis, and a system
designed to control these emissions must be capable of handling
repeated evaporative emission loads. Since the early 1970's,
most vehicles have come equipped with a control system to limit
the amount of diurnal evaporative emissions. The next section
discusses the type of control system typically used on today's
vehicles.
B. Evaporative Emission Control System
Figure 1 depicts a fuel tank equipped with an evaporative
emission control system.[6] As can be seen from this figure,
the control system is relatively simple in design and requires
very few components. The purpose of this section is to
describe each of the system's components in terms of both
physical appearance and function.
In order to effectively prevent the escape of fuel tank
vapors to the atmosphere, an evaporative control system must
perform three basic functions. First, the system must limit
the number of exits through which fuel tank vapors might
escape. Second, the exit that does allow fuel tank vapors to
escape must lead to a container where the vapors can be
captured. Third, the system must eventually restore the
capacity of the storage container by purging it of the trapped
vapors. The discussion below describes how an evaporative
emission system performs these three functions.
The first function an evaporative emission system must
perform is to limit the outlets through which vapors can
escape. As can be seen in Figure 1, there are only three
openings through which vapors can pass: 1) the fillpipe
opening, 2) the external vapor vent line to the fillpipe top
(about 1/2" diameter), and 3) the small limiting orifice
(approximately 0.050-0.055 inch) in the top of the tank. The
fuel tank cap is designed to form a tight seal with the
fillneck so that once the cap is secured in place, vapors from
the fillpipe opening and the external vent line are trapped
within the system. Thus, only one outlet exists through which
fuel tank vapors can escape. This single available outlet is
the small limiting orifice in the top of the tank.
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Figure 1
Typical Current Evaporative System
PRESSURE/VACUUM
RELIEF CAP
EXTREMAL VENT
LINE
-LIMITING ORIFICE
NAFLOAT/ROLLOVER I
^ ^—3/8" DIA.
8' LONG
VALVE
14 GALLON FUEL TANK
PURGE VALVE
3/8" DIA.
1 LITER
CARBON
CANISTER
TO PURGE
INDUCTION
POINT
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As the tank undergoes temperature changes, and hydrocarbon
vapors are generated, pressure builds up in the tank (as long
as the fuel tank cap is secure in place). This pressure
build-up is slowly relieved as gas tank vapors eventually force
their way through the only available exit: the small limiting
orifice in the top of the fuel tank which leads to the vapor
storage device (charcoal canister). By limiting the number of
vapor escape passages and routing the evaporative hydrocarbons
to a single point, the control system has successfully
performed the first of its three basic functions. Before
discussing the evaporative emission system's second function,
it is important to understand why the orifice in the top of the
tank is so limited in size.
The orifice in the top of the tank is very small in size
for three reasons. First, it allows pressure to build up in
the tank when vapors are generated. This pressure build-up
inhibits further evaporation and creates a pressure
differential which eventually leads to hydrocarbon vapor being
forced through the limiting orifice. Second, the limiting
orifice acts as a liquid/vapor separator. If liquid gasoline
were to splash up into the vent line leading to the evaporative
emission control storage device (charcoal canister), damage
could potentially occur to the storage media (charcoal).
However, the orifice in the top of the tank is so small that
liquid passes through it at only a very slow rate. Essentially
only vapor is allowed to continue to the canister. This point
leads to the final reason for limiting the size of the vent
orifice to such an extent. Were the vehicle ever to be in a
rollover accident, a very little amount of liquid fuel would be
able to leak from the tank through such a small orifice. Thus,
the limiting orifice is sized large enough to allow for
adequate escape of evaporative emissions, but is small enough
to permit only a slow leak from the fuel tank in the case of a
vehicle rollover and thus provides the protection needed to
comply with FMVSS 301. The cost for this is low. However,
some manufacturers incorporate an additional valve for added
protection; an example is shown in Figure 2.[7]
Storing the evaporative hydrocarbons is the second basic
function an evaporative emission system must perform. Once the
vapors escape from the fuel tank through the small limiting
orifice, they proceed through a vent line (usually about
l/4"-3/8" inside diameter and made of some type of flexible
rubber compound) that leads to a canister containing charcoal.
The canister itself is usually made of plastic and is generally
a cylindrical or rectangular container. Once inside the
canister, the hydrocarbons are adsorbed onto activated charcoal
where they are stored temporarily.
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Figure 2
STANDARD
VERSIONS
ORIFICE
FLOAT
SPRING
HIGH FLOW
FILTERED
The tank mounted spring balanced float valve is a low cost unit designed for venting
fuel tank vapor to the carbon canister. The device employs a float which remains open
under normal conditions. Should the tank level reach a critical height, the float will
close the canister vent line. In the event of extreme vehicle attitude or roll-over, the
float will close the canister vent line.
A filtered tank mounted spring balanced float valve is available that performs the
same functions as the above sketches except the tank side of the part is filtered to
prevent contaminates from entering the part which might effect float closing of the
canister vent line.
For high flow applications that require a large volume of vapor venting, such as fuel in-
jection applications, a high flow valve has been developed that has more than twice
the present flow capacity without loosing other critical performance parameters.
FLOAT VALVE
Borg-Warner Automotive, Inc.
707 Southside Dr., Oecatur, Illinois 62525
Phone 217/428-4631
437
SKETCH
NUMBER
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The working capacity of the charcoal, the quantity and
frequency of the evaporative emissions, and the capability of
the system to restore its working capacity all affect the
amount of charcoal required. Current passenger car .evaporative
emission control systems typically utilize a 0.85-1.5 liter
canister.[8] (This size is sufficient for both diurnal and hot
soak evaporative emissions.) However, a finite amount of
charcoal is used in the canister, so the storage capability of
the canister is limited. Once the evaporative hydrocarbons
have been adsorbed onto the charcoal in the storage canister,
they will remain there until removed. The hydrocarbons must be
stripped from the charcoal periodically in order to restore
enough working capacity to adequately capture each successive
evaporative emission load.
While the vehicle is operated, the evaporative emission
system performs its third basic function of restoring the
storage capability of the charcoal canister. After the
vehicle's engine is running, manifold vacuum is used to draw
hydrocarbon-free air through the charcoal canister.
Hydrocarbons stored in the canister are desorbed into the air
stream which flows into the fuel metering system via a flexible
rubber purge line of about 3/8" diameter. Once purged, the
evaporative hydrocarbons are burned as fuel through normal
combustion in the engine. This process "empties" the canister,
thereby preparing it for the next evaporative emission load.
One aspect of the purge process which needs to be
mentioned but will not be explained in great detail is the fact
that the canister is not continuously purged during vehicle
operation.[8,9] A valve located between the canister and the
fuel metering system is opened and closed at opportune times to
control the purge process and limit disturbances which affect
engine performance and exhaust emissions.
To summarize, the current evaporative emission control
system performs three basic functions: 1) it limits the exits
through which fuel tank vapors can escape; 2) it traps the
vapors in a storage device; and 3) it restores the capacity of
the storage device to prepare it for the next evaporative
emission load.
Onboard systems are very similar to evaporative emission
control systems because they must also effectively perform the
same three basic functions to efficiently control refueling
emissions. However, due to differences in the quantity of
vapors and the rate of generation of evaporative and refueling
emissions, equipping vehicles with onboard systems will require
that some minor modifications be made to current fuel and
evaporative emission control systems.
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The next section provides additional detail regarding
refueling emissions to help explain the fuel and evaporative
system modifications that would be required to equip vehicles
with onboard systems.
C. Refueling Emissions
Three processes contribute to the release of hydrocarbons
during a refueling operation. The first two are collectively
termed displacement losses, the third spillage. First, the
hydrocarbon vapor present in the tank is displaced from the
fuel tank by liquid fuel entering through the fillpipe. If the
vehicle fuel tank is equipped with an external vapor vent line
(as shown in Figure 1), much of the fuel tank vapor escapes via
the external vent line which is connected to the top of the
fillpipe. However, if no such vapor passage exists, the vapor
makes its way out through the fillpipe concurrent to the
incoming liquid fuel. Hydrocarbons are also generated and
released during refueling as a result of liquid fuel
evaporating as it is dispensed into the tank. This second type
of displacement loss is caused by the turbulence in the
liquid/air interface during the refueling process and is
enhanced by the higher volatility of the dispensed fuel
relative to the fuel in the tank. A third source of
hydrocarbon refueling emissions is the evaporation of any
liquid fuel spilled during the refueling operation. Of the
three refueling emission sources, the two displacement sources
are generally much greater (by far), unless a large spill
occurs.
Because the bulk of refueling emission emanate from within
the fuel system, refueling emissions are in many ways similar
to diurnal evaporative emissions. Therefore, it follows that
an effective onboard system can be designed which utilizes the
same basic technology and approach utilized by current
evaporative emission systems. In fact virtually all onboard
systems considered by manufacturers in their comments
incorporate this approach as do the prototype systems developed
to date.[10,11,12,13,14,15] The similarities between onboard
and evaporative emission systems are discussed below.
D. Onboard Refueling Control Systems
1. Similarities with Evaporative Emission Control
Systems
In order to control refueling emissions, onboard systems
must perform the same three basic functions as described
previously for diurnal evaporative emission systems. These
include limiting the number of exits through which refueling
vapors can escape, storing refueling emissions temporarily in a
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charcoal canister, and purging the charcoal canister of the
stored refueling vapors to restore its capacity prior to the
next refueling operation. Because these three functions are so
similar to the three functions a diurnal evaporative emission
control system must perform and the emissions arise from the
same location, extrapolation of known technology leads to the
conclusion that an onboard system would use the same approach
and similar hardware to that which is currently used to control
evaporative emissions. Figures 3 and 4 depict two
representative onboard systems and a comparison with Figure l
shows that onboard controls are very similar in overall design
to current diurnal evaporative emission control systems.
However, while onboard systems do use many of the same basic
components as evaporative systems, (i.e., charcoal canisters,
flexible rubber tubing, purge control valve, etc.), the basic
differences between refueling and evaporative emissions require
a few additional components, and an enlargement of certain
existing hardware is required for the onboard system. These
are the key differences between the two systems.
Before discussing the component additions and
enlargements, an important aspect of the onboard refueling
vapor recovery system must be introduced.
Since both emissions emanate from the same location, a
properly designed onboard system could control both refueling
emissions and diurnal evaporative emissions. Thus, if an
onboard refueling system were incorporated into a vehicle's
fuel system, the current diurnal evaporative emission control
system would no longer be needed. This aspect of onboard
systems has several implications. First, it reduces the
conceived degree of complexity the system adds to the vehicle's
fuel system. An entirely new, larger, more complex system
would not be needed in addition to that which currently
exists. Rather, the current control system would be modified
to be somewhat larger with a small increase in the number of
components. Second, since onboard systems are basically
modified evaporative emission systems, many of the safety
design concerns associated with onboard systems have already
been addressed in current evaporative emission control system
designs. These approaches could also be used in the integrated
system. One final effect a "dual function" control system has
is it requires less "packaging" space and is less expensive to
produce than two separate systems.
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Figure 3
Integrated Evaporative/Refueling System
Nozzle Actuated Valve
Front Mounted Canister
Mechanical Seal
PRESSURE/VACUUM
RELIEF CAP
MECHANICAL
SEAL
•NOZZLE ACTUATED
ROLLOVER/VENT VALVE
" DIA.
/z~.,*-y
r
5/8" DIA.
3' LONG
PURGE
\VALVE
f( P^l /"
,05" DIA. LIMITING ORIFICE
LOAT/ROLLOVER
VALVE
3/8" DIA. TO PURGE
3 LITER
CARBON
CANISTER
14 GALLON FUEL TANK
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Figure 4
Integrated Evaporative/Refueling System
Tank Mounted Valves
Rear Mounted Canister
J-Tube Seal
-PRESSURE/VACUUM
RELIEF CAP
r NOZZLE ACTUATED
ROLLOVER/VENT VALVE ,— 5/8" DIA. I PURGE
^_ r"» ft Q?™ , .
*&
x./\V\
/8" DIA.^.
^:05" DIA. LIMIT
XXA/>^i^ >| —
^^FLOAT/ROLLOVER
N^ SJ VALVE L
••-""""1 >
/^J-TUBE SEAL
DESIGNED SLOW LEAK
V _^
T—3/8" DIA
ING 5' LONG T0 PURGE
CE INDUCTION
POINT
3 LITER
CARBON
CANISTER
14 GALLON FUEL TANK
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2. Additions/Modifications to Evaporative Emission
Control Systems.
The differences between onboard systems and current
diurnal evaporative emission control systems can be separated
into two broad categories: 1) those related to the sealing of
the system, and 2) those related to the magnitude and frequency
of the refueling emissions. Because of these differences,
onboard systems require several additional components, and
several components of the current evaporative system must be
increased in size or slightly modified.
a. Additions to the Present System
Diurnal evaporative emission control systems limit the
number of vapor exits by using a fuel tank cap to close off the
fillneck. However, during a refueling operation, the fuel tank
cap is not in place, and consequently, onboard systems must
rely on some other type of sealing mechanism to prevent the
escape of vapor through the fillneck opening. Currently, two
types of fillneck seals are available for use on onboard
systems — liquid and mechanical.
Liquid fillneck seals utilize modified fillpipe designs to
route incoming gasoline in such a way that a column of gasoline
is formed which prohibits the vapors in the fuel tank from
escaping to the atmosphere via the fillneck. While this may
sound somewhat complicated at first, the concept is fairly easy
to understand with the help of a drawing. Several liquid seal
configurations have been developed, but one design which has
been shown to be particularly attractive from both a design and
cost perspective is the "J-tube" (shown in Figure 5).[16] As
fuel is dispensed into the fillneck, it is forced to pass
through the "U" shaped portion of the fillpipe. A liquid trap
is formed in the "U" shaped portion of the fillpipe which
prevents vapors from escaping via the fillneck. The "J-tube"
extension could be made of metal, plastic or hard rubber.
Another type of fillneck seal which has been shown to be
effective is the mechanical type seal.[14,15] The mechanical
type seal (see Figure 6) is basically an elastomeric device
which forms a close connection with the inserted fuel nozzle
and thereby eliminates any space in the fillneck opening
through which vapor could escape. While both the liquid and
mechanical type seals perform the same basic function of
limiting the available vapor exits, the liquid type seal is
inherently a simpler design.
-------
-20-
Figure 5
J-Tube Liquid Seal
-------
-21-
Figure 6
Mechanical Seal
FU.RPE MODIFICATIONS
ROTARY SEAL
ROTARY
TRAPDOOR
LEAD RESTRJCTCR
FILL PIPE MODIFICATIONS
ROTARY SEAL
ROTAPY SEAL
TRAPDOOR
SPOUT
LEAD FESTFDCTOR
-------
-22-
If a mechanical type seal were used, excessive pressure
could build in the fuel tank if the fuel nozzle automatic shut
off mechanism failed, or if for some unusual reason the vapor
line leading to the charcoal canister became blocked-. To avoid
the possibility of a fuel spitback which could be caused by
this overpressure, a simple pressure relief device would be
needed. More detail on this device will be provided in Section
IV.
Therefore, either type of sealing mechanism - liquid or
mechanical - can be used to prevent the escape of refueling
vapors to the atmosphere via the fillneck. Both sealing
approaches have been tested and provide similar control
efficiencies.[14,15]
b. Modifications to the Present System
The differences in the frequency, magnitude, and rate of
generation of refueling and diurnal evaporative emissions leads
to the need for several modifications to the present
evaporative system. Each of these is discussed below.
(1) Charcoal Canister Size
Generally speaking, on a per event basis, refueling
emissions are produced less frequently but are larger in
magnitude than diurnal evaporative emissions. Consequently,
more hydrocarbon storage capacity (larger charcoal canister) is
needed to control refueling emissions than is needed for
evaporative emissions.
For any given vehicle, the size of the canister needed
depends primarily on the fuel tank volume and the refueling
emission rate. The refueling emission rate is chiefly a
function of the fuel volatility (RVP), dispensed fuel
temperature, and the temperature of the fuel in the vehicle's
tank prior to refill. For canister design purposes the
temperatures and fuel volatility specified in EPA's draft
refueling emission test procedure would be used to determine
the design emission rate which the canister would need to be
able to capture. Canister sizing would then be a function of
tank volume, the design emission rate, as well as
considerations for safety and deterioration factors to assure
an adequate working capacity over the life of the vehicle.
The size of the canister needed for an integrated
refueling/evaporative control system cannot be stated
categorically since there are several other variables which
must be considered such as purge rate, charcoal working
capacity, and canister geometry. However, on average it is
expected that a canister for an integrated
refueling/evaporative system would be approximately 3 times as
large as the one used for the present evaporative system. [17]
-------
-23-
While the larger canister does not present any technical
problems it may cause packaging problems on a few smaller
vehicle models which could lead to canisters being placed in
locations other than under the vehicle hood. While virtually
all evaporative emission system canisters are now located under
the vehicle hood there is nothing inherent in the design of an
onboard system which requires that canisters for integrated
systems also be located there. In fact, there may be some cost
advantage to locating the canister near the fuel tank since the
amount of larger vapor lines can be minimized. It is expected
that manufacturers would place canisters in a location which
provides the optimum mix of safety, cost, and performance
characteristics.
(2) Refueling Vent Line Modifications
Also, in order to accommodate the higher vapor flow rates
associated with refueling emissions, a larger vent line between
the fuel tank and charcoal canister is needed along with a
larger opening in the top of the fuel tank to accommodate the
larger vent line. The current vent line to the canister
associated with the evaporative system is about 3/8 inch. The
vent line with the integrated evaporative/refueling system
would be approximately 1/2 - 5/8 inch in diameter.[ 16] The
larger vent line (and larger opening in the top of the fuel
tank) introduce a few added complexities.
Unlike the limiting orifice used in evaporative emission
systems, the larger opening required for an onboard system
cannot provide liquid/vapor separation or rollover protection.
Consequently, additional devices are required on an onboard
system to meet these needs. The liquid/vapor separator,
examples of which are shown in Figures 7 and 8, is simple in
design and purpose.[14,18] It acts to remove gasoline droplets
from the vapor stream and returns the liquid to the fuel tank
to prevent liquid gasoline from entering the charcoal
canister. Many design approaches are available in addition to
those shown here. The separator itself may be a distinct
component, or its function may be built into another component
such as shown later in Figure 21. In terms of rollover
protection, several simple devices are available which can
prevent fuel spills during an accident, and also provide the
benefits of a limiting orifice described above. These will be
discussed in more detail in Section IV of this document since
rollover and accident protection for the fuel system is
primarily a safety issue.
Aside from the differences discussed above, onboard and
evaporative emission control systems are very similar in
design. They both act to direct, trap, and consume hydrocarbon
vapor. Onboard systems require only a few additional
components, and because they could be integrated into vehicle
fuel systems to handle both refueling and evaporative
-------
-24-
Figure 7
VAPOR-LIQUID SEPARATOR
Mounting Holes
Float Weight
-------
Figure 8
VAPOR OUT
.125 TYR
ADHESIVE SEAL
-.75 .HOSE TYR
- VAPOR/LIQUID IN
LJQUD/COUKNSATE RETURN
UOUD REUEF SLOT
T
MOUNTINQ TABS (3)
4 AR OPCN CEU. FOAM
AR
MESH
UPPER HOUSIM4
PtAST»C
LOWER HOUMNQ
PlAbTIC
CMCCMFTMMI
MATIMM.
•MOV.
VAPOR - LIQUID SEPARATOR
liUtLLlK AttOCIATii. IMC
. MD
»"«ti/ip/ed>CAtii
-------
-26-
emissions, overall control system complexity is not increased
significantly. Also, because of the integration of the
refueling/evaporative emission control functions, it should be
apparent that many of the safety concerns associated with
onboard systems have already been considered in designs of the
present evaporative emission systems. The experience and
knowledge gained in implementing safe evaporative emission
systems provides a substantial base of information to use in
designing and developing safe integrated evaporative/refueling
systems.
3. Volatility Effects
As was mentioned above, the refueling emission rate is a
key factor in the size of the onboard system canister, and the
refueling emission rate itself varies with the fuel volatility
and the dispensed and fuel tank temperatures. For design
purposes, the canister would be sized based on the volatility
and temperature specifications prescribed in EPA's refueling
emissions test procedure. The parameters prescribed in EPA's
procedure are based on near worst case summer season
conditions, so the onboard canister would have capacity to
achieve control under virtually all summer conditions.
However, as average temperatures decrease in the winter,
RVP levels increase and dispensed and fuel tank temperatures
decrease.[19] The question arises as to whether the onboard
canister would have adequate capacity to capture winter
emissions with higher RVP fuels. If the capacity is inadequate
canister breakthrough may occur and some emissions may be
uncontrolled.
Previous studies and analyses conducted by EPA and others
have shown that the refueling emission rate increases with the
fuel volatility (RVP) and fuel tank temperature and decreases
with the dispensed fuel temperature.[19] One study (CAPE 9)
used volatilities and temperatures typical of winter
conditions.[20] Using winter season fuel volatilities and
temperatures in the relationship derived from this study yields
winter refueling emission rates less than the design load
emission rate for the canister dictated by the refueling
emissions test procedure. Winter season values (Dec - Feb)
range from 5.1 to 5.9 g/gal for the northern states where RVPs
are quite high (14-15 psi) while the design load value is 7.25
g/gal. Thus winter emissions would be controlled as well.
EPA is presently considering a program to control the
volatility level (RVP) of in-use fuels during the summer months
(mid-May to mid-September). As part of that program, in-use
volatility levels nationwide would be limited to levels about
21.7 percent less than the current ASTM level for that area
during the affected months. If that program was enacted, the
volatility of the fuel for refueling emissions testing would be
-------
-27-
set at 9.0 psi RVP, the design load emission rate for the
canister could drop to 6.0 g/gal, and onboard canisters could
be somewhat smaller. However, as can be seen from comparison
with the emission rate figures presented above, winter
emissions would still be controlled. \,
While not the primary motivator, in-use volatility control
may have some attendant safety benefits. Lower RVP fuels
generate less vapor and thus could be considered somewhat safer
in a general sense. More specifically, lower volatility fuels
generate less fuel tank evaporative emissions and thus could
reduce fuel tank pressurization problems which occur on some
vehicles with damaged or altered evaporative emission systems
(e.g. non-standard gas caps) operating under extremely atypical
conditions. This pressurization could lead to some fuel/vapor
being released from the fillpipe when the gas cap is removed,
especially if the fuel tank was relatively full at the time.
Lower vapor pressure fuel would reduce the degree of
pressurization which could occur under these circumstances and
thus reduce or eliminate the spillage which may result. Thus
the safety of refueling operations would be improved.
IV. Design Considerations for a Safe System
As was discussed previously, several commenters have
expressed concern regarding the potential safety implications
of onboard systems. A review of these comments indicates that
these concerns fall into two broad areas: the design of a safe
onboard system and effects on in-use fuel system safety.
Concerns in the first area will be addressed in this section.
The section which follows (Section V) will address the later
area of concern.
Comments received regarding the design of a safe onboard
system fall in three categories: 1) safety test design
requirements, 2) safety effects of maintenance, defects,
tampering and repairs, and 3) refueling operation safety.
EPA's summary and analysis of the comments in each category is
presented below.
A. Safety Test Design Recruirements
1. Introduction
Before analyzing the safety test design requirements it is
interesting to look at fuel system safety from an in-use
perspective for passenger cars meeting FMVSS 301. Presently,
about 1.6 percent of all accidents involve a vehicle rollover
of some type and about 0.5 percent of the rollover accidents
result in a fire. [21] This results in a fire rate of 0.008
percent. Thus, neither rollover accidents or subsequent fires
are common. Similarly, 0.14 percent of all front and rear end
-------
-28-
collisions lead to a vehicle fire.[21] Although vehicle crash
fires are seemingly uncommon, approximately 1600 fatalities
result each year from these fires.[22] Thus, from an in-use
perspective, vehicle crash fires are unusual but serious events.
One of the most effective ways to protect against vehicle
crash fires is to restrict fuel leakage during accidents by
insuring the overall integrity of the vehicle's fuel system.
To insure fuel system integrity during a crash, all currently
manufactured passenger cars and light-duty truck's with a Gross
Vehicle Weight Rating (GVWR) of 10,000 Ibs or less, must comply
with Federal Motor Vehicle Safety Standard (FMVSS) 301.[23]
Basically, FMVSS 301 requires a vehicle to restrict fuel
leakage to less than one ounce per minute when subjected to a
rollover test following front and rear collisions at 30 miles
per hour (mph), and side collision(s) at 20 mph. In a rollover
test, a vehicle is turned on each of its sides and completely
upside down and held in each of these three positions for a
period of five minutes. Onboard system designs must take into
account and protect against fuel leakage or other fire hazards
which could occur in FMVSS 301 testing.
Along these lines, two issues exist regarding the design
of an onboard system capable of passing FMVSS 301. These
include rollover protection and the crashworthiness of key
onboard system components and connections. As was discussed
previously, onboard systems require the use of a somewhat
larger vent line (about l/2"-5/8" diameter as compared to
l/4"-3/8" on current vehicles) between the fuel tank and
charcoal canister, and a similar sized orifice would exist in
the fuel tank. While the external vent line used on many
current fuel tanks also requires a 1/2" orifice, manufacturers'
onboard system designs may incorporate a rollover protection
device to protect against fuel leakage during an FMVSS 301
rollover test even though present designs do not. Also,
vehicle crashes present the possibility of direct or indirect
damage to fuel system components. In some cases this damage
could lead to a fuel leak or increase the potential for a
vehicle fire in some other portion of the fuel system. Thus a
properly designed onboard system must not compromise the
crashworthiness of the system and key components.
2. Rollover Protection
A rollover protection device is basically a valve that
would close off the refueling vent line whenever the risk of
fuel leakage existed. Several rollover protection designs have
been proposed by auto manufacturers and other interests which
could adequately perform this safety function. Several of
these are discussed below.
-------
-29-
One design which has been proposed by several sources can
be termed the nozzle actuated valve. The valve is integral to
the fillpipe and is located near the top of the fillpipe,
perhaps near the leaded fuel restrictor. During refueling, the
valve is opened by the insertion of a fuel nozzle. With the
valve open, a clear passage through the vent line is available
to allow for the routing of refueling vapors to the charcoal
canister. Other than during refueling, the valve remains
closed and effectively eliminates the potential for fuel
leakage through the refueling vent line during a rollover
accident. Figures 9 thorough 15 show five different nozzle
actuated valve assemblies capable of performing the rollover
protection function.[13,15,18,24] Figures 9 through 13 also
demonstrate how nozzle insertion would open the valve to
provide a large orifice for the venting of fuel tank vapors
during refueling and when the nozzle is removed the vent line
would be closed.
Also, while a rollover protection device might be
necessary, it is interesting to note that many current
production passenger car and light truck models (mostly side
fill) employ an external vapor vent line of about 1/2" diameter
that connects the fuel tank to the top of the fillpipe (see
Figure 1). This external vent line is approaching the size
needed for a refueling vent line, and yet manufacturers have
included these external vent lines without any rollover
protection device. As will be discussed below, depending on
the design used, a rollover protection system may actually
enhance safety over current designs.
This analysis has presented several basic rollover valve
designs capable of providing the protection required by FMVSS
301 tests. Manufacturers could choose to implement one of
these approaches, or could develop another. The approach
ultimately selected will be that which provides cost efficient
protection, is compatible with the other components of the
manufacturers onboard system, and can be integrated effectively
into the vehicle design from both safety and operational
perspectives.
3. Component/System Crashworthiness
The second issue regarding safety test design requirements
involves the crashworthiness of the key components of an
onboard system. This includes those components most
susceptible to damage in an accident (nozzle actuated rollover
valve, charcoal canister) and the structural integrity of the
vapor line (and connections) which may exist between the top of
the fuel tank and the rollover valve. A problem in one of
these three areas could cause a vehicle to fail FMVSS 301 tests
and must be addressed in proper system design. Each of these
concerns is discussed below.
-------
Figure 9
SEALED FILLER ftiECIt SYSTEM
TANK VENT VALVE ASSEMBLY
(DURING NORMAL VEHICLE OPERATION)
TO CANISTER -
LIQUID STOP
SHUT-OFF
SEAL
LEADED FUEL
DEFLECTOR
GAS CAP
OVERFILL
RELIEF VALVE
-------
Figure 10
SEALED FILLER NECK SYSTEM
TANK VENT VALVE ASSEMBLY
(DURING REFUEUNQ EVENT)
TO CANISTER -
VAPOR
FROM
TANK
LIQUID STOP
r- LEADED FUEL
DEFLECTOR
I
to
OVERFILL
RELIEF VALVE
SEAL
FUEL NOZZLE
-------
Figure 11
LIQUID SEAL SYSTEM
TANK VENT VALVE ASSEMBLY
(DURING NORMAL VEHICLE OPERATION)
TO CANISTER -
SHUT-OFF VALVE
LEADED FUEL
DEFLECTOR
GAS CAP
I
OJ
M
-------
Figure 12
LIQUID SEAL SYSTEM
TANK VENT VALVE ASSEMBLY
(DURING REFUELING EVENT)
TO CANISTER -
VAPOR
FROM TANK
SHUT OFF
VALVE
LEADED FUEL
DEFLECTOR
U)
FUEL NOZZLE
-------
Figure 13
NOZZLE-ACTUATED REFUELING EMISSIONS VAPOR VENT VALVE
Vapor from
Vapor/Liquid Separator
Vapor to
Canister
-------
Figure 14
NOTES:
I. REMOVE AIL BURRS 4 SHARP EOGti.
2. NYLOU PARTS MAX BE FABRICATE o FROM
RAYTIC COMPATIBLE W/OASOUNe A METHANOU.
3. ALL DIMENSION* MOT &HOWN.
— .06TY«
ALL OVER
.04
.19
10
RWET WASHER PLATE
R»VET
CAM
CAM PtM
IAMIMATED.
CAM FOU-OWEP,
CAM
FLOAT BALL
UPPER VALVC
LOWER VALVE. H&N4.
Ot*CM»flON
S. STtEL.
ft.
ALUM.
5T.
H-H.OH
ALUM.
MYLOH
NYLON
NYLON
31 ft
314
REFUELING VAPOR VENT VALVE
ASSEMBLY
MlitLLtH Afl3QCIATe$. IMC •»lllmOf«. UP
SCALE: FOU. |
-------
-36-
Figure 15
"Toyota Concept"
Rubber Seal
Valve
to Canister
from Fuel N,
Tank '
Refueling
Nozzle
to Fuel Tank
-------
-37-
However, before beginning these discussions, it should be
noted that component/system crashworthiness is not at all a new
concern. Manufacturers must address these same concerns in the
design of the current evaporative emission systems.- Given the
similarity of onboard refueling and evaporative controls, and
that many systems will be integrated, there should be no new or
unique problems in this area.
a. Rollover Valve
First, the crashworthiness of the rollover protection
device is a design consideration for nozzle actuated valves,
since they would be located near the exterior shell of the
vehicle. Integration of nozzle actuated valves into the
overall vehicle design would have to include a consideration of
the potential to sustain damage if struck in a collision.
However, this design consideration is straightforward, and
it is reasonable to expect that manufacturers can and will
integrate rollover valves into their fillpipe designs without
decreasing the structural integrity of the fillpipe while
providing crashworthiness for the valve. For example, it is
worth noting that vehicle manufacturers have dealt with similar
problems in their designs of fillpipes, external vapor vent
lines, and gas caps, and in fact, one would not expect the
nozzle actuated rollover valve to be any more susceptible to
damage than these components. As was mentioned previously, the
1/2" external vent line lies in this same area on the vehicle,
and yet manufacturers have included such vent lines without a
rollover protection device.
b. Vapor Line
Similarly, manufacturers will have to be cognizant of the
structural integrity of the vapor line and vapor line
connections, if any, between the fuel tank and the rollover
valve. These would have to be designed to withstand the
stresses which might occur in a crash in order to maintain fuel
system integrity. However, there is no significant engineering
challenge to accomplishing this objective.
The integrity of this portion of the vehicle's vapor line
can be assured through use of a vapor line material of proper
strength, flexibility, and durability. A number of vapor lines
of different material, wall thickness, and construction are
currently available. In addition, routing of this portion of
vapor line is another design parameter available to
manufacturers. As a matter of course, manufacturers are
expected to insure that the line is protected from abrasion and
normal wear and that it is not in a vulnerable location in the
event of a collision. This is considered straightforward given
that on integrated systems the refueling vapor line now
replaces that used for control of diurnal evaporative
-------
-38-
emissions. Similar routings would be expected. Vapor line
integrity and connections in current vehicles must meet similar
requirements, and it is reasonable to expect that similar
materials and connecting approaches would be used.
Finally with regard to vapor line integrity and
connections, it is worth noting that many vehicle models now
use a flexible insert between the fillpipe and fuel tank to
enhance the fuel system safety in-use (see Figure 16).[15]
Similarly, in many vehicle models the external vent line
actually incorporates a flexible vapor line which connects the
metal portions of the external vent line from the top of the
fuel fillpipe and the fuel tank (see Figure 16). These
connections are subject to the same performance requirements as
would be needed for onboard system vapor lines and in some
cases are even more critical and demanding. Evidence is that
these have been incorporated safely. The manufacturers'
experience with current vehicle evaporative and fuel systems
described above demonstrates that vapor line and vapor line
connections can be made to withstand the stresses which occur
in a vehicle accident.
c. Charcoal Canister
Concerns regarding the crashworthiness of the charcoal
canister center on the possibility that a canister ruptured in
an accident could present a fire hazard if an ignition source
exists nearby.
Even if the rupture of the integrated refueling/
evaporative canister occurred in some cases, the potential
hazard should not be overstated. While carbon canisters do
contain gasoline vapor, they are strongly adsorbed to active
sites within the carbon bed and not easily released to the
atmosphere. Thus, even if a canister were crushed and its
contents dumped, gasoline vapor would not be present in the
atmosphere in sufficient quantity to be flammable. There is no
available evidence of "canister fires" in any accidents
involving vehicles with evaporative systems. The fact that
onboard canisters would be larger and would hold more vapors
initially than current evaporative systems makes no
difference. While the refueling load to the canister is larger
than the evaporative load, after the first few miles of driving
the canister would be purged such that the amount of vapor
remaining in the canister is essentially the same as that
present in current evaporative emission canisters alone.* The
* Due to the nature of the charcoal used to trap hydrocarbon
vapors, and strict certification test requirements,
hydrocarbons would be quickly stripped from the charcoal
early in the purge process. Therefore, during most of the
operation of the vehicle (90 percent), the charcoal
canister does not contain enough hydrocarbon vapor to
present any safety risks.[9]
-------
Figure 16
BUICK CENTURY FUEL TANK AND FILLPIPE
PRODUCTION CONFIGURATION
Fuel Sending Unit
and Vent Orifice
Nozzle
Spout
12%"
-------
-40-
lack of risk from charcoal canisters is supported by a recent
submission from Nissan to EPA, stating that no safety problems
would be expected with refueling canisters.[25] Thus it could
be argued that the hazard, if any, is not significantly
different than that now found on present systems. Thus, it is
hard to perceive any added risk from the use of a larger
charcoal canister.
Nevertheless, if a manufacturer believed that the canister
posed a potential risk, the risk could be eliminated through
placement of the canister in a protected area such as the rear
of the engine compartment or in some underbody area as has been
suggested by some manufacturers.[12,13] In most cases it is
expected that manufacturers would simply place the integrated
refueling/evaporative canister where the present canister is
now located; in these cases no new design issues really exist.
d. Summary
In summary, current fuel and evaporative emission systems
must meet the same FMVSS 301 requirements and much of the
experience gained in designing and building current systems can
be directly extrapolated to implementing an onboard system.
The analysis presented above leads to the conclusion that
straightforward, viable engineering solutions exist to address
any potential safety design concerns, and that onboard systems
can be incorporated into the vehicle's fuel/evaporative system
without compromising fuel system integrity or reducing the
vehicle's ability to pass FMVSS 301 requirements.
While an onboard system can be designed to provide fuel
system integrity both in FMVSS 301 testing and in-use, it is
prudent to consider the effects of maintenance, defects,
tampering, and repairs on these systems, and means to address
any potential problems which may exist. These issues will be
addressed next.
B. Maintenance, Defects, Tampering and Repairs
Even if a system is designed properly and functions safely
under "normal" and "extreme" in-use conditions, some question
remains as to the potential effects of maintenance, defects,
tampering and repairs on onboard system safety.
Maintenance is the prescribed actions needed to keep a
system operating as designed. Defects involve the improper
operation of the system or system components caused by design,
manufacturing, or assembly errors. Tampering involves the
intentional disablement (partial or total) or removal of the
system or a component within the system, and repairs involve
restoring or replacing the system or system components because
of malfunction or damage. Each of these events and their
safety effects are discussed below.
-------
-41-
1. Maintenance
First, an onboard system is expected to be essentially
maintenance free (no scheduled maintenance) as are current
evaporative control systems. EPA's emission factor testing has
found that non-tampered fuel-injected vehicles generally comply
with the evaporative emission standards without maintenance.
Furthermore, EPA's requirements for light-duty truck and
heavy-duty gasoline vehicle emissions certification do not
allow evaporative system maintenance up to 100,000 miles, and a
similar requirement is being considered for an onboard system.
The technology used here can be used for passenger cars as
well. Thus, maintenance will not be necessary for proper
functioning of an onboard system over the life of a vehicle.
Therefore, lack of prescribed maintenance will not lead to
safety problems.
2. Defects
Second, with regard to defects, the primary safety related
concern deals with the possibility that defects in the
operation of one or more components of the onboard system
in-use might lead to safety problems for the vehicle. This
includes possible problems with components such as the
liquid/vapor separator, purge valve, charcoal canister and
rollover valve.
Since onboard system components such as the liquid/vapor
separator, purge valve, and charcoal canister are very similar
to those used in evaporative systems, one method to assess the
potential safety effects of defects is to review the experience
seen with evaporative systems. In an effort to quantify the
potential for defect problems regarding onboard systems, three
different computer files provided by NHTSA were reviewed for
evidence as to defects pertaining to the evaporative emission
system which could impact vehicle safety in-use.[26] The files
reviewed covered recalls, service bulletin reports, and owner
complaints current as of November, 1986 for all three vehicle
classes (passenger car, light truck, and heavy-duty gasoline).
A review of the recall files revealed only 12 cases that could
be even remotely linked to the evaporative emission system out
of an estimated 3,000 families which have been certified with
evaporative emission systems. Service bulletin reports for
dealers added an additional 21 cases for a total of 33 possible
problems out of over 3,000 families. None of these were
identified as having caused an accident; the vast majority were
more emission system performance than safety defects. Finally,
a review of the owner complaints indicated only about 100
problems out of over 180 million vehicles sold with evaporative
emission controls. In only a few of the owner complaints did
safety problems actually occur, and no significant damage was
reported. On a percentage basis these potential problems are
very small.
-------
-42-
Two other valuable observations can be drawn from a review
of these files. Problems/complaints have diminished with newer
model year vehicles with evaporative controls, which
demonstrates that gaining experience leads to product
improvement. Given the similarity between onboard refueling
and evaporative emission controls, and the fact that the two
systems will be integrated in most cases, much of this
experience will be directly transferable to onboard systems and
thus improve in-use performance. Second, the review of the
owner complaints files indicated no trends other than those
related to improvements in newer model year vehicles; thus no
systematic problems in components or systems were evident.
Further, it is important to note that the very mechanisms
used to generate the files for this survey would actually act
to help eliminate any potential in-use safety effects of
onboard systems defects. Dealer service bulletin reports are
effective in dealing with problems raised at the dealerships,
and owner complaints assist the manufacturers and NHTSA in
assessing the need to conduct voluntary or mandatory recalls.
Finally, to place the potential for defect problems from
onboard systems in context, it should be noted that the onboard
risk is essentially incremental to that now seen for
evaporative systems, since in most cases the refueling and
evaporative systems would be integrated. On an incremental
basis, the frequency of defects would likely be unaffected.
Finally, since a rollover valve could be used on some
onboard system designs specifically to enhance safety and they
are not used on current vehicles, it is worth discussing the
possibility of valve defects. First, it should be noted that
defects in these valves should be rare. Manufacturing
engineering techniques permit the development and production of
highly reliable valves and statistical quality control
techniques are available to insure that production valves meet
design standards. In fact, if a rollover valve is defective at
the vehicle assembly point, the vehicle will probably not be
able to accept the fuel provided at the end of the assembly
line, and repairs will be needed even before the vehicle leaves
the plant. Second, to insure in-use protection, rollover
valves must be designed to fail in the closed position. This
would be considered "safe" because a closed position valve
failure would never cease providing rollover protection and it
would effectively block the refueling vent line and make
refueling the vehicle extremely difficult. This difficulty
would provide incentive for the vehicle operator to identify
and repair the failure. If the valve failed during operation
of the vehicle, the fuel tank would vent any vapors through the
limiting orifice or gas cap to prevent any pressure build up
(See Figures 3 and 4). Also, rollover valve failure might be
one component of an onboard system which could be incorporated
into onboard vehicle diagnostics and thus allow the operator
notice of the problem when it occurs and provide an opportunity
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-43-
for repair before the fuel level becomes critical. Fail safe
designs would be effective in achieving both protection and
repair, and that the other measures discussed above would
assist in eliminating or addressing any in-use defects.
3. Tampering
A third area of potential safety problems involves the
effects of possible system tampering. While several types of
tampering occur with evaporative emission systems (see Table
1), past in-use experience with these systems shows that only
one type, disconnection and/or removal of the charcoal
canister, might be a safety problem for onboard systems. This
type of tampering poses a possible safety hazard because during
the refueling operation it would lead to a flow of gasoline
vapor into the atmosphere at the point where the missing
canister had been located. While the gasoline vapor mixture
reaching the canister location in this situation would be well
above the upper flammability limit, it would briefly be
flammable as the vapor dissipates and at the air/vapor
transition zones. If a spark or other ignition source were
present, the mixture could briefly burn. While this situation
is likely to be rare, the possible safety effects of such an
occurrence must be considered in the onboard system design.
There are several points which need to be made relative to
canister tampering. First, this is not unigue to onboard
systems - similar potential problems now exist with evaporative
emission canisters but a safety concern regarding tampering
with evaporative emission system canisters has not surfaced.
Second, using current evaporative emission canisters as an
indicator, this situation is likely to be rare for integrated
onboard refueling/evaporative canisters. As is shown in Table
2, current average canister tampering is only about 3 percent
of all vehicles, and similar rate would be expected for
integrated refueling/evaporative emissions canisters. Third,
if the canister were located in an area which would be
difficult to access, tampering could be further discouraged.
Further, the potential problem could be reduced through
proper placement of the canister in a location distant from any
ignition sources. Possible locations include the rear of the
engine compartment (as is done with some evaporative canisters)
or in some underbody area as has been suggested by some
manufacturers for packaging reasons. Placing the canister in
an underbody area would also reduce the potential for tampering
by making it less accessible to the owner as mentioned above.
While canister tampering is infrequent, and means exist to
discourage such actions even further, good engineering judgment
dictates that canisters not be placed in a location where
tampering could create a safety hazard. It is expected that
manufacturers will take all reasonable steps necessary to
reduce tampering, and that refueling canisters would not be
placed in locations where their removal could create a safety
risk.
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-44-
Table l
Types of Tampering Problems
Arid Typical Rates of Occurrence
Rate of
Problem Occurrence (%)
Gas Cap Removed- .. . 1.2%
Canister Vacuum Disconnected - 1.7
Cap Removed & Canister Vacuum Disconnected 0.1
Canister Removed 0.3
Non-vacuum Canister Disconnection 0.2
Total Disablements 3.5%
Tampering rates calculated from the combined data from the
EPA Tampering surveys performed in 1982, 1983 and 1984
(9,142 vehicles).
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-45-
Table 2
.Canister Tampering Survey Results
By Year*
Passenger Car and Light Truck**
-Year
1978
1979
1980
1981
1982
1983
1984
1985
Tampered
3
2
No Report
2
2
5
3
4
Avg
* Motor Vehicle Tampering Survey - 1985, US EPA, OAR, QMS,
FOSD, November 1986.
** Since HDGVs did not require evaporative controls until
1985, survey data is currently not available for these
vehicles.
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-46-
4. Repairs
Finally, repairs of onboard systems may have some safety
implications. Since an onboard system is essentially
maintenance free, any damage to the system (besides that from
defects or tampering) would in most cases result from a vehicle
accident. An accident which damages the vehicle's fuel system
would be relatively severe and require critical vehicle
repairs. Such vehicle repairs, in general, would demand a
professional certified mechanic in a licensed facility. These
mechanics should be properly trained and have access to current
shop manuals to repair and package the fuel system and onboard
components correctly to ensure effective and safe performance.
They also should be aware of any potential safety hazards of
improper installation or omission of onboard system
components. Furthermore, these mechanics would normally have
no economic incentive for improperly repairing an onboard
system or omitting some components since the facility would be
compensated for all of the parts and time spent repairing the
vehicle.
In any repairs of the fuel system with an onboard control
system, there is only one critical area with respect to
safety. This critical area is the connecting line between the
top of the fuel tank and the rollover valve at the top of the
fillpipe. An improper installation or connection in this area
could result with fuel leakage in the event of a vehicle
rollover. This connection, however, is not unique to fuel
tanks with onboard systems. It is very similar to the external
vapor vent line that appears on many of today's vehicles, and
thus incrementally the situation may be no different than on
today's vehicles. Thus, repairs of onboard systems should not
create any potential safety hazards as compared to present day
fuel systems.
5. Summary
In summary, component maintenance, defects, tampering, or
repairs should not create the potential for in-use safety
risks. An onboard system is expected not to require any
scheduled maintenance. Thus, any lack of maintenance by the
vehicle owner should not introduce safety hazards.
There is no evidence to indicate that possible defects in
other onboard system components would lead to safety problems.
There are very few defects with present evaporative emission
systems, and since it is likely that refueling and evaporative
emission systems would be integrated, the overall defect rate
is likely to be no different than that seen in present
vehicles. Further, methods are available to assure that
reliable rollover valves are installed in vehicles and to
insure rollover protection in the unlikely event of a valve
failure.
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-47-
While canister tampering effects must be considered, it
should be noted that it presently is uncommon, and this low
rate is expected to continue for onboard systems. Also,
tampering could actually decrease through judicious canister
placement on the vehicle. Nevertheless, prudent design
practices dictate that manufacturers not place canisters in a
location where tampering could lead to a safety problem, and it
is expected that this approach would be followed.
Any repairs of an onboard system, besides those resulting
from defects or tampering, will probably occur as a consequence
of accident damage to the vehicle. Since the damage will most
likely be severe, it will require the use of a certified
mechanic who is properly trained for such repairs. Further,
the only critical area of the onboard system which could impose
any safety hazard if improperly repaired are the components and
connections between the fuel tank and fillpipe top. Repairs
are also critical in this area for current vehicles using
external vapor vent lines, so there may be no change in risk
over present vehicles. Repairs to an onboard system should not
inherently increase the potential for in-use safety risks.
An onboard system design must also include consideration
of potential effects on the safety of refueling operations.
This is discussed in the next section.
C. Refueling Operation Safety
1. Fuel Tank Overpressure During Refueling
The first potential safety issue involves the possibility
of pressure build-up in the fuel tank during the refueling of a
vehicle equipped with an onboard system. Whenever a system is
designed to be "sealed" from its environment, some forethought
must be exercised to evaluate the possibility and consequences
of an overpressure within the system.
Although an onboard system does not completely seal off a
vehicle's fuel tank, it is designed to allow for only one
opening, the refueling vapor vent line. If for some unusual
reason, the vent line were to become fully or partially blocked
or the nozzle automatic shut-off mechanism failed during a full
refill, excess pressure could build in the fuel tank. This
concern is only associated with an onboard system utilizing a
mechanical seal as illustrated in Figure 3. With a liquid seal
system (see Figure 4), excess pressure cannot build up in the
tank during refueling because fuel would simply flow out the
fillneck opening (the same way it currently does) and the
nozzle operator could then stop the fuel flow. Liquid seal
systems would function in the same manner as current fuel
systems. From the nozzle operator's viewpoint, the refueling
operation remains the same.
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-48-
If a manufacturer elects the mechanical seal design, he
must incorporate a simple pressure relief device capable of
relieving fuel tank pressure. In the event of a nozzle failure
or vent line blockage, this device would eliminate potential
tank overpressurization by opening an "emergency" passage to
the atmosphere through which pressurized vapor and any gasoline
would spill onto the pavement or some other location noticeable
to the nozzle operator. This spillage would make the fuel pump
operator aware of the problem and fuel flow could be stopped
without causing damage to the fuel system or causing fuel to
spitback on to the operator.
There have been several different designs suggested for
such pressure relief devices. A sample design is shown in
Figure 17 which would be incorporated directly into the design
of the fillpipe so that the condition would be noticeable by
the operator.[18] The operator would then be prompted to
repair any problems in order to resume normal refueling
actions. (The need for prompt repair would have positive
safety and air quality implications.) As was shown in Figure
9, it might also be possible to incorporate the pressure relief
function into some other component of the system such as the
rollover valve. Any overpressure concerns can be eliminated
through a simple pressure relief device such as these.
2. Pre-Refuelinq Overpressure Effects
Another potential safety issue raised relating to
refueling operations has to do with the "U" bend in the
"J-tube" fillneck seal. If the tank vent became blocked, and
pressure built up substantially in the tank, upon removal of
the fuel cap, the liquid gasoline which was left standing in
the "U" bend could be spit back out the fillpipe.
This concern can be easily addressed by drilling a small
hole in the bottom of the "U" bend (see Figure 4 and 5), which
would allow any fuel left standing in the fillpipe subsequent
to a refueling event to drain out into the fuel tank. Given
the range of fuel dispensing rates seen in-use, this hole can
be sized to quickly provide drain capacity and still provide
the seal needed during refueling. Furthermore, the hole size
can be sized so that no foreign object will block it during a
refueling event. By evacuating the column of fuel left
standing in the fillpipe, the potential for spitback to occur
upon removal of the fuel tank cap would be eliminated.
Fillpipes with a "J-tube" seal employing a drain hole have been
tested. These tests show that these seals provide refueling
emission control efficiencies comparable to those of mechanical
seals.[16]
-------
l-'iyure 17
BOTTOM
VIEW
.O* MIN. I
TOP VIEW
SECT. A-A
NOTES:
ALL OURIU> AKIO SHARP
.01 R MAX OR CHAMBER.
ROTA.RV SHAFT SEAL I) A
PART. PART NO. rw>.
'Of'
UPPCR
ROTARY stiArr ieAi_
LOWER RETAINER
VITOM
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NOZZLE 5CAL/REUEF VAU/E
ASSEMBLY
»aOCIATH. INC
i. MO
-------
-50-
3. Summary
The analysis presented above demonstrates that simple,
straightforward engineering solutions exist for the specific
concerns raised by the commenters. In all cases, manufacturers
have a number of design options available to address these
concerns.
V. In-Use Fuel System Safety
1. Summary of Concerns
Some concern has been expressed that any time a system
increases in size or complexity, the potential for a failure
within the system also increases. Applying this line of
thinking to vehicle emission control systems, it has been
suggested that onboard systems would inherently decrease
overall fuel system safety because several components are
larger and a few more components are needed than for current
evaporative emission systems. In-use vehicles are subject to
innumerable accident situations, and some concern exists as to
whether or not an increase in component size/number could lead
to safety problems.
Further, it has been stated that even if a vehicle fuel
system is safe enough to pass FMVSS 301, it does not insure
that it is free of all safety risks in-use as evidenced by the
number of vehicle crash fires that occur each year. It has
been argued that vehicles eguipped with an onboard system could
pass all FMVSS 301 tests and yet directionally increase risk
in-use by some unguantifiable (presumably small) amount. Thus,
it follows that because some in-use situations differ from
FMVSS 301 tests, onboard systems must not only be designed to
be capable of passing Federal safety standards, but these
systems must also be designed so as not to increase in-use risk
for fuel system related hazards.
2. Analysis of Issues
Fundamentally, EPA believes that overall risk in-use
should not increase. And, while it is true that FMVSS 301
cannot protect against every conceivable in-use situation,
manufacturers are motivated to consider fuel system safety
implications for reasons other than insuring that their
vehicles pass Federal safety standards. Manufacturers must
determine what they consider to be an appropriate level of
safety and in-use risk, and then design their vehicles to meet
this level. Often this leads to different overall levels of
safety in different vehicle models. Before discussing how to
address this issue, it is valuable to discuss how safety
concerns are integrated into the overall vehicle design and
development process.
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-51-
First, safety is an integral part of the design process
and is normally not considered incrementally. However,
managing risk involves a series of trade-offs, balances, and
compromises with other key design criteria. Manufacturers
choose not to make their vehicles free of all risk because of
other valid design considerations such as performance, styling,
weight, cost, and other factors. It is generally accepted that
no technological constraints exist which would prevent the
production of a nearly "fire-proof" vehicle, and certainly
vehicles could be made safer than they currently are as
evidenced by numerous "safety car" designs.[27] However, cost
and other considerations are valid and they prevent "zero" risk
(or a perfectly safe vehicle) from being considered
appropriate. One analyst has stated, "It is definitely not
reasonable to expect manufacturers to produce 'Sherman Tanks'
... as such vehicles would neither serve the needs of societal
safety, mobility, or economy."[28]
This same logic and risk management process applies to
fuel system safety. Factoring safety into fuel system design
is a complicated process that involves numerous tradeoffs and
compromises as above. Fuel system designs are not all alike,
and fuel system safety considerations vary from one design to
another. For example, fuel tank size and location on the
vehicle have a substantial impact on a vehicle's safety during
a collision. Rear fill tanks are in a more accident prone
location than side fill tanks, and are usually located closer
to the exterior shell of vehicle. Side fill tanks are
generally considered safer than rear fill tanks, and
consequently, rear fill fuel tanks are gradually being phased
out of vehicle designs. However, it should be noted that this
change over has not occurred immediately due to other design
considerations such as cost and conflicting interaction with
other aspects of the total vehicle design. A similar set of
arguments can be made with plastic versus metal fuel tanks.
These simple examples demonstrate how risks are managed
relative to other considerations. Even current fuel systems
could be safer but some risk is accepted.
Another interesting example lies in the area of fuel
system external plumbing such as emission control vapor lines
or external vent lines along the fillpipe. At one time added
piping connections similar to the external vapor vent lines
that appear on some of today's vehicles were characterized as
an unacceptable added safety risk by General Motors.[29] After
further testing and design, that same manufacturer incorporates
an external vapor vent line into many of its current vehicle's
fuel systems. With safety engineering and field testing any
potential safety risks associated with these external vent
lines has been managed.
-------
-52-
This particular design change illustrates a very
significant aspect of fuel system safety. Even though concern
existed over the potential safety aspects of additional fuel
system plumbing, the mere fact that these additional lines
appear on today's vehicles confirms that safety concerns can be
technically addressed if desired. Any perceived in-use risk
can be managed. Safety does not have to be an obstacle to fuel
system improvements or modifications. The technology to reduce
safety risks is currently available, and the degree to which it
is utilized depends on how much risk a manufacturer is willing
to accept.
As illustrated in the discussions above, manufacturers
accept or manage varying amounts of risk in order to strike a
balance or compromise with all of the important design
criteria. Clearly safer vehicles could be made, and the amount
of in-use risk reduced. As considerations change, the amount
of risk accepted may also change. Often the level of
acceptable risk may be more constrained by in-use liability
concerns than government safety tests. For example, crash
testing results from NHTSA's new car assessment program show
that the vehicles' ability to protect its occupants from injury
vary by vehicle model.[30] Different vehicle models provide
different levels of protection for the head, chest, and femur
during barrier crash testing at 35 mph. Some manufacturers
chose to incorporate safer designs on some models for liability
and perhaps marketability reasons.
Similarly, the safety of an onboard system on in-use
vehicles will depend on the design decisions made by the
manufacturers. Onboard systems would increase the size and
number of fuel system emission control components, and some
concern has been expressed that the safety of these components
in FMVSS 301 testing may not necessarily be indicative of
in-use performance. However, adding these systems does not
need to affect the level of risk a manufacturer is willing to
or can afford to accept. As with any other system change,
manufacturers would integrate onboard systems into their
vehicles' fuel systems without increasing overall system risk,
and clearly, there are no inherent technical constraints
prohibiting them from doing so.
Further, there is little merit to the assertion that an
onboard system must be inherently less safe than an evaporative
emission system because it is more "complicated". Adding a few
components and enlarging a couple of others presents no risk
which cannot be managed to levels now deemed acceptable. As a
matter of fact, many of the improvements recently implemented
on passenger cars and light trucks have resulted in
vehicles/systems which are increased in both safety and
complexity. Consider for example advances made in
vehicle/engine control systems. Electronic engine controls
have increased vehicle engine complexity tremendously over
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-53-
previous systems, yet there is no evidence that these system
"complications" have jeopardized safety. In fact,
manufacturers are now considering computer controls for other
vehicle systems such as the suspension and handling, with the
direct purpose of improving vehicle safety.[31] A more
complicated system does not imply a less safe one if given
proper consideration during design.
As discussed in detail earlier, manufacturers have many
options available in the design of an onboard system which can
manage or eliminate any perceived increase in in-use risk.
However, for manufacturers with special concerns regarding
in-use safety there are even more design options available.
Fail safe, redundant, or breakaway rollover valves could be
used. The integrity of the critical portion of vapor line
between the fuel tank and rollover valve could be assured
through the use of steel braid covered rubber hose in key areas
or steel tubing.[32] Both rubber and steel vapor line have
been used on past vehicle models. If chafing of this critical
portion of vapor line is a concern, the affected areas could be
wrapped in a spiral spring for protection. Also, slack could
be provided in this critical portion of vapor line to minimize
the possibility of separation or rupture in an accident.
Improved or additional fittings, adhesives, or clamps could be
used to increase the strength of key vapor line connections
between the fuel tank and the rollover valve. Concerns related
to the charcoal canister can be addressed by using a reinforced
canister shell or a protective barrier. While ' these may be
somewhat extraordinary, this brief listing demonstrates that
further design options are available which if used could
improve safety over current vehicles.
In summary, manufacturers can manage their in-use risk and
can choose to make an onboard system as safe as they deem
appropriate. Onboard systems present no safety concerns which
cannot be eliminated through proper design, and each
manufacturer will develop the fuel system design which
represents the best balance for each particular vehicle model,
with full consideration of the safety risks and all other key
factors.
3. Opportunities for Improvement
Implementing onboard controls could actually result in a
net improvement in overall fuel system safety. Since
manufacturers would need to redesign some aspects of their
vehicles' fuel systems to incorporate onboard systems, the
opportunity would be provided to reexamine other aspects of
fuel system safety as well. Some of the potential fuel system
improvements that could result from this reexamination include
an acceleration of the transition from rear fill to side fill,
integration of the current external vapor vent line inside the
fillpipe, better placement of the fuel tank, or even
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-54-
improvement in the fuel tank integrity itself. Also, any number
of other minor modifications or improvements in the fuel or
emission control systems could be made which could enhance
safety and performance and perhaps reduce cost. These include
areas such as tank venting, purge valve operation, and
eliminating many problems identified through owner complaints
and other similar survey measures.
Also, it is likely that an onboard refueling control
requirement would lead to a decrease in the amount of fuel
spilled in-use and thus improve the overall safety of refueling
events. In the certification refueling test, vehicles would
have to be designed to accommodate a refueling dispensing rate
near the high end of the present range of in-use values (8-10
gallons per minute) without any spillage or spitbacks. This is
because any fuel spilled during the test is considered as part
of the test results. Since one tablespoon of gasoline
evaporates to a substantial amount of vapor (about 10 grams),
almost any spillage that occurred during the certification test
would result in a failure. Thus, the test procedure
requirements will insure that manufacturers' fuel system
fillpipe designs are capable of handling dispensed fuel at flow
rates up to 10 gallons/minute without allowing any spitback.
The use of these fillpipe designs are predicted to lead to a
reduction in the amount of fuel spilled in-use. This is
compared to some current vehicle fillpipe designs which have
difficulty accepting fuel at the lower end of the in-use range
(8-10 gpm) without spitback. To assure this benefit accrues in
the long term, EPA is considering an in-use dispensing rate
limit of 10 gallons per minute along with any onboard
requirement.
Also, from the analysis presented above, it is evident
that implementing onboard controls would provide at least three
other direct safety benefits over present systems. First,
depending on the design used, adding a rollover protection
device may improve the safety of present fuel tank systems
which use a 1/2" external vent line without rollover
protection. Second, adding a rollover valve may enhance the
safety for those vehicles which now use a limiting orifice for
rollover protection, since a rollover valve will provide a
positive seal in lieu of the "controlled leak" approach
provided by the limiting orifice. Last of all, it should be
noted that refueling vapors are currently vented to an area
which poses somewhat of a safety hazard. This is because the
potential exists for refueling vapors to ignite inadvertently
as they escape from the fillneck opening. However, as onboard
controls are phased in, and more and more vehicles route
refueling vapors away from the fuel pump operator to a safer
point (the charcoal canister) the overall risk involved in
refueling a vehicle will be reduced.
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-55-
Finally, to address any special concerns regarding onboard
system crashworthiness and to perhaps improve crashworthiness
over current vehicles, there is an alternative onboard system
design available which manufacturers may elect. As is shown in
Figure 18, this system is similar to Figure 4, except all the
needed valves (rollover, vent, liquid/vapor separator) are
built into the top of the fuel tank, instead of externally.
A solenoid activated rollover valve could be used (Figure
19) which is located on top of or inside the fuel tank. [33]
This valve would normally be closed except during refueling
when it would be electronically opened by a switch located near
the opening of the fillpipe. The switch could be activated
either by the opening of the door over the fuel cap or removal
of the fuel cap itself (see Figure 20).
Yet another approach is a mechanical ball valve. This
device would normally remain open to provide a clear vapor
passage. However, in the event of a rollover accident gravity
causes a metal ball to roll into a fitted seat and seal off the
vent line. One variation on this design (see Figure 21) would
be simple mechanical ball valve built in combination with other
needed valves.[15]
As is shown in Figure 18, this onboard system design may
need a fill limiter to allow for normal refueling operations
(i.e., automatic shut-off) and to prevent overfilling the tank
during full refills. A sample design is shown in Figure
22.[33] The operation of the fill limiter is quite simple.
When the tank is full the float rises in the fill limiter and
closes off the refueling vent line. This causes pressure to
rise in the tank, subsequently fuel runs up the fillpipe and
activates the nozzle automatic shut off mechanism. While
incorporation of a fill limiter is quite simple from an
engineering perspective, the design would have to incorporate a
"soft close" to avoid back pressure "spikes" and possible
spills at the end of a full refill.
From a safety perspective this alternative is attractive
because all the external components are either removed or
mounted in a more protected location. The external vent line
(Figure 1) can be eliminated and the other system valves and
vapor lines are moved away from the vehicle shell to a more
protected area within the vehicle body. Also, no vapor line
exists between the fuel tank and the rollover valve, so vapor
line integrity and connections are less critical.
Finally, depending on how high a priority a manufacturer
assigns to safety or if significant in-use risk is perceived, a
collapsible bladder tank design could be used to meet the
onboard requirement. Bladder tanks could lead to a substantial
improvement in fuel system safety by providing an additional
shell of protection to help reduce fuel spillage in case of an
-------
. PRESSURE/VACUUM
RELIEF CAP
Figure 18
ALTERNATIVE INTEGRATED EVAPORATIVE/REFUELING SYFTEM
TANK MOUNTED VALVES
REAR MOUNTED CANISTER
J-TUBE Sl^AL
M1JCI1ANICAL OR SOI.ENOID
ACTUATED VENT/ROUOVER
VALVE, LIMITING ORIFICE
& LIQUID/VAPOR SEPARATOR
5/8" DIA.
3' LONG
/ ^-J-TUDE SEAL
LEAK
3.
I
tn
T
PURGE
VALVE
Jc
3/8" DIA.
5' LONG
•jf—txH-
TO PURGE
INDUCTION
POINT
~3 LITER
CANISTER
14 GALLON FUEL TANK
-------
Figure 19
TO
SOLENOID VALA/Ł
MO
SCHEMATIC OF POTENTIAL ONBOARD VAPOR RECOVERY SYSTEM
MUELLER ASSOCIATES. INC.
140I •. CDQCWOOD STMCCT
• AlTIMOHC. MAMVtAND 31217
JANUARY at. !•••
-------
Figure 20
CAP OOOG.
CAP
^
» "i r
~Tn • i *
(SAP
U1
T
|.()Ti:NTIAL MOMKNTAKY SWITCH LOCATIONS
MUELLER A630CIATE3. INC.
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JANUARY 31. !•••
-------
-59-
Figure 21
COMBINATION VALVE
I 1/8
.*• 1.0.
WLLOVE* SHUTOFf
1/2" OIA SS BALL
OVERFILL SMUTQFF
S.S ICSH
VW»QR LIQUID
SEPARATOR
-------
Figure 22
0.050" BY PASS
01
o
UALL-IN-CAGE FLOAT VALVE
MUELLER ASSOCIATES. INC.
7401 •- fPQlWOOO
4ANUAIIT 9«. '•••
-------
-61-
accident. Also, a bladder tank could eliminate essentially all
of the safety concerns raised regarding control of refueling
emissions. This is because a vapor space would not be present
in a bladder tank, and without a vapor space,, refueling
emissions would not occur. Thus neither a refueling emissions
canister, external plumbing, or a rollover valve would be
needed. It might even be possible to eliminate the present
evaporative system and enhance safety even more. Also,
bladders should be an attractive option for those who claim
high costs or packaging problems with canister-based onboard
systems. EPA is quite interested in collapsible bladder tanks
as an option to canister-based onboard systems. This analysis
of design and in use safety issues and the associated costs and
leadtime is not directly applicable to collapsible bladder
tanks. However, EPA plans to further explore the cost and
technological feasibility of bladders as well as their safety
and emission benefits.
In conclusion, the information and rationale presented
above refute the assertion that adding an onboard system would
directionally increase in-use risk, even if only by some
unquantifiable (presumably small) amount. Any perceived risk
is manageable, and furthermore, it appears that the net effect
of an onboard refueling control requirement could be a
potential increase in fuel system safety. As discussed above,
and in Section IV there are numerous design alternatives to
address the safety concerns raised. To varying degrees all
options have the potential to improve the safety of fuel
systems in-use.
VI. Cost and Leadtime Considerations
The comments received regarding onboard vapor recovery
systems also addressed the cost and leadtime implications of
implementing such controls. More specifically, several of the
comments addressed onboard safety costs in some form (usually
addressing hardware costs), and several commenters expressed
some concern over EPA's leadtime estimate. An analysis of the
costs and leadtime necessary to implement onboard controls
safely is an integral part of the overall evaluation of the
feasibility of this control approach. As was mentioned above,
cost is one of the other key considerations which is often
balanced carefully against safety concerns, and the costs
needed to implement onboard systems safely must be reasonable
relative to other safety costs and the overall costs, of onboard
systems. Further, the analysis must carefully consider the
manufacturer leadtime needed to implement onboard controls on
their production vehicles. This includes the time needed to
identify, evaluate, and address all safety concerns and to
comply with the test requirements prescribed in FMVSS 301.
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The first portion of this section addresses onboard safety
costs; the second discusses leadtime and describes the basis
for EPA's leadtime estimate. Some of the cost figures cited in
the safety cost analysis are drawn from a broader EPA analysis
which develops total onboard system costs in 1984 dollars.[17]
A. Safety Costs
As is evident from the discussion presented in Section IV,
the costs needed to implement onboard controls safely fall in
several areas. R&D type costs will be incurred, some new or
modified components will be needed which may slightly affect
vehicle operating costs, and safety certification testing will
be necessary. However before beginning a discussion of these
costs, it is valuable to discuss how the FMVSS 301 standards
and EPA's evaporative emission control requirements impact
onboard safety costs.
The control of refueling emissions through an onboard
system would not be the first Federal regulation to require an
investment to improve fuel system safety. The first fuel
system integrity standards (FMVSS 301) were implemented by
NHTSA for 1968 vehicles, and since then there have been 2 major
additions to these requirements. Each of these new
requirements has caused a small cost increase, but each has
also led to an improvement in fuel system safety on in-use
vehicles. In the mid 1970's, FMVSS 301 was substantially
upgraded to extend the coverage of impact types to include
rollover events and, rear end and side collisions. A 1983
NHTSA Technical Report describes the nature of the
modifications made in response to the upgrading of the standard
and estimates the costs incurred by vehicle manufacturers in
order to meet the revised standard and provide a higher level
of in-use assurance.[21]
Table 3 describes modifications that were made to 1977
model year vehicle fuel systems in response to the increased
requirements of FMVSS 301. These modifications ranged from
minor changes such as the slight revision of mounting bolts or
clips to more major ones such as recontouring the fuel tank.
Based on information submitted to NHTSA by vehicle
manufacturers, the average (sales-weighted) cost increase
required to make these modifications was $4.60 per vehicle.*
These modifications were also estimated to increase vehicle
weight slightly (an average of three pounds per vehicle), which
would tend to marginally increase the amount of fuel consumed
over the life of the vehicle (about 3 gallons of fuel). When
these two- costs are added, NHTSA estimated the total safety
cost resulting from the 1977 revisions to FMVSS 301 averaged
about $8.50 per vehicle (1982 dollars).
A Bureau of Labor Statistics analysis estimated that
vehicle costs incurred to meet the 1977 revision to FMVSS
301 were $4.70 and costs to meet the 1976 revision to the
standard (added rollover test) cost $2.10.[34,35]
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-63-
Table 3
Summary of Vehicle
Modifications in Response to 301-77
Vehicle Components
Fuel System
Components...
Fuel Tank
Fuel Gauge Sensor
Fuel Lines
Fuel Vapor Lines
Fuel Pump
Modification(s) to •
Improve Crashworthiness
- Increase gauge, of tank material
- Add protective shield
- Recontour to minimize c
contact/puncture by other adjacent
vehicle components.
- Strengthen/shield filler neck
- Increase strength of solder/weld
seams
- Strengthen mounting by adding
brackets, revising mounting bolts,
increasing torque of mounting
straps
- Strengthen filler cap seal,
improve impact resistance
- Strengthen mounting
- Recontour
- Recontour, revise, revise clamps
- Provide shield
Other Vehicle Components Changed to Improve Fuel System Integrity
Rear Floor Pan/Support
Rails/Wheel Housing
Rear Suspension (Springs,
Shock Absorbers)
Rear Axle Assembly
i
Rear Axle Assembly
Seat Belt Brackets
Engine Mount
Power Steering Pump Bracket
- Revise, add supports
- Change support brackets, revise
mounting bolts, revise mounting
procedure, and shield
- Minor changes in contour of lines,
screw heads, mounting clips,
recontour vent cover
- Revise hinge assembly
- Revise anchorage
- Slight revision
- Slight revision
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-64-
Based on an evaluation of in-use accident information for
1977 and later model year vehicles, NHTSA's 1983 Technical
Report also estimated that the upgrading of FMVSS 301 would in
the long term annually prevent 400 fatalities, 630 injuries,
and 6500 post crash fires. This indicates that FMVSS 301 has
been effective in substantially improving many aspects of
overall fuel system safety and that these improvements were
purchased relatively inexpensively.
The second area of interest is the effect of current
evaporative emission systems on potential onboard system safety
costs. As was described in Section III of the report, an
onboard system is in many ways an extrapolation of current
evaporative emission control technology and the two systems are
quite similar. Many of the control techniques and basic system
components used would be similar, and the same system and
vehicle assembly approaches could be used. In fact, many
manufacturers will likely integrate their refueling and fuel
tank evaporative control systems. All current vehicle fuel
systems incorporate fairly sophisticated evaporative emission
control systems. Since these fuel systems have all been
designed to meet the most recent and most stringent version of
FMVSS 301 and also provide a high level of in-use safety
performance, it follows that a thorough evaluation of the
potential safety implications of evaporative control systems
has already been conducted. Since onboard systems are
basically extensions of evaporative emission systems, clearly
many of the safety design considerations associated with
onboard systems related to passing FMVSS 301 or providing
in-use assurance have already been resolved or at least
addressed in evaporative emission system designs.
Consequently, much of the "ground work" required to insure
onboard safety has already been performed. Therefore, it is
important to keep the magnitude of the onboard safety design
process in perspective, because clearly much of the safety
technology needed for onboard is simply an extension of that
which already exists.
Remembering the relatively inexpensive and yet effective
nature of current fuel system integrity measures and the
"incremental" nature of onboard safety in terms of the
magnitude of the task and actual cost relative to evaporative
systems, it is now possible to describe the components which
factor into onboard safety costs. Basically, the integration
of safety into a fuel system incorporating an onboard controls
involves four types of costs. These four costs are for 1)
design and development (R&D), 2) specific hardware, 3) safety
testing, and 4) weight penalty (or added fuel consumption).
The paragraphs that follow describe how each of the cost
components are affected by onboard safety.
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To begin with, some research and development will have to
be performed to safely integrate onboard controls into vehicle
fuel systems. EPA has estimated that the total design and
development cost required to incorporate onboard systems in
vehicle fuel systems is about $112,000 per family" or in the
range of $0.35 to $0.55 per vehicle (passenger car and light
truck). This cost is for any development effort involved in
combining the components of an onboard system with the rest of
the vehicle to form a unit that interacts safely and
effectively. Because safety is evaluated inherently in the
design and development process and yet is only one part of the
total effort, only a fraction of the total cost should be
directly allocated to safety. Also, because much of the safety
related system development work has already been completed it
is not unreasonable to expect that onboard safety development
costs would only be a small fraction of the total cost in this
area. In addition, because of the incremental nature of the
onboard system, much of the research and development that went
into making evaporative control systems safe can be applied
directly to onboard controls.
Given that manufacturers are designing an onboard system
in the context of many requirements and certain design features
serve multiple functions, it is very difficult to isolate the
level of expenditures directly attributable to safety. For
this analysis it was assumed that about 20 percent of R&D
expenditures relate to safety, which translates to about $0.10
per vehicle. However, total onboard cost is quite insensitive
to this assumption, even if the safety related development
costs were tripled, per vehicle costs would increase by only
one percent.
The second component of onboard safety costs relates to
specific hardware that may be required to insure fuel system
safety. EPA has estimated costs for three specific items which
have been identified as potential components to be included as
part of the onboard system design explicitly for safety
reasons. These three items are 1) a rollover valve, 2) a
pressure relief mechanism, and 3) fuel system modifications
necessary to safely incorporate a rollover valve, pressure
relief mechanism, or other onboard hardware. EPA has estimated
the cost of a solenoid rollover valve (like the one shown in
Figures 19 and 20) to be $4.60. [17] This price included the
cost of the valve, an actuator located at the fillcap, and the
necessary wiring and connectors. Manufacturers estimate the
cost of a valve assembly similar to that described by EPA's
cost estimate would be in the range of $5.00 to $6.00. It
should be noted that these estimates are for the most complex
rollover valve type, and that the cost of a simpler valve
assembly such as the fillneck mounted type (see Figures 9-15)
is estimated to be more in the $3.00 to $4.00 range. The
available information indicates that an appropriate rollover
valve cost falls into a range of $3.00 to $6.00.
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-66-
The second safety hardware cost is for a pressure relief
mechanism. This mechanism would only be needed for onboard
systems incorporating a mechanical fillneck seal, and
consequently not all vehicles would require its use. However,
for those systems that would require a pressure relief
mechanism, EPA has estimated that this device would increase
system costs by approximately $0.50. This estimate is based on
pressure relief mechanisms currently used in automotive
applications which perform the same basic function and are
similar in complexity.[36]
The final onboard safety hardware cost accounts for any
fuel system modifications that would be necessary in order to
safely accommodate any onboard control hardware. For example,
a vehicle's fuel tank or fillpipe might have to be re-shaped or
modified in order to accept a rollover valve. Also, for safety
reasons, some slight re-routing of the fuel system's vapor
lines may be required. EPA has estimated a total modification
cost to be $0.50 per vehicle. Only part of this total cost
would be required for safety purposes. However, because safety
inherently enters into the decision to make any modifications,
it is difficult to access what part of the total modification
cost should be allocated to safety; perhaps half or more ($0.25
to $0.30 per vehicle) could be considered as driven by safety
related concerns.
Summing up the three individual safety hardware costs
yields a total estimated figure in the range of $3.25 to
$6.80. However, this cost estimate does not include
manufacturer overhead and profit. In order to obtain the
retail price equivalent cost, these estimates must be
multiplied by a markup factor. Presently, a markup factor
value of 1.26 appears representative.[37] Therefore, after
inclusion of the markup factor, a total retail price equivalent
safety-related hardware cost falls within the range of $4.10 to
$8.60.
The third component of safety costs accounts for any
safety crash testing that would be necessary. EPA has
estimated the cost of FMVSS 301 crash testing to assure fuel
system integrity for onboard systems to be about $34,000 per
bodyline/style or about $0.12 per vehicle.[38] This estimate
is based on four tests for FMVSS 301 only required per body
line/style with two vehicles required for each sequence of four
tests. Clearly safety crash test costs are very minimal in the
long term and do not pose an obstacle to the adoption of
onboard controls. In some cases these costs may be higher but
even if total costs were double the estimate, the overall per
vehicle cost would rise by less than one percent. Also, costs
could be lower if FMVSS 301 test were combined with crash
testing required for compliance with other safety standards.
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-67-
The fourth component of safety costs is the estimate of
the added fuel consumed over the life of the vehicle due to the
increase in vehicle weight resulting from added safety
hardware. The amount of weight added to a vehicle for a
rollover valve and pressure relief mechanism is very small (0.4
Ibs), and EPA estimates that only about $0.25 in added fuel
costs will result from their inclusion into the onboard
system.[17]
A total onboard safety cost is calculated by summing all
four individual component costs. Total capital costs per
family average about $56,000. The per vehicle safety-related
costs range from $4.50 to $9.00, or about 25 percent of EPA's
estimate of the total cost, depending on the type of rollover
valve used.
One final point needs to be made with regard to these
safety cost estimates. To the degree that manufacturers take
the opportunity introduced by an onboard requirement to further
reduce in-use risk beyond that now accepted with present
systems, some additional costs might be involved which have not
been identified or quantified. On a fleetwide basis these
would be quite small. Also, it should be noted that the added
benefits of these measures have not been included either.
EPA estimates safety related onboard costs to be
$4.50-9.00 per vehicle. While there is some uncertainty in the
development cost portion of the estimate, the total range shown
here is quite insensitive to any error. These costs are quite
similar to those previously incurred by manufacturers to insure
fuel system safety. Many of the potential problems related to
implementing onboard systems safely have already been
considered in the design and development of present evaporative
systems. The manufacturers previous experience in implementing
evaporative systems safely and the incremental nature of
onboard systems reduces costs and the level of potential
problems. This analysis demonstrates that high levels of
in-use fuel system safety can be achieved at low cost, and
there is no need for a manufacturer to "cut corners" on onboard
safety to reduce costs.
B. Leadtime
If EPA were to implement an onboard requirement, it would
be necessary to allow a sufficient period of leadtime between
the date the rule is promulgated and the model year the systems
are to be required on production vehicles. This leadtime is
provided so that manufacturers will be able to adequately
prepare for the requirement through system design, development,
testing, tooling, certification, and safety evaluation. Some
of the tasks involved in the preparation process could be
worked on simultaneously, while some tasks cannot begin before
others are complete. While EPA estimates that none of the
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-68-
individual tasks require more than twelve months to complete,
due to the sequential nature of some of the tasks, a leadtime
period of approximately 24 months will be required by
manufacturers.
Figure 23 shows how the individual leadtime components
result in a total estimate of 24 months. First, four to six
months are included for manufacturers to develop and optimize
working prototype systems applicable to all of their different
vehicle models. This is not at all unreasonable given the fact
that working prototypes already exist and many manufacturers
have evaluated these or their own prototype to some degree.
Not all manufacturers have developed working prototype onboard
systems, but the technology required to develop such systems is
readily available and in-depth technical descriptions of such
systems have been described in publicly available literature.
Four to six months should be adequate time for these
manufacturers to develop and evaluate prototype systems.
Once the prototype development is complete, initial
durability testing of the prototype could be conducted under
laboratory conditions. This laboratory testing is not expected
to last more than two months.
Following laboratory testing, three separate actions can
begin simultaneously. These three tasks are: 1) in-vehicle
testing, 2) safety optimization, and 3) tooling and prove out
of the overall control system through efficiency and durability
verification. Similar in-vehicle testing programs have
required four to six months for completion. Safety evaluation
is the second task which could begin subsequent to the
completion of the prototype laboratory testing. Safety
evaluation would involve the use of computer crash simulation
models and vehicle crash testing (four tests per body
line/style) to verify the crashworthiness of the vehicle's
modified fuel system. Because this evaluation could begin
immediately after the completion of laboratory testing, a full
14 months of leadtime would be available to manufacturers if
needed to perform this task. Based on discussions with NHTSA,
6 months is normally enough time to complete a safety
evaluation. Therefore, 14 months appears more than adequate to
perform the necessary safety optimization and testing for a
manufacturer's product line. Tooling could also begin once
laboratory testing is complete. Figure 23 shows EPA's estimate
that tooling could require as little as 3 months and as much as
12 months depending on the magnitude of the task. Different
factors are weighed before a manufacturer commits to various
tooling changes. Manufacturers can commit to some tooling
changes for onboard controls immediately after the in-vehicle
testing (e.g., purge valves), whereas they may choose to wait
until after safety analysis before committing to other tooling
changes (e.g., rollover valves). However, in an overall sense,
12 months would provide manufacturers with enough time to delay
some tooling changes and still complete the task well within
the 24-month leadtime.
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-70-
The only other process which requires completion within
the 24-month leadtime period is emissions certification. EPA
has found from past experience that a manufacturer normally
requires between 10 to 12 months to certify its product
line.[39] This estimate is based on a 10 month engine family
certification schedule which allows time for durability,
emission data, fuel economy, and confirmatory testing. Because
certification cannot begin prior to the completion of
in-vehicle testing, certification is critical path, and EPA
estimates a total leadtime period of 24 months will be needed
overall.
Twenty-four months of leadtime is quite reasonable,
especially since most of the fundamental development work is
already complete. Onboard system prototypes are presently
available, and many aspects of the system's performance have
already been tested and proven to be effective. Also, because
onboard control technology is incremental in nature to
evaporative emission controls, there is no need to design and
develop entirely new systems. As a matter of fact, many of the
critical onboard design issues have already been incorporated
into current fuel system designs with the inclusion of
evaporative emission control systems. For example, evaporative
emission control systems have already added the following to
fuel systems: vapor vent lines, vapor storage device, canister
purge capability, and corresponding safety provisions
associated with each of these additions. Since much of the
development work is already complete, implementing onboard
systems should be no more of a problem to vehicle manufacturers
than was implementing evaporative emission control systems.
EPA's 24-month leadtime estimate is supported by past
experience with three previous evaporative emission
rulemakings. These rulemakings included the original 1978 6.0
g/test LDV/LDT evaporative emission standard which was
implemented with just 12 months of leadtime, the 1981 2.0
g/test LDV/LDT evaporative emission standard which was
implemented with 24 months of leadtime, and the 1985 HDGV
evaporative standard which was implemented with 24 months of
leadtime. In each of these three rulemakings, manufacturers
faced leadtime factors identical to the ones that would
accompany an onboard requirement, including safety. Since
manufacturers were able to safely and effectively integrate
evaporative emission controls into their vehicles' fuel systems
with 24 months of leadtime, and since the magnitude of the
onboard implementation task is similar, this suggests that
manufacturers should also be able to safely and effectively
integrate onboard into vehicle fuel systems with 24 months of
leadtime.
As far as safety development and evaluation is concerned,
EPA's leadtime estimate is also supported by the past
experience of NHTSA in implementing the various versions of
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-71-
FMVSS 301. Table 4 shows the chronological history of FMVSS
301. The original 1968 FMVSS 301 applicable to passenger cars
was implemented with less than 12 months of leadtime. When the
standard was revised for 1976 model year passenger ears, 17
months of leadtime was provided. For 1977 model year passenger
cars, manufacturers had to contend with the most substantial
upgrade to the standard, and this was accomplished with only 29
months of leadtime, and only 12 months between new
requirements. Also, beginning in the 1977 model year, FMVSS
301 was extended to include light trucks. This extension
involved a 29-month leadtime period with further crash
requirements in effect 12 months later, thus requiring
recertification. Finally, in 1977, FMVSS 301 was extended to
include school buses (with a GVWR greater than 10,000 Ibs), and
this requirement was implemented with 17 months of leadtime.
This experience indicates that 24 months of leadt.ime allows
manufacturers sufficient time to factor in safety.
Based on the information provided above, 24 months appears
to be adequate time to implement onboard controls, with full
consideration of all safety concerns. Because safety
evaluation can proceed in parallel to three other tasks, more
than a year is available for computer simulation and actual
safety crash testing. This allows adequate leadtime to
properly integrate safety into onboard systems especially since
manufacturers can utilize and expand safety technology used in
current evaporative emission control systems to develop
effective onboard systems. Also, much of the safety
development which would be required has already taken place
with the identification and resolution of such potential safety
issues as rollover protection and fuel tank pressure relief.
Consequently, a 24-month leadtime period would provide
manufacturers with sufficient opportunity to develop safe and
effective onboard systems.
While this analysis indicates that the current leadtime
estimate of 24 months is reasonable for most if not all vehicle
models, EPA is sensitive to manufacturers concerns regarding
leadtime requirements. Public comments regarding EPA's
24-month leadtime estimate were submitted as part of comments
on EPA's original Gasoline Marketing Study (July 1984).[40]
While most cornmenters did not object to the 24-month leadtime
estimate presented in the Gasoline Marketing Study, auto
manufacturers felt that a 24-month leadtime was insufficient to
implement onboard controls. The leadtime periods suggested by
these commenters ranged from three to six years. Those
commenters suggesting that four or more years would be
necessary also suggested that onboard controls should be
phased-in gradually as normal vehicle model redesign and
turnover occurs. Using this approach, implementing onboard
controls would be less burdensome and would allow extra time to
deal with implementation or packaging problems on unique
vehicles. However, it is worth noting that comments received
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-72-
Table 4
Chronology of FMVSS 301 Requirements
Model Year Vehicle Promulgation
Requirement Type Date
1968[1]
1976[2]
1977[2]
1977[2]
1978[2]
1977[2]
1978[2]
1977[3]
• PC
PC
PC
Class 1 LOT
Class 1 LOT
Class 2 LOT
Class 2 LOT
School Buses
2
3
3
3
3
3
3
10
-3-67
-21-74
-21-74
-21-74
-21-74
-21-74
-21-74
-15-75
Effective
Date
1
9
9
9
9
9
9
4
-1
-1
-1
-1
-1
-1
-1
-1
-68
-75
-76
-76
-77
-76
-77
-77
Leadtime Time Since
(Months) Last Requirements
11
17 7 2/3 yrs.
29 12 mos.
29
41 12 mos.
29
41 12 mos.
17
[1] Motor Vehicle Safety Standard No. 301, Fuel Tanks, Fuel
Tank Filler Pipes, and Fuel Tank Connections - Passenger
Cars; 32 FR 2416, February 3, 1967, Part 571; S 301-1.
[2] Federal Motor Vehicle Safety Standard No. 301, Fuel System
Integrity, 39 FR 10588, March 21, 1974.
[3] Federal Motor Vehicle Safety Standard No. 301, Fuel System
Integrity, 40 FR 48352, October 15 1975.
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-73-
from the manufacturers suggesting the need for a longer
leadtime were not supported with any compelling arguments which
would substantiate the insufficiency of a 24-month leadtime.
While the analysis above indicates that approximately 24
months of leadtime should be sufficient, there are some factors
which must be considered but are difficult to factor into the
analysis. First, as was mentioned above, some manufacturers
have not developed working onboard prototypes due to resource
or facility constraints and the possibility exists that these
manufacturers will take no definitive action on systems
development prior to a final action by EPA. Some have
commented that these manufacturers should not be penalized
because of this and may require a greater amount of leadtime.
Second, vehicles with atypical duty cycles (ambulances, mail
trucks, etc.) may require more leadtime to implement onboard
controls safely. Vehicles assembled by secondary manufacturers
such as recreational vehicles and airport mini-buses could
also require more time especially if adding an onboard system
requires other vehicle changes. Finally, more leadtime ma'y be
necessary because manufacturers may not have the test facility
and safety engineering resources to effectively comply with
multiple vehicle safety standard requirements concurrently. A
similar concern may exist for emissions recertification since
manufacturers would in most cases have to recertify virtually
all gasoline powered vehicles for exhaust and evaporative
emissions in addition to the new refueling requirement. Because
of these concerns, more leadtime may be necessary for the
implementation of safe onboard control systems.
EPA is committed to providing manufacturers the leadtime
necessary to implement onboard controls safely and
effectively. Consequently, EPA is open to considering the need
for more leadtime and/or a short phase-in period for onboard
controls. Such a phase-in period would provide manufacturers
with additional time to solve any onboard system packaging and
testing problems for unique vehicle models. Also, if a
manufacturer had unique safety concerns on one or two body
lines/styles, this approach would offer a manufacturer more
leadtime to properly address them. In addition, it could
improve the cost efficiency of controls by allowing
manufacturers to forego development of onboard systems for
vehicle models scheduled for retirement or permit manufacturers
other flexibilities with new models being planned and those now
in production. The implementation of other unique control
strategies, such as bladder systems, would require more
leadtime.
It is also important to note that if onboard controls are
required, the date of promulgation of the final rule may be
such that more than 24-months leadtime is actually available.
The model year generally begins in September or October. If
the publication of the final rule is much beyond that period,
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-74-
the manufacturers would have the remainder of that model year
in addition to the 24 months discussed previously. Therefore,
in actuality manufacturers could have substantially more than
24 months, but EPA's analysis indicates that only 24 months is
needed.
In conclusion, given the magnitude of the task, this
analysis indicates that 24 months of leadtime is adequate to
allow manufacturers to safely and effectively implement onboard
controls. This estimate is supported by EPA's experience with
implementing evaporative emission standards and NHTSA's
experience with implementing the various versions of
FMVSS 301. However, EPA is committed to providing the leadtime
necessary to implement onboard controls both safely and
effectively. Thus EPA is open to considering more leadtime
and/or a short phase-in period or other approaches which are
pertinent.
Up to this point, this report has addressed onboard safety
issues from primarily a passenger car and light truck point of
view. It should be noted however that just as evaporative
emission control technology was extended to heavy-duty gasoline
fueled vehicles (HDGVs), onboard control technology could also
be applied to HDGVs. While many of the safety issues discussed
thus far would be identical in an HDGV application, some
aspects of HDGV onboard safety would be distinct from
light-duty issues. The next section in this report has been
included to address the similarities and differences between
heavy-duty and light-duty onboard safety issues.
VII. Heavy-Duty Gasoline Vehicle Requirements
Since an EPA onboard refueling control requirement would
cover heavy-duty gasoline vehicles (HDGVs), in addition to
passenger cars and light trucks, it is important to evaluate
any potential HDGV onboard system safety considerations as well
as those encountered in light-duty applications. (It is
important to note that an onboard requirement will not apply to
heavy-duty diesel trucks and buses.) While none of the
comments received regarding the safety implications of onboard
specifically addressed HDGVs, overall light-duty concerns
discussed earlier are expected to apply. However, it is
important to note that HDGV fuel system configurations differ
somewhat from those found on passenger cars and light trucks,
and the fuel system safety requirements also differ.
This section of the report identifies distinct HDGV
onboard safety issues and discusses the implications these
distinctions could have on manufacturers fuel system safety
designs. It begins with a brief description of some of the
more common HDGV configurations. Following these descriptions,
a discussion of the HDGV fuel system safety standards will be
presented, and differences between light- and heavy-duty
vehicle onboard systems due to fuel system configurations and
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-75-
safety test requirements will be discussed. Next, HDGV onboard
safety issues will be introduced and analyzed. Finally, this
section will end with a brief segment concerning the effect of
HDGV onboard safety on costs and leadtime.
Before beginning this analysis one key clarification is
needed. FMVSS 301 covers all vehicles with a gross vehicle
weight rating (GVWR) of 10,000 Ibs or less (plus school buses
over 10,000 Ibs GVWR). For emission control purposes EPA
classifies all gasoline-powered vehicles with a GVWR of 8,501
Ibs or more as HDGVs. Out of EPA's HDGV category only 90,000
vehicles (or approximately 25 percent) have a GVWR greater than
10,000 Ibs. Thus most (or approximately 75 percent) of EPA's
HDGV class (those vehicles with a GVWR between 8,501 and 10,000
Ibs-Class lib) is covered by the LDT requirements in FMVSS
301. Since the fuel systems on Class lib HDGVs are essentially
identical to those on lighter weight LDTs, and FMVSS covers all
LDTs up to 10,000 Ibs GVWR, the previous portion of this
analysis applies to the Class lib HDGVs. The remainder of this
analysis will focus on gasoline-powered vehicles whose GVWR
exceeds 10,000 Ibs.
This analysis addresses compliance costs with the
assumption that HDGV manufacturers will use only certified fuel
tanks on their vehicles. Currently, it is the owner's
responsibility to purchase and use a certified tank if required
by regulation. The current Motor Carrier Safety Regulations
exempts a vehicle or driver used entirely within a municipality
or commercial zone, although they may voluntarily comply with
the regulations. These regulations may be changed in the
future to be applicable to all HDGVs and eliminate the
aforementioned commercial zone exemption. Therefore, this
analysis assumes that all HDGVs will use fuel tanks certified
to comply with the regulations discussed below.
A. HDGV Fuel System Configurations
Just as there are chassis and drivetrain differences
between heavy and light-duty vehicles, there are also some
differences in their fuel system configurations. Fuel tanks
are generally of a heavier construction and are larger in
volume; dual fuel tanks are also more common. Fuel tank shapes
vary somewhat as does the location of the tanks on the
vehicle. Also, it is often the case that the fillpipe is
integral with the fuel tank, or has a very limited length as
compared to lighter weight vehicles.
As a part of a recent contract study, EPA surveyed the
characteristics of the fuel/vapor handling systems of HDGVs
over 10,000 Ibs GVWR. [41] The key results of the survey
portion of that report are summarized in Table 5, which will
serve as the basis for the remainder of this discussion.
-------
Table 5
Selected Characteristics of Heavy-Duty Gasoline Vehicle Fuel/Vapor Handling Systems by Vehicle Model/Series
Model or
Manufacturer Series Fuel Tank Shape
GM
P4T042 Rectangular
Fuel Tank Location
30 gal. Mount On Right
Hand Frame
Number of
Canisters
Size of
Canisters
1500 and
2500 cc
Diameter Diameter
of Vent of Purge
Lines Lines
0.312 in. 0.375 in.
P6T042
Rectangular
30 and 60 gal. Mounted
on Left Hand Frame
1500 and
2500 cc
0:312 in. 0.375 in.
C5D042
C6D042
C7D042
C7D064
Rectangular and
Rectangular Step
Rectangular and
Rectangular Step
20 gal. Mounted Right
Hand Frame
50 gal. Step Mounted
Right or Left Hand Frame
20 gal. Mounted Right
Hand Frame
50 gal. Step Mounted
Right or Left Hand Frame
Dual 50 gal. Step
Mounted Left and Right
Hand Frame
1500 and
2500 cc
0.312 in. 0.375 in.
1500 and
2500 cc
0.312 in. 0.375 in. |
-j
en
B6P042 Rectangular
30 gal. Mounted Right
Hand Frame
1500 and
2500 cc
0.312 in. 0.375 in.
FORD
F-Series Rectangular
60 gal. Mounted Right
Hand Frame
35 gal. Right Hand
Side Frame Mounted
1400 ml. ea.
3/8 in. 3/8 in.
B-Series Rectangular
C-Series D-Type
30 gal. Right Hand
Side Frame Mounted
50 gal. Right Hand
Side Frame Mounted
1400 ml. ea.
1400 ml. ea.
3/8 in. 3/8 in.
3/8 in. 3/8 in.
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-77-
First, as can be seen in Table 5, there are only two
manufacturers which market HDGVs. Between them they offer only
about 10 different chassis models to which any number of
different bodies or payloads can be attached (tanks, dumps,
cargo boxes, motor homes, school buses, flat beds, etc).
The second area of interest is the fuel tanks.
Essentially three different tanks shapes are used: standard
rectangular, step rectangular, and D-shape. Examples of these
tanks are shown in Figure 24. The tank volumes range from 20
gallons to 60 gallons, with an average in the range of 35 to 40
gallons for single tank HDGVs and 75 gallons for dual-tank
HDGVs. EPA estimates that about 15 percent of HDGVs use dual
tanks, with most of those being in heavier weight trucks
(>20,000 Ibs GVWR).[17] Most passenger car and light truck
fuel tanks are located under the vehicle body and this is also
the case for some HDGV configurations (e.g., school buses).
However, on some HDGV configurations, the fuel tanks are
mounted on the outer side of the vehicle frame (right or left
hand side for single tanks, both sides for dual tanks) and are
exposed to the road rather than shielded by the vehicle body.
As was alluded to above, most HDGV tanks have only a limited
fillpipe length (<8") and some have essentially none at all,
with the fuel cap being integral to the tank.
Finally, with regard to the HDGV evaporative emission
systems two observations are important. (See Figure 25 for an
example of a HDGV evaporative system.) First, for the same
reasons as described for passenger cars and light trucks, HDGVs
use a limiting orifice in the evaporative emission system.
Second, the total evaporative emission canister capacity on an
HDGV is more than twice the average on passenger cars and LDTs
(2.8-4.0 liters). However, on HDGVs diurnal emissions from the
fuel tank and hot soak emissions from the fuel metering system
are routed to different canisters. Hot soak emissions are
somewhat more of a concern on HDGVs because presently most are
carbureted rather than fuel injected. To the degree that HDGV
engines fuel systems are converted from carbureted to fuel
injected as is now projected, concerns over hot soak emissions
may diminish and allow the elimination of the second canister
on those vehicles.[42,43]
With this brief background on HDGV fuel/evaporative
systems we turn now to a discussion of the fuel system safety
standards which apply to HDGVs over 10,000 Ibs GVWR.
B. HDGV Fuel System Safety Standards
Fuel system safety regulations differ according to vehicle
and fuel system configuration. The Department of
Transportation/Office of Motor Carrier Safety (OMCS) has
requirements which apply to all HDGVs over 10,000 Ibs GVWR. In
addition, school buses must meet the requirements prescribed
specifically in FMVSS 301. The OMCS and FMVSS 301 requirements
are summarized below.
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-78-
Figure 24
HDGV Fuel Tanks
D-Shape
Standard Rectangular
Step Rectangular
-------
Figure 25
TYPICAL HDGV EVAPORATIVE SYSTEM
-BALL CHECK VALVE
TANK RESTRICIDR
^PRESSURE/VACUUM
RELIEF
PURGE
VALVE
L
SEALED
GAS CAP
3/16" DIA
13' LONG
TO PURGE
INDUCTION
POINT
2.5 LITER
CANISTER
^j
vo
30 GALLON FUEL TANK
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-80-
1. Office of Motor Carrier Safety Requirements
OMCS safety regulations include both specific design
requirements and actual fuel tank safety tests.[44] The design
requirements contain rules governing the location,
installation, and construction of fuel tanks used on HDGVs.
Also, fuel lines, fittings, and fillpipes must conform to
certain requirements.
The actual testing requirements depend on whether a fuel
tank is side-mounted or non-side mounted. To paraphrase the
definition, a truck fuel tank is considered side mounted if it
extends beyond the outboard side of a front tire positioned in
the straight ahead position. This is shown pictorially in
Figure 26. Any fuel tank which does not have this
characteristic is considered non-side mounted, and in this
analysis will be referred to as frame mounted. The testing
requirements for frame-mounted tanks will be discussed first.
A frame mounted HDGV fuel tank has to be able to pass two
fuel tank safety tests. The first of these two tests, the
safety venting system test, involves applying an enveloping
flame to an inverted fuel tank to insure that the fuel tank's
safety venting system activates prior to the tank's internal
pressure exceeding fifty pounds per square inch. The second
fuel tank safety test is a leakage test which involves filling
the tank to capacity and rotating the tank through an angle of
150° in any direction from its normal position to insure that
neither the tank nor any fitting leak more than one ounce of
fuel per minute in any position the tank assumes during the
test.
HDGVs with side mounted fuel tanks must pass two other
tests which involve dropping the fuel tank to test impact
resistance. The first test, termed the drop test, involves
dropping a fully loaded (equivalent weight of water) tank from
30 feet onto an unyielding surface, so that it lands squarely
on one corner. A second similar test (termed the fillpipe
test) requires that a fully loaded tank be dropped from 10 feet
onto an unyielding surface, so that it lands squarely on its
fillpipe. In neither case, may the tank nor any fitting leak
more than one ounce per minute.
Based on conversations with the two HDGV manufacturers,
the vast majority of HDGV fuel tanks are frame mounted
(non-side mounted). No side mounted tanks are offered as
standard equipment, and only occasionally one is sold as a
special order.[45,46] Thus, this analysis will focus primarily
on the safety venting and leakage test requirements which apply
to frame mounted tanks. However, the drop tests for side
mounted tanks will also be considered.
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Figure 26
Pictorial Definition of Side-Mounted Fuel Tank.
If the tank extends to the left of line A or to
the right of line B, then the tank is side-mounted.
Lines A and B are tangent to the outer sides of
the front tires.
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-82-
2. School Bus Requirements
In addition to the OMCS requirements for frame-mounted
tanks, outlined above, school buses are required to meet
specific FMVSS 301 standards. However, this coverage does not
include all of the test requirements as prescribed for
passenger cars and light trucks. FMVSS 301 for school buses
over 10,000 GVWR requires an impact with a contoured moving
barrier at any speed up to and including 30 mph, at any point
and angle. Depending on the design and location of the fuel
tank and its protective structure, the "worst case" point and
angle of contact is determined for each school bus model, and
the contoured moving barrier impacts there. In this test, the
fuel system must be designed so as not to leak more than one
ounce of fuel per minute.[47]
This briefly summarizes the current Federal safety
standards applicable to fuel systems on HDGVs over 10,000
GVWR. It is important to note that more safety requirements
could be applied to HDGVs over 10,000 GVWR in the future. The
Department of California Highway Patrol recently submitted a
petition to NHTSA to amend FMVSS 301 to include fuel system
integrity testing for heavy-duty vehicles over 10,000
GVWR.[48] With this background information we are now prepared
to discuss how the differences in vehicle/fuel system
configurations and the Federal safety standards may affect the
design of an onboard system for an HDGV relative to the design
for passenger cars and light trucks.
C. Distinctions in HDGV Onboard Systems
Just as the evaporative emission control systems used on
HDGVs are very similar to those used on passenger cars and
light trucks, it is also expected that an HDGV onboard system
would be very similar in design and approach to that conceived
for lighter-weight vehicles (a possible HDGV onboard system is
shown in Figure 27). However, some minor variations would
exist due to differences in HDGV fuel system configurations and
the requirements levied by the applicable Federal safety
standards. Before beginning a discussion of these minor
variations, it is valuable to reiterate a few key points raised
previously with regard to the magnitude of the task of
implementing onboard controls.
First, like passenger cars and light trucks, all HDGVs now
incorporate evaporative emission control systems (see Figure
25) and their fuel systems must meet the present Federal fuel
system integrity standards (OMCS and NHTSA). Thus, as before
with the lighter weight vehicles, the application of onboard
systems is best evaluated incrementally to the measures already
taken to incorporate evaporative emission controls and meet
safety standards. Much of the ground work has already been
completed, the needed modifications made and components added.
-------
Figure 27
POSSIBLE HDGV INTEGRATED EVAPORATIVE/REFUELING SYSTEM
• PRESSURE/VACUUM
IEF
MECHANICAL OR SOLENOID
ACTUATED VENT/ROLLOVER
VALVE, LIMITING ORIFICE
„& LIQUID/VAPOR SEPERATOR
oo
SEALED-'
GAS CAP
MECHANICAL
SEAL
5/8" DIA
~13' LONG
-3/8" DIA
~ 3* LONG
TO PURGE
INDUCTION
POINT
7.5 LITER
CANISTER
30 GALLON HDGV FUEL TANK
-------
-84-
In many cases no changes to present fuel system safety
assurance or evaporative emission control measures will be
needed. Second, it is important to note that HDGV onboard
refueling and fuel tank evaporative emission control systems
will likely be integrated as with lighter weight vehicles.
This is quite easy to accomplish on HDGVs, since they now have
separate canisters and control systems for fuel tank and fuel
metering system evaporative emissions. Thus a whole new system
will not be added to control HDGV refueling emissions; instead
the refueling and fuel tank evaporative emission control
systems will be integrated into one (compare Figure 25 with
Figure 27). Thus many of the primary design considerations
which applied for the evaluation of onboard systems to
passenger cars and light trucks also apply to HDGVs.
Remembering the expected similarities between light and
heavy-duty vehicle onboard systems and that the factors
affecting the implementation are also the same, the expected
minor variations in HDGV onboard systems can now be discussed.
For sake of presentation, discussion will begin at the fillpipe
and follow along the system to the canister. The analysis will
assume an integrated onboard refueling/fuel tank evaporative
control system as discussed above.
To begin with, because the fillpipes on HDGV fuel tanks
are either relatively short or integral with the tank, liquid
fillneck seals which require an appreciable fill height may not
be a practical approach in some configurations. Due to this
lack of fill height, HDGV manufacturers might elect to utilize
a mechanical seal approach and thus would need to incorporate
some type of pressure relief device such as was described
previously. HDGV fuel tanks, which are made of steel or
aluminum, now use a pressure-vacuum relief valve, and it is
conceivable manufacturers will simply modify that valve for
this application. However, under the proper backpressure
conditions, it might be possible to use a liquid fillneck seal
by extending the fillpipe horizontally in the tank as has been
demonstrated in a prototype light-duty program.[15]
A second potential difference lies in the diameter of the
refueling vapor line and related fuel tank vent. From a design
perspective, the tank vent and refueling vapor line size
(diameter) could be affected by the fuel dispensing rate. As
part of the refueling emissions test procedure, EPA is
proposing that HDGV fuel systems be designed for refueling at a
maximum rate of 10 gallons per minute, the same rate as
prescribed for other vehicles.* This 10 gallon per minute
Discussions with gasoline marketing interests and nozzle
manufacturers indicate that gasoline available to
passenger cars, light trucks, and HDGVs (either at retail
or private pumps) is normally not dispensed at rates
greater than 10 gpm.
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-85-
dispensing rate results in an increase in the current orifice
and evaporative vapor line diameter from about 3/8 inch to
about 5/8 inch for an HDGV onboard system.
However, to minimize spillage during refueling, the OMCS
has requirements that any liquid fuel tank over 25 gallons in
capacity must be able to accept fuel at a rate of 20 gallons
per minute.[49] For an onboard system this requirement could
lead to a increase in the diameter of the tank vent outlet and
refueling vapor line. It should be noted, however, that while
this requirement applies to all heavy-duty liquid fuel tanks
(both diesel and gasoline), fundamentally it is aimed more at
diesel fuel tanks. It is not uncommon to encounter an in-use
diesel fuel dispensing rate of 20 gpm or more to reduce the
time needed to fill a diesel tank since these tanks are
typically much larger than gasoline tanks and dual diesel tanks
are also more common.[50] In-use gasoline dispensing rates on
the other hand normally do not exceed 10 gpm. Since in-use
gasoline dispensing rates usually do not exceed 10 gpm, and
EPA's refueling certification test would involve a 10 gpm
maximum dispensing rate, OMCS's requirement in this area may
not be needed. EPA has discussed this matter with DOT/OMCS,
and they have expressed a willingness to consider changing this
requirement to apply only to diesel fuel tanks.[51,52] If this
standard is not changed, and a 10 gpm dispensing rate limit is
enacted, the only effect would be that the refueling vent
orifice/line for these vehicles would be over sized.
Nevertheless, because HDGV fuel tanks do not use long
fillnecks, fuel dispensing operations would not be as sensitive
to higher backpressure as they would be in light-duty. Even if
the refueling vent orifice/line were sized for a 10 gallon per
minute dispensing rate, fuel could be dispensed at a greater
rate without premature shutoffs. Thus it may not be necessary
to size the refueling orifice/vent line to match the dispensing
rate requirements. However, in optimizing system designs with
regard to fuel tank pressure, manufacturers may choose to use a
slightly larger refueling vent orifice than seen on light-duty
applications.
One final manner in which HDGV onboard systems might
differ from those on lighter weight vehicles is in the design
of the rollover protection device. The solenoid activated
rollover valve (Figure 19) or the combination valve (Figure 21)
could be applied to HDGV fuel tanks in their present
configurations. One manufacturer's fuel tank design now
incorporates a ball type check valve similar in principle to
the combination valve.[41] Also, the nozzle actuated valves
shown in Figures 9-15 could also be used on HDGV fuel tanks
which have a fillpipe length of 6 inches or more. However,
nozzle actuated valve designs would have to be modified
slightly to perform on fuel tanks whose fillneck is essentially
integral with the tank. Nonetheless, the basic approach and
operation would be the same.
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-86-
Any of the three rollover valve designs mentioned above
could be used on HDGV fuel tanks. However the best choice for
any tank would depend on the fillpipe length or other
trade-offs relative to cost, packaging etc. With proper design
and integration any of these valve designs could provide
rollover protection in-use.
With this background on HDGV fuel system configurations,
safety requirements, and HDGV onboard system characteristics,
it is now possible to address some of the unique safety
concerns related to HDGV onboard. The next segment of this
report discusses and addresses potential impacts of HDGV
onboard on fuel system safety considerations.
D. HDGV Onboard Safety Issues
1. Introduction
While none of the comments received regarding the safety
implications of onboard controls specifically addressed HDGVs,
it is reasonable to expect that overall concerns would be
similar because of the expected close resemblance between light
and heavy-duty vehicle onboard systems. To avoid repeating
much of what has previously been discussed, this segment will
primarily focus on unique HDGV onboard safety considerations.
The analysis presented in Section IV regarding maintenance,
repair, tampering and defects and refueling operation safety
apply equally to HDGVs and will not be repeated here. The
potential problems are similar and the same basic approach and
straightforward engineering solutions can be used. Also, the
extensive analysis in Section V regarding in-use fuel system
safety also applies to HDGVs. As before, manufacturers are
expected to manage risk appropriately; there is no reason that
adding an onboard system would directionally increase in-use
risk over that now accepted with present HDGV fuel/evaporative
emission systems.
However, as was discussed above the fuel system
configurations and the safety test requirements for HDGV fuel
tanks are somewhat different from light-duty, so some
discussion of distinct safety test design requirement issues is
appropriate.
2. Safety Test Design Requirements
As mentioned above, there are two separate areas of safety
test design considerations for HDGV fuel systems. The Office
of Motor Carrier Safety (OMCS) has fuel system safety
regulations which apply to all HDGVs, and NHTSA has additional
requirements for school buses. This segment begins with a
summary and analysis of safety design considerations related to
OMCS requirements. Following this is a discussion of the
effects of NHTSA1s crash test requirements.
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-87-
a. OMCS Requirements/Considerations
OMCS has established fuel system requirements for HDGVs to
insure their structural and in-use integrity. As part of the
current requirements, HDGV fuel tanks must be capable of
passing the safety venting system and the leakage tests
described previously. Currently HDGV fuel tanks employ a ball
check valve and pressure vacuum relief valve to pass these two
tests. Since the refueling vent orifice would be somewhat
larger with an onboard system (5/8") the ball check valve would
have to be upgraded to provide the necessary protection.
Little or no change to the pressure vacuum relief valve would
be needed.
For an HDGV onboard system, the protection now supplied by
the ball check valve could be supplied by the rollover valve
designs described previously. The same three general types of
rollover protection devices that were discussed for use in
light-duty applications (nozzle actuated, solenoid, and
mechanically activated valves) would all be feasible in various
heavy-duty applications as well. However, for tanks with
little or no fillpipe (<6") the nozzle actuated valve design
would probably have to be modified slightly and mounted in the
tank instead of on the fillheck. A solenoid or mechanical
rollover (ball) valve design could essentially be used as shown
earlier.
HDGV and light-duty onboard systems would be functionally
identical and would be very similar in design and configuration
except for canister size and vapor line length. Of course, to
meet safety requirements and to provide in use protection,
manufacturers will have to consider the structural integrity
and the materials used in key system components just as they do
now with other components of the fuel/evaporative system.
Thus, some components of the HDGV onboard system (notably the
rollover valve) may need to be constructed of metal to provide
impact resistance and the flammability protection demanded in
the safety venting test.
Also, with regard to impact resistance, any one optional
side-mounted tank model, would be subject to two additional
safety tests (drop tests) designed to evaluate the tank's
impact resistance. A side-mounted fuel tank would likely
utilize a rollover valve mounted integral to or within the tank
to insure its integrity during the drop tests. While this
would not be difficult to design (many current fuel tanks
contain interior components), it would represent an additional
design consideration for side-mounted fuel tanks. From an
in-use safety perspective, the impact resistance and overall
integrity of rollover valves on frame mounted tanks would be
enhanced if they were mounted integral or internal to the
tank. Thus, this approach would be attractive for all HDGV
fuel tanks.
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-88-
In conclusion, the only HDGV onboard safety design feature
introduced by the need to meet OMCS safety requirements is the
upgrade of the current rollover protection device. All of the
rollover protection approaches discussed for light-duty
applications (nozzle actuated, solenoid, or mechanically
activated valves) could be used to meet this requirement. The
design, placement, and construction of the rollover valve on a
particular HDGV fuel tank would depend in part on fillpipe
configuration, impact resistance concerns, and flammability
potential.
b. NHTSA Requirements/Considerations
In addition to OMCS requirements, all school buses over
10,000 Ibs. GVWR must also meet specific requirements of
NHTSA1s FMVSS 301. As described earlier, this involves a
single moving contoured barrier test at a maximum of 30 mph and
does not include a rollover test. In this test, the barrier
impacts the school bus at the most vulnerable location of the
fuel tank, and the fuel system must be designed so as not to
leak more than one ounce of fuel per minute. As was true of
OMCS requirements, an acceptable school bus onboard system is
one which does not impair the fuel tank's ability to meet- this
requirement.
As in the light-duty test, the crashworthiness of all the
onboard system components (rollover valve, charcoal canister,
critical vapor line and vapor line connections between the top
of the fuel tank and the rollover valve) would all be evaluated
in the test. Design measures similar to those described for
passenger cars and light trucks would have to be taken to
assure the integrity of these three key components.
The crashworthiness discussion in Section IV-A and the
further options discussed in Section V addressed specific
safety design approaches for these components which could also
be applied to school buses, so this will not be addressed
further. As before with light-duty applications, evaporative
emission systems provide directly relevant techniques and
experience to assist in proper design, and specific engineering
measures have been suggested to deal with potential concerns.
Furthermore, the in-use safety of onboard refueling
controls for HDGVs must be considered. The location of onboard
system components, as with the current fuel tank and
evaporative emission controls, must minimize any potential
safety risks. Much of the HDGVs fuel system damage seen today
is caused by foreign objects from the road surfaces.
Therefore, critical onboard control system component should be
located on the HDGV in a position which will minimize any
foreign object damage.
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-89-
In conclusion, HDGV onboard systems do not introduce any
new or significant problems to manufacturers' attempts to
design safe fuel systems capable of meeting NHTSA and OMCS
safety requirements. Straightforward, viable .engineering
solutions are available to address all problems that have been
identified. Therefore, onboard systems are expected to be
integrated into HDGV fuel systems without reducing the system's
ability to meet all applicable Federal safety requirements.
3. Summary
As was mentioned in the light-duty section of this report,
EPA's philosophy in evaluating the safety implications of
requiring onboard controls (including those for HDGVs), is
that no increase in overall risk should be caused or accepted,
beyond that now present with today's fuel/evaporative system.
This applies to both compliance with the applicable Federal
Safety standards and the in-use safety of vehicles equipped
with onboard systems. This portion of the analysis has
addressed the safety test design requirements related to
implementing HDGV onboard systems, and as was the case for
light-duty it concludes that straightforward engineering
solutions are available for all of the potential safety
problems which have been identified, and safe fuel system
designs are achievable by all.
E. Cost and Leadtime Considerations
EPA has received no comments which directly address
specific HDGV onboard safety cost and leadtime implications.
However, an analysis of the costs and leadtime necessary to
implement HDGV onboard controls safely is an integral part of
the overall evaluation of the feasibility of this control
approach. The first portion of this section addresses HDGV
onboard safety costs; the second discusses HDGV leadtime
requirements and describes the basis for EPA's leadtime
estimates. Some of the cost figures cited in the safety cost
analysis are drawn from a broader EPA analysis which develops
total HDGV onboard system costs in 1984 dollars.[17]
1. Safety Costs
As was true of light-duty onboard safety costs, the costs
needed to implement HDGV onboard controls fall in several
areas. R&D type costs will be incurred, some new or modified
components will be needed which may slightly affect vehicle
operating costs, and safety certification testing will be
necessary. However, before beginning a discussion of these
costs, it is valuable to discuss how EPA's HDGV evaporative
emission control requirements impact onboard safety costs.
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As was described in the light-duty section of the report,
an onboard system (even those for HDGVs) is in many ways an
extrapolation of current evaporative emission control
technology and the two systems are quite similar. Since
onboard systems are basically extensions of evaporative
emission systems, clearly many of the safety design
considerations associated with onboard systems related to
meeting OMCS/NHTSA requirements or providing in-use assurance
have already been addressed in evaporative emission system
designs. Consequently, much of the ground work required to
insure onboard safety has already been performed. It is
important to keep the magnitude of the HDGV onboard safety
design process in perspective, because much of the safety
technology needed is simply an extension of that which already
exists. Noting the "incremental" nature of onboard safety in
terms of the magnitude of the task and actual cost relative to
evaporative systems, it is now possible to describe the
components which factor into onboard safety costs.
Basically, the integration of safety into a fuel system
incorporating an onboard system involves four types of costs.
These four costs are for: 1) design and development (R&D), 2)
specific hardware, 3) safety testing, and 4) weight penalty (or
added fuel consumption). The paragraphs that follow describe
how each of the cost components are affected by onboard safety.
To begin with, some research and development will have to
be performed to safely integrate onboard controls into HDGV
fuel systems. EPA has estimated that the total design and
development cost required to incorporate onboard systems in
HDGV fuel systems is about $34,200 per family or $1.50 per
vehicle (over 10,000 Ibs GVWR). This cost is for any
development effort involved in combining the components of an
onboard system with the rest of the vehicle to form a unit that
interacts safely and effectively. Because safety is evaluated
inherently in the design and development process and yet is
only one part of the total effort, only a fraction of the total
cost should be directly allocated to safety. The light-duty
cost section explained why this fraction is likely to be
small. The same reasoning is also applicable for heavy-duty
applications, and therefore it was assumed that about 20
percent of R&D expenditures relate to safety, which translates
to about $0.30 per vehicle.
The second component of HDGV onboard safety costs relates
to specific hardware that may be required to insure fuel system
safety. EPA has estimated costs for three specific items which
have been identified as potential components to be included as
part of the onboard system design explicitly for safety
reasons. These three items are 1) a rollover valve, 2) a
pressure relief mechanism, and 3) fuel system modifications
necessary to safely incorporate a rollover valve, pressure
relief mechanism, or other onboard hardware. HDGV rollover
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-91-
valves should not differ in cost from light-duty valves since
they would essentially be the same. Therefore, the light-duty
estimate of $3.00 to $6.00 will also be used here.
The second safety hardware cost is for a pressure relief
mechanism. Since this mechanism would be needed for onboard
systems incorporating a mechanical fillneck seal, many HDGVs
would require its use. EPA's analysis prices this device at
$2.50.[13] At this point, this estimate is considered to be
very conservative, since the possibility exits that the present
pressure relief device can be modified to perform this function.
The final onboard safety hardware cost accounts for any
fuel system modifications that would be necessary in order to
safely accommodate any onboard control hardware. For example,
a HDGV fuel tank or fillpipe might have to be re-shaped or
modified in order to accept a rollover valve. Also, some
slight re-routing of the fuel system's vapor lines may be
required. EPA has estimated a total modification cost to be
$0.50 per fuel tank. Only part of this total cost would be
required for safety purposes. However, because safety
inherently enters into the decision to make any modifications,
it is difficult to access what part of the total modification
cost should be allocated to safety; perhaps half ($0.25 per
fuel tank) could be considered as driven by safety related
concerns.
Summing up the three individual safety hardware costs per
fuel tank yields a total estimated figure in the range of $5.75
to $8.75. However, this cost estimate does not include
manufacturer overhead and profit. Consequently, in order to
obtain the retail price equivalent cost, these estimates must
be multiplied by a markup factor. Presently, a markup factor
value of 1.27 appears representative.[37] Therefore, after
integration of the markup factor, a total retail price
equivalent HDGV safety-related hardware cost per fuel tank
falls within the range of $7.30 to $11.10. Since 15 percent of
HDGVs have dual tanks, the total HDGV safety-related hardware
cost range is $8.40 to $12.80
The third component of safety costs is for any safety
testing that would be necessary. Unlike light-duty test costs,
EPA has not thoroughly investigated HDGV safety test costs.
However, safety test costs were estimated in an attempt to
determine the approximate magnitude of the per vehicle HDGV
safety test cost. Table 6 shows that even when fairly liberal
safety test costs are assumed, the resulting cost/vehicle of
$0.70 is very minimal in the long term.
The fourth component of safety costs is the estimate of
the added fuel consumed over the life of the vehicle due to the
increase in vehicle weight resulting from added safety
hardware. The amount of weight added to vehicle from a
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Table 6
HDGV Fuel Tank Safety Test Costs Estimate
1. OMCS Requirements:
2 tests per HDGV fuel system configuration
(Safety Vent Test and Leakage Test)
Conservative Cost/Test Estimate: $2,000
8 HDGV Fuel Tank Configurations
Total OMCS Safety Test Cost: $32,000
2. NHTSA Requirements:
1 test per HDGV fuel system configuration
(30 mph moving barrier)
Conservative Cost/Test Estimate: $30,000
7 School Bus Configurations (7 manufacturers,
1 config./manufacturer)
Total NHTSA Safety Test Cost: $210,000
3. Total HDGV Fuel Tank Safety Test Cost: $242,000
4. Cost/Vehicle (Amortized at 10 percent over 5 years of
vehicle sales*): $0.70
* Assumed that all bus manufacturers will crash test their
vehicles.
** Vehicle sales were estimated at 90,000/year.
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rollover valve or pressure relief mechanism is very small (0.4
Ibs), and because HDGVs are less sensitive to weight changes
than lighter weight vehicles, on average less than $0.30 in
added fuel costs will result from their inclusion into the HDGV
onboard system.[24]
A total onboard safety cost is calculated by summing all
four individual component costs. Total safety-related onboard
costs per family average about $270,000, and the per vehicle
costs range from $9.70 to $14.10 or about 20-25 percent, of the
total cost depending on the type of rollover valve used.
2. Leadtime
If EPA were to implement an HDGV onboard requirement, it
would be necessary to allow manufacturers enough leadtime to
adequately prepare for the requirement. The HDGV preparation
process would involve the same individual tasks that would
enter into the light-duty process: system design, development,
testing, tooling, certification, and safety evaluation.
Although two of these leadtime tasks (certification and safety
evaluation) would involve somewhat different procedures for
HDGVs, they will essentially require the same amount of time
and would factor into the total process in the same manner as
in light-duty. Therefore, it is estimated that 24 months would
be the total amount of leadtime required by HDGV manufacturers,
and Figure 25 which shows the parallel/sequential progression
of the individual leadtime components would be essentially the
same for HDGVs.
Of the various leadtime components shown in Figure 25, all
but two would be essentially the same for HDGVs as they would
for light-duty applications. These two are certification and
safety evaluation. In both cases, the HDGV processes appear as
though they would take less time to complete than their
light-duty counterparts because these tasks would be likely to
be less difficult to perform. For example, in some cases,
durability assessments for certification of HDGVs does not
require any actual vehicle testing; bench evaluations can be
substituted based on the manufacturers engineering judgment.
This could save considerable time.
As far as safety evaluation goes, HDGV fuel tank tests
performed to meet OMCS requirements would be much simpler to
perform than NHTSA's safety crash tests for passenger cars and
light trucks. Also, when NHTSA requirements do apply (as in
the case of school buses) they only involve a single crash test
with no rollover. (This is minor in comparison to tests which
involve multiple crashes with rollover.) Therefore, the amount
of time allowed for light-duty certification (10-12 months) and
safety evaluation (>12 months) should also be sufficient for
HDGVs since the heavy-duty processes are less involved.
Overall, 24 months of leadtime for HDGV onboard is quite
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reasonable. This is especially true when one considers the
development work already completed and the "incremental" nature
of onboard in relation to current evaporative emission systems.
EPA's 24-month leadtime estimate is supported by past
experience with previous HDGV evaporative emission
rulemakings. These rulemakings include the California Air
Resources Board original 1978 6.0 g/test HDGV evaporative
emission standard which was implemented with just 21 months of
leadtime.[53] The stringency of this standard was increased
for 1980 model year HDGVs allowing only 2 g/test. [54] While
this stricter standard was promulgated with 37 months of
leadtime, manufacturers had to meet the 1978 standard first,
which effectively limited the leadtime for the 1980 standard to
about 24 months. One final evaporative emission standard which
was implemented with 24 months of leadtime was EPA's 1985 HDGV
standard. In each of these three rulemakings, manufacturers
faced leadtime factors identical to the ones that would
accompany an onboard requirement, including safety. Since
manufacturers were able to safely and effectively integrate
evaporative emission controls into their vehicle's fuel systems
with 24 months of leadtime, and since the magnitude of the
onboard implementation task is similar, manufacturers should
also be able to safely and effectively integrate onboard into
vehicle fuel systems with 24 months leadtime.
As far as safety development and evaluation is concerned,
EPA's HDGV leadtime estimate is also supported by the past
experience of OMCS and NHTSA in implementing various HDGV fuel
system retirements. In 1973, OMCS extended its safety test
requirements to include previously unaffected non-side-mounted
(frame-mounted) HDGV fuel tanks. This requirement was
implemented with just 18 months of leadtime. [ 55] Also in 1977,
FMVSS 301 was extended to include school buses, and this
requirement was implemented with 17 months of leadtime.[56]
This experience indicates that 24 months of leadtime allows
manufacturers sufficient time to factor in safety.
Based on the information provided above, it appears that
24 months is adequate time to implement HDGV onboard controls,
with full consideration of all safety concerns. Because safety
evaluation can proceed in parallel to three other tasks, more
than a year is available for actual fuel tank safety tests,
school bus crash testing, or any desired computer simulation.
This allows adequate leadtime to properly integrate safety into
HDGV onboard systems especially since manufacturers can utilize
and expand safety technology used in current evaporative
emission control systems to develop effective onboard systems.
Also, much of the safety development which would be required
has already taken place with the identification and resolution
of such potential safety issues as rollover protection and fuel
tank pressure relief. Consequently, a 24-month leadtime period
would provide manufacturers with sufficient opportunity to
develop safe and effective onboard systems.
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While the current leadtime estimate of 24 months is
reasonable for all vehicle models including HDGVs, EPA is
sensitive to manufacturers concerns regarding leadtime
requirements. EPA is committed to providing manufacturers the
leadtime necessary to implement onboard controls "safely and
effectively. Designing safe onboard controls for some unique
HDGVs may require more leadtime. Such HDGVs include those with
atypical duty cycles, unique fuel tank or body configurations,
and those HDGVs from secondary manufacturers. Consequently,
EPA would include HDGVs as part of any overall consideration of
additional leadtime or a short phase-in period for onboard
controls.
F. Summary/Conclusion
The purpose of this section was to identify and address
the potential effect^ onboard controls could have on a HDGV
manufacturer's fuel system safety designs. After analyzing the
potential safety concerns related to implementing HDGV onboard
systems, EPA has found that like passenger cars and light
trucks, heavy-duty onboard systems are extensions of current
evaporative systems and corresponding safety considerations are
similar in nature to those discussed for light-duty
applications. While a few unique considerations do exist (in
part because of differences in testing requirements, tank
designs/locations, structural integrity, size etc.), no
increase in overall risk should be caused or accepted, beyond
that now present with today's HDGV fuel/evaporative system.
This applies to both compliance with the applicable Federal
safety standards and the in-use safety of HDGVs equipped with
onboard systems. As was the case for light-duty,
straightforward engineering solutions are available for all of
the potential safety problems which have been identified, and
that while final choices regarding exact system designs lie
with the manufacturers, safe fuel system designs are achievable
by all. EPA estimates that HDGV safety costs contribute about
20-25 percent of the total ^iDGV onboard system cost and should
fall within the range of $9.70 to $14.10. With regard to
leadtime, this analysis indicates that 24 months appears to
provide HDGV manufacturers with adequate time to prepare for
the safe and effective implementation of onboard controls, but
as before with passenger cars and light trucks the possibility
of the need for more leadtime for some vehicle models may exist.
VIII. Conclusion
EPA has investigated and analyzed each of the potential
onboard system safety issues raised by the commenters. After
carefully considering all of the potential, impacts an onboard
system could have on the overall safety df a vehicle's fuel
system, it is concluded that straightforward, reliable,
relatively inexpensive engineering solutions exist for each of
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the potential problems identified. Furthermore, no increase in
risk need occur or be accepted because of the presence of an
onboard system. Onboard equipped vehicles can be designed to
pass FMVSS 301 and provide a level of in-use fuel system
integrity equal to or better than that achieved on present
vehicles which incorporate evaporative emission control
systems. Of course final choices regarding exact onboard
system designs lie with the manufacturers, and each
manufacturer will choose the approach/system which provides the
best balance of cost, safety, and other key factors. EPA would
not adopt an onboard requirement unless it was clear that safe
fuel system designs were available. This report demonstrates
this to be the case. Safe fuel system designs are achievable
by all manufacturers.
Furthermore, it it is quite possible that overall fuel
system improvements could accompany the implementation of
onboard controls and lead to a net improvement in the level of
fuel system safety on in-use vehicles. For example,
collapsible bladder tanks are one design option that could
control refueling emissions, reduce evaporative emissions and
at the same time improve fuel system safety.
Manufacturers can and are expected to design and implement
onboard systems in a manner which provides at least the same
level of fuel system safety as achieved on present vehicles.
In addition, a number of design options and other measures are
available with onboard systems, which suggest that fuel system
safety in-use can be improved along with the incorporation of
onboard control systems.
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IX. References
1. Letter, Thomas Hanna, MVMA and George Nield, AIA to
Lee Thomas, US EPA, December 22, 1986.
2. Letter, Brian O'Neill, IIHS to Lee Thomas, US EPA,
September 23, 1986.
3. Letter, Ralph Hitchcock, NHTSA to Charles L. Gray,
Jr., US EPA, November 13, 1986.
4. American Petroleum Institute Comments on US EPA
Gasoline Marketing Study, November 8, 1984, Docket A-84-07.
5. Letter, Clarence Ditlow, Center for Auto Safety to
Lee Thomas, US EPA, March 20, 1987.
6. "Survey of Evaporative Emission Systems Condition of
In-Use, High Mileage Automobiles", API Publication 4393,
February, 1985.
•
7. Borg Warner Control Systems Catalog, February 1986.
8. "Study of Gasoline Volatility and Hydrocarbon
Emissions from Motor Vehicles", US EPA, AA-SDSB-85-5, November
1985.
9. "Summary and Analysis of Comments on the Recommended
Practice for the Measurement of Refueling Emission", US EPA
AA-SDSB-87, March 1987.
10. Letter, T.M. Fisher, General Motors to James B.
Weigold, US EPA, November 8, 1984, Docket A-84-07.
11. Ford Motor Company Comments on Evaluation of Air
Pollution Regulatory Strategies for the Gasoline Marketing
Industry, November 8, 1984, Docket A-84-07.
12. Chrysler Corporation Comments on Evaluation of Air
Pollution Regulatory Strategies for the Gasoline Marketing
Industry, November 5, 1984, Docket A-84-07.
13. "Toyota Information on Refueling Vapor Recovery",
Presentation to US EPA, March 19, 1986.
14. "Onboard Control of Vehicle Refueling Emissions
Demonstration of Feasibility", API Publication 4306, October
1978.
15. "Vehicle Onboard Refueling Control", API Publication
4424, March 1986.
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16. "Evaluation of the Feasibility of Liquid Fillneck
Seals," US EPA AA-SDSB-86-003, December 1986.
17. . Evaluation of Air Pollution Regulatory Strategies
for Gasoline Marketing Industry - Response to Public Comments,
March 1987.
18. "Onboard Refueling Vapor Recovery Cost Study,"
Mueller Associates Inc., December 1986.
19. "Refueling Emissions from Uncontrolled Vehicles,"
EPA-AA-SDSB-85-6, Dale Rothman and Robert Johnson, 1985.
20. "Expansion of Investigation of Passenger Car
Refueling Losses," EPA-460/3-76-006, U.S. EPA, OAWM, OMSAPC,
ECTD, September 1975.
21. "Evaluation of Federal Motor Vehicle Safety Standard
301-75, Fuel System Integrity: Passenger Cars," DOT HS-806-335,
January 1983.
22. Fatal Accident Reporting System, NHTSA, DOT,
1980-1984.
23. Motor Vehicle Safety Standard No. 301-75, Fuel
System Integrity: 39 FR 10588, March 21, 1974, PART 571; S
301-75-5.1, 5.2, 5.3, and 40 FR 48352, October 15, 1975, PART
571: S 301-75-5.1, 5.2, 5.3, 5.4.
24. Letter, David E. Martin, GM to Barry Felrice, NHTSA,
March 24, 1986.
25. Letter, Hiroyuki Shinbura, Nissan Research and
Development to Charles Gray, U.S. EPA, April 14, 1987
26. Note from Bob Williams, NHTSA, to Glenn Passavant,
US EPA including 3 computer file printouts, November 13, 1986.
27. "Design of a Fire Proof Vehicle," Chan, C.Y.K./Chi,
L.L., California University, Berkeley, Fire Research Group.,
Report No. UCB-FRG-75-18, July, 1975.
28. "A Perspective on Automobile Crash Fires", SAE
850092, C. Warner, M. James, R. Wooley.
29. "Supplement to General Motors Commentary to the
Environmental Protection Agency Relative to Onboard Control of
Vehicle Refueling Emissions," June 1978.
30. NHTSA Press Release, June 11, 1987 and NHTSA Fact
Sheet on The New Car Assessment Program and a Summary of the
New Car Assessment Program Test Results, August 5, 1986.
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31. Ann Arbor News, "'Smart' Suspension System Includes
Sensors; Computers," Ann Arbor News, Newhouse News Service,
March 1, 1987.
32. "Spilled Fuel Ignition Sources and Countermeasures,"
Johnson, N. , DOT Contract No. HS-4-00872, Report No.
2310-75-118, September, 1975.
33. "Costs of Onboard Vapor Recovery Hardware", Jack
Faucett and Mueller Associates, February 1985.
34. "Report on Quality Changes for 1977 Model Passenger
Cars" USDL-76-1376, BLS November 1976.
35. "Report on Quality Changes for 1976 Model Passenger
Cars," USDL-75-626, BLS November 1975.
36. "Cost Estimations for Emission Control Related
Components/Systems and Cost Methodology Description,"
EPA-460/3-78-002, March 1978.
37. "Update of EPA's Motor Vehicle Emission Control
Equipment Retail Price Equivalent Calculation Formula," Jack
Faucett Associates for U.S. EPA, September 4, 1985.
38. "Cost of Crash Testing to Assure Fuel System
Integrity for Onboard Systems," EPA Memorandum, Robert Johnson
to the Record, U.S. EPA, OAR, QMS, ECTD, SDSB, September 2,
1986.
39. "Trap Oxidizer Feasibility Study", U.S. EPA, OANR,
OMSAPC, ECTD, SDSB, March 1982.
40. "Characterization of Fuel/Vapor Handling Systems of
Heavy-Duty Gasoline Vehicles over 10,000 Pound GVW", Jack
Faucett Associates, September 1985.
41. "Evaluation of Air Pollution Regulatory Strategies
for the Gasoline Marketing Industry", US EPA, OAR,
EPA-450/3-84-012a, July 1984.
42. Memorandum to File, Review of General Motors Heavy
Duty Engine/Valued Certification Procedures, Team IV
Certification Branch, August 4, 1986.
43. Memorandum to File, Review of Ford HDE Certification
Procedures, Team IV Certification Branch, August 5, 1986.
44. 49 CFR Part 393.65 to 393.67.
45. Conversation with Jim Feiten, GM, March 16, 1987.
46. Conversation with Bob Bisaro, Ford, March 16, 1987.
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47. Motor Vehicle Safety Standard NO. 301-75, Fuel
System Integrity: 40 FR 48352, October 15, 1975, PART 571: s
301-75-5.4 and 41 FR 36026, August 26, 1976, PART 571: S
301-75-5.4
48. Letter, L.M. Short, Department of California Highway
Patrol to Diane Steed, National Highway Traffic Safety
Administration, May 30, 1986.
49. 49 CFR 393.67 (c)(7)(ii).
50. Based on a AP of 10 psi for Emco Wheaton Model
A6000 and OPW Model 7H diesel fuel nozzles.
51. Letter, Charles L. Gray, Jr., US EPA, to Office of
Motor Carrier Safety, May 27, 1987.
52. Conversation with Jim Brittell, DOT/OMCS, February
18, 1987.
53. Public Hearing to Consider Amendments to California
Fuel Evaporative Emission Test Procedures for 1978 and
Subsequent Model Gasoline-Powered Vehicles, Resolution No.
76-15, March 31, 1976.
54. Public Hearing on Proposed Changes to Regulations
Regarding Vehicle Evaporative Emission Standards for 1980 and
Subsequent Model Motor Vehicles, Resolution No. 76-45, November
23, 1976.
55. OMCS Regulations, Part 393-Parts and Accessories
Necessary for Safe Operations (Fuel Systems): 36 FR 15444,
August 14, 1971, and 37 FR 4340, March 2, 1972.
56. FMVSS 301, 40 FR 48352, October 15, 1975.
*U.S. GOVERNMENT PRINTING OFFICE: 1987 - 744-622
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