EPA-AA-LDTP 78^-15
December 1978
Recommendation on Feasibility
for
Onboard Refueling Loss Control
NOTICE
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 tech-
nical information and to inform the public of technical develop-
ments 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 Source Air Pollution Control
Office of Air, Noise and Radiation
U.S. Environmental Protectioa Agency
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I. Introduction
Refueling loss hydrocarbon emissions, estimated to be in the
range; of 4-5 g/gallon, can be controlled by use of control equip-
ment at the service station (Stage II control) or by use of control
equipment in the vehicle (onboard control). As required by the
1977 amendments to the Clean Air Act, the Emission Control Techno-
logy Division (ECTD) of EPA has reviewed and analyzed available
data on the feasibility and desirability of onboard refueling loss
control which will be discussed in this report. This information
will be combined by the Office of Policy Analysis with available
Stage II control information to provide the basis upon which the
Administrator may choose the best of the two strategies.
II. Summary of Conclusions and Recommendations
Several hardware demonstrations and paper studies, Ref. 1, 2,
have been conducted to determine the technical feasibility and cost
effectiveness on onboard refueling loss control. Much of the
current information is from the American Petroleum Institute (API)
onboard demonstration program, Ref. 3. Other current information
was obtained from motor vehicle manufacturers in response to a June
27, 1978 Federal Register (43FR 27892) request for relevant informa-
tion. These demonstrations and analyses deal with the state-of-
the-art emission control technology.
Analysis of this information supports the following conclu-
sions:
1. Onboard refueling loss control is feasible for light-
duty vehicles;
2. The most probable control system uses hydrocarbon adsorp-
tion on charcoal (the same strategy that is used for evaporative
emission control);
3. Control effectiveness can be as high at 97% but depends
especially upon the vehicle fillpipe/service station nozzle inter-
face and upon control technology design;
4. An analysis of data from three fillpipe/nozzle concepts
(fillpipe seals, nozzle seals, and combination fillpipe/nozzle
seals) shows that the effectiveness of all three concepts is
approximately equal. Durability effects have not been extensively
evaluated, especially for the nozzle seal concept;
5. A vapor/liquid pressure relief valve is required to
protect the integrity of the vehicle fuel tank during the refueling
process. The pressure relief valve can be designed to function on
the fuel nozzle, or it may be incorporated as part of the fillpipe
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seal mechanism, which would be sealed-off by the fuel cap during
vehicle operation. Durability effects have not been evaluated for
either the fillpipe or nozzle pressure relief. ECTD recommends
that the fillpipe/nozzle sf:al and pressure relief be located on the
vehicle if onboard controls are required.
6. Cost to the consumer for control of refueling losses on
light-duty vehicles will probably range around $17/vehicle. The
$17 estimate does not include costs for a seal or pressure relief.
Cost for a seal and pressure relief, if used on the vehicle, is
estimated to be about $2.70. The cost of a seal on the nozzle
should be the same as the cost for a Stage II nozzle. Except for
the as yet undefined durability of the interface seal no mainte-
nance costs are expected;
7. The feasibility of controlling refueling loss emission
from gasoline fueled trucks and diesel fueled vehicles has not been
evaluated to date. Technical feasibility and cost effectiveness of
controlling these sources should be determined;
8. Minor increases in CO exhaust emissions seen for some of
the vehicles can probably be controlled by minor changes to either
the refueling loss control system or to the exhaust emission
control system. The ability to certify a vehicle to a 3.4 g/mi CO
standard to 50,000 miles should not be seriously impaired;
9. The use of a bladder in the fuel tank appears to be a
viable alternative control strategy, but some problems exist and
technical feasibility is yet to be demonstrated.
10. Considering the lead time needed for regulation develop-
ment and review within EPA and the lead time required by the
industry for development and application of technology, implemen-
tation of onboard controls cannot occur before 1983.
ECTD recommends that the choice between onboard control and
Stage II control of refueling loss emissions be based upon the
relative cost effectiveness of the two strategies for the same
overall level of control and air quality considerations.
It is recommended that methods of reducing the cost of onboard
refueling control systems be examined by considering tradeoffs
between control system capacity and cost. It may be possible to
sacrifice some capacity that is only required under infrequent
conditions and achieve proportionately more significant cost
savings.
The feasibility and desirability of control of refueling
losses from light and heavy-duty gasoline fueled trucks and from
diesel fueled vehicles should be considered. EPA should support
the development of the bladder tank alternative for refueling loss
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control strategy. If regulations are to be developed for onboard
refueling loss control, a certification test procedure must be
developed.
III. Review of Available Information
The data and information summarized in this section are based
on material submitted to EPA by the American Petroleum Institute
and information received in response to a request for information
(43FR 27892) published on June 27, 1978. The API material, Ref. 3,
is the result of their most recent study to assess onboard techni-
cal feasibility and compare the cost effectiveness of onboard
refueling controls and Stage II controls. This study was initiated
at the urging of EPA. Respondents to the Federal Register notice
include General Motors, Ford, and AMC. The API, GM, and Ford
information contain data from tests with onboard control hardware.
All respondents, with the exception of AMC, submitted information
on the cost and the desirability of onboard control systems.
1. API Onboard Study
The API Onboard Control Study was structured to address
questions regarding onboard feasibility which were posed to API in
a December 1977 meeting with EPA. The API study consisted of three
tasks: a vehicle concept demonstration, a fillpipe/nozzle concept
demonstration, and a cost/benefit analysis. Exxon Research and
Engineering Company and Mobil Research and Development Corpora-
tion were the API contractors for the vehicle concept demonstra-
tion. Atlantic Richfield Company was the API contractor for the
fillpipe/ nozzle concept demonstration. Exxon R & E completed the
cost/benefit analysis for API.
The vehicle concept modification task Tiad the following design
objectives:
1) Minimum 90% overall refueling vapor recovery.
2) No significant effect on exhaust emissions.
3) No significant effect on evaporative emissions.
4) Design should be durable, practical, and safe.
The fillpipe/nozzle demonstration had the following objec-
tives:
1) 90% overall vapor control.
2) Compatible with existing vehicle population.
3) Compatible with existing Stage II nozzles.
4) Design should be durable, practical, and safe.
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A review of the three API contractor's activities is presented
below.
Test procedure guidelines for the API work were discussed at a
meeting with API on March 15, 1978. Important procedural guide-
lines which resulted from that meeting are summarized as follows:
Fuel specification: Indolene unleaded test fuel was used for
all exhaust, evaporative, and refueling loss measurements.
Dispensed fuel quantity: Test vehicles were refueled to 100%
of capacity from a condition of 10% tank capacity.
Fuel tank temperature/Dispensed fuel temperature: The dispen-
sed fuel temperature was selected to be representative of summer
refueling conditions in Los Angeles during the month of August, or
about 85°F. The fuel temperature in the tank was also selected to
be 85°F. Thus, the refueling was isothermal.*
Purge Cycle: For the purposes of the API study, the only
driving cycle which was used for purging the refueling loss can-
ister is the LA-4 cycle.
Individually, these test procedure guidelines are considered
to represent real world situations in a high oxidant.forming
location, e.g., Los Angeles during the month of August. Collec-
tively, these guidelines imply that the API vehicles demonstrated
the feasibility of onboard control systems in an approximate worst
case condition. This reasoning is consistent with, earlier EPA
recommendations that API err on the conservative side during
their study. For example, Exxon used the following test sequence
to quantify the exhaust emissions interaction between the refueling
control system and the exhaust emission control system:
1) Load ECS (Evaporative Control System) canister to break-
through .
2) Condition the vehicle by driving 2 LA-4's.
3) Soak vehicle overnight.
4) Load RCS (Refueling Control System) canister to break-
through.
*This represents a conservative situation as survey data, Ref. 4,
show that nationwide dispensed fuel temperatures are typically
lower than tank fuel temperatures, thereby representing a vapor
shrinkage situation during the refueling process.
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5) Condition the vehicle by driving 5 to 6 simulated city
driving days (4.7 LA-4's with one hour hot soaks in between and a
diurnal at the end of the day) to consume 90% of the fuel in the
tank.
6) Drain the fuel tank.
7) Block RCS canister line.
8) Fill tank to 40%, unblock RSC canister lines.
9) Conduct diurnal evaporative test in SHED.
10) Drain tank to 10%.
11) Bring fuel tank liquid and vapor to equilibrium at 85°F
(shake the vehicle to accelerate the equilibrium process).
12) Refuel the vehicle to 100% in SHED with 85°F fuel.
13) FTP
14) Hot soak evaporative test in SHED.
Obviously, these test procedures do not lend themselves to a
routine laboratory certification test procedure. They do, however,
permit an approximation of how an onboard control system would
function in a severe "real-world" situation.
Exxon
Exxon assumed the responsibilty for modifying four test
vehicles. Their vehicles included the following:
1978 Chevrolet Caprice
1978 Ford Pinto
1978 Plymouth Volare*
1978 Chevrolet Chevette
All vehicles are designed to comply with 1978 California
exhaust and evaporative emission standards (.41 HC, 9.0 CO,
1.5 NOx, 6.0 Evap).
* Vehicle subsequently dropped from test program because of high
baseline NOx levels.
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Table 1
FTP Exhaust and Evaporative Emissions - Caprice
Baseline Configuration
Modified Configuration
Percent
n=4
Ave.
S.D.
n=4
Ave.
S.D.
Change
FTP Exhaust
Baseline Configuration
Modified Configuration
n=4
Ave.
S.D.
n=4
Ave.
S.D.
Exhaust (g/mi)
HC CO
0.345 6.48
0.033 0.56
0.338 7.10
0.010 0.59
-2 +10
Table
and Evaporative
Exhaust (g/mi)
HC CO
0.187 1.70
0.021 0.10
0.217 1.83
0.006 0.12
NOx
0.95
0.06
0.86
0.05
-10
2
Emissions
NOx
0.77
0.01
0.79
0.07
Diurnal
n*3
0.8
0.4
n=3
1.1
0.3
- Pinto
Diurnal
n*=3
1.0
0.2
n=3
0.9
0.3
Evap. (g)
Hot Soak
2.1
0.4
2.1
0.2
Evap. (g)
Hot Soak
2.5
0.3
2.4
0.5
Total
2.9
0.8
3.1
0.4
+7
Total
3.5
C.4
3.3
0.7
Percent Change
+16
+8
-6
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Table 3
FTP Exhaust and Evaporative Emissions - Chevette
Exhaust g/mi)
Baseline Configuration
Modified Configuration
Percent
n=3
Ave.
S.D.
n=3
Ave.
S.D.
Change
HC
0.27
0.02
0.26
0.05
-4
CO
3.7
0.32
3.6
0.28
-3
NOx
1.09
0.04
1.13
—
+4
Evap. (g)
Diurnal
n = 4
0.8
0.36
0.3
0.08
Hot Soak
2.6
0.79
1.2
0.15
Total
3.4
1.03
1.5
0.15
-56
00
*FTP + 3 Hot Start LA-4s
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Table 4
Engine-Out Emissions - Caprice
FTP (g/mi) City Driving
HC CO NOx HC CO
Baseline Configuration n=5
Ave. 1.28 26.42 1.17 41.86 733.86
S.D. 0.05 0.72 0.04 2.00 39.27
Modified Configuration n=5
Ave. 1.29 32.04 1.17 42.32 853.52
S.D. 0.09 2.4 0.04 1.90 61.51
Percent Change +1 +21 — +1 +16
*FTP + 3 Hot Start LA-4s
Table 5
Engine-Out Emissions - Pinto
FTP (g/mi)
HC CO NOx
Baseline Configuration n=4
Ave. 1.83 52.7 1.25
S.D. 0.06 1.2 0.08
Modified Configuration n=4
Ave. 1.77 60.1 1.12
S.D. 0.09 0.8 0.04
Day* (g)
NOx
38.68
1.17
41.34
3.17
+7
Percent Change
-3
+14
-10
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Table 6
Refueling Loss Measurements
Potential HC (g)
SHED HC (g) Percent Control Effectiveness
Caprice
Ave.
Pinto
Ave.
Chevette
Ave.
93.4
91.0
89.3
91.2
51.0
59.3
53.1
54.5
62.5
65.5
60.1
64.6
63.2
0.4
0.4
0.3
0.4
1.0
1.3
1.1
1.1
0.5
1.5
1.1
1.6
1.2
99
98
98
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Table 7
Benzene Emissions
Potential Benzene Emissions*SHED Measurements (ppm)
Measured Loss*SHED Measurements(ppm)
Caprice
Pinto
3.0
2.7
<0.05
<0.05
*A11 refueling at 85°F, RVP 9 Ibs., Benzene content 0.7%.
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12
The Caprice is a conventional oxidation catalyst vehicle,
while the Pinto is a three-way catalyst vehicle with feedback
carburetor control. Vehicle descriptions and complete refueling
loss control system descriptions are presented in Table A-l and
Figure A-l of the Appendix. The refueling loss canisters in the
Caprice, Pinto and Chevette are described as follows:
RCS
Vehicle Carbon Volume Carbon Mass Carbon Type* Location
Caprice 5.0* 1800 g BLP-F3 Underhood
Pinto 3.0* 1100 g BLP-F3 Underhood
Chevette 3.0* 1100 g BLP-F3 Trunk
* Same carbon currently used for controlling evaporative emissions.
The Exxon exhaust and evporative emission test^ results which
compare baseline and modified versions of the Caprice, Pinto and
Chevette are summarized in Tables 1, 2 and 3. Engine-out data are
summarized in Tables 4 and 5. Refueling loss effectiveness test
results are summarized in Table 6. All Exxon refueling emission
tests assumed a no-leak seal at the fillpipe/nozzle interface. In
laboratory practice this was achieved with leak free connections
from the fuel nozzle to the fillpipe.
Benzene emissions were measured during the refueling loss SHED
tests with both the Caprice and Pinto. These results are summari-
zed in Table 7. The Exxon data indicate that benzene control is
directly proportional to refueling loss control effectiveness,
although current benzene levels in the SHED are at the detectable
limit of the instrumentation.
Table 8 presents Exxon's manufacturer cost estimates for
onboard control systems for the 1978 Caprice and Pinto. These
estimates do not include the costs for fillpipe sealing devices and
pressure reliefs, and this hardware represents an additional cost
of approximately $1.50 (manufacturer's cost) per vehicle. Exxon's
cost estimates assume an estimated $.50 credit for downsizing the
,ECS canister, which in the two canister system, controls only
carburetor losses. Exxon estimates the incremental cost of two-
canister refueling control systems to range from $8.25 to $10.53.
This estimate includes the above mentioned $.50 credit but does not
include the $1.50 cost for the fillpipe seal and pressure relief.
The corresponding cost range for single canister refueling control
systems is $6.75 to $9.00. For light-duty trucks, Exxon estimates
a cost range of from $12 (large single canister) to $20 (two
separate refueling loss canisters or multistage purge systems).
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13
Table 8
COST ESTIMATES FOR ONBOARD SYSTEMS*1'
(2)
Charcoal^ '
Canister and Valves
Tank Modifications
Hoses and Tubing
Assembling and Ins
@ $20.00/hr.
Credit for Downsized
s(3)
(4)
)
talling(6)
ed ( }
>l System^ '
Caprice
$4.96
2.50
0.50
1.57
1.50
$11.03
$0.50
$10.53
Pinto
$3.03
2.00
0.50
1.72
1.50
$8.75
$0.50
$8.25
(1) Estimates are made for cost to manufacturer for large volume
production.
(2) 1800 g for the Caprice canister, 1100 g for the Pinto
canister at $1.25/ibm (Calgon BPL-F3 carbon).
(3) Plastic container and valves.
(4) Larger size float/roll-over valve.
(5) 3/4" vapor line from fuel tank to canister, 3/8" purge line.
EPDM tubing for vacuum control lines.
(6) Additional 4.5 minutes labor at $20/hour.
(7) Reduced size evaporative control canister.
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Exxon estimates the average cost for onboard control systems
to be $9/vehicle. This is based on the following assumptions:
1) Onboard systems are designed to control refueling emis-
sions from light duty vehicles with an average fuel tank size of 17
gallons refueled to 100% capacity from a condition of 10% tank
capacity. The onboard systems are designed to control hydrocarbon
emissions at a level of 6 g/gal.
2) 70% of light-duty vehicles and single tank light-duty
trucks are assumed to use single canister (evap + refueling)
systems.
3) 30% of light-duty vehicles and single tank light-duty
trucks are assumed to use two canister systems.
4) Light duty trucks with dual or large fuel tanks consti-
tute approximately 10% of the light-duty vehicle light-duty truck
population.
In summary, Exxon finds that onboard refueling controls for
light-duty vehicles are a technically feasible, practical, and cost
effective alternative to Stage II vapor recovery. They are of the
opinion that the same may also be said for light-duty trucks.
Mobil '
Mobil R&D has modified a 1978 Pontiac Sunbird for control of
refueling losses. This vehicle has a three-way catalyst with a
feedback carburetor control system, and is certified for complaince
with California exhaust and evaporative emission standards.
This modified vehicle uses a single canister which contains 1550
grams of Calgo'n BLP-F3 carbon. The complete vehicle and refueling
loss control system descriptions are presented in the Appendix.
Table 9 presents comparisons of exhaust and evaporative emissions
from the Sunbird for the baseline and modified configurations; a
summary of the refueling emission data is presented in Table 10.
Similar to Exxon's findings, Mobil states that their test
results have demonstrated that onboard controls are a feasible and
desirable method of controlling refueling losses from light-duty
vehicles and light-duty trucks.
Atlantic Richfield Company
One of the requirements for the operation of an effective
refueling loss control system is the existence of a no-leak seal at
the fillpipe nozzle interface. Atlantic Richfield (ARCO) has
developed working prototypes of fillpipe seals and nozzles. ARCO
has investigated three types of sealing systems. They included:
1) Modification of the vehicle fillpipe to achieve a seal
when used with conventional lead-free nozzles.
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Table 9
FTP Exhaust and Evaporative Emission Comparisons ~ Sunbird
Exhaust (g/mi)
Baseline Configuration
Modified Configuration
Percent
n=9
Ave.
S.D.
n-6
Ave.
S.D.
Change
HC
0.39
0.03
0.40
0.03
+3
CO
6.41
0.91
6.35
0.74
-1
NOx
0.98
0.07
0.99
0.03
+1
Diurnal
n=2
0.87
030
n=4
0.72
0.23
Evap. (g)
Hot Soak
1.12
0.13
1.27
0.37
Total
2.00*
0.34
2.11
0.56
+6
* Includes five tests at low mileage where individual diurnal and hot soak results are not available.
Table 10
Refueling Loss Measurements — Sunbird
Fuel Dispensed (gal)
16.4
15.3
16.9
17.1
HC Collected in Canister (g)*
85
73
113
109
Refueling Emissions
SHED Measurements (g/gal)
0.18
0.02
0.44
0.36
Control
Efficiency (%)
97
99
94
95
* Canister purged from a nominal working capacity load of 210 g.
Fuel of nominal 9 Ibs. RVP.
8 gpm refueling rate, using modified Stage II nozzle.
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16
2) Modifications to both the fillpipe and lead-free nozzle.
3) Modification of a Stage II vapor recovery nozzle.
A description of each type of seal and a summary of the
durability data collected with each system are presented below:
Fillpipe seals: Two types of fillpipe seals have been ex-
amined. They are a rotary grease seal (similar to grease seals
used on rotating machinery shafts), and a doughnut shaped seal.
The material types for these two seals are a compounded nitrile and
thermosetting urethane, respectively. More complete descriptions
of these seals, including durability data, are found in Figure
A—5 and Tables A—2 and A-3 of the Appendix. Appproximately thirty
days of durability tests with both types of seals have demonstrated
that the rotary seal is more effective, basically due to the
absence of expansion problems when exposed to gasoline liquid and
vapor atmospheres. The seal effectiveness of the prototype fill-
pipe and nozzle hardware are determined by a bench test apparatus
which pressurizes a particular system and measures the resulting
leak rates. Seal effectiveness calculations are determined by
dividing the leak rate by a nominal fueling rate (assumed to be 7.5
gallons/min.}. Durability tests conducted with the rotary seal
have demonstrated that the rotary seal is effective after 700-1000
nozzle insertions, which correspond to the life of the vehicle.
Combination fillpipe/nozzle seals: These systems consist of
connecting parts on both the fillpipe and nozzle. Figure A-6 is an
example of a prototype design evaluated by ARCO. Durability test
results with these systems are similar to results obtained with the
rotary seal.
Nozzle Modification: Working prototypes of vapor recovery
nozzles, modified for refueling loss control, have been developed
by OPW and Emco Wheatpn and evaluated by ARCO for effectiveness and
durability. These nozzles are designed to seal on standardized
fillpipes. The modified vapor recovery nozzles incorporate a
pressure relief valve, which is located at the vapor return exit or
cast into the nozzle body, which is designed to open at approxi-
mately 14-17 in. water pressure*, thereby permitting the nozzle
to refuel onboard control vehicles and in-use vehicles. Nozzle
durability data are very limited but one nozzle has been inserted
and latched 7500 times, representatitve of a year's service at a
high volume station, and showed a seal effectiveness of greater
than 99%.
ARCO concludes that the preferred seal techniques are either
the fillpipe seal method or the combination fillpipe/nozzle seal.
* Refueling loss control systems designed by Exxon and Mobil are
designed to operate at fill pressures of'less than 4 in. of water
pressure.
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17
No statements are made as to the desired location of the pressure
relief mechanism.
2. Vehicle Manufacturer Comments
General Motors
GM's March 1978 submission to EPA, Ref. 5, presents a summary
of their work on the control of diurnal evaporative emissions and
refueling losses through the use of fuel tank bladders. Their
information represents the most complete study of bladder tank
feasibility known to EPA. Regarding bladder tank feasibility, GM
admits bladder tanks have the potential for a substantial amount of
emissions control, but they are of the opinion that the technical
problems which must be solved before bladder tanks are capable of
demonstrating the same degree of control effectiveness as carbon
adsorption systems, do not permit this technology to be considered
applicable in the same time frame as the other candidate control
technologies, including Stage II control methods. The March 15
submission states that the major problem with controlling evapora-
tive and refueling emissions with the bladder tank is the formation
of gasoline vapor mixtures from dissolved air in gasoline. The
temperature at which the vapor pressure of the dissolved air equals
the partial pressure of air in the vapor space (bubble formation)
is known to be very sensitive to the quantity of dissolved air in
gasoline. Other design problems include pressure relief Valves,
and a puncture resistant fuel gaging indicator.
The March, 1978 submission presents calculations showing that
the additional weight of the components of an onboard control
system would cancel out any potential energy saving which would
result from the combustion of the refueling vapors.
The June, 1978 submission, Ref. 6, is basically a cost effec-
tiveness study comparing onboard and Stage II cost effectiveness.
GM's March, 1978 submission estimates the cost of typical
carbon adsorption onboard control systems to range from $11 for
single canister systems, to $15 for two-canister systems. The GM
estimates represent costs to the consumer. The June, 1978 submis-
sion indicates that these figures must be increased by $5-$9 per
vehicle to cover the costs for an enlarged vapor/liquid separator
and additional carbon. Thus, GM's estimates are now $16-$24 per
vehicle. These estimates do not include costs for fillpipe seals
or pressure reliefs as GM assumes that this hardware would be part
of the service station fuel dispensing equipment.
GM has stated that both onboard and service station controls
are technically feasible methods of reducing refueling loss emis-
sions. However, GM's cost effectiveness calculations find onboard
controls to be much less cost effective than Stage II vapor re-
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18
covery. Rather, GM emphasizes certain technical concerns which
they say are not fully addressed by the API study. According to
GM, these include API's unsubstantiated support for the onboard
fillpipe seal and pressure relief (lack of adequate durability
results), an unknown CO penalty for light-duty vehicles (no sensi-
tivity data relating CO to test procedure differences), and un-
proven feasibility for trucks. .
GM is of the opinion that accelerated laboratory durability
tests are not sufficient to prove that proposed elastomer type
seals will be effective in the extreme usage and environmental
conditions of the real world, particularly when considering a ten
year average lifetime for a light-duty vehicle.
Ford
Ford has submitted test results from four 1978 model year
vehicles (three non-feedback systems and one feedback control
system) modified for refueling loss control. These vehicles are
described in detail in Table A-4 in the Appendix and in their
submission to EPA, Ref. 7. The purge control systems for these
vehicles are shown in Figures A-7 and A-8 in the Appendix.
Ford estimates the cost to the consumer of onboard controls to
range from $15-$20. They note that the $15-$20 estimate does not
include additional expense for such items as: packaging costs,
incremental labor costs, or the costs for additional exhaust
emission control, such as feedback control over a wider air/fuel
ratio range.
Recent Ford material, Ref. 12, suggest that the cost of
onboard systems may range from $30 to $253. The $30 estimate
includes costs over the original $15-20 estimate, including costs
for such items as vehicle modifications to package onboard systems,
incremental assembly, and material substitution. The $253 estimate
includes the cost for a feedback fuel system and electronic con-
trols for vehicles which are not planned to be equipped with these
control devices.
On the basis of their in-house test results, Ford has conclu-
ded that onboard controls are not technically feasible for light-
duty vehicles.
American Motors
AMC has submitted a letter to EPA, Ref. 9, which states their
concerns with the possible use of onboard controls. They state
that packaging concerns, reduced quantities of purge air from
downsized engines, and compliance with stringent evaporative
emission standards are unresolved technical issues which have not
been addressed by the API work to date.
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AMC does not find that API has demonstrated light-duty vehicle
technical feasibility.
IV. Analysis of Available Information
1. API Work
Exxon
Exxon R&E appears to have done a credible job in character-
izing the components of a hydrocarbon adsorption system. An
examination of the results from baseline tests and tests with the
modified Pinto (3-way + feedback carburetor system) show small but
finite increases in engine-out (14%) and tailpipe (8%) CO emis-
sions. HC, CO, and NOx emissions are still well below statuatory
emission levels for low mileage vehicles. Engine-out CO emissions
from the Caprice are approximately 20% higher than baseline test
results; tailpipe CO emissions are approximately 10% higher than
the baseline results. No increase in tailpipe CO was observed
during tests with the Chevette. Exxon suggests that differences in
CO emissions for the Caprice and the Pinto can be further reduced
by minor modifications to the refueling loss control system or the
exhaust emission control system, although this has not been demon-
strated.
Figure A-2 shows canister purge as a function, of time.
Although the data are bench test results, the results are also
representative of actual control system purge data. It is signifi-
cant to note that the refueling loss canister is essentially purged
to its working capacity after three LA-4 driving days. This
implies that the refueling control/exhaust emission interaction is
likely to be less in a typical driving day than Exxon has measured
using conservative test methods, which required running a cold
start FTP immediately after a 90% refueling.
ECTD expects that refueling loss control systems will result
in slightly higher CO feedgas levels. Exxon estimates that the
average increases in CO feedgas between refuelings will be approx-
imately 5% for non-feedback control systems and less than 3% for
feedback control systems. ECTD has no other data concerning either
the magnitude of the average CO feedgas penalty or the resulting
effect on catalyst durability. It is ECTD's opinion that the Exxon
estimates are reasonable and that these additional CO penalties
will make it more difficult for vehicle manufacturer's to certify
some engine/families to the 3.4 g/mi CO standard. The higher CO
levels somewhat reduce the margin available to allow for exhaust
system deterioration over 50,000 miles.
ECTD finds that light-duty vehicles equipped with onboard
systems are capable of meeting a 2 gram evaporative emission
standard.
-------
An analysis of the control effectiveness of benzene emissions
during refueling, Table 6, indicates that charcoal canisters can
control in excess of 99% of the uncontrolled benzene emissions.
Exxon conducted additional tests with the Caprice and Pinco using
indolene test fuel with a high benzene content (4.2%). The results
from these five tests with the modified vehicles support the
earlier findings — benzene emissions are controlled in excess of
99% during refueling.
Packaging refueling loss control systems is a difficult
problem, but definitely not an insurmontable one. The refueling
loss canister is located behind the rear seat and above the rear
axle in the Caprice, and in the engine compartment of the Pinto.
It is Exxon's opinion, and ECTD agrees, that it is possible for
manufacturers to locate a refueling loss canister on downsized
vehicles without major engine compartment or sheetmetal modifica-
tions.
The feasibility of refueling loss controls for light-duty
trucks has not been evaluated by Exxon, but they are of the opinion
that refueling loss control is feasible for light-duty trucks by
using larger control systems and more sophisticated purging con-
trols (refueling loss control canisters for each tank and/or two
stage purging systems). It is ECTD's opinion that the control of
refueling losses from light-duty trucks needs to be demonstrated,
especially the ability to comply with a 2 g evap standard, before
onboard controls are judged to be effective for these vehicles at
the costs Exxon has estimated.
Table 8 shox^s Exxon's detailed manufacturer's cost estimates
for refueling control systems which have two canisters. ECTD finds
these cost estimates to be reasonable for onboard systems designed
to control 100% of refueling emissions from 90% fill conditions.
Exxon estimates the average manufacturer's cost for the light-duty
truck and light-duty vehicle population to be about $9. That
number is derived as follows:
Assumed % of
Average Cost Population
One-cansiter vehicles* $7.88 70
Two-canister vehicles* $9.38 20
6,000 to 8,500 Ibs. trucks** $16.00 10
Weighted average $9.00
* Includes light-duty vehicles and light-duty trucks under 6000
GVW - average fuel tank size = 17 gal.
** Average fuel tank size = 35 gal.
The charcoal cost per gallon of tank volume is assumed to be about
$0.20.
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21
The $9 incremental manufacturer cost may be translated to a
consumer cost estimate of $16.20 by multiplying the manufacturer's
cost estimate by a factor of 1.8 (Ref. 10, EPA 'Report "Cost Esti-
mations for Emission Control Related Components/Systems and Cost
Methodology Description" by Rath and Strong, March 1978). The 1.8
factor is in general agreement with previous EPA studies, such as
the EPA Report, Ref. 11, "Investigation and Assessment of Light-
Duty Vehicle Evaporative Emission Sources and Control," June 1976,
which used a manufacturer to consumer cost factor of 2.0. The
$16.20 estimate is in good agreement with consumer cost estimates
submitted by GM ($16-$24) and Ford ($15-$20). It is possible to
further reduce the cost of an onboard system by trading off some
degree of refueling loss control effectiveness.
Exxon has designed refueling loss control systems based on
conservative criteria, and thus a different set of design criteria
will afford reductions in the cost of onboard control systems.
Texaco has submitted data (Figure A-ll) Ref. 12, which relates the
number of light-duty vehicle refuelings and the percent of tank
fill. A reasonable design criterion is to size the refueling
canisters to control 90% of nationwide refueling emissions.
Calculations (Figure A-12) show that 90% control can be achieved by
designing systems to control 100% of refueling emissions from fills
to 63% of fuel tank volume. If onboard control systems are de-
signed to control emissions from refueling to 63% of tank capacity
rather than 90% of tank capacity, the Exxon estimate of $9 per
vehicle can be reduced by $1.60 as the result of reduced charcoal
quantity. This cost reduction is proportional to the reduction in
carbon bed volume. The net effect of this design change is a cost
reduction to the consumer of approximately $2.88. Changes in
design specifications such as the 90% fill requirement may afford
additional cost reductions for other control system components as
well as a general reduction in the problem of packaging onboard
control systems.
ECTD estimates the consumer cost of light-duty vehicle onboard
control systems designed for maximum control effectiveness to be
about $17. This estimate does not include an estimate for the cost
of the fillpipe seal or pressure relief valve. The $17 estimate is
based on Exxon estimates, which when translated to consumer costs,
are in agreement with consumer cost estimates provided by GM and
Ford.
Exxon estimates the manufacturer's cost for a fillpipe seal
and onboard pressure relief valve to be approximately $1.50.. ECTD
estimates the consumer cost of an onboard fillpipe seal and pres-
sure relief to be approximately $2.70.
Mobil
Comparisons of baseline and modified vehicle test results
indicate that Mobil R&D is able to add refueling controls to the
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22
1978 Pontiac Sunbird (3-way + feedback carburetor system) without
adversely affecting exhaust or evaporative emissions. No changes
in engine-out or tailpipe CO emissions are observed. Evaporative
emissions are also unchanged, with both baseline -and modified
vehicle test results near the 2 g evaportive emission level.
It must be emphasized, however, that Mobil and Exxon use
different test procedures for measuring the refueling control/
exhaust emission interaction. Mobil's test procedure consists of
the following sequence of events:
1) Load canister to approximately one-half of working
capacity.
2) Condition vehicle by driving two simulated city driving
days (4.7 LA-4's with one hour hot soaks in between and a diurnal
at the end of the day).
3) Drain fuel tank to 10% of volume.
4) Refuel to 90% of volume in SHED.
5) Conduct hot start emission test.
6) Soak vehicle for 11 hrs.
7) Conduct diurnal evaporative test in SHED.
8) FTP
9) Hot soak evaporative test in SHED.
Steps 1, 2, and 5 are the .important differences between the
test procedures used by Exxon and Mobil. Mobil starts their test
sequence with a canister loaded to one—half of working capacity,
versus a saturated condition for the Exxon procedure.' Mobil purges
the refueling loss canister with two LA-4 driving days, versus the
Exxon method of purging by running a series of LA-4 driving days
until the fuel tank reaches 10% of capacity. Mobil runs a hot
start emission test prior to the FTP; no such additional condition-
ing is used in the Exxon test sequence. It is ECTD's opinion that
the the Mobil test sequence, particularly the addition of a hot
start exhaust emission test, will result in a less severe refueling
control/exhaust emission interaction. This is due to the smaller
quantity of hydrocarbon which is purged during the cold start FTP
when using the Mobil test sequence. The actual emission sensi-
tivity to various test procedure arrangements has not yet been
determined.
Atlantic Richfield Company
ARCO states that the fillpipe modification approach and the
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23
combination fillpipe/nozzle seal concept are the preferred tech-
niques for achieving a no-leak seal. This recommendation is not
supported from an analysis of leak rate and durability data because
the test results show that seal effectiveness among all three
concepts are equal. Cost estimates for the three designs have not
been submitted. ARCO is continuing to collect field durability
data on their prototypes, but the lack of a more extensive durabil-
ity demonstration under simulated conditions of real world usage
makes it questionable to assume that their seals will function as
well in the field as they have in the laboratory.
In particular, ARCO has not adequately addressed the issue of
onboard pressure relief valves versus liquid pressure relief valves
located on the fill nozzle. Pressure relief valves are necessary
to prevent over-pressurization of the fuel tank in the event of a
failure of the automatic shutoff on the fill nozzle. For the
purpose of fuel tank integrity in the event of a vehicle crash,
NHTSA recommends that the pressure relief not be located on the
fuel tank. However, a relief valve might be incorporated safely
with a fillpipe seal mechanism, which would be sealed-off by the
fuel cap during vehicle operation.
The achievement of a safe and durable seal at the nozzle
fillpipe interface is critical to the performance of an onboard
refueling loss control system. ARCO has demonstrated that the
effectiveness of fillpipe seals, combination seals and nozzle
seals are equal; but, the design, locations, and durability of the
pressure relief valve have not been adequately addressed.
Conceptually, a pressure relief may be designed to function
properly when located on the vehicle or on the nozzle. However, if
refueling losses are controlled on the vehicle, it is recommended
that the fillpipe/nozzle seal and pressure relief valve also be
located on the vehicle. Locating all parts of an onboard system on
the vehicle will prevent the potentially serious problem of refuel-
ing a controlled vehicle without protection from overpressurization
(no relief valve). Administrative and certification concerns also
suggest that onboard controls are practical only if the seal and
pressure relief are located onboard.
An alternative technique of achieving a seal at the fillpipe/
nozzle interface is the liquid trap or submerged fill. This seal
concept has not been adequately investigated. Submerged fill
offers the potential for significant advantages iii terms of simpli-
city of operation and durability (mechanical, magnetic, or elas-
tomer type seals are avoided). It is ECTD's opinion that the
submerged fill concept should be investigated. Submerged fill (and
seal techniques investigated by ARCO) must be evaluated in the
context of a complete refueling and evaporative emission control
system. This includes incorporating features to provide adequate
thermal expansion capability and rollover protection while still
permitting normal safe refueling.
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24
2. Vehicle Manufacturer Information
General Motors
General Motors has several reservations concerning the appli-
cability of onboard controls, citing such things as: the uncer-
tainty of the effectiveness of fillpipe/nozzle seals, potential
cost increases associated with exhaust emission control systems
which must be designed to control increased CO emissions, negative
fuel penalties which are the result of this increased emission
control, and the long lead time which is required to obtain a
substantial reduction in atmospheric hydrocarbon and benzene
loading. However, with the exception of GM's concern with using
accelerated laboratory tests to assess fillpipe/nozzle seal dura-
bility, these reservations are not detailed in their submissions.
GM has stated that refueling losses can be controlled on the
vehicle (feasibility for trucks has not been demonstrated) or at
the service station. GM's disagreements with controlling refueling
emissions with onboard controls are primarily based on the issue of
cost/effectiveness.
GM's March, 1978 submission to EPA presents a summary of their
work on the control of diurnal evaporative emissions and refueling
losses using fuel tank bladders.
It is EPA's opinion that the theoretical control effectiveness
of evaporative and refueling loss emissions using bladder tank
technology is high and that these problems can be solved. It is
recommended that bladder tank feasibility be researched by funding
a bladder tank hardware demonstration contract.
The March, 1978 submission presents calculations showing that
the additional weight of the components of an onboard control
system will cancel out any potential energy saving which results
from the combustion of the refueling vapors. ECTD agrees with
this analysis.
The June, 1978 submission is basically a cost effectiveness
analysis comparing onboard controls with Stage II controls (balance
displacement and vacuum assist systems). GM estimates that onboard
control systems, effective with the 1982 model year, will range
from $16 to $24. These figures are about $5 to $9 higher than the
March, 1978 estimates due to higher estimates for larger canisters
and a new vapor/liquid separator. GM assumes that the seal at the
fillpipe/nozzle interface will be obtained using modified vapor
recovery nozzles. GM does hot include seal costs in its estimate.
They assume these costs will be the same for either Stage II or
onboard controls and, hence, leave these costs out of their analy-
sis of both options. General Motor's onboard cost estimates are
costs to the consumer. These estimates are based on costs for
hydrocarbon adsorption systems which control evaporative and
refueling emissions with one canister (cheapest) and systems which
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25
use two separate canisters for containing evaporative (diurnal and
hot soak) and refueling emissions (most expensive). The GM cost
estimates are consistent with Exxon's manufacturers cost estimates
for onboard controls. As discussed earlier, it is possible to
design cheaper refueling loss control systems by not providing 100%
control of refueling emissions under worst case conditions. If the
design criterion of 100% control for a 90% refueling is changed to
100% control for a 63% refueling, it is possible to reduce the
required working capacity of the charcoal canister, thus reducing
the average system cost to the consumer by about $3.00.
GM does not find that onboard controls are feasible for the
1982 model year, although their cost effectiveness analysis
calculations are based on the assumption that onboard control could
become effective beginning with the 1982 model year. It is ECTD's
opinion that onboard refueling loss controls cannot be implemented
prior to 1983 model year. GM did not comment on the feasiblity of
refueling loss controls for light-duty trucks and heavy-duty
gasoline powered vehicles.
Ford
Ford emphasizes that the refueling loss/exhaust emissions
interaction is a function of the test procedure and that the
differences between emissions interactions measured by Exxon and
Mobil are due to test procedure differences. This statement is
correct, although the actual emission sensitivity to the test
procedure is unknown.
Ford attributes the high CO effects, which they have observed
with both conventional oxidation catalyst systems and three-way
"plus feedback carburetor systems, to the presence of refueling loss
controls. However, the reason for their high CO emissions is due
to a non-optimally designed system for controlling the hydrocarbon
purge rate. Ford uses a manifold vacuum controlled purge system,
which results in cold start hydrocarbon loadings that are two to
three times higher than results obtained with venturi vacuum
controlled systems (Exxon system). This is the reason the Ford
results are so high, particularly engine-out CO emissions. Ford
maintains that refueling loss control systems produce peak enrich-
ment effects equal to two air/fuel ratios, which is beyond the
capability of their current feedback carburetor control system.
Exxon has demonstrated, however, that venturi vacuum maintains the
air/fuel ratio within the control limits of the feedback control
system. Problems with the existing Ford feedback control system
are likely to be the result of response time problems, not control
range problems.
Some of Ford's concerns with onboard refueling control sys-
tems, such as packaging, weight of onboard systems, and the design
of vapor/liquid separators have been examined during the API study
and shown not to be significant problem areas. Other concerns with
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26
onboard controls, including system durability, onboard feasiblity
for light and heavy duty trucks, and high altitude feasibility,
have not been adequately addressed in any of the information
submitted to ECTD. It remains ECTD's judgment that these issues
need further examination, particularly before onboard controls are
determined to be feasible for light and heavy-duty trucks. Al-
though onboard durability data are not available, ECTD finds that
onboard control systems should be as durable as current evaporative
emissions control systems, which last for the lifetime of the
vehicle.
Ford estimates the consumer cost of onboard controls for
light-duty vehicles to range from $30 to $253. EPA estimates that
the consumer cost of onboard control systems will be about $20
(includes $2.70 for the cost of an onboard seal and pressure
relief).
American Motors
AMC's concerns with the use of onboard controls are addressed
to the issues of exhaust and evaporative emissions interactions,
feasiblity of vehicles using small engines, costs, and light-duty
truck feasibility. With the exception of feasibility for light-
duty trucks, AMC's concerns have been examined in detail by the API
study. EPA's analysis of that data is that refueling loss controls
are feasible for light-duty vehicles at a consumer cost of approxi-
mately $17.
V. Conclusions
Feasibility
An Analysis of the available information has shown that
onboard refueling loss controls are feasible for light-duty
vehicles designed to meet low exhaust and evaporative emission
standards (0.41 HC, 3.4 CO, 1.0 NOx and 2.0 Evap.). However, the
feasibility for light-duty trucks, particularly the assurance that
onboard control systems are compatible with a 2 gram evaporative
emission standard, has not been established. Feasibility for
heavy-duty gasoline vehicles has not been established.
An analysis of information and test data presented to EPA
regarding the control of light-duty vehicle refueling emissions
offers the following conclusions:
1. Onboard control systems in laboratory use situations can
control in excess of 97% of the uncontrolled hydrocarbon refueling
losses.
2. The same systems in laboratory use situations can control
in excess of 97% of the uncontrolled benzene refueling losses.
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27
3. Test results from two light-duty vehicles equipped with
three-way catalysts, feedback carburetors, and prototype refueling
loss systems shew that tailpipe CO emissions range from a 0 to 8%
increase.
Test results from the same vehicles show that engine-out CO
emissions range from a 0 to 14% increase.
4. Emission data from two conventional oxidation catalyst
equipped light-duty vehicles show that tailpipe CO emissions
range from a 0 to 10% increase.
Data from one of the conventional oxidation catalyst vehicles
show that engine-out CO emissions increase by 10 to 20%.
5. The addition of refueling loss controls to light-duty
vehicles does not significantly affect evaporative emission losses.
6. Minor increases in CO exhaust emissions seen for some
vehicles can probably be controlled by minor change to either the
refueling loss control system or to the exhaust emission control
system. However, the addition of refueling loss controls will
likely make it more difficult to certify some vehicles to the 3.4
g/mi standard at 50,000 miles.
7. Onboard controls do not affect vehicle fuel economy.
8. Onboard controls do not affect vehicle driveability.
9. Refueling loss control systems for light-duty vehicles
are estimated to add $17 to the vehicle sticker price. The $17
estimate does not include the costs associated with the fillpipe/
nozzle seal or pressure relief valve. The consumer cost of a seal
and pressure relief in the fillpipe is estimated to be about $2.70.
The cost of a seal on the nozzle should be roughly the same as the
cost for a Stage II nozzle. However, it is recommended that all
components of an onboard control system be located on the vehicle.
Lead time
Onboard refueling loss control can be implemented for 1983
model year light-duty vehicles, provided that potential problem
areas such as the design and development of effective fillpipe/
nozzle seals and pressure relief valves do not require additional
hardware demonstration programs. It is anticipated that the
fillpipe/nozzle seal and the control feasibility for light and
heavy-duty trucks are issues which can be resolved during the NPRM
process.
ECTD estimates that a minimum of two years lead time will be
required by manufacturers for development (purge system optimiza-
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28
Quarter;
Develop Certification
Test Procedure
Continued Study of
Fillpipe/Nozzle Seal
Concepts
Decision on Seal
Concepts
EIS, EIA, NPRM
Preparation
Publish NPRM
Final Rule
Manufacturers
Lead Time
Figure 1
Lead Time
Calendar Year
1979 1980 1981
I34.I1234J1234J1234
1982
1234
1983
11234
(Decision to publish service station nozzle
requirements or put seal on vehicle)
1983 MY
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29
tion, design and verification of fillpipe seal mechanisms) and
production tooling changes (tooling associated with fabrication and
relocation of new evaporative control components). These estimates
are based in part upon data provided by manufacturers relating to
carburetor tooling changes, and in part upon data supplied by GM
relating to retooling changes for body panel modifications.
Additional time will be required for EPA to develop a certification
type test procedure and issue regulations, however, the certifica-
tion procedure development can overlap the production tooling lead
time. Therefore, the projection is that an NPRM can be published
late in 1979 with final rules promulgated by 1980 with the earliest;
possible implementation date being 1983. (See lead time chart,
Figure 1).
Compliance Costs
ECTD estimates that certifying light-duty vehicles for compli-
ance with a refueling loss standard will require an additonal
one-half person-year at the EPA-MVEL. This is based on an estimate
of 100-150 refueling loss tests per year. Facility modifications/
equipment procurements will cost from $30K to $80K.
A potentially significant impact on refueling loss compliance
costs is Inspection/Maintenance testing of light-duty vehicles.
EPA has not developed, and is not aware of, a valid I/M test for
determining the performance of evaporative emission control sys-
tems. Monitoring the performance of in-use refueling loss control
systems will be difficult and cumbersome. At this time, it may be
assumed that the onboard compliance costs associated with an I/M
test will be equal to the cost of Stage II enforcement.
VI. Recommendations for Future Work
•1. ECTD recommends that additional hardware testing be
conducted to determine the optimal fillpipe-nozzle seal. Addition-
ally, the operation and durability of a fillpipe or nozzle pressure
relief must be demonstrated. The use of an onboard liquid trap
seal (submerged fill) as an alternative to elastomer type seals
should be investigated.
2. ECTD recommends that additional hardware testing be
conducted to assess the feasibility of controlling refueling losses
on light-duty trucks and heavy-duty gasoline powered trucks.
3. ECTD recommends that the need for controlling refueling
losses from diesel powered vehicles be investigated since these
vehicles are predicted to represent a substantial fraction of the
entire motor vehicle population in the 1980's..
4. ECTD recommends that the bladder fuel tank be investi-
gated as an alternative to carbon adsorption technology. It
is ECTD's opinion that the theoretical control of evaporative and
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30
refueling loss emissions with bladder tanks is high and that
technical problems can be solved. It is recommended that bladder
tanks feasibility be researched by funding a hardware demonstration
contract.
5. Finally, ECTD recommends that methods of reducing the
cost of onboard refueling control systems ba examined. Such
studies should be directed toward tradeoffs between level of
control effectiveness and cost. It may be possible to sacrifice
control capacity that is required under only infrequent conditions
to achieve a proportionally more significant cost savings.
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. 31
Bibliography
1. "Control of Refueling Emissions," Statement by General Motors
Corporation, June 11, 1973.
2. "Control of Refueling Emissions with an Activated Carbon
Canister on the Vehicle - Performance and.Cost Effectiveness
Analysis," Interim Report Project EF-14, prepared for the
American Petroleum Institute, Washington, D.C., October 1973.
3. "On-Board Control of Vehicle Refueling Emissions - Demonstra-
tion of Feasibility," API Publication No. 4306, October 1978.
4. "Summary and Analysis of Data from Gasoline Temperature Survey
Conducted at Service Stations," Radian Corporation, Austin,
Texas. Prepared for the American Petroleum Institute, Wash-
ington, D.C., November 1976.
5. "General Motors Commentary to the Environmental Protection
Agency Relative to On-Board Control of Vehicle Refueling
Emissions," March 1978.
6. "Suppplement to General Motors Commentary to the Environmental
Protection Agency Relative to On-Board Control of Vehicle
Refueling Emissions," June 1978.
7. "Ford Motor Company Response to EPA Concerning Feasibility and
Desirability of a Vehicle On-Board Gasoline Vapor Recovery
System."
8. "Ford Motor Company Position Concerning Feasibility and
Desirability of Vehicle On-board Refueling Vapor Control
Systems," November 6, 1978.
9. AMC letter to Paul Stolpman, August 3, 1978.
10. "Cost Estimations for Emission Control Related Components/Sys-
tems and Cost Methodology Descriptions," Rath and Strong,
Inc., Lexington, Massachusetts. Prepared for the Environ-
mental Protection Agency, Ann Arbor, Michigan, March 1978.
11. "Investigation and Assessment of Light-Duty Vehicle Evapora-
tive Emission Sources and Control," Exxon Research and
Engineering Company, Linden, New Jersey. Prepared for the
Environmental Protection Agency, June 1976.
12. Texaco statement submitted to Paul Stolpman, July 18, 1978.
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32
APPENDIX
The Appendix contains detailed descriptions and data from the
test vehicles and fillpipe/nozzle seals which were used in the most
recent testing and evaluation of refueling loss control systems.
Exxon
Table A-l presents a description of all Exxon test vehicles.
Figure A-l is a schematic of the basic control system designed for
the Chevrolet Caprice and the Ford Pinto. The refueling emissions
(RCS) canister controls both refueling emissions and diurnal
evaporative emissions; the evaporative emissions (ECS) canister
controls carburetor hot soak losses. Exxon investigated several
different purge mechanisms, including combinations of manifold
vacuum and venturi vacuum, and two stage purge control valves
controlled by fuel volume, but venturi vacuum, which is propor-
tional to engine air flow, is the most effective purging method.
Exxon's control system is designed to maintain the total purge air
volume (RSC + ECS) equal to the purge air volume of the unmodi-
fied vehicle's evaporative control system.
The air bleed control valve, shown in Figure A-l, is necessary
because the RCS canitser is purged more efficiently (higher hydro-
carbon purge per unit volume of air) than the unmodified ESC
system, thereby resulting in richer A/F mixtures. This air bleed
may not be necessary for other vehicles with feedback carburetor
controls.
Figure A-2 is a plot of the RCS canister purging as a function
of time. These data are based on consecutive LA-4 driving days.
As noted, the RCS system is purged at a rate of about 4 litres/
rain., which corresponds to a total canister purge volume of about
40 litres during an LA-4 driving cycle.
Mobil . .
Specifications for the vehicle Mobil has modified for refuel-
ing loss control are summarized as follows:
Vehicle: 1978 California Pontiac Sunbird
Engine Size: 151 cu. in. L-4
Interia Weight: 3000 Ibs.
Emission Control System:
Exhaust: 3-way catalyst with feedback carburetor,
EGR
Evaporative: Carbon canister
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33 A_
A-2
Fuel Tank Capacity: 18.5 gallons
The production vehicle is modified for controlling refueling
emissions by enlarging the existing carbon canister, (one canister
controls refueling, diurnal, and hot soak loss), enlarging the
vapor line between fuel tank and canister, redesigning the vapor/
liquid separator, and installing a purge control orifice between
the canister and intake manifold. A schematic of the Sunbird's
control system is shown in Figure A-3. Various flow control
orifices were inserted in the canister purge line but best results
are obtained with an orifice of 0.100 in. diameter. Mobil uses
1550 grams of Calgon BPL-F3 carbon for their control system, which
assumes a 20% safety factor. This quantity of carbon is based on a
90% fill of the 18.5 gallon tank, and assumes a hydrocarbon loading
of six grams per gallon of dispensed fuel. The working capacity of
the.canister is approximately 240 grams. The basic components of
the canister control system are shown in Figure A-4. The ported
vacuum purge control valve is from a 1978 Chevrolet Impaia evapora-
tive canister, while the two fuel tank vapor valves (two are
used to reduce the pressure drop during the refueling operation)
are carburetor bowl valves from a 1978 Impaia. Using two fuel tank
vapor valves results in fillpipe pressures as low as two. inches of
water pressure during refueling. The fuel tank vapor valves are
also controlled by manifold vacuum such that the vapor valves
are closed when manifold vacuum is present at the control port.
Atlantic Richfield Company
Figure A-5 shows the fillpipe seal which ARCO has developed
and tested for durability. Tables. A-2 and A-3 are typical of the
durability results obtained with this seal. Figure A-6 is an
example of a prototype combination fillpipe/nozzle seal which has
been developed and evaluated by ARCO.
Ford
The vehicles which Ford has used for refueling loss testing
are shown in Table A-4. A single 4.35 1 canister is used in the
Mustang, while a duel canister system, 829 ml and 3.4 1, are used
for controlling carburetor vapors and diurnal/refueling losses,
respectively, in the Pinto. The purge systems for the Mustang and
the Pinto are shown in figures A-7 and A-8.
Figures A-9 and A-10 are plots of canister loading versus test
procedure sequence. These plots indicate that Ford's refueling
loss control system is quite sensitive to the particular test
procedure which is used to quantify the refueling control/exhaust
emission interaction.
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34
A-3
Table A-l
Vehicle Descriptions
Make
Engine Displacement/
Model Configuration
Control Systems
Fuel Tank
Capacity
(gallons)
Chevrolet Caprice 5.0 litre (305 CID)/V-8
Ford Pinto 2.3 litre (140 CID)/L-4
Plymouth Volare 3.7 litre (225 CID)/L-6
Chevrolet Chevette 1.6 litre (98 CID)/L-4
Ox. Cat., AIR, EGR
3-Way, Ox. Cat.,
AIR, EGR
Ox. Cat., AIR, EGR
Ox. Cat., AIR, EGR
21.0
13.0.
18.0
12.5
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35
Table A-2
FILLPIPE MODIFICATION
ROTARY SEAL-CR 7538
LEAK RATE A3 AFFECTED BY
FILLNECK PRESSURE AND WEAR
NO. OF SPOUT
INSERTIONS
0
100
100
• 100
100
100
100
100
100
100
100
TYPE
SPOUT
Smooth
Rough
Smooth
Rough
Smooth
Rough
Smooth
Rough
Smooth
Rough
CUMULATIVE
INSERTIONS
0
100
200
300
400
500
600
700**
800
900
1000
FT3/MIN
@ 5" W.C.
0
0
0
0
0
0
0
0
0
0
0
LEAK *
(§ 15" '
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.001
0.002
0.002
0.002
* Leak rate average of six nozzle insertions.
** Expected number of insertions during vehicle life.
RGJ:ip
7/13/78
-------
36
Table A-3
FILLPIPE MODIFICATION
ROTARY SEAL-CR 7538
EFFECT OF LIQUID AND VAPOR GASOLINE
SOAK ON SEAL ID AND LEAK RATE*
HOURS OF
LIQUID
SOAK
0
16
35
TOTAL WEEKS
OF VAPOR
SOAK
0
0
0
2
3
4
5
6
7
8
SEAL
ID, IN.
.712
.712
.711
.705
.699
.701
.703
.698
.693
.691
FT3/MIN
@ 5" WC
0
0
0
0
0
0
.001
0
0
.001
LEAK**
@ 15" W<
0
0
0
0
.001
.001
.001
0
.001
.002
* Vapor and liquid soak at 72°F.
** Leak rate average of nine nozzle insertions,
RGJ:ip
7/13/78
-------
Figure A-l
EVAPORATIVE AND REFUELING EMISSIONS COF^TROL SYSTEMS
REFUELING AND
DIURNAL VAPORS
PURGE
CONTROL
ii VALVE
CONTROL VACUUM
AIR BLEED
CONTROL
RESTRICTION la r VALVE
CARBURETOR VACUUM PURGE
RESTRICTION
VENT
CARBURETOR BOW
CARBURETOR
MANFOLD VACUUM.
PURGE
ECS CANISTER
REFUELING EMISSIONS
CONTROL CANISTER
-------
PURGE <§ A LITRE/MIN. WITH DIURNAL ADDITIONS
ADSORPTION TO 35 g. FROM BREAKTHROUGH
"' 3.5 litre Canister (BPL-F3)
320
300 -
1 LA-4 = 40 litres =10 min.
5 LA-4's = 1DD= 50 min.
240
270
-------
Figure A-3
ONBOARD SYSTEM TO CONTROL REFUELING EMISSIONS
Control
Vacuunr
Lines
Flow Control
Valves
Carburetor
Intake Manifold
Carburetor Bowl Vent
Engine
Canister Purge Line
.With Flow Control Orifice
Fuel Tank Vapor Line
Vapor-Liquid
Separator
(5/8" I.D.)
Carbon Canister (4.4 L)
Seaiing
Nozzle
Fuel Tank
-------
Figure A-4
Refueling System Carbon Canister
Sunbird
Carb. Bowl
Fitting
Chevy Purge
Valve, Drilled
To 0.180"
Chevy Carb.
Bowl Valves
0,047" Bleed
To Fuel Tank
Side View Of Top Disc
Carbon-
1 Na 1=3 1 =
1
//// // //// /i ////"/ y/
iJ
X
fj//ff //////// ///////////I
=mrtT<'n'rmTprrrt'ff tr m-
<: —
^r—-1
,. \
•Foam
•Foam
-Wire Mesh *
Fiberglass Air Filterc
Canister Dimensions
6" High
8" Diameter
Carbon: BPL-F3
1550 grams
4350 ML
1 L
Wire Mesh Glued To
Bottom of Tube
~l/8" Plexiglass
.l"dia. x 13/4" long
Plexiglass Tube
-------
41
Figure A-5
FILL PIPE MODIFICATIONS
ROTARY SEAL.
ROTARY SEAL
TRAP DOOR
SPOUT
LEAD RESTRICTOR
FILL PIPE MODIFICATIONS
ROTARY SEAL
ROTARY SEAL
TRAP DOOR
SPOUT
LEAD RESTRICTOR
-------
42
Figure A-6
NOZZLE / FiLLPIPE MODIFICATION
CONE SEAL
LEAD RESTRICTOR
TRAP DOOR
SPOUT
DISK
LATCH COLLAR
CONICAL SEAL
NOZZLE / FILLPIPE MODIFICATION
CONE SEAL
LEAD RESTRICTOR
TRAP DOOR
SPOUT
LATCH COLLAR
CONICAL SEAL
-------
VACUUM ACTUATED PURGE
VALVE AND TANK VAPOR '
liiLST VALVES ARE SIMILAR
TO CURRENT PURGE VALVES
ON BOARD VAPOlfRECOVERY SYSTEM
Mustang 8Z18 & 8Z19
System A
TANK.-VAPOR INLET VALVES
VACUUM CLOSED "~"~
PURGE VALVE WITH
0.180 IN ORIFICE .
VACUUM OPEN
SERVICE STATION
NOZZLE
FILL PIPE OPENING
THIS VALVE CONTAINS
A .0^1 IN. BY-PASS
.ORIFICE FOR TANK RUNNING
LOSES
GARB BOWL
VENT CONNECTION
PURGE LINE TO
PCV HOSE
GARB EOWL
VENT LINE
PURGE SIGNAL
~X_3/8"DIA
TUBING
(REPLACES CONVENTIONAL
TUBING)
^"-4350 ML CARBON VOLUME
OPEN CELL FOAM
WIRE SCREEN
FIBERGLASS
8 IN.
DIA"
CANISTER (REPLACES CONVENTIONAL CANISTER)
H«P o(-,vo fiPTMTVT1
TANK VAPOR
LINE
7
• FUEL TANK
H-
OQ
C
>
-------
ON BOARD V/"""Q:ECOVERY SYSTEM
PINTO 8E?9
System B
~3 *- PURGE LINE TO PCV HOSE
GARB BOWL VENT LINE
i i ________ .
PURGE
TO PCV LINE
'^_t.j THRU BOTH .090"
'
,'vi—;-..i iriiio ijuin .uyu"
//' I & .085" ORIFICES
// V
//
_x
-^EF^C ")\ **
\ ^7^:~==
-"•- PURGE SIGNAL
-1-'PURGE LINE
PURGE
'SIGNAL
\ | C_J (PROD. VLV.)
T"!.'. r.i--, ' •
\090" REMOTE PURGE VLV.
31+00 ML CARBON VOL.
925 ML CARBON VOL.
I/
ATMOS.
"
TANK VAPOR
FILL PIPS
. .
FUEL TANK
H-
OQ
oo
-------
45
Procedure #2 Sc* 2.
Mustang 5«OL (J5Z18) 197d 49 States
Date. 7-17-78 Test 29
tsl Caaieter, TcmK % Garb. Bowl w/.lSO" Purge
I Grows cr Vapor Purged (.-)> Absorbed CT;
Figure A 9
I +55 I -93 I +27 ! -50 1 +35 I -38 1+39 1+3 1.495 ' -7^ l +1
Produetic
Sys. Parzs
NN 23 G-s7
s
§
I
;P
^
•P
c.
o
.Fscdas
Mi CO
Qli BOARD SIS. Bag 1,25:3 CO Cms.
Bag 1 CO Gas.
1 CO. Gas.
BASELir-S SI'S. B»g I,2i3 CO G=s.
Gcs/Mi CO
15.9
205
118
f-{
a
C
M
o
6-1 sO
r-
o t
ac 3
0 »•
o*
Q ^
S? I10
CVS
Sequence
-------
Procedure #3 Set 2
Mustang 5.0L (8Z19) 1978 ty States
Date 7-8 & 9-78 Tost //Ht, 15
Jr350 ml Canlatsr, Tank & Garb. Bowl Vapors w/.l80" Purge Orifice
I Grains of vapor, Purged (-), Absorbed (+)
+30 I -33 I +77 I ~^5 I +22 I +3 I -17 I
X
g
•S«*6
i
I
tf»
•8
o
fc
66
Foedsas CO Grama Bag
t t t f t t
a]
•H
-P
•H
CJ
M
a
in
^ 2!
•Ou
o +>
vl O
w W
w
•H CO
B t:"
cu b
O
•P
O
CO
t
o
to
a:
H-
OQ
fC
>
-------
Figure A-11
DISTRIBUTION OP GASOLINE PURCHASES
too
80
<
I
o
cc.
u.
O
h-
2
UJ
O
CC
UJ
Q-
LU
Z)
2
3 20
10
._»-.
20
»*•
»*««••*»»»
•«*
**•»
30 40 50 60 70 60
PERCENT OF TANK CAPACITY
90
100
-------
Figure A-12
REFUELING EMISSIONS CONTROLLED
too
Q ao
LU
oc
H
2
O 60
(/)
Z
o
CO
CO
ui «°
a:
O
20
tu
'ac
«*
»»*
**«»
#»»»«
«*»»***«»»««»««*•«*»»»
oo
10 20 30 <10 80 60 70 00 90
REFUELING TEST REQUIREMENT'FOR NO EMISSIONS, % of TANK CAPACITY
too
------- |