OAR Box 1856 

Prepped by Keeia Richards 

Document Number: 

67) II--A04 

Docket Number: 

A-87-11 

Printed 11/24/2008 12:41:50 PM Sheet 67 of 82 

P.1 
P.2 

^ " I ~1 f\4n\ a-ft-off ^ 

* . . * • EPA-AA-SDSB-85-5c\ 

Technical Report 

Draft Recommended Test Procedure 

for the Measurement of 

Refueling Emissions 

By 

Lisa D. Snapp 

July 1985 

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 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 
P.3 

Table of Contents 

I. Introduction 1 

II. History of the Procedure . 1 

III. Recommended Procedure 3 

A. Equipment 3 

B. Procedure 4 

C. Parameters 7 

1. Test Fuel Volatility 12 

2. Dispensed Fuel Temperature 16 

3. Temperature Differential 20 

4. Fuel Level Prior to Refueling 24 

5. Fuel Dispensing Rate 25 

D. Vehicle Preconditioning 28 

E. Canister Purging and Vehicle Drivedown 30 

F. Testing Requirements for In-Use Vehicles ... . 33 

1. Preconditioning Problems 33 

2. Testing Problems 36 
P.4 

I. INTRODUCTION 

The emissions which occur as a result of vapors displaced 

during the refueling of motor vehicles are currently of public 

and Agency concern. These vapors have possible adverse health 

effects, as does benzene, a substance in gasoline vapors linked 

to cancerous and mutagenic effects. They also contribute to 

the formation of photochemical smog, which is of great concern 

in areas which exceed the National Ambient Air Quality Standard 

(NAAQS) for ozone. Because of these concerns, EPA has 

undertaken a detailed evaluation of various regulatory 

strategies which could be used to reduce emissions due to 

refueling.[1] One aspect of this evaluation involves the 

measurement of refueling emissions from both current vehicles 

and vehicles equipped with prototype refueling vapor control 

systems. 

EPA has been involved in the development of a test 

procedure designed to measure these emissions for quite some 

time. EPA began working with test procedure issues during the 

summer of 1984. A workshop was held on October 17, 1984 at 

which EPA shared its ideas on the test procedure and on 

critical test parameters with workshop participants. Those 

present at the workshop were urged to submit comments on the 

draft recommended practice and some of them did so. A 

follow-up meeting was held on February 15, 1985 at which 

industry representatives further detailed their thoughts about 

the draft test procedure as proposed by EPA. 

EPA has considered the comments submitted in response to the 

initially proposed test procedure in development of this 

current version of the recommended practice. This report 

summarizes the development of the recommended test procedure 

including discussions of equipment needed and values for 

critical test procedure parameters. 

II. HISTORY OF THE PROCEDURE 

In 1973, the Society of Automotive Engineers (SAE) 

approved Recommended Practice J1045, "Instrumentation and 

Techniques for Vehicle Refueling Emissions Measurement," which 

was designed to measure refueling emissions from uncontrolled 

vehicles.[2] The procedure was designed mostly for 

experimental purposes, in that it was to be used to determine 

the effects of various parameters, such as temperatures, fuel 

volatility, and so forth, on refueling emissions. With these 

parameters held constant, it could also be used to measure the 

control efficiency of refueling emission control devices. 
P.5 

-2-

The SAE procedure incorporated four key parameters for use 

when measuring refueling emissions. These were the fuel 

volatility, fuel tank temperature, dispensed fuel temperature, 

and fuel level prior to refill. Also specified was the testing 

equipment to be used, most notably the sealed housing for 

evaporative determination (SHED), and procedures for conducting 

the tests. 

In the SAE recommended practice, the test fuel specified 

had a volatility of 9.0+0.5 psi as measured by Reid Vapor 

Pressure (RVP), which is comparable to normally specified 

values in Federal test procedures and SAE recommended practices 

for evaporative and tailpipe emissions testing. Fuel tank 

temperature was recommended to be 95+2°F, which SAE found to be 

a reasonable temperature to expect in summer driving 

conditions; no supporting data was cited. Dispensed 

temperature was 82+1°F, an average summer dispensed temperature 

reported by Scott Research Laboratories.[3] Fuel level prior 

to refill was suggested at one-fourth tank capacity; again, no 

data was cited in support of this value. 

The equipment to be used, particularly the SHED, was also 

prescribed by the SAE procedure. It was specified to be the 

same as the SHED generally used for evaporative emissions 

testing, with minor alterations such as an added fuel 

dispensing hose and nozzle. Also specified in some detail were 

the equipment components necessary for heating the fuel tank, 

analyzing the HC emissions, mixing and purging the air, and 

recording temperatures. 

Procedures for using the equipment were given, along with 

tolerances of applicable parameters. The basic test procedure 

involved draining the fuel tank to nominally empty, filling it 

to one-fourth of tank capacity, and pushing the vehicle into 

the SHED. Fuel tank temperature was then to be raised to the 

specified test temperature by means of an electric heating pad 

applied beneath the tank, generally referred to as single 

blanket heating. When the desired temperature was reached, the 

SHED was to be closed and, upon stabilization of background 

hydrocarbon concentration, the operator was to enter the SHED 

and refuel the vehicle, allowing the nozzle to automatically 

shut off when the tank was full. Readings of hydrocarbon 

concentration, elapsed time, ambient temperature, and 

barometric pressure were to be taken, and the mass of emissions 

due to the refueling could then be calculated. 

The SAE procedure described above and the Federal test 

procedure for evaporative emissions were used to develop the 
P.6 

-3-

EPA recommended test procedure for refueling emissions outlined 

below. This procedure uses the basic SHED test approach for 

measuring HC refueling emissions, and integrates it into the 

existing federal test procedure (FTP) for exhaust and 

evaporative emissions. 

The remaining sections of this report discuss this 

procedure and are organized as follows. First, the equipment 

to be used to perform the testing will be described in Section 

III.A. This will be followed in Section III.B. by a review of 

the test procedure sequence itself. Sections III.C.1-5 will 

deal with the derivation of specific test conditions, including 

test fuel volatility, dispensed fuel temperature, temperature 

differential, fuel level prior to refueling, and fuel 

dispensing rate. Vehicle preconditioning is discussed in 

Section III.D, followed by a more detailed discussion of the 

canister purging and vehicle drivedown portion of the test 

sequence in Section III.E. Finally, the application of this 

test procedure to in-use vehicles is described in Section III.F. 

III. RECOMMENDED PROCEDURE 

A. Equipment 

The equipment to be used in the EPA refueling test is 

similar to that recommended by SAE and that specified in the 

evaporative emissions portion of the Federal test procedure. 

This equipment consists of a SHED, fuel dispenser, meters, and 

recording devices. The SHED itself is essentially the same, 

except that the *|uel line opening in the SHED wall must be 

lower than the fuel tank opening on the vehicle, to eliminate 

the potential for siphonage and spillage onto the floor. Other 

pieces of equipment - the flame ionization detector (FID) 

hydrocarbon analyzer, purge and mixing blowers, thermocouples 

and recording devices - are also essentially the same in the 

EPA test procedure as in the SAE procedure. The fuel 

dispensing system varies in that the EPA procedure requires a 

self-supporting nozzle and a fuel flow shut-off switch on the 

fuel cart. This eliminates the need for a nozzle operator 

inside the SHED when vapors are accumulating. Another 

difference is in the fuel tank heating system used during 

preconditioning. The SAE procedure prescribes a maximum 

liquid-vapor temperature differential of 6F°, which limits the 

speed of liquid heating, while the EPA prpcedure allows heating 

as quickly as possible, with the temperatures then held in 

equilibrium for ten minutes after completion of heating. This 

equipment is used to conduct the refueling test, which is 

integrated into the FTP as described in the following section. 
P.7 

-4-

B. Procedure 

The proposed test sequence for exhaust, evaporative, and 

refueling emissions uses the current sequence for exhaust and 

evaporative emissions and adds refueling tests at the beginning 

and end. These two new tests are designed to check the 

capacity and purge capability of the refueling control system 

separately. Their integration into the FTP is shown in Figure 

1 and described below. 

The test begins with a refueling test performed to ensure 

that the overall vapor control capacity of the canister is 

sufficient for a complete fill-up. Certification test vehicles 

are expected to arrive at the test site purged to a level 

commensurate with a nearly empty fuel level. Prior to testing, 

the fuel tank will be drained and filled to 10 percent of 

capacity with standard test fuel. The refueling canister will 

be disconnected during this operation. In-use vehicles may 

arrive in any condition, and will be preconditioned by 50 miles 

of driving on standard test fuel using the durability driving 

schedule contained in Appendix IV of Part 86 of the Code of 

Federal Regulations (CFR), or equivalent urban driving. 

Following the 50 miles of driving, the fuel tank will again be 

drained and fueled to 10 percent of capacity. As with 

certification vehicles, the refueling canister will be 

disconnected for this step. To prevent any canister loading 

while any vehicle awaits testing at the facility, the gas cap 

will be loosened or removed when the vehicle is not in 

operation. 

Immediately prior to testing, the vehicle will be pushed 

into: the SHED and the doors and luggage compartments will be 

opened. The fuel in the vehicle fuel tank will then undergo a 

heat build to the prescribed test temperature, followed by a 

ten minute equilibrium period. The fuel dispensing nozzle will 

be placed in the vehicle fill neck, and the SHED closed and 

sealed. A switch outside of the SHED will then be used to 

start the flow of fuel. Gasoline shall be dispensed into the 

fuel tank until the automatic shutoff feature on the fuel 

nozzle is tripped. At the time that fuel flow is terminated, 

the fuel tank must be filled to at least 95 percent of nominal 

tank capjacjity. The total vehicle refueling emissions will be 

defined am the hydrocarbon level in the SHED (as measured by 

FID) at the time of termination of the fueling event. 

For baseline testing of vehicles equipped with current 

technology, some difficulties with spillage at nozzle shutoff 

may occur. In order to avoid excessive emissions and high 
P.8 

Figure 1 

§ M.130-7S TrHo 40—Protection of Environmont 

DIURNAl MAT IUH0 

• HEAT FUEL-1 HOUR 

• *0-l4*F 

IVArV TEST 

NOT RtQ 

OIURNAl 

ENCLOSURE 

TIST 

r* 

i 

i 

i 

i 

i r 

COlO START EXHAUST TEST 

Refueling Capacity Test 

- 85% fill test 

- canister saturation 

I HOUR MAX 

J MIN. MAX. 

_ Disconnect Canister 

Reconnect 

> <? 36 HOURS 

(no max. lor 

EVAP. TEST 

NOT 

PERFORMED 

HC RUNNING 

IOSSES-AS RtQ 

} 0-1 HOUR 

I 

I 

I 

L. 

3Z> MIN 

. MOT START EXHAUST TEST 

• > » MIN. MAX 

HOT SOAK 

ENCLOSURE 

TEST 

CND 

Refueling Purge Test 

- IA-4 drivedown 

- 30% fill test 

PlfWt l/ l 10 TtIT SIOUINCI 
P.9 

-6-

test-to-test variability caused by spillage, manual nozzle 

shutoff at the 95 percent full level is sometimes necessary in 

this case. For new vehicles equipped with onboard controls, 

however-^jEueling systems should be designed such that no 

spillage^will occur when a properly functioning nozzle is used 

to fuel thfr vehicle. Any emissions caused by spillage would be 

included as part of the vehicle's total refueling emissions. 

Next, the vehicle fuel tank will be drained and refilled 

repeatedly until the canister is saturated and hydrocarbon 

breakthrough occurs. "Breakthrough" will be defined as that 

point in time that the concentration indicated by the FID 

hydrocarbon trace increases by a factor of at least 3 in a one 

minute period. At this point, the vehicle will begin the 

existing test sequence for exhaust and evaporative emissions. 

Currently, the test procedure specifies a fuel drain and fill 

at this point. In the refueling test procedure the vehicle 

manufacturer will have the option to adjust the fuel level in 

the tank to the specified level of 40 percent following 

canister saturation, or perform the existing drain and 40 

percent fill operation. In either case the refueling canister 

will be disconnected. 

The next steps in the procedure follow the existing FTP. 

First, a single dynamometer preconditioning cycle is done, 

followed by a cold soak for between 10 and 35 hours. 

Additional preconditioning, allowed under the current FTP, will 

no longer be permitted. After the soak, the FTP calls for the 

fuel tank to be drained and filled to 40 percent of tank 

capacity. For the refueling procedure, the canister will be 

disconnected before this fuel drain and fill in order to avoid 

additional canister loading.* The canister will then be 

reconnected and the FTP will continue as usual, with the 

diurnal breathing loss SHED test, cold and hot start 

dynamometer exhaust tests, and hot soak evaporative SHED test. 

This aspect of the procedure is still subject to change. 

Leaving the canister connected would require substantially 

increased purge capacity during the dynamometer 

preconditioning cycle and might be unnecessarily severe. 

On the other hand, it may happen that a purge strategy 

capable of adequately purging all the collected refueling 

vapors during normal driving would have a purge capability 

at saturated canister conditions which approximates this 

higher rate. This subject is discussed further below in 

connection with the drivedown portion of the test. 
P.10 

-7-

The&f-inal... stage in the refueling test procedure is a purge 

test sequence involving dynamometer operation of the vehicle to 

drive* dovnif approximately 30 percent of the fuel in the tank, 

followedl~b5gj a partial refueling operation to replace the 

consumed? fuel. The purpose of this stage is to demonstrate 

that the refueling control system has adequate purge capacity 

to purge accumulated refueling vapors. For reasons to be 

discussed further below, the drivedown sequence in this draft 

recommended practice is initially being applied only to 

vehicles employing refueling emissions control systems which 

are completely separate from any evaporative emissions 

controls. Vehicles having refueling emissions control 

integrated with either the diurnal fuel tank emissions control 

or all evaporative emissions controls are not being required to 

undergo the drivedown portion of the test at this time. 

However, it is not yet clear to EPA that the refueling 

procedure lacking the drivedown is, in fact, completely 

adequate for testing integrated refueling and evaporative 

control systems. In fact, there are indications that a 30 

percent drivedown operation may itself be inadequate to verify 

proper canister purge for a full refueling. These 

uncertainties are discussed further below in Section E, 

Canister Purging and Vehicle Drivedown. 

The purge test will begin with a drivedown sequence on the 

dynamometer, consisting of sequential Urban Dynamometer Driving 

Schedules, contained in Appendix I of Part 86 of the CFR and 

normally referred to as the LA-4, alternating with one hour hot 

soaks. This sequence is intended to use fuel and allow 

refueling canister purge, in order to subsequently perform a 

partial refueling with an amount of fuel large enough to 

adequately test the system's purge capability. The LA-4/hot 

soak sequence will be repeated until approximately 30 percent 

of the tank fuel capacity has been used. The vehicle will then 

be put back into the SHED, and a refueling test conducted as at 

the beginning of the proposed procedure, except that the 

refueling amount shall approximately correspond to the amount 

of drivedown. 

C. Parameters 

In the draft procedure, five key test parameters affecting 

refueling emissions were identified: test fuel volatility, 

dispensed fuel temperature, differential between dispensed fuel 

temperature and vehicle liquid fuel tank temperature, initial 

and final fuel tank volumes, and fuel dispensing rate. The 

values for these test parameters have been chosen so that 

roughly 90 percent of the refueling events under ozone-prone 
P.11 

-8-

summer conditions would be covered.* Test parameter values are 

shown in Table 1. 

In order to choose the appropriate values, it was 

necessary to know typical levels or have frequency 

distributions of the levels of the key parameters during the 

months and in the regions of interest. Information used to 

select the appropriate values for the key parameters was taken 

from several sources. These sources are briefly described 

below and summarized in Table 2. 

One important study was conducted by the American 

Petroleum Institute (API) Product Temperature Task Force in 

1975. In this survey, gasoline temperature data was collected 

at 56 service stations throughout the United States.[4,5] The 

data analysis report by Radian Corporation under contract to 

API, and the final API report generated from this data, 

provided information which EPA used to establish frequency 

distributions of dispensed fuel temperature and temperature 

differential for the country, divided into six regions as shown 

in Figure 2. 

Distributions of the fuel level in a vehicle before it is 

taken in for a fill-up were derived from six studies done as 

part of California's service station Stage II vapor control 

program.[6,7,8,9,10,11] These studies recorded amount of 

gasoline dispensed per refueling at a variety of service 

stations. Typical flow rates used in dispensing such fuel were 

provided to EPA by an informal API survey of member 

companies.[12] 

Maximum fuel volatility prescribed in the summer months of 

the appropriate regions was taken from the American Society for 

Testing and Materials (ASTM) standards.[13] The effects of 

weathering on volatility were studied in the EPA baseline 

refueling testing program and in an API study conducted by 

Stanford Research Institute to develop a test procedure for 

service station vapor control systems.[14] The values which 

these sources provided for the key test parameters are 

discussed in the following sections. 

Since refueling emissions control is also important for 

reasons other than ozone reductions, the test parameters 

must also ensure adequate control requirements for 

non-summer conditions. Based on the refueling emission 

factors developed in EPA's baseline study[16], the choice 

of summertime condition will ensure year-round control. 
P.12 

Designation 

Volatility, 

RVP 

Table 1 

Critical Test Parameters 

Meaning 

dispensed temperature, 

TD 

temperature differential, 

AT 

fuel level 

dispensing rate 

test fuel volatility, 

expressed in Reid 

Vapor Pressure 

temperature of 

dispensed fuel 

tank temperature minus 

dispensed temperature 

level of fuel in vehicle 

prior to refueling, 

percent of capacity 

to nearest 0.1 U.S. gal 

flow rate of fuel as it 

is dispensed 

Value 

11.5 + 0.5 psi 

88 + 2°F 

+2 to +5 F« 

10% 

8-10 gal/min 
me i 

P.13 

Year Conducted 

1975 

1984 

1974 

1984 

1976 

1976 

1979 

1982 

1976 

1981 

1984 

Table 2 

Sources for Parameter Values 

Source 

Radian/API[4,5] 

ASTM[13] 

Stanford[14] 

SWRIC17] 

Union 76[6] 

Union 76[7] 

Union 76[8] 

HealyC9] 

Exxon[10] 

Emco Wheaton[ll] 

API Letter[12] 

Parameter 

TD, AT 

RVP 

RVP 

RVP 

fuel level 

fuel level 

fuel level 

fuel level 

fuel level 

fuel level 

dispensing 

rate 

Comments 

Measured underground, 

dispensed, and tank 

fuel and ambient 

temperatures 

Prescribed fuel 

volatility classes by 

state and month 

Studied effect of 

variables, including 

tank fuel RVP 

(weathering) on 

refueling emissions 

Studied amount of fuel 

weathering experienced 

by in-use vehicles 

Gave fill fraction for 

105 refuelings, 

fill-ups only 

Gave gallons of fuel 

dispensed for 117 

refuelings, fill-ups 

only 

Gave gallons of fuel 

dispensed for 103 

refuelings, with 89 

fill-ups 

Gave gallons of fuel 

dispensed for 99 

refuelings, with 18 

fill-ups 

Gave gallons of fuel 

dispensed for 573 

refuel ings, with 327 

fill-ups 

Gave gallons of fuel 

dispensed for 99 

refuelings, with 40 

fill-ups 

Surveyed API member 

companies informally 

for typical fuel flow 

rates 
P.14 

CN 

•ri 

fa 

CO 

! 

tl 

i .9 4J •H Ul .2 
P.15 

m i 

-12-

1. Test Fuel Volatility 

Fuel volatility has a significant impact on the level of 

refueling emissions, and as such is one of the critical 

parameters to be specified in this test procedure. Commercial 

fuels with volatilities that are higher than that of EPA 

certification fuels are currently sold in areas and months that 

are ozone-prone. Ozone-prone states currently include any 

state with a Standard Metropolitan Statistical Area (SMSA) 

which had a violation of the NAAQS for ozone in 1982 or 

1983.[15] The months of violation are mainly May through 

September, and the states are predominately in the Midwest, 

Northeast, Southeast and Southwest areas of the United States, 

as can be seen in Figure 3. 

The 30 ozone-prone states fall predominantly within four 

of the six regions which Radian had designated in its study of 

gasoline temperature[4], also shown in Figure 3. These 

regional designations are: 1 (Northeast), 2 (Southeast), 3 

(Southwest), and 4 (West), and since they correspond so closely 

to the ozone-prone regions, they will be used as the relevant 

regions in subsequent choices of parameter values. 

ASTM specifies, by state and month, maximum volatility 

levels which can be used by gasoline distributors. These 

levels are sufficiently high to ensure ease of engine start-up, 

but are not so high as to cause vapor lock. They are 

identified as classes A through E, with A being the lowest 

maximum volatility at 9.0 psi, and E being the highest at 15.0 

psi. Generally, classes A, B and C are for use in the summer 

months, while D and E are for winter use; in each season, the 

lower volatility classes are specified for the hotter regions. 

Class C volatility, with a maximum allowable Reid Vapor 

Pressure (RVP) of 11.5 psi, is the highest level prescribed for 

the summer. It is widely prescribed in those months in states 

which EPA has identified as ozone-prone, as can be seen in 

Figure 4. 

It is clear, at least from the ASTM specification, that 

summertime fuels can have significantly higher volatility than 

the 9 psi RVP of EPA's current certification fuel. EPA is now 

in the process of examining fuel volatility to more accurately 

establish the characteristics of summertime fuels for the 

foreseeable future, and is therefore not- in a position to 

definitively establish its test fuel RVP for this procedure. 

In the interim, EPA plans to require the use of 11.5 psi for 

test fuel volatility. This volatility represents the RVP of 

summer commercial fuel as used in current EPA emission factors 
Figure 3 

Correlation of 

Ozone-prone States. (•)and 

Radian/API Regions flQ^ 

0) 
Figure 4 

Number of Class C (.11.5 RVP) Months 

in May thru September 

in Ozone-prone States T) 
P.18 

-15-

test programs, as well as the ASTM class C volatility limit 

which shows a widespread correlation with the ozone prone areas 

and months. 

Weathering of the . fuel in the vehicle tank is also a 

factor in refueling emissions. Agitation, thermal cycling, 

temperature extremes, and time aging can all lower the RVP of 

the fuel in the vehicle. The effects of this weathered fuel 

are only beginning to be studied; however, it seems that two 

counteracting effects occur. The first is that the weathered 

fuel in the tank has a lower RVP, and hence a lower 

concentration of vapors. This would result in lower refueling 

emissions compared to non-weathered fuel, if refueled with 

similar RVP fuel. However, the fuel being added is 

non-weathered, and there is thus a balancing of the pressures 

of the new, non-weathered fuel being added and the older, 

weathered fuel in the tank. The higher RVP fuel vaporizes as 

it enters the tank in order to equalize the vapor pressures. 

Excess vapors are then vented from the tank, causing higher 

emissions. 

Of the two effects, the second is apparently dominant 

under most conditions, according to limited data. These data 

come from weathering effects tests conducted as part of EPA's 

baseline testing for refueling emissions[16], and from a report 

by Stanford Research Institute concerning refueling.[14] The 

EPA tests involved dispensing commercial fuel (RVP of 

approximately 12 psi) into a tank filled to 10 percent of 

capacity with an Indolene-commercial blend (RVP of 

approximately 10 psi). The emissions were about 2 g/gal higher 

than when dispensing blended into blended fuel. This was 

apparently due to vaporization of the commercial fuel, with 

higher RVP, as it was dispensed into the tank. In fact, the 

grams per gallon emissions when adding commercial to blend fuel 

(12 psi to 10 psi) were approximately 1 g/gal higher than those 

generated when adding commercial to commercial fuel (12 psi to 

12 psi). 

In the Stanford study, increases in emissions for 

weathered fuel were also seen. However, these increases were 

significant only with large positive AT, created by 

increasing tank temperature while holding dispensed temperature 

constant. The difference in emissions between weathered and 

non-weathered fuel, increasing with increasing ATs, reached a 

high of 1.7 g/gal at the highest tested AT, 35F°. At AT 

between 0 and 10F°, there was no noticeable difference in 

emissions with weathered or non-weathered fuel initially in the 

tank. It could be that the lower volatilities used in the 
P.19 

-16-

Stanford program (6.9 and 8.6 psi) account for the smaller 

difference seen at small ATs. 

For the Stanford study, tank fuel RVP was about 20 percent 

lower than dispensed RVP, at 6.9 and 8.6 psi, respectively. 

For the EPA study, the difference was about 17 percent. In a 

project by Southwest Research Institute, the amount of 

weathering a tank of fuel actually experiences was 

studied. [17] Two vehicles were each driven 50 miles a day and 

parked overnight until a full tank was used. Three fuels were 

tested, with initial RVPs of 9.0, 10.5, and 12.0. For each 

fuel, the RVP dropped approximately 9 percent as the tank of 

fuel was consumed. Very limited data indicates this value may 

increase if the fuel sits in the tank for extended periods, 

especially when approaching empty. 

Using the Southwest data as an indicator of typical fuel 

weathering to be expected in-use, it appears that fuel 

weathering could increase refueling emissions by up to about 

0.5 g/gal. However, because of the uncertainty of this amount, 

coupled with the difficulty of requiring the handling of two 

test fuels and the inherently conservative nature of the rest 

of the test parameters, no specific provisions to account for 

fuel weathering are included in the recommended practice. 

2. Dispensed Fuel Temperature 

SAE recommended a dispensed fuel temperature of 82+1°F, 

which was the average dispensed fuel temperature observed for 

summer months, as reported by Scott Research Laboratories.[3] 

However, EPA desires to test at conditions which will assure 

control for the majority of cases, rather than at average 

conditions. Data described below shows a 90th percentile point 

of 88°F for daily average dispensed temperatures in May through 

September for ozone-prone areas. Therefore, the recommended 

practice uses 88+2°F for the dispensed fuel temperature. 

This 90th percentile point was determined by EPA using 

data taken from the Radian report analyzing the gasoline 

temperature data gathered in 1975 by the API Task Force. [4]* 

For the months of interest (May-September), 1975 

temperatures were only approximately 0.2°F higher than the 

recorded historical average (over about 40 years) for the 

cities in which data was gathered. Therefore, the ambient 

temperatures for the Radian study are considered 

adequately representative of normal conditions. 
-17-

In this study, temperatures recorded were of fuel in: 1) the 

bulk delivery tank, 2) the underground storage tank, 3) the 

dispensing nozzle, and 4) the vehicle fuel tank. From this 

data, a mathematical model of dispensed temperature was 

formulated, in which the dispensed fuel temperature 

exponentially approaches either the underground tank 

temperature (during fill cycles), or ambient temperature 

(between fill cycles), as a function of cycle time. This model 

has been subsequently validated by API, and may be useful in 

retail dispensed fuel temperature adjustment in the future. 

Dispensed temperatures have been shown to be predicted to 

within +0.5 percent. 

The dispensed fuel temperatures actually measured in this 

study were used to determine the appropriate value for the test 

procedure. Of special significance are temperatures in ozone 

problem areas during months in which ozone effects are 

significant. These are the four regions which correspond to 

the ozone-prone states, shown previously in Figure 3, with the 

critical months being May through September. Distributions of 

dispensed fuel temperatures in each of these four regions show 

that 5-day average dispensed fuel temperatures range from 59 to 

93°F during the months of interest.- Higher temperatures 

predominate in Region 2 (SE), as can be see in Figure 5. This 

region also has a majority of states with four or five of the 

five ozone-prone months classified as volatility class C, as 

indicated previously in Figure 4. 

It might be argued that inclusion of Region 2 would unduly 

bias the data toward higher dispensed temperatures. However, 

there are two other factors which must also be considered. 

First, the figure shows 5-day averages, and so does not show 

the peaks from days which exceed the average. Second, the 

maximum dispensed temperature of the day, calculated from the 

model described above and using typical ambient temperature 

differentials[4,18], would generally be 4 to 7°F above the 

average, again indicating a need to include higher temperatures 

(such as those found in Region 2) in the test procedure. 

The 90th percentile point covering all four regions is 

88°F for the five ozone-prone months of May-September, as shown 

in Figure 6. More stringent conditions could be found by 

looking at just the two major ozone months, July and August. 

For such conditions, the 90th percentile for all four regions 

combined is 9l°F. However, the five month dispensed 
95. 

Figure 5 

Regional Dispensed Fuel Temperature 

Five-Day Average, Summer 1975 

90 . 

85 

80_ 

Dispensed 

Temperature 7C-

(°F)

 /D J 

70-

65. 

60-

!• 

55-

Region 1 (NE) „ 

Region 2 (SE) ——. . 

Region 3 (SW) ——— • 

Region 4 ( W) ' 

»zr s n IS » 25 5 To IS 202 4 J 5Ti b IS 20 25 

—jnffi" i n u » 5 U 15 20 25 

MAY TJUEY" AUGUST SEPTEMBER 

Ozone-Prone Months 
Figure 6 

Distritaition of Dispensed Fuel Temperatures 

May thru Sept 1975, lily Averages, Regions 1,2,3 and 4 

100-t-12. 

80. 

S 

I 

-P 

tH 

60. 

20- -

40- - 5.0--

50th percentil e 

* 80°F 

85 91 

90th percentil e 

a 98<>F 

& 

Dispensed Temperature (F°) 

T) 

ho 
P.23 

-20-

temperature value of 88°F was deemed more representative for 

the ozone-prone months overall. 

3. Temperature Differential 

The difference between fuel tank temperature and dispensed 

temperature, AT, is a critical parameter. It directly 

affects the magnitude of vapor growth or shrinkage in the fuel 

tank, and thus the amount of vapor displaced from the tank. 

The SAE recommended practice does not indicate any particular 

AT, although it does state a desired fuel tank temperature of 

95+2°F. This value, in conjunction with the recommended 

dispensed temperature, gives a AT of +10 to +16 F°. Either 

parameter could be specified in the procedure, but AT is the 

parameter which EPA feels should be directly constrained, since 

it is so critical to the level of refueling emissions. It is 

also the parameter that was recorded for individual refueling 

events in the Radian/API study, used above to determine the 

dispensed temperature value.[4,5] It is clearly desirable to 

use the same study for such closely related parameters, as the 

data were gathered at the same stations and times. 

In the API report, AT values were tabulated separately 

from dispensed temperature values. In general, direct 

correlation of fuel tank to dispensed temperature cannot be 

made, because dispensed temperature is strongly a function of 

the slowly fluctuating underground temperature, while fuel tank 

temperature varies with ambient temperature, trip length, 

number of recent trips, and so on. Thus, there are many fuel 

tank temperatures which could occur for each dispensed 

temperature. It is impossible to tell, from the available 

independent distributions, exactly how the AT distribution 

would be affected by choosing a given dispensed temperature. 

However, the AT distributions by region (Figure 7), derived 

from the API report, give the indication that this problem may 

not be significant. 

Of particular interest is the distribution for Region 2, 

which was identified earlier as having the highest dispensed 

fuel temperatures. In terms of AT, Region 2 falls in the 

middle ground of the regional distributions, indicating that it 

is reasonable to use the average AT distribution with the 

dispensed fuel temperature already developed. That is, the 

figure shows that the high average dispensed temperatures found 

in Region 2 do not unduly influence the corresponding AT 

distribution. If anything, the inclusion of Region 1 data 

(representing the lowest recorded dispensed temperatures) will 

tend to shift the AT distribution toward more positive (less 
Figure 7 

Cumulative Distribution of AT = TT-TD 

Cunulative 

Percent 

100 

90 ' 

80 • 

70 

60 

50 • 

40 

30 

20 . 

10 • 

A Region 1, Northeast 

878 Vehicles 

Q Region 2, Southeast 

296 Vehicles 

Q Region 3, Southwest 

324 Vehicles 

+ Region 4, West 

391 Vehicles 

-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 

Tank Temp. - Dispensed Tenp. (°F) 

45 50 55 60 
P.25 

-22-

stringent) AT values than would otherwise be found using only 

high dispensed temperature data.* Therefore, the average AT 

distribution for the four regions combined was used to 

determine the 90th percentile value for the recommended 

practice. 

The basic distributions were given in the API report in 

tabular form by increments of 5F° for each region by month, for 

those cases when the ambient temperature was between 65 and 

85°F**. From these, a distribution was developed for the 

ozone-prone months (May through September) for each ozone-prone 

region. The range of AT for these distributions is from -20 

to +55 F°, with negative values giving vapor growth as the 

warmer dispensed fuel enters the cooler tank. Since vapor 

growth is the more stringent condition in that it creates the 

largest amount of emissions, the 90th percentile point was 

found by accumulating from the top down, that is, from positive 

AT. An examination of the tabulated data shows that the 90th 

percentile point falls in the 0 to +5 F° range for all four 

regions together, as can be seen in Figure 8. 

* This conclusion has been confirmed, by subsequent analysis 

performed by EPA on the raw data used for the API report. 

These data indicate that, for high dispensed fuel 

temperatures between (85 and 95°F), the 90th percentile 

AT would be slightly more negative than that derived 

below, with a value near -3°F. However, EPA has decided 

not to adjust the test conditions in order to counter any 

tendency for the overall test parameter set to become 

unreasonably stringent. This might occur through the use 

of a 90 percent limit of one parameter which is itself 

derived from a 90 percent limit of another parameter, thus 

defining a condition which might only occur one percent of 

the time. 

** While it would be preferable to have the AT distribution 

based upon all ambient temperature conditions, it was not 

possible to derive this information from the tabulated 

data. Subsequent analysis by EPA of the raw data files 

has verified that this limitation did not substantially 

affect the AT distributions. 
Figure 8 

Distribution of AT = TT - TD 

May thru Sept 1975, regions 1,2,3 and 4 

100 

80- -

y 

& 

A-3 

60 

40. 

20-

505 5 

Tank Temp. - Dispensed Temp. (°F) 
P.27 

-24-

It was also determined that the AT distribution for all 

six regions - the 48 contiguous states - indicates a mild vapor 

growth condition, with a 90th percentile value in the -5 to 0 

F° range. The desire for a worst case condition might 

therefore indicate the choice of the nationwide AT value 

rather than that found for the ozone-prone regions only. 

However, there is an important reason why this approach was not 

adopted. In 1975, when data for the Radian/API study was 

gathered, very few fuel injected (Fl) vehicles were in the 

fleet. Such vehicles, which are becoming increasingly popular 

and will dominate the fleet in future years, presumably have 

higher fuel tank temperatures due to fuel return lines, which 

recirculate heated fuel to the fuel tank. Therefore, data 

without Fl vehicles gives a somewhat smaller AT than might be 

expected for Fl vehicles. To provide some compensation for 

this situation, EPA has decided not to use the 48-state data, 

and to use the upper end of the 0 to +5 F° range from the 

ozone-prone regions. Providing a range for testing 

variability, the recommended practice employs a AT value of 

+2 F° to +5 F°. 

4. Fuel Level Prior to Refueling 

Fuel level is important as a vapor control canister design 

parameter; the canister must be sized to contain all of the 

vapors displaced during the refueling test in order to avoid 

breakthrough. Vapor quantities involved are 7 to 8 g of HC per 

gallon of dispensed fuel, at the temperature and RVP conditions 

specified in the test procedure. As an example of sensitivity, 

this translates into approximately an 11 to 13 gram difference 

in emissions per 10 percent increment in fuel level, for a 

medium size 16 gallon tank. Therefore, accurately specifying a 

fuel level prior to refill is important to assure in-use 

control. 

Data on fuel level prior to refill comes from studies 

conducted as part of California's Stage II vapor control 

program.[6,7,8,9,10,11] These studies observed refueling 

events at various service stations in California to determine 

control efficiency of Stage II systems, and, as part of the 

program, reported amount of gasoline dispensed for each 

refueling event that took place. One study, by Union 76, 

provided fill fractions in the report, while five other 

studies, by Union 76 (2 studies), Exxon, Healy, and Emco 

Wheaton did not. However, these studies did provide 

information on vehicle make, model, model year and fill 

amount. EPA estimated fill fraction for these last five 

reports by assuming 13, 18 and 23 gallon tanks for compact, mid 

and large size cars, respectively. These estimates were made 

by averaging the tank sizes, by vehicle size category, of 44 

vehicles using the service stations in the studies. 
P.28 

-25-

The vehicle sample for these six reports includes 696 

vehicles and light-duty trucks receiving complete fill-ups. 

The distribution of fuel level prior to refill for these 

vehicles is shown in Figure 9. It can be seen that, in order 

to cover 90 percent of fill-up events, tanks should be filled 

from about 10 percent of tank capacity before refueling. 

The above value is taken from data for fill-ups only; 

partial fills are likely to have sufficient control since purge 

rates are higher when the canister is fully loaded, and hence 

have been deleted from this data base. The question arises, 

however, of how much total fuel is actually dispensed in 

fill-ups, and how many events are fill-ups, in order to ensure 

that basing control on fill-up conditions is not unnecessarily 

stringent. The reports mentioned above show that a substantial 

amount of the fuel dispensed is part of a fill-up event, such 

that full control by the canister is necessary: in the four 

reports which tabulated both full and partial fills, 54 percent 

of the refueling events and 62 percent of the gasoline 

dispensed was used in fill-ups. Also noteworthy is the fact 

that most of the events — 86 percent — at an entirely 

full-service station used in one Union 76 report are fill-ups. 

Therefore, it is important that control be adequate for a full 

refueling. 

The SAE recommended practice indicates that the fuel tank 

should be filled to one-fourth capacity before the refueling. 

It is EPA's desire to give a more precise specification, as 

well as one which duplicates 90 percent of actual refueling 

events. On the basis of the above data, this value has been 

chosen to be 10 percent of tank capacity, to the nearest 

one-tenth of a U.S. gallon. 

The refueling capacity test as defined in this test 

procedure will be terminated when automatic nozzle shutoff 

occurs. In order to ensure adequate canister capacity, this 

automatic shutoff must occur when the tank is at a level 

between 95 and 100 percent of its nominal capacity. Thus the 

total amount of fill for a valid test will be between 85 and 90 

percent of the nominal capacity of the tank. 

5. Fuel Dispensing Rate 

No value for a fuel dispensing rate is specified in the 

SAE recommended practice. However, this is an important 

parameter because it directly influences the rate of vapor 

displacement and also the occurrence of nuisance shut-offs, and 
Figure 9 

Distribution of Fuel Level Prior to Refill 

696 Vehicles 

20 -. 

15 -

% of 

Events 

10 _ 

13.5% 

5 _ 

18.7% 

L

> fV io 

• \ 

19.4% 

-^ 

18.2% 

0.1 0.2 0.3 

15.7% 10.1% 

3.2% 

U0L 

0.4 0.5 0.6 0.7 0.8 

Fuel Level Prior to Refill 

(fraction of full tank) 
P.30 

-27-

perhaps to some degree the amount of fuel spillage. Excessive 

back pressure and premature nozzle shut-off occurs in a system 

which is too small to handle the volume of fuel being 

dispensed. Thus, the dispensing rate affects the design of the 

refueling control system, and it is necessary that this 

parameter have a realistic value. 

A value of 8 to 10 gallons per minute (gpm) has been 

chosen to cover the majority of fill events. A 1984 informal 

survey by API of member companies and nozzle manufacturers 

indicates flow rate extremes of 6.5 to 12 gpm.[12] Lower rates 

of 6.5 to 8 gpm are found at full-service pumps, where the 

attendant may purposely choose the low notch setting on the 

fuel nozzle to allow enough time to service the vehicle. The 

low rate also reduces the chance of nuisance shut-off, which 

may cause the nozzle to fall off the vehicle and cause large 

fuel spills. Higher flow rates of 9 to 11 gpm are typically 

found at self-serve pumps. 

Facility type also affects flow rates. Newer, larger 

facilities generally have submersible pumps which serve all of 

the dispensers at each underground tank, and their flow rates 

tend to be high, with as much as 10. to 12 gpm capability. 

Older, smaller stations usually have individual suction pumps 

on each dispenser, with normal rates of 8 to 9 gpm. All flow 

rates are affected by such factors as the number of vehicles 

being refueled, distance from the pump, age of the pump, and 

vehicle design constraints which cause nuisance shut-off. Such 

shut-offs begin to occur generally at flow rates above 8 to 9 

gpm. The nozzle does not appear to be a significant factor in 

altering flow rate, although in conjunction with flow rate it 

can affect fuel spitting. 

From the available surveys, it was not possible to 

quantify a distribution of fuel dispensing rates. However, the 

information generally available indicates that most refuelings 

take place at 10 gpm or less. Higher rates are possible, 

especially at newer, self-serve facilities, but often result in 

nuisance shut-off, which should be minimized below 10 gpm for a 

well designed onboard system. Therefore, the specified value 

of 8 to 10 gpm should cover the majority of the refueling 

events while minimizing nuisance shut-off. It is worth noting 

that California specifies a 10 gpm maximum flow rate with its 

Stage II vapor control systems, making the two sets of 

specifications compatible, which is important for fuel system 

design purposes. 
P.31 

-28-

D. Vehicle Preconditioning 

A variable with potential for affecting the outcome of the 

test is vehicle preconditioning. For this test sequence, there 

are several aspects of preconditioning, including initial 

canister purging, canister saturation, and fuel tank heating. 

Initial preconditioning has been described earlier, and 

involves ensuring a well but not abnormally purged canister and 

a nearly empty fuel tank, so that all vehicles will have both 

canister and fuel tank capacity for the 85% refueling test. 

Certification vehicles are expected to arrive at the test 

facility with canisters purged to a level commensurate with a 

nearly empty fuel tank. Preparation for testing will involve 

draining the fuel tank and fueling to one-tenth of fuel tank 

capacity (with the. refueling canister disconnected). In-use 

vehicles, on the other hand, will arrive at the facility in 

various conditions; therefore, such vehicles will be driven for 

50 miles on the EPA durability driving schedule or equivalent 

so that the canister can be adequately purged. Prior to this 

mileage accumulation, the fuel tank will be drained and fueled 

with test fuel. Following mileage accumulation, the fuel tank 

will again be drained and then fueled to one-tenth of tank 

capacity. The refueling canister will be disconnected for this 

fueling just as for certification vehicles. Both certification 

and in-use vehicles will also have their gas caps loosened 

while awaiting testing in order to avoid any canister loading 

during that time. 

The specification of a 50 mile driving schedule for in-use 

vehicles is still tentative at this time. EPA believes that 

this amount of continuous driving should be sufficient to purge 

even a fully loaded canister for a refueling control system 

capable of passing the rest of the test procedure. However, 

data is still being gathered to verify this conclusion and it 

remains subject to change. The Agency desires to allow 

sufficient preconditioning to adequately purge the system, but 

also desires to minimize the overall testing time and expense. 

Following the initial capacity test, it is important that 

vehicles be standardized in a condition which will permit the 

subsequent testing to verify proper system purging. For this 

purpose, the recommended practice requires that the canister be 

fully loaded following the capacity test. This is accomplished 

by putting the vehicle in the SHED and repeatedly filling and 

draining the tank; in most cases, one or two fills should be 

enough. Saturation is detected by monitoring the SHED 
P.32 

-29-

hydrocarbon concentration with a FID; a sudden rise indicates 

break-through of vapors from the canister. Based upon limited 

EPA testing to date, the recommended practice defines this 

condition* as producing a change in the FID reading by a factor 

of at least 3 in a one minute period. 

A third aspect of preconditioning for refueling testing is 

the heating of the fuel in the fuel tank; this brings the 

liquid and vapor of the fuel into equilibrium as well as 

simulates the warmer fuel of a vehicle which has been driven. 

Four tank heating methods were tested by EPA as part of the 

baseline refueling emissions study. 

The four procedures tested included three types of heating 

with an electric blanket, and driving over an actual road 

route. "Single blanket" heating is the simplest of the 

preconditioning methods. It applies an electric heating pad to 

the bottom of the fuel tank, which imparts heat directly to the 

liquid fuel. This procedure was initially used with the 

constraint from the original SAE recommended practice that the 

temperature difference between vapor and liquid in the tank 

must remain within 6F° in order to maintain equilibrium 

throughout the heat build. It was, therefore, a relatively 

long procedure, taking one and a half to three hours to reach 

the desired temperature, because the fuel heating must be 

gradual in order stay within this constraint. "Dual blanket" 

heating was therefore evaluated, using a second heat blanket 

applied to the top of the tank. This method heats the vapor as 

well as the liquid and allows more rapid heating within the 6F° 

temperature difference constraint, typically requiring under 

one hour for heat build. It has the drawback of requiring the 

removal of the fuel tank to gain access to its top surface. 

A final type of blanket preconditioning was tested by. EPA 

in an attempt to eliminate the problems encountered with the 

first two methods: excessively slow heat builds for the single 

blanket, and the necessity of dropping the tank for the dual 

blanket. This preconditioning uses a single blanket but 

removes the constraint of no more than a 6F° temperature 

difference between the vapor and liquid during the heat build. 

Instead, the fuel is heated to the desired temperature as 

quickly as possible, which allows the vapor to be heated much 

more rapidly than with the original single blanket approach. 

Once the vapor temperature comes within 3F° of the liquid 

temperature and the temperature conditions prescribed in the 

test procedure have been reached, a ten minute waiting period 

is begun so that the vapor and liquid can attain equilibrium. 
-30-

This fast heat build single blanket method of preconditioning 

gives emission results similar to the slow heat build and dual 

blanket methods as shown in Figure 10, and has therefore been 

adopted for the recommended practice. 

The fourth method of preconditioning allows heating of the 

fuel by having the vehicle driven over an actual road route. 

The route involves three hours of rural and urban driving in 

the area near Ann Arbor, Michigan, and is run in order to 

approximate a real life situation. While not practical in 

itself due to its length and potential for variability, it 

confirms the appropriateness of blanket preconditioning by 

giving similar emissions results, as described in the baseline 

report.[16] 

E. Canister Purging and Vehicle Drivedown 

As mentioned previously, there are two key aspects of the 

refueling vapor control system which must both be tested in 

order to assure that emissions are being properly controlled. 

These are the capacity of the canister which captures the 

vapors and the capability of the system to purge these vapors 

during vehicle operation. These aspects must be tested without 

affecting the results of other portions of the test sequence. 

It is also desirable to keep costs low and testing time as 

short as possible, without placing an excessive burden on 

manufacturers. All this has to be accomplished while 

maintaining a representative and standardized test. 

To ensure adequate purge design, EPA has developed a 

vehicle drivedown sequence consisting of consecutive LA-4's and 

one hour hot soaks which are repeated until approximately 30 

percent of the fuel tank capacity has been consumed. This 

drivedown is then followed by a 30 percent refueling test to 

verify that the system has purged sufficient vapors to handle a 

proportionate refueling. 

Subsequent analysis of this drivedown requirement 

indicates that it may not be needed in all cases. Depending on 

the design of the refueling control system, the test sequence 

from initial canister capacity testing and subsequent 

saturation through the remainder of the existing FTP may be 

sufficient to ensure adequate refueling system performance. 

For those refueling control systems which are fully or 

partially integrated with the vehicle's evaporative emission 

controls, a substantial amount of system purge is required to 

pass the diurnal evaporative test following the initial 
Figure 10 

O 

13 

3 

COMPARISON OF REFUELING LOSSES 

R n —, O ,LJ 

7.5 -

7.0 -

6.5 -

6.0 -

5.5 -

5.0 -

4.5 -

A. n _ i •"+ . u 

+ 

i 

ESCORT - DISP.TEMP.= 8G RVP=11. 9 

D D 

n 

D 

+- + + 

D

 + . • 

+ 

1 1 1 1 1 i 1 1 1 1 

a 

D & 

1 1 1 

•2.0 0.0 2. 0 

STANDARD HEAT BUILD 

4.0 6.0 8.0 

DELTA T (DEGREES F) 

10.0 12. 0 

FAST HEAT BUILD 

14.0 

co 

J> 
P.35_ 

-32-

canister saturation step, and it may be that the stringency of 

this requirement is sufficient to ensure that the vehicle will 

also purge collected refueling vapors over the course of the 

drivedown sequence. 

As an initial test of this hypothesis, EPA evaluated the 

amount of vapors required to be purged for compliance with the 

diurnal evaporative emissions test in comparison with the 

amount of purge required to satisfy the drivedown requirement. 

This was initially done on the assumption that the refueling 

canister had a linear purge response as a function of canister 

loading. With this assumption the calculated purge rate for 

passing the diurnal test was approximately ten times the purge 

rate needed to pass the drivedown, and the drivedown appeared 

to be unnecessary. 

EPA then repeated the analysis, incorporating an estimate 

of the actual non-linear purge characteristics expected from 

the refueling canister. On this basis, the diurnal test 

requirement was only marginally adequate for ensuring 

sufficient refueling purge. The analysis also indicated that, 

since the canister purge rate continues to decline as the 

canister is purged, a 30 percent drivedown may not be adequate 

to account for system performance as an empty tank is 

approached. 

At this time it is unclear whether the drivedown is needed 

for integrated systems, or if it is, whether a 30 percent 

drivedown amount is sufficient. EPA is currently in the 

process of gathering more data on the purge characteristics of 

refueling and evaporative canisters and on ways to avoid the 

need for an extended vehicle drivedown. One option being 

considered is to replace the drivedown with the requirement 

that the refueling canister remain connected during the 40 

percent fill preceding the diurnal evaporative emissions test. 

The added purge required by this approach may turn out to 

correspond well with the performance characteristics of a 

refueling system capable of fully purging collected refueling 

vapors, and thus eliminate the need to further demonstrate 

purge capability via a drivedown. 

For refueling control systems which employ separate 

canister- systems for refueling emissions and evaporative 

emissions, the drivedown sequence appears to be unavoidable. 

The completely separate refueling system incurs no loading from 

evaporative emissions, so that the adequacy of the purge cannot 

be tested during the preconditioning cycle and evaporative 
P.36 

-33-

loading sequence in the FTP. In these instances, then, the 

purge test will have to be conducted, involving the 30% 

drivedown/refueling sequence appended to the usual sequence. 

At this time, the draft recommended practice includes a 

drivedown requirement for only those vehicles employing a 

non-integrated refueling control system. It remains possible, 

however, that the drivedown requirement, or some other 

modification to the test sequence, may be needed for integrated 

systems. 

F. Testing Requirements for In-Use Vehicles 

It is EPA's intent that motor vehicles meet emissions 

standards throughout their useful life, in order to best 

protect the public and environment from the harmful effects of 

mobile source pollutants. Certification of new motor vehicles 

is, of course, one major aspect of assuring that only vehicles 

likely to have low emission levels in-use are produced. In 

order to ensure that production vehicles continue to meet the 

standards throughout their useful lives, EPA routinely performs 

tests on in-use vehicles, following the certification testing 

procedure as closely as possible. However, some adjustments to 

the procedure are needed to accommodate in-use situations which 

are distinct from certification testing. 

EPA's proposals for handling the unique aspects of in-use 

emissions testing are discussed in this section. Included are 

the procedures to standardize the vehicles via preconditioning, 

as well as potential testing problems not encountered with 

specially-equipped certification vehicles. These issues have 

largely been identified by manufacturers, and EPA's approaches 

to resolving them are outlined here. The Agency remains open 

to further comments on preconditioning and testing of refueling 

emissions from in-use vehicles. 

1. Preconditioning Problems 

Residence Time Before Testing 

It is important, for fully or partially integrated 

systems, that vehicles not stand with a closed system for 

extended periods of time prior to the refueling test, as this 

may cause loading of the canister which is unrepresentative of 

a vehicle which is driven regularly. However, while vehicles 

are tested as soon as possible, it is not possible for EPA to 

assure that every vehicle brought to the test site will be 

tested soon after arrival, due to fluctuations in vehicle 
P.37 

-34-

procurement and test site/technician availability. Therefore, 

in order to keep the level of canister loading down, the 

refueling system will be opened by loosening or removing the 

gas cap to allow the escape of vapors. It should be noted that 

certification vehicles can also have their gas caps loosened 

upon arrival at the test site. 

Residual Fuel 

The variety of the RVP of fuels in the tanks of in-use 

vehicles could cause excessive variation in test results if 

such fuels were allowed to remain in the tank. Therefore, 

vehicles will have their tanks drained of residual fuel and 

will be preconditioned and tested only with the specified test 

fuel. For present testing, such fuel will have an RVP of 

11.5+0.5 psi; the fuel to be used in actual certification and 

in-use enforcement testing will be specified after further 

investigation, and will be similar to average in-use fuels. 

Manufacturers have also expressed concern that consumer 

use of high RVP fuels will cause long-term effects on the 

refueling and/or evaporative system which will significantly 

affect test results. These concerns are, in the Agency's 

opinion, unwarranted. First of all, as already noted, EPA is 

changing its test fuel to more closely match in-use fuels. 

Therefore, normally available fuels should not differ widely 

from certification fuels. Secondly, vehicles should be 

designed so that systems are not permanently disabled by the 

use of any normally available fuel, and in fact should remain 

largely operational. Any loss in function should be restored 

by adequately preconditioning with the test fuel. This is not 

to say that concern about such things as alcohol additives, 

which may damage emission controls if used improperly, is 

unwarranted. Such an issue is simply beyond the scope of this 

proposal, and must be dealt with separately. 

Finally, manufacturers have expressed a desire that the 

test fuel used for residual tank fuel be weathered, i.e., have 

a lower RVP than the dispensed fuel. EPA has considered the 

use of weathered fuel, as described earlier, and decided 

against it. Weathered tank fuel increases emissions slightly, 

but not enough to warrant the added complexity of handling two 

test fuels. Such a decision should not be objectionable to 

manufacturers since it reduces the stringency of the test 

somewhat. 
-35-

In-Use Driving Patterns 

The driving patterns encountered in-use can affect 

refueling emissions control by altering the purge capability of 

the refueling system. Permanent damage to the system caused by 

a low trip frequency and corresponding low level of purge is a 

manufacturer concern, but, in Agency opinion, should not 

occur. Like the effects of various fuels, a range of normal 

driving patterns should not cause any irreversible disablement 

of systems; that is, vehicles should be designed to withstand 

the vast majority of in-use conditions. A proper 

preconditioning cycle should be able to standardize vehicles 

which will have arrived at the test site under a variety of 

driving conditions. 

The procedure currently to be used involves driving the 

vehicle for 50 miles on the durability driving schedule or 

equivalent, on a tank of standard test fuel. This is intended 

to allow the system to purge the canister, thereby restoring 

the system, and should adequately standardize the purge level 

of in-use vehicles for subsequent testing. As noted in earlier 

discussion of vehicle preconditioning, EPA is open to comment 

should manufacturers have information showing that this 

preconditioning cycle will not meet their needs, or have 

suggestions for alternative preconditioning for canister purge. 

Fuel Tank Heating 

An additional aspect of preconditioning involves fuel tank 

heating, which further standardizes the vehicles by attaining a 

uniform tank temperature and liquid/vapor equilibrium. Tank 

heating is often done using the dual blanket method discussed 

in Section III.D., which was originally presented by EPA as the 

chosen method for refueling testing. However, this method 

presents practical problems for in-use vehicles, since it 

involves dropping the fuel tank from its normal position. On 

the other hand, the traditional single blanket method, with a 

constraint of a maximum 6F° difference between liquid and vapor 

fuel temperatures, requires several hours to complete, and so 

is also undesirable. 

In response to these problems, a new method was devised 

which is much quicker than the original single blanket method 

and requires no major alterations of the. vehicle. This method 

allows rapid heating of the liquid with the use of a single 

blanket applied beneath the tank. Upon arrival of the liquid 

fuel at the specified temperature, the vapor and liquid are 
P.39 

-36-

allowed to come into equilibrium during a 10 minute waiting 

period, once they are within a 3F° difference. Rapid single 

blanket heating gives results comparable to other methods, and 

is the method that will be used on in-use vehicles to save time 

and keep consumer vehicle fuel systems intact. 

2. Testing Problems 

Canister Disconnect 

The recommended practice contains several steps which 

require the refueling canister to be disconnected in order to 

avoid excessive loading with vapors. Manufacturers have 

expressed the concern that the canister may be inaccessible for 

disconnect, and that the integrity of the vapor line seal upon 

reconnect may be suspect, causing leaks or spillage. 

It is EPA's expectation that the easiest way to allow for 

the refueling canister to be disconnected for testing will be 

through the insertion of a valving mechanism in the vapor 

line. This would be done during initial vehicle preparation, 

allowing adequate opportunity for the integrity of the vapor 

line seals to be verified. Thereafter, the required canister 

disconnects can be produced through simple operation of the 

valve. As for accessibility, EPA does not believe that the 

requirement for vapor line accessibility poses any serious 

design constraint to manufacturers. 

Test Voids 

Tests which do not meet specifications will need to be 

aborted and rerun, and it is apparent that these vehicles will 

need to be rest andardi zed and reenter the test sequence at an 

appropriate point. For the refueling test there are several 

convenient places where partial testing can be restarted to 

avoid having to rerun the entire sequence in the case of a test 

void. 

For those vehicles which have not completed the initial 

refueling capacity test, the prime concern will be to return 

the canister to a purged condition similar to that with which 

it entered the test. This can be accomplished by recycling the 

vehicle through the preconditioning sequence for in-use 

vehicles (50 mile drive sequence) and beginning the testing 

anew. 
P.40 

-37-

For vehicles which have completed the refueling capacity 

test and subsequent canister saturation, but which have not yet 

completed the diurnal test, it will be sufficient, in the event 

of a test void, to return to the canister saturation step and 

proceed from there. Subsequent to the diurnal test and prior 

to beginning the drivedown test, the current FTP remains 

essentially unchanged and test voids may be handled according 

to current practice. 

The last portion of the refueling test is the drivedown 

and partial refueling test. A test void during the refueling 

operation here can be accommodated by completing the prescribed 

amount of fill, repeating the drivedown sequence (appropriately 

calculating the required amount of driving and refueling) and 

repeating the refueling test. 

As the above discussions indicate, EPA believes that the 

recommended practice as currently designed adequately deals 

with issues of concern relative to testing in-use vehicles. Of 

course, EPA is always open to further comments concerning the 

appropriateness of these solutions, and to alternate solutions 

should these be deemed unsatisfactory. 
P.41 

References 

1. "Evaluation of Air Pollution Regulatory Strategies for 

Gasoline Marketing Industry," (EPA-450/3-84-012a), U.S. EPA, OAR, 

OAQPS and OMS, July 1984. 

2. "Instrumentation and Techniques for Vehicle Refueling 

Emissions Measurement," SAE Recommended Practice J1045, August 1973. 

3. "Investigation of Passenger Car Refueling Losses," 

(SRL 2874-12-0972), Scott Research Laboratories. 

4. "Summary and Analysis of Data from Gasoline Temperature 

Survey Conducted by American Petroleum Institute," Radian 

Corporation, May 1976. 

5. "Analysis of Temperature Effects on Gasoline Marketing 

Operations," API Publication No. 1625, American Petroleum 

Institute, January 1979. 

6. "Testing of Union Oil's Vapor Balance Service Station 

Vapor Control System by the California ARB Test Procedure," 

Memorandum from Donald C. Gearhart, Assistant Counsel, Union Oil 

Company of California, to Members of API Subcommittee on 

Environmental Law, September 10, 1976. 

7. "Testing of a Vapor Balance Service Station Vapor 

Control System by the California ARB Test Procedure - Brea, June 

1976," Technical Memorandum from M.J. Dougherty, Refining and 

Products Research, Union Oil Company of California, to Mr. Cloyd P. 

Reeg, August 19, 1976. 

8. "Efficiency Evaluation of Union 76 Balance-Type Stage II 

Vapor Control System with OPW 7VC Dispensing Nozzles - Attendant 

Serve Operating Mode," Scott Environmental Technology, August 30, 

1979. 

9. "Healy Phase II Vapor Recovery System Certification 

Report," Scott Environmental Technology, June 1982. 

10. "A Service Station Test of a Vapor Balance System for 

the Control of Vehicle Refueling Emissions," A.M. Hochhauser and 

L.S. Bernstein, Exxon Research and Engineering Company, July 1, 

1976. 

11. "Efficiency Evaluation of Emco Wheaton A3006 Dispensing 

Nozzle," Scott Environmental Technology, July 8, 1981. 
References Cont'd. 

12. Letter from Edward P. Crockett, American Petroleum 

Institute, to Charles L. Gray, U.S. EPA, regarding fuel flow rates, 

August 8, 1984. 

13. Annual Book of ASTM Standards, Part 23, Standard 

D439-83, American Society for Testing and Materials, 1983. 

14. "A Study of Variables that Affect the Amount of Vapor 

Emitted During the Refueling of Automobiles," Edward M. Liston, 

Standford Research Institute, May 16, 1975. 

15. "1981-83 Standard Metropolitan Statistical Area (SMSA) 

Air Quality Data Base for Use in Regulatory Analyses," Technical 

Memorandum from Richard G. Rhoads, U.S. EPA, MD-14, to Charles L. 

Gray, U.S. EPA, OMS, February 25, 1985. 

16. "Refueling Emissions from Uncontrolled Vehicles," Dale 

Rothman and Robert Johnson, EPA-AA-SDSB-85- , July 1985. 

17. "Fuel Volatility Trends," Final Report, Letter from 

Bruce B. Bykowski, Southwest Research Institute, to Craig Harvey 

and Amy Brochu, U.S. EPA, September 28, 1984. 

18. The Weather Almanac, Third Edition, James A. Ruffner and 

Frank E. Bair, Ed., Gale Research Company: Detroit, 1981. 

i 

A.