United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/2-78-051
OAQPS No. 1.2-119
December 1978
Air
Control of Volatile
Organic Compound Leaks
from Gasoline Tank
Trucks and Vapor
Collection Systems
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EPA-450/2-78-051
OAQPS No. 1.2-119
Control of Volatile Organic Compound
Leaks from Gasoline Tank Trucks
and Vapor Collection Systems
Emission Standards and Engineering Division
Chemical and Petroleum Branch
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 2771 1
December 1978
- : '-H - (5PL-1C-J
.-o-v. •.. ,'/.'reet, Hooni
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OAQPS GUIDELINE SERIES
The guideline series of reports is being issued by the Office of Air Quality Planning and Standards (OAQPS) to
provide information to state and local air pollution control agencies; for example, to provide guidance on the
acquisition and processing of air quality data and on the planning and analysis requisite for the maintenance of
air quality. Reports published in this series will be available - as supplies permit - from the Library Services Office
(MD35), U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, or, fora nominal
fee, from the National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161.
Publication No. EPA-450/2-78-051
(OAQPS No. 1.2-199)
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TABLE OF CONTENTS
Page
I. Background 1
A. Need to Regulate 1
B. Control Approach 2
II. Regulatory Approach 2
A. Affected Facilities 2
B. Recommended Regulation 3
C. Monitoring Requirements 4
D. Record Keeping and Reporting Requirements .... 4
E. Other Considerations 5
III. Compliance Test Method and Monitoring Techniques ... 5
A. Compliance Test Method Description 6
B. Description of Monitoring Techniques 8
C. Vapor Control System Monitoring 13
IV. References 14
Appendix A
Pressure-Vacuum Test Procedure for Leak
.Tightness of Truck Tanks A-l
Appendix B
Gasoline Vapor Leak Detection Procedures by Combustible
Gas Detector B-l
Appendix C
Leak Detection Procedure for Bottom-Loaded Truck Tanks
by Bag Capture Method C-1
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ABBREVIATIONS AND CONVERSION FACTORS
EPA policy is to express all measurements in Agency documents in metric
units. Dual units are sometimes given in the text for clarity. Listed
below are abbreviations and conversion factors for English equivalents
of metric units. Frequently used measurements are also presented in dual
units below for the reader's convenience.
METRIC UNIT ALTERNATE UNIT CONVERSION
centimeter (cm)
Pascals (Pa)
liters (1)
inches
atmospheres
inches of water
gallons
cm x 0.394 = in
Pa x 9.87 x 10"6 = atm
inch
of water
Pa x 4.02 x 10"3 = inches
1 x 0.264 = gal
FREQUENTLY USED MEASUREMENTS
750 pascals ^ 3 inches of water
1500 pascals ^ 6 inches of water
4500 pascals ^ 18 inches of water
6250 pascals ^ 25 inches of water
2.5 cm ^ 1 inch
.625 cm ^ 1/4 inch
20,000 liters ^ 5280 gallons
IV
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I. BACKGROUND
This guideline is related to the control of volatile organic compounds
(VOC) from gasoline tank trucks and vapor collection systems at bulk terminals,
bulk plants and service stations. Guideline documents have already been
12 3
published on bulk plants, bulk terminals and service stations. The intent of
this guideline is to define leak tight conditions and related test procedures
for vapor collection systems and tank trucks while loading and unloading at
these facilities. VOC emitted from leaks in collection equipment are primarily
C. and C5 paraffins and olefins which are photochemically reactive (precursors
to oxidants).
Methodology described in this guideline represents the presumptive norm
or reasonably available control technology (RACT) that can be applied to an
existing facility. RACT is defined as the lowest emission limit that a
particular source is capable of meeting by the application of control technology
that is reasonably available considering technological and economic feasibility.
It may require technology that has been applied to similar, but not necessarily
identical, source categories. It is not intended that extensive research and
development be conducted before a given control technology can be applied to the
source. This does not, however, preclude requiring a short-term evaluation
program to permit the application of a given technology to a particular source.
This latter effort is an appropriate technology-forcing aspect of RACT.
A. NEED TO REGULATE
Control techniques guidelines are being prepared for source categories
that emit significant quantities of air pollutants in areas of the country
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where National Ambient Air Quality Standards (NAAQS) are not being attained.
Vapor balance and processor systems have been applied to bulk plants, terminals,
and service stations in many areas of the nation. Leaks from tank trucks and
vapor collection systems should be minimized to ensure that vapor control
systems at these systems function effectively.
B. CONTROL APPROACH
The approach described in this document is to ensure that good maintenance
practices are followed. Maintenance would be enforced through the surveillance
and periodic testing of suspect leak points. It should be noted that while
some leak sources (such as vapor piping joints) may stay in leak tight condition
for extended periods of time, others (such as pressure and vacuum vents, and
hatch seals) may leak shortly after maintenance. It is expected that compliance
with the suggested control measure will in some cases require replacement of
truck pressure and vacuum vents and dome covers. In addition, a greater degree
of surveillance and maintenance will be needed at bulk plants and terminals
equipped with top loading (vapor head) systems than at those using bottom
loading. Additional information on control techniques, costs, and monitoring
4
procedures is presented in an EPA report.
II. REGULATORY APPROACH
A. AFFECTED FACILITIES
The two separate affected facilities are gasoline tank trucks that are
equipped for vapor collection and the vapor collection systems at bulk
terminals, bulk plants, and service stations that are equipped with vapor
balance and/or vapor processing systems.
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B. RECOMMENDED REGULATION
B.I Gasoline Tank Trucks
Gasoline truck tanks and their vapor collection systems shall not
sustain a pressure change of more than 750 pascals (3 inches of H20) in
5 minutes when pressurized to 4500 pascals (18 inches of water) or evacuated
to 1500 pascals (6 inches of water) using the test procedure described in
Appendix A. In addition, there are to be no avoidable visible liquid leaks.
Invariably there will be a few drops of liquid from disconnection of dry
breaks in liquid lines even when well maintained; these few drops should
be allowed.
B.2 Vapor Collection Systems
B.2.1 - During loading or unloading operations at service stations,
bulk plants and bulk terminals, there shall be no reading greater than or equal
to 100 percent of the lower explosive limit (LEL, measured as propane) at
2.5 centimeters around the perimeter of a potential leak source as detected
by a combustible gas detector using the test procedure described in Appendix B.
In addition, there are to be no avoidable visible liquid leaks. Invariably
there will be a few liquid drops from the disconnection of well maintained
bottom loading dry breaks and the raising of well maintained top loading
vapor heads; these few drops should be allowed. The vapor collection system
includes all piping, seals, hoses, connections, pressure-vacuum vents, and
other possible leak sources between the truck and the vapor processing unit
and/or the storage tanks and vapor holder; and .
B.2,2 - The vapor collection and vapor processing equipment must
be designed and operated to prevent gauge pressure in the tank truck from
exceeding 4500 pascals (18 inches of water) and prevent vacuum from exceeding
1500 pascals (6 inches of water).
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C. MONITORING REQUIREMENTS
C.I Gasoline Tank Trucks
Gasoline truck tanks must be certified leak tight as described
in Section B.I annually.
In addition, truck tanks can be monitored by regulatory agencies as
needed during loading and unloading using the combustible gas detection
procedure described in B.2.1, provided that the requirements in Section
B.2.2 are met. Trucks with leaks greater than or equal to 100 percent of
the LEL are to be repaired within 15 days and be required to take and pass
the pressure and vacuum test described in Section B.I The truck tank and
its vapor collection system includes all piping, seals, hoses, connections, hatch
covers, pressure vacuum vents, vapor hoods and other possible leak sources
on the truck tank.
C-2 Vapor Collection Systems
Vapor collection systems can be monitored by regulatory agencies
as needed using the combustible gas detection procedure described in
B.2.1.
D. RECORD KEEPING AND REPORTING REQUIREMENTS
D.I Gasoline Tank Trucks
Each truck must have a sticker displayed on each tank indicating
the identification number of the tank and the date each tank last passed the
pressure and vacuum test described in Section B.I. This sticker must be
located near the Department of Transportation Certification plate (DOT,
Title 49, Part 178.340-lOb).
D.2 Vapor Collection System
Bulk terminal, bulk plant and service station owners or operators must
keep records for two years indicating the last time the vapor collection facility
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passed the requirements described in B.2 and identifying points at which
VOC leakage exceeded the provisions of Section B.2.1.
E. OTHER CONSIDERATIONS
Presently, there is limited information available on the amount of
monitoring necessary to ensure that leaks are kept to the limits described
above. Therefore, regulations should allow for modifications in the monitoring
schedule when experience proves it to be either inadequate or excessive.
If, after over one year of monitoring, i.e., at least two complete annual
checks, the operator of an affected facility feels that modifications
of the requirements are in order, he may request in writing to the air
pollution control officer that a revision be made. The submittal should
include data that have been developed to justify any modifications in the
monitoring schedule. On the other hand, if the air pollution control officer
finds an excessive number of leaks during an inspection, or if the operator
finds an excessive number of leaks during scheduled monitoring, consideration
should be given to increasing the frequency of inspections.
III. COMPLIANCE TEST METHOD AND
MONITORING TECHNIQUES
The measurement procedures that were developed for determining leak
tightness of truck tanks and vapor control systems at bulk terminals,
bulk plants, and service stations, are discussed in this section. The
presentation covers the various methods considered with the advantages
and disadvantages of each, testing problems encountered, and the accuracy,
reliability, and allowable modifications of the recommended methods.
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A. COMPLIANCE TEST METHOD DESCRIPTION
A.I General Description and Background^
The recommended compliance test method as detailed in Appendix A
can be used to determine the leak-tightness of gasoline truck tanks. Pressure
and vacuum are applied to the tanks of a gasoline delivery truck and the
change in pressure/vacuum is recorded after a specified period of time.
The recommended regulation in Section II.B.I in effect defines a "leak
tight condition" which is equivalent to 99 percent recovery efficiency during
vapor transfer from a truck tank. The recommended compliance procedure is
actually an equipment performance criteria rather than a true emission
measurement test. However, emissions from a truck tank can be estimated
from the known required degree of leak-tightness.
Developmental work on a leak test method was performed by the California
Air Resources Board (CARB), San Diego Air Pollution Control District (SDAPCD),
and Standard Oil of California, among others. Leak-tightness regulations
have been in effect in California for over two years. The pressure and
vacuum limits recommended in Section II.B.I are based on a consensus of the
above mentioned groups, and on an EPA field testing program which was
conducted in order to evaluate the leak test method and performance criteria.
The study shows that EPA's recommended performance criteria is realistic
and achievable and the test method is inexpensive, reliable, and repeatable.5
A.2 Modifications
There are two areas of common modifications to the test procedure in
Appendix A.
The recommended EPA compliance test procedure uses air to
pressurize and evacuate the truck tank. In EPA field testing, this was
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found to be the most convenient and inexpensive procedure. However, some
owners prefer loading and draining the tank with a liquid, usually diesel
fuel or water, to create the required pressure and vacuum. This is an
acceptable and equivalent alternative.
The EPA procedure also requires that gasoline vapors be purged from
the truck tank before conducting the leak-tightness test. This is easily ac-
complished by carrying a diesel load immediately prior to the compliance test
or blowing air into the tank with the dome lids open. Gasoline vapors
in the tank cause testing inconsistencies. With volatile vapors, the tank
pressure varies more readily with slight changes in temperature. However
it is possible to test without purging the gasoline vapors if there is
enough time for the vapors to stabilize and reach a constant temperature
in the covered testing area. One can ensure that the vapors have stabilized
and are not affecting the test results by conducting the test two times
with the same results.
A. 3 Effectiveness
The EPA field testing program6 and a recent CARB study both
indicate that truck tanks rarely remain in a leak-tight condition within
two or three months after the compliance test. After the initial leak-
tightness compliance test, the leaks that occur are usually easily
detectable and correctable with good normal maintenance. It is hoped that
conducting unannounced spot-checks with monitoring procedures described in
the following section, will encourage more frequent and effective
maintenance.
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B. DESCRIPTION OF MONITORING TECHNIQUES
B.1 Background
Monitoring techniques for leak detection were developed to ensure the
continuing existence of leak-tight conditions between compliance tests.
A test method was sought that would give pass/fail compliance information
for leakage from truck tanks and vapor control systems at bulk terminals,
bulk plants, and service stations. It was desired that the monitoring
test method be low cost, quick, and used without disturbing normal
operations. It is essential that leak detection by a monitoring technique be
be equivalent to the leak-tightness criteria of the pressure/vacuum
compliance test.
Several leak detection monitoring methods were investigated in EPA's
field testing program: combustible gas detector, sonic detector, bubble
indication, sensory detection (i.e., sound, sight, smell, touch), vapor to
liquid volume ratio, quick leak decay, and bag capture. Bag capture and
combustible gas detector were both found to be reliable, quick, low cost,
and closely equivalent to the compliance criteria. The recommended method
is the combustible gas detector procedure because it is more reliable and
can be applied to top and bottom-loaded tanks. However, the bag capture
procedure is an acceptable alternative for leak detection of bottom-loaded
tanks. A discussion of the other non-recommended methods is included.in
Q
an EPA contractor report.
B.2 Description of Combustible Gas Detector Procedure
B.2.1 - Selection and applicability. The combustible gas detector
is the recommended leak detection method because it is simple, quick,
inexpensive, reliable, and non-subjective. It can be used for leak
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detection of truck tanks and vapor control systems without disturbing
normal operations. Although a combustible gas detector is often considered
a qualitative monitoring instrument, the detailed specifications of its
use and operation, as defined in Appendix B, make this an acceptable
procedure.
Leak detection of truck tanks by combustible gas detector
correlates well with the pressure/vacuum compliance criteria in Section
II.B.I, when a leak is defined as a meter reading greater than or equal to
100 percent LEL as propane. The monitoring procedure will correctly
identify 42 percent of the non-complying tanks, while incorrectly identifying
only 5 percent of the complying tanks. The combustible gas detector pro-
cedure is purposely designed to detect gross violations of the leak-
tightness performance criteria, but will not confirm compliance, i.e.
tanks with marginal violations will evade detection.
B.2.2 - Equipment and operation specifications. In order to make
leak detection by combustible gas detector more reliable and repeatable,
equipment and operation specifications are tightly defined . For valid
monitoring, it is important that the procedure is the same as the one used
in EPA's field testing and data collection.
Equipment specifications require that the meter is calibrated to
propane, inside probe diameter is 0.625 cm (1/4 inch), and response time
for full-scale deflection with the sampling probe and line attached is less
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than 8 seconds. A standard calibration gas is needed to standardize the detector
response. The selection of propane as the calibration gas is arbitrary.
Propane was used for calibration in the data gathering tests, and it is
probably the most readily available gas.
The probe diameter requirement allows some dilution air drawn in if
the leak is very small, and thus the detector will not register a leak. If
the same leak were sampled with a smaller diameter probe, the sample line
would be filled with leaked vapors with no dilution, and a leak would be
detected. Thus, a larger probe diameter ensures that only insignificant
leaks are registered.
The response time requirement ensures that the meter pump is strong
enough to draw the sample quickly through the sampling probe and line. This
quick response is necessary since there is little time during a loading to
check air potential sources of leakage.
Operation of the combustible gas detector for leak monitoring is
also tightly defined to eliminate variability. However, any arbitrariness
or sloppiness in the procedure is in favor of the truck tank owner.
Operation specifications require measurement at 2.5cm (1 inch) distance from the
leak source, positioning the probe in the path of (parallel to) the vapor
flow, moving the probe slowly locating the point of highest meter response, and
blocking wind interference when possible. Measurement at 2.5cm distance allows
some dilution if only a very small leak exists. The distance can be maintained
during monitoring by putting a 2.5cm extension on the probe tip. Maintaining
this distance is essential or else insignificant leaks will be detected.
Higher meter readings will be obtained when the probe is properly
positioned, moved slowly, and if care is taken to locate the center of a
leak. These specifications were followed diligently in the testing which
was used to develop the data base and correlation with the compliance test.
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Any sloppiness in these areas would detect less leaks and be in favor
of the truck. Furthermore, the field testing was conducted on windless,
hot days. Winds would dilute the vapors before detection, and cooler
temperatures would reduce the hydrocarbon concentration. Again, under these
conditions, the meter would detect less leakage, and the variability in the
method favors the truck tank owners.
B.2.3 - Modifications. It should be noted that the adequacy of the
combustible gas detector method, and the LEL level where the method is usable,
are based on the performance test criteria in Section II.8.1. If other
criteria are used to define a leak-tight tank, the detector method will have
to be re-evaluated to determine the applicable LEL level to be used for
monitoring.
The combustible gas detector method can be made less stringent by simply
increasing the sampling distance. However, this is not recommended since the
purpose of monitoring is to ensure compliance, and the recommended procedure
is closely equivalent to the leak-tightness performance test.
B.3 Description of Bag Capture Procedure
B.3.1 - Background. The bag capture procedure is an acceptable
alternative method for leak monitoring of bottom-loaded truck tanks. The
complete procedure is included in Appendix C. The procedure was developed
by San Diego Air Pollution Control District, and has been in use for over
two years. The volume of leakage is measured directly by placing calibrated
bags over all dome covers. The volume of allowable leakage is calculated
from the parameters of the pressure/vacuum compliance test (as shown in
equation 7.1, Appendix C).
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This procedure, like the combustible gas detector, is designed to
detect gross violations while not detecting marginal violations. Again,
any sloppiness or variability in the method is in the favor of the truck
tank. Only leakage from dome covers, hatches, and relief valves is
captured; leakage from the tank vapor collection system is not included.
If the seal between the bag apparatus and tank is not tight enough, the leakage
may be underestimated. Furthermore, the allowable volume of leakage is
based on 4500 pascals (18 inches H20) pressure, which rarely occurs during
loadings.
B.3.2 - Disadvantage and Advantages. This method does have
serious drawbacks. It can only be applied to bottom-loaded tanks. Some
tanks cannot be monitored because the equipment configuration prevents a
tight seal. Also, not all potential leakage sources are monitored.
On the other hand, the method has some real advantages. The equipment
is very inexpensive and easy to use. It can be applied regardless of the
type of vapors inside. Emissions can be measured directly, instead of by
estimation. In San Diego, with this method, a leak has never been
incorrectly detected for a complying tank. Finally, the bag method can
be modified to detect leaks for any degree of leak-tightness if the
parameters of the performance test are altered.
Many agencies and companies resist the use of a combustible gas
detector. The bag capture method is a good alternative. It is probably
less stringent than the explosimeter, but it will still detect all gross
violations.
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C. VAPOR CONTROL SYSTEM MONITORING
C.I Pressure and Vacuum Limits.
The regulation in Section II.B.2.2 requires that the pressure/
vacuum in a vapor control system remain within the pressure/vacuum limits
of the truck tank compliance test. This ensures that a vapor control
system will not create a leak on a tank. During leak detection monitoring
of the tanks, the pressure must remain within these limits or else the
detection of any leak will be invalidated.
C.2 Leak Detection.
The combustible gas detector procedure in Appendix B can be
applied to potential sources of leakage at terminal, plant, and service
station vapor control systems. These points of leakage can be easily
identified and corrected during normal maintenance, and once corrected
remain in leak tight condition for extended periods of time.
This application of the combustible gas detector procedure is a
qualitative measurement; there is no way to relate this leak detection to
emission levels.
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IV. REFERENCES
1. "Control of Volatile Organic Emissions From Bulk Gasoline Plants,"
U.S. EPA, Report No. EPA-450/2-77-035, Office of Air Quality Planning and
Standards, Research Triangle Park, North Carolina, November 1977.
2. "Control of Hydrocarbons From Tank Truck Gasoline Loading Terminals,"
U.S. EPA, Report No. EPA-450/2-77-026, Office of Air Quality Planning and
Standards, Research Triangle Park, N.C., October 1977.
3. "Design Criteria for Stage I Vapor Control Systems, Gasoline Service
Stations," U.S. EPA, Office of Air Quality Planning and Standards, Research
Triangle Park, N.C., November 1975.
4. "Gasoline Tank Trucks and Bulk Plants: Evaluation of Vapor Leaks and
Development of Monitoring Procedures," Pacific Environmental Services, Inc.
prepared for U.S. EPA, Emission Standards and Engineering Division, Draft
report, September 1978.
5. "Leak Testing of Gasoline Tank Trucks," Scott Environmental Technology,
Inc., prepared for U.S. EPA, Emission Standards and Engineering Division,
Draft report, August 10, 1978.
6. Reference 4, Op. Cit.
7. "Investigation of the Compliance of Vapor Recovery Equipment at Gas'oline
Bulk Terminals in the South Coast Air Quality Management District and
Kern County Air Pollution Control District," State of California Air Resources
Board, Report No. LE-78-003, November 8, 1978.
8. Reference 4, Op. Cit.
9. Reference 4, Op. Cit.
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APPENDIX A
PRESSURE-VACUUM TEST PROCEDURES
FOR LEAK TIGHTNESS OF TRUCK TANKS
1. PRINCIPLE
Pressure and vacuum are applied to the compartments of gasoline
truck tanks and the change in pressure/vacuum is recorded after a
specified period of time.
2. APPLICABILITY
This method is applicable to determining the leak tightness of
gasoline truck tanks in use and equipped with vapor collection
equipment.
3. DEFINITIONS
3.1 Truck tank. Any container, including associated pipes and
fittings, that is used for the transport of gasoline.
3.2 Compartment. A liquid-tight division of a truck tank.
3-3 Truck tank vapor collection equipment. Any piping, hoses, and
devices on the truck tank used to collect and route the gasoline
vapors in the tank to the bulk terminal, bulk plant, or service
station vapor control system.
4. APPARATUS
4.1 Pressure source. Pump or compressed gas cylinder of air or inert
gas sufficient to pressurize the truck tank to 6250 pascals
(25 inches H~0) above atmospheric pressure.
4.2 Regulator. Low pressure regulator for controlling pressurization of
the truck tank.
4.3 Vacuum source. Vacuum pump capable of evacuating the truck tank
to 2500 pascals (10 inches H20) below atmospheric pressure.
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4.4 Manometer. Liquid manometer, or equivalent, capable of measuring
up to 6250 pascals (25 inches H20) gauge pressure with - 25 pascals
(- 0.1 inch f^O) precision.
4.5 Test cap for vapor recovery hose fittings. This cap should have a
tap for manometer connection and a fitting with shut-off valve for
connection to the pressure/vacuum supply hose.
4.6 Pressure/vacuum relief valves. The test apparatus shall be equipped
with an in-line pressure/vacuum relief valve set to activate at
7000 pascals (28 inches H20) above atmospheric pressure or 3000
pascals (12 inches H20) below atmospheric pressure, with a capacity
equal to the pressurizing or evacuating pumps.
4.7 Caps for liquid delivery line.
4.8 Pressure/vacuum supply hose^.
5. PRETEST CONDITION
5.1 Purging of vapor. The truck tank shall be purged of gasoline
vapors and tested empty. The tank may be purged by any safe
method such as flushing with diesel fuel or heating fuel.
5.2 Location. The truck tank shall be tested where it will HP
protected from direct sunlight.
6. TEST PROCEDURE
6.1 The dome covers are to be opened and closed.
6.2 Connect static electrical ground connections to tank. Attach the
delivery and vapor hoses, remove the delivery elbows, and plug
the liquid delivery fittings.
6.3 Attach the test cap to the vapor recovery line of the truck
tank.
A-2
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6.4 Connect compartments of the tank internally to each other if
possible. (If not possible, each compartment must be tested
separately.)
6.5 Connect the pressure/vacuum supply hose and the pressure/vacuum
relief valve to the shut-off valve. Attach the pressure source to
the hose. Attach a manometer to the pressure tap.
6.6 Open the shut-off valve in the vapor recovery hose cap. Applying
air pressure slowly, pressurize the tank, or alternatively the first
compartment, to 4500 pascals (18 inches H20).
6.7 Close the shut-off valve and allow the pressure in the truck
tank to stabilize, adjusting the pressure if necessary to maintain
4500 pascals (18 inches H20). When the pressure stabilizes, record
the time and initial pressure.
6.8 At the end of 5 minutes, record the time and final pressure.
6.9 Disconnect the pressure source from the pressure/vacuum supply
hose, and slowly open the shut-off valve to bring the tank to
atmospheric pressure.
6.10 Connect the vacuum source to the pressure/vacuum supply hose.
6.11 Slowly evacuate the tank, or alternatively the first compartment,
to 1500 pascals (6 inches H20).
6.-12 Close the shut-off valve and allow the pressure in the truck
tank to stabilize, adjusting the pressure if necessary to maintain
1500 pascals (6 inches H20) vacuum. When the pressure stabilizes,
record the time and initial pressure.
6.13 At the end of 5 minutes, record the time and final pressure.
6.14 Repeat steps 6.5 through 6.13 for each compartment if they were
not interconnected.
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7. ALTERNATIVE TEST METHODS
Techniques, other than specified above, may be used for purging and
pressurizing the truck tanks, if prior approval is obtained from the air
pollution control officer. Such approval will be based upon demonstrated
equivalency with the above method.
A-4
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APPENDIX B
GASOLINE VAPOR LEAK DETECTION PROCEDURE
BY COMBUSTIBLE GAS DETECTOR
1. PRINCIPLE
A combustible gas detector is used to indicate any incidence
of Jeakage from gasoline truck tanks and vapor control systems.
This qualitative monitoring procedure is an enforcement tool to
confirm the continuing existence of leak-tight conditions.
2. APPLICABILITY
This method is applicable to determining the leak-tightness of
gasoline truck tanks during loading without taking the truck
tank out of service. The method is applicable only if the vapor
control system does not create back-pressure in excess of the
pressure limits of the truck tank compliance leak test. For
vapor control systems, this method is applicable to determining
leak-tightness at any time.
3. DEFINITIONS
3.1 Truck tank. Any container, including associated pipes and
fittings, that is used for the transport of gasoline.
3.2 Truck tank vapor collection equipment. Any piping, hoses, and
- devices on the truck tank used to collect and route the gasoline
vapors in the tank to the bulk terminal, bulk plant, or service
station vapor control system.
3.3 Vapor control system. Any piping, hoses, equipment, and devices at
the bulk terminal, bulk plant, or service station, which is used
to collect, store, and/or process gasoline vapors.
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4. APPARATUS AND SPECIFICATIONS
4.1 Manometer. Liquid manometer, or equivalent, capable of
measuring up to 6250 pascals (25 inches H,,0) gauge pressure
with -25 pascals (0.1 inch H20) precision.
4.2 Combustible gas detector. A portable hydrocarbon gas analyzer with
associated sampling line and probe.
4.2.1 Safety. Certified as safe for operation in explosive „
atmospheres.
4.2.2 Range. Minimum range of 0-100 percent of the lower
explosive limit (LEL) as propane.
4.2.3 Probe diameter. Sampling probe internal diameter of
0.625 cm (1/4 inch).
4.2.4 Probe length. Probe sampling line of sufficient length
for easy maneuverability during testing.
4.2.5 Response time. Response time for full-scale deflection of
less than 8 seconds for detector with sampling line and
probe attached.
5. TEST PROCEDURE
5.1 Pressure. Place a pressure tap in the terminal, plant, or service
station vapor control system, as close as possible to the connection
with the truck tank. Record the pressure periodically during
testing.
5.2 Calibration. Calibrate the combustible gas detector with 2.2 per-
cent propane by volume in air for 100 percent LEL response.
B-2
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APPENDIX C
LEAK DETECTION PROCEDURE FOR BOTTOM-LOADED
TRUCK TANKS BY BAG CAPTURE METHOD
1, PRINCIPLE
The volume of leakage from a truck tank during loading is measured
directly by placing calibrated bags over all potential sources of leakage.
This quantitative monitoring procedure is an enforcement tool to confirm
the continuing existence of leak-tight conditions.
2. APPLICABILITY
This method is applicable to determining the leak-tightness of
truck tanks during bottom-loading without taking the truck tank out of
service. The method is applicable only if the vapor control system does
not create back-pressure in excess of the pressure limits of the truck
tank compliance leak test. This method cannot be applied to truck tanks
during top-loading, vapor collection equipment on truck tanks, or vapor
control systems at terminals, plants, or service stations.
3. DEFINITIONS
3.1 Truck tank. Any container, including associated pipes and fittings,
1 that is used for the transport of gasoline.
3.2 Compartment. A liquid-tight division of a truck tank.
3.3 Truck tank vapor collection equipment. Any piping, hoses, and
devices on the truck tank used to collect and route the gasoline
vapors in the tank to the bulk terminal, bulk plant, or service
station vapor control system.
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3.4 Vapor control system. Any piping, hoses, equipment, and devices
at the bulk terminal, bulk plant, or service statior; which is
used to collect, store, and/or process gasoline vapors.
4. APPARATUS
4.1 Manometer. Liquid manometer, or equivalent, capable of measuring
up to 6250 pascals (25 inches h^O) gauge pressure with +_ 25 pascals
(+. 0.1 inches H20) precision.
4.2 Plastic bag. An air-tight bag, large enough to cover the truck
tank's dome cover. One bag is needed for each compartment.
4-3 Bicycle tire. A bicycle innertube, or similar apparatus, modified
to the appropriate diameter to fit over the truck tank's dome cover
and lie flat on the top of the truck tank. One tire is needed for
each compartment.
4.4 Dry gas meter.
4.5 Pump.
4.6 Calibration piat form. A platform constructed such that air can be
introduced through hole in the center of platform, and large
enough for bicycle tire to lie flat on it.
5. BAG VOLUME CALIBRATION
5.1 Attach bag to innertube and seal with tape or other applicable
sealant to ensure no leakage around interface, »
5.2 Fill innertube with water.
5.3 Place bag apparatus on the calibration platform so that the air
inlet is situated under the bag.
5.4 Remove air from bag.
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5.5 Connect pump to dry gas meter and dry gas meter to inlet on the
calibration platform.
5.6 Pump air into bag until bag is full. Record the volume from the
dry gas meter and indicate volume on bag.
6. TEST PROCEDURE
6.1 Place a pressure tap in the terminal, plant, or service
station vapor control system, as close as possible to the connection
with the truck tank. Record the pressure periodically during testing,
6.2 During loadings, place a bag apparatus over the dome cover of
each compartment in the truck tank being filled.
6.3 Remove air from bags.
6.4 Check to ensure there is a tight seal between the base of the
bag apparatus and the top of the truck tank.
6.5 During loading, estimate volume of vapors collected in bags. If
a bag fills before loading is complete, empty bag and resume
testing.
6.6 Estimate total volume of vapors collected in the bags, making
allowances in the volumes for tank domes or other equipment
6.7 Record capacity of truck tank.
6.8 Determine allowable volume of vapor leakage from truck tank as
in Section 7.
6.9 Determine total loading time. This includes only time when filling
is actually occurring, not breaks during the loading operation.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
p. REPORT NCX
EPA 450/2-78-051
2.
4. TITLE AND SUBTITLE
Control of Volatile Organic Compound
Leaks from Gasoline Tank Trucks and Vapor Collection
Systems
7. AUTHOR(S)
Stephen A. Shedd, ESED, CPB
Nancy D. Mclaughlin, ESED, EMB
9 PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Emission Standards and Engineering Division
Research Triangle Park, North Carolina 27711
12. SPONSORING AGENCY NAME AND ADDRESS
RECIPIENT'S ACCESSION NO.
REPORT DATE
December, 1978
x PERFORMING ORGANIZATION CODE
I. PERFORMING ORGANIZATION REPORT NO~
OAQPS No. 1.2-119
!AM ELEMENT NO.
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
regulation and testing procedures.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
Air Pollution
Regulatory Guidance
Gasoline Tank Trucks
Gasoline Vapor Control Systems
Bulk Plants
Bulk Terminals
Service Stations
c. COSATI iMcld/Group
Air Pollution Control
Stationary Sources
Hydrocarbon Emissions
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
Unclassified
30
llimited
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION i s OBSOLETE
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