United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-90/050 Feb. 1991
& EPA Project Summary
Standard Test Procedures for
Evaluating Leak Detection
Methods: Pipeline Leak
Detection Systems
Joseph W. Maresca, Jr., Robert M. Smedfjeld, Richard F. Wise,
and James W. Starr
This report presents a standard test
procedure for evaluating the perfor-
mance of leak detection systems for use
in the pipelines associated with under-
ground storage tanks. The test proce-
dure is designed to evaluate these
systems against the performance stan-
dards of the U.S. Environmental Protec-
tion Agency's (EPA's) underground
storage tank (UST) regulations (40 CFR
Part 280, Subpart D), which cover an
hourly test, a monthly monitoring test,
and an annual line tightness test. The
test procedure can be used to evaluate
any type of system that is attached to
the pipeline and that monitors or mea-
sures either flow rate or changes in
pressure or product volume. This proce-
dure can be used to evaluate leak de-
tection systems that can relate the
measured output quantity to leak rate (in
terms of gallons per hour) and systems
that use an automatic preset threshold
switch. The test procedure can be used
to evaluate systems used to test pres-
surized pipelines or suction pipelines
that are pressurized for the test. The test
procedure offers five options for collect-
ing the data required to calculate perfor-
mance. The results of the evaluation are
reported In a standard format on forms
provided in the appendices of the report
summarized here.
This Project Summary was devel-
oped by EPA's Risk Reduction Engi-
neering Laboratory in Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
The EPA's regulations for underground
storage tanks require owners and opera-
tors to check for leaks on a routine basis
using one of a number of detection meth-
ods (40 CFR Part 280, Subpart D). To
ensure the effectiveness of these meth-
ods, the EPA has set minimum perfor-
mance standards for equipment used to
comply with the regulations. Deciding
whether a system meets the standards
has not been easy, and the EPA will not
test, certify, or approve specific brands of
commercial leak detection equipment. In-
stead, the EPA has developed and pub-
lished a series of standard test procedures
that describe how equipment should be
tested to prove that it meets the standards.
Each document on a type of system or
method explains how to conduct the test,
how to perform the required calculations,
and how to report the results. The results
from each standard test procedure provide
the information needed by tank owners
and operators to determine whether the
method meets the regulatory requirements.
The final report summarized here is part of
the series published by the EPA.
The performance results are reported
in terms of leak rate (in gallons per hour),
probability of detection (PD), and probabil-
ity of false alarm (PFA). The protocol ad-
dresses the performance of these leak
detection systems for the leak rates, PD, and
PFA specified in the EPA regulation. The
protocol covers all of the internal EPA
Printed on Recycled Paper
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release detection options for piping but
does not cover the external leak detection
options (those for vapor and groundwater
monitoring). Separate protocols have been
developed for these external systems.
Common types of leak detection systems
that can be evaluated with the protocol
summarized here include systems that
measure pressure, volume, or flow-rate
changes in the pipeline. Both pressurized
and suction piping systems are addressed,
and if release detection is required for a
suction system, it is assumed that the line
will be pressurized for the test.
The EPA regulation requires two types
of leak detection tests for underground
pressurized piping containing petroleum
fuels. First, underground piping must be
equipped with an automatic line leak de-
tector that will alert the operator to the
presence of a leak by restricting or shut-
ting off the flow of the regulated substance
through the piping or by triggering an audi-
tory or visual alarm. The automatic line
leak detector must be capable of detecting
Isaks of 3 gal/h defined at a line pressure
of 10 psi within an hour of the occurrence
of a leak and with a P? of 95% and a PFA
of 5%. The test is designed to detect the
presence of very large leaks that may oc-
cur between regularly scheduled checks
with the more accurate monthly monitoring
tests or annual line tightness tests. Many
of these systems use a preset-threshold
switch.
Second, the regulation also requires
either an annual line tightness test or a
monthly monitoring test. The annual line
tightness test must be capable of detecting
a leak as small as 0.1 gal/h (defined at a
pressure that is 150% of the operating
pressure of the line) with a PD of 95% and
a PFA of 5%. The monthly monitoring test
evaluated by this protocol must be capable
of detecting leaks as small as 0.2 gal/h
(defined at the operating pressure of the
line) with a Pp of 95% and a PFA of 5%. This
monthly monitoring test can be satisfied by
the use of any type of pipeline leak detec-
tion system (line pressure monitor, auto-
matic shutdown line leak detector, etc.)
that conducts a precision test on the pipe-
line system and that can satisfy the perfor-
mance requirements.
The evaluation protocol requires that
the performance characteristics of the in-
strumentation be estimated and that the
performance in terms of leak rate, PD, and
PFA be determined for the specified pipe-
line configuration and a wide range of
product temperature conditions. The prob-
ability of false alarm is estimated at the
threshold used by the manufacturer (the
threshold being the value at which a leak is
declared), and the probability of detection
is estimated at the leak rate specified in
the EPA regulation. With one slight differ-
ence, the same procedure is used to
evaluate the performance of the monthly
monitoring test, the annual line tightness
test, and the hourly automatic line leak
detection test. For the monthly monitoring
test, the probability of detection is estimated
at a leak rate of approximately 0.2 gal/h,
while for the line tightness test the prob-
ability of detection is estimated at a leak
rate of approximately 0.1 gal/h; a 3-gal/h
leak is used in the hourly test.
Options for Estimating
Performance
A complete specification of system per-
formance requires a statement of the PD at
a defined leak rate, a statement of the PFA,
and an estimate of the uncertainty of the
PD and PFA. The performance estimate
should be made over the range of condi-
tions under which the system will actually
be used. They can be made from a perfor-
mance model based on the histograms of
the noise and the signal-plus-noise. The
actual calculations will be made with an-
other representation of the histogram called
the cumulative frequency distribution.
To estimate the performance of a pipe-
line leak detection system, one must de-
velop histograms of the noise and the
signal-plus-noise. Each histogra.m gener-
ated according to this protocol requires a
minimum of 25 independent tests. This
number ensures that an estimate of the PD
of 95% and the PFA of 5% can be made
directly from the data and that the uncer-
tainty in the estimate of the PD and PFA, as
measured by the 95% confidence inter-
vals, is approximately 5%.
This protocol provides five options for
generating the data necessary to develop
noise and signal-plus-noise histograms.
The first option is to conduct the evaluation
at an instrumented test facility s,pecifically
designed to evaluate pipeline leak detec-
tion systems, and the second is to do it at
one or more operational LIST facilities that
are specially instrumented for the evalua-
tion. Both of these options require that the
data be collected under a specific set of
product temperature conditions, which are
measured as part of the test procedure,
and on a pipeline system that hais defined
characteristics. The instrumentation is
minimal and does not require that tem-
perature sensors be placed inside the
pipeline. The next two options require that
data be collected over a period of 6 to 12
months, either at 5 operational LIST facili-
ties where the integrity of the pipeline
systems has been verified, or at 10 or
more operational LIST facilities. The sta-
tions should be geographically located so
as to represent different climatic condi-
tions. Each of the operational UST facilities
selected should receive a delivery of
product to the tank at least once per week.
Options 3 and 4 should provide approxi-
mately the same range of temperature
conditions specified in Options 1 and 2
because of seasonal variations in the tem-
perature of the ground and the temperature
of the product delivered to the tank. In the
fifth option, a simulation is used to estimate
the performance of the leak detection
system. This simulation is developed from
experimentally validated mathematical
models of all the sources of noise that
affect the performance of a particular sys-
tem.
Generating the Noise Histogram
The primary source of noise for a pipe-
line leak detection system is the thermal
expansion and contraction of the product
in the line. Thus, the performance of most
pipeline leak detection systems is con-
trolled primarily by temperature changes in
the product that is in the line. These
changes are present unless no product
has been pumped through the pipeline for
many hours. To take these changes into
account, the protocol requires that all leak
detection systems be evaluated under a
wide range of temperature conditions.
The range of temperature conditions
used in this protocol is based on the re-
sults of an analytical study of the climatic
conditions found throughout the United
States. The study estimated the average
difference in temperature, AT, between the
product in the tank and the temperature of
the ground around the pipe. The results
indicated that values of ±25°F would cover
a wide range of conditions. All systems will
be evaluated in accordance with their own
test protocols under the matrix of tempera-
ture conditions given in Table 1. The pro-
tocol in this document describes specifically
how to create these conditions.
Table 1 summarizes the number of tests
that must be done for each of the nominal
conditions for which histograms must be
generated. A temperature condition is
generated by circulating product for 1 h or
longer at one temperature through a pipe-
line system surrounded by backfill and soil
at another temperature. It is assumed that
the temperature conditions within the range
of each 10°F increment will be as uni-
formly distributed as possible. This is par-
ticularly important for the conditions
centered on 0°F; about half of the condi-
tions should be positive and about half
should be negative.
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Table 1. Number of Tests Required for Each Range of Temperature Conditions
Number of Percentage Range of Temperature
Tests of Tests Differences AT?F)
1
4
5
5
5
4
1
4
16
20
20
20
16
4
AT<-25
-25£&T<-15
-15<.&T<-5
-5Z&T<+5
+5ZAT<+15
+15£&T<+25
A7S +25
The pressure and volume changes
produced by the thermal expansion or
contraction of any trapped vapor in the
line also affect the performance of most
detection systems; in some instances, a
leak detection device will simply not work
if vapor is trapped in the line. It is as-
sumed in this protocol that the leak detec-
tion system being evaluated would require
that the line be tested for vapor and, if
vapor were found to be present, would
either cancel the test or require that the
trapped vapor be removed before the test
was begun. Because the protocol makes
this assumption, evaluators should en-
sure that, when the evaluation is con-
ducted at an instrumented test facility (i.e.,
Options 1, 2, and 5), all vapor has been
removed from the pipeline for all tests
used in estimating performance. To assess
the sensitivity of the system to trapped
vapor, this protocol requires a minimum
of three tests with a small volume of
trapped vapor in the line. The results of
these three tests will not be included in
the performance estimates but will be
presented in the evaluation report so that
the manufacturer's claims about the effects
of trapped vapor on the test results can
be better assessed.
Generating the SIgnal-plus-nolse
Histogram
A histogram of the signal-plus-noise is
a requirement for estimating the PD for
each leak rate of interest. The threshold
value is used to determine the PD directly
from the histogram of the signal-plus-noise
for a given leak rate. A separate histo-
gram of the signal-plus-noise is required
for each signal (i.e., leak rate) for which
the performance in terms of PD is desired.
For each leak rate of interest, the histo-
gram of the signal-plus-noise must be
developed over the same temperature
conditions and pipeline configurations
used to generate the noise histogram.
This protocol requires, at a minimum, that
the PD be estimated against the leak rate
specified in the EPA regulation for the
type of leak detection system being evalu-
ated (i.e., 0.1, 0.2, or 3.0 gal/h).
Generating the signal-plus-noise histo-
gram may be simple or may involve signifi-
cant effort. There are two options. The direct
approach is to develop the histogram by
generating a leak in the line and conducting
a large number of leak detection tests un-
der the same conditions used to develop
the histogram of the noise. This direct ap-
proach can be used regardless of whether
the leak detection system uses a preset
threshold or measures the flow rate directly.
Noise and signal-plus-noise histograms are
required for each temperature condition. In
this approach, the histogram of the
signal-plus-noise is measured directly for
the leak rate at which the PD is desired, and
thus the relationship between signal and
noise is determined directly. If the leak de-
tection test is short, the data necessary to
develop the noise and signal-plus-noise
histograms can be acquired by conducting
two tests in succession. The direct approach
is most beneficial when a PD is required for
only a few leak rates; otherwise, the time
required to collect the data can be exces-
sive. This approach is easy to implement
when data are collected at an instrumented
test facility or one or more instrumented
operational UST facilities, but it is cumber-
some if the data must be collected over an
extended period at many noninstrumented
operational UST facilities. If there is a large
number of leak rates, each requiring an
estimate of the probability of detection, or if
the test duration is sufficiently long that only
one leak detection test can be conducted
for a given temperature condition, the sec-
ond approach would be more logical.
The second approach is to develop a
signal-plus-noise histogram from the histo-
gram of the noise by developing a theoreti-
cal relationship between the signal and the
noise. An experimentally validated model
that gives the relationship between the sig-
nal and each source of noise must be de-
veloped. With this model and the histogram
of the noise, the signal-plus-noise histo-
gram can be developed for any leak rate,
and an estimate of the PD can also be made
for any leak rate. This relationship must be
valid over the range of test conditions and
pipeline configurations covered by the
evaluation. It can be used with all five of
the options for data collection. It is particu-
larly useful for evaluating the performance
of leak detection systems that require long
tests or long waiting periods or that ac-
quire the noise data at many operational
UST facilities over a long period of time.
General Features of the
Evaluation Protocol
The general features of the evaluation
protocol, including how the pipeline con-
figuration affects performance and the 13
steps required to conduct the evaluation,
are summarized below.
Pipeline Configuration
There is a wide range of pressurized
pipeline systems that must be tested peri-
odically for leaks, and leak detection sys-
tems must comply with the EPA regulation.
The performance of many pipeline leak
detectors, especially pressure detection
systems, will vary according to the configu-
ration of the pipeline system. The magni-
tude of the signal as well as that of the
noise will be affected. This occurs be-
cause the overall compressibility charac-
teristics of the pipeline system are
influenced by the choice of material (fiber-
glass or steel), the use of flexible hosing
(and its length), and the presence of ap-
purtenances on the line. This interaction
between the pipeline and the performance
of the leak detection system presents a
challenging problem: the same leak detec-
tion system can perform very well on one
pipeline system and poorly on another.
Fortunately, the compressibility character-
istics of the line can be described by the
bulk modulus of the pipeline system. Two
pipelines may have different configurations
but may have the same compressibility
characteristics. In this protocol, the bulk
modulus, which can be readily measured,
is used to characterize the pipeline used in
the evaluation.
Pipelines constructed at special instru-
mented test facilities should simulate the
important features of the type of pipeline
systems found at operational UST facili-
ties. This protocol assumes that the leak
detection systems to be evaluated are in-
tended for use on underground storage
tanks that are typically 10,000 gal in ca-
pacity, where the diameter of the pipe is
typically 2 in. and the length is usually less
than 200 ft. If the leak detection system will
be used on pipelines with larger diameters
or longer lengths, the evaluator should use
a proportionately larger pipeline in
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conducting the evaluation. Whether the
evaluation is conducted at a special instru-
mented testing facility or at one or more
instrumented operational UST facilities, the
requirements are as follows.
The pipeline, which can be constructed
of either fiberglass or steel, must have
a diameter of at least 2 in. ± 0.5 in.
The pipeline must be at least 75 ft
tang.
• The pipeline system should have a
bulk modulus of approximately 25,000
psi± 10,000 psi.
• A mechanical line leak detector must
be present within the line if the leak
detection system being evaluated
normally conducts a test with this de-
vice in place.
There must be a way to pressurize the
pipeline system.
There must be a tank or storage con-
tainer to hold product withdrawn from
the line during a test.
There must be a pump to circulate
product from the storage container
through the pipeline for up to 1 h. (At
operational UST facilities and at most
test facilities, this container will be an
underground storage tank, and a sub-
mersible pump will be used to pres-
surize the pipeline and circulate
product through it.)
• The pipeline must have valves that
can be used to isolate it from the
storage tank and the dispenser. These
valves must be checked for tightness
under the maximum operating pres-
sure of the pipeline system.
• The pipeline must contain a petro-
leum product, preferably gasoline,
during the evaluation.
• In addition, when an evaluation is done
at a special test facility, there must be
a unit to heat or cool the product in the
storage container.
When the evaluation is done at five or
more operational UST facilities that are
geographically separated, it will suffice if
only one of the facilities meets these crite-
ria, with the exception of the bulk modulus
criterion, which does not have to be met by
any of the facilities.
The performance of some of the sys-
tems that can be evaluated with this proto-
col will decrease as the diameter and/or
length of the pipeline increases. This is
particularly true for volumetric measure-
ment systems that are directly affected by
thermal expansion or contraction of the
product in the pipeline. The performance
estimate generated by this protocol is con-
sidered valid if the volume of the product in
the pipeline system being tested is less
than twice the volume of product in the
pipeline used in the evaluation. This is an
arbitrary limitation because it does not take
into account the type of system, the method
of temperature compensation, or the ac-
tual performance of the system. It was
selected to allow flexibility in the applica-
tion of the system. Thus, in selecting the
length of the pipeline to be used in the
evaluation one should consider how the
system will ultimately be used operation-
ally. Because the limitation is arbitrary, this
protocol also allows the manufacturer to
present a separate written justification indi-
cating why the method should be consid-
ered applicable to pipelines having twice
the capacity, or more, of the one used in
the evaluation. Concurrence with this jus-
tification must be given by the evaluator.
Both the written justification and evaluator's
concurrence must be attached to the
evaluation report.
Conducting the Evaluation
A 13-step procedure is used to conduct
an evaluation. The particulars of the evalu-
ation procedure depend on
which performance standard the sys-
tem will be evaluated against (i.e.,
hourly test at 3 gal/h, monthly monitor-
ing test at 0.2 gal/h, or line tightness
test at 0.1 gal/h)
whether the leak detection system
measures the flow rate and uses it to
determine whether the pipeline is
leaking or uses an automatic preset
threshold switch and does not directly
measure and report flow rate.
The protocol can be used to evaluate
systems that require multiple tests as well
as those based on a single tost.
Step 1—Describe the leak detection
system. Specifying the important features
of the leak detection system is important
for three reasons. First, a brief description
will identify the system as the one that was
evaluated. Second, changes to the system
may be made at a later date, but the
manufacturer may not feel that the changes
are important enough for him to rename
the system. Such changes may affect the
performance, either for better or worse. If
the characteristics of the system have been
specified in a brief descriptive statement,
the owner/operator of an underground
storage tank system will have a way to
determine whether the detection system
he is using is actually the one that was
evaluated. Third, the owner/operator will
be able to interpret the results of the evalu-
ation more easily if he has this information.
The description of the leak detection
system need not be excessively detailed,
and proprietary information about the sys-
tem is not required. The description should,
however, include the important features of
the instrumentation, the test protocol, and
detection criterion. If the system requires
multiple tests before a leak is declared,
this should be clearly stated. (A summary
sheet on which to describe the system is
provided in the final report.)
Step 2—Select an evaluation option.
It must be determined which one of the five
evaluation options will be used: test facil-
ity, one or more instrumented operational
UST facilities, 6- to 12-month data collec-
tion effort at 5 operational UST facilities at
which pipeline integrity has been verified,
6- to 12-month data collection effort at 10
or more operational UST facilities, or vali-
dated computer simulation.
Step 3—Select temperature and leak
conditions for the evaluation. The tem-
perature and leak conditions must be de-
termined. If the evaluation is done at a test
facility, at one or more instrumented op-
erational UST facilities, or by computer
simulation, the temperature conditions
necessary to compile the noise histogram
will be developed according to a test ma-
trix, which is generated before the data
collection begins, and will be verified by
means of specific diagnostic ground and
product measurements made immediately
before the test. A matrix of leak conditions
will also be generated so that a histogram
of the signal-plus-noise can be compiled;
the type of test matrix will depend on
whether the leak rates are known a priori
or whether a blind-testing procedure is
used. The protocol is designed to minimize
any advantages that the test crew might
have because of its familiarity with the test
conditions described in the protocol. Thus,
the performance estimates should be
identical regardless of whether the test
conditions were known a priori. Two blind
testing techniques are provided; these can
be implemented most easily at an instru-
mented test facility.
If the data are collected at operational
UST facilities over a period of 6 to 12
months, temperature conditions do not
need to be artificially generated, but the
relationship between the measured quan-
tity and the flow rate that would be pro-
duced by a leak at the manufacturer's
standard test pressure (i.e., the relation-
ship between the signal and the noise)
should be defined and provided by the
manufacturer before the system is evalu-
ated. This relationship is used to generate
the signal-plus-noise histogram from the
noise histogram at the EPA-specified leak
rate. The relationship can be either a
theoretical one that has been validated
experimentally or an empirical one that
has been developed through experimenta-
tion.
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Step 4—Assemble equipment and
diagnostic instrumentation. The proto-
col specifies certain equipment, appara-
tuses, and measurement systems to be
used in the evaluation. Although these must
be assembled and calibrated, none is par-
ticularly complex or sophisticated. A de-
scription of each is provided. The protocol
allows for the use of other equipment not
specified by this protocol provided it has
the same functionality and performance as
the equipment described.
Step 5—Verify the integrity of the
pipeline system. Conducting a perfor-
mance evaluation of a leak detection sys-
tem requires a nonleaking pipeline. If the
pipeline is not tight, the performance of the
system being evaluated will be degraded.
For all but one of the evaluation options
presented in this protocol (Option 4), it is
recommended, though not required, that
the integrity of the pipeline be verified be-
forehand by means of a leak detection
system whose performance is already
known.
Step 6—Determine the characteris-
tics of the pipeline system. It must be
determined whether the pipeline system
used in the evaluation meets the minimum
specified conditions. The same pipeline
configuration can be used regardless of
whether the evaluation is done at a test
facility, one or more instrumented opera-
tional LIST facilities, or by the simulation
approach. The compressibility of the pipe-
line system must be within a specified
range; if it is not, a mechanical device can
be used to modify the compressibility char-
acteristics of the line for the test. An ex-
ample of a device that can be used to
modify the compressibility characteristics
of the pipeline system is described in the
final report.
Step 7—Evaluate the performance
characteristics of the sensor sub-
systems. The resolution, precision, accu-
racy, and minimum detectable quantity of
the measurement subsystems (instrumen-
tation), as well as what the instrumentation
is measuring (i.e., specificity), should be
determined. Also, the flow rate at the
threshold should be determined. Although
this step is not actually required in order for
an evaluator to estimate the performance
of the system, it serves two important pur-
poses. First, it indicates, before the evalu-
ation is performed, whether the
instrumentation is working according to the
manufacturer's specifications. If the instru-
mentation is not performing properly or if it
is out of calibration, the evaluation should
not proceed until the problems are rem-
edied. Second, the instrumentation will ul-
timately limit the performance of the leak
detection system. If it is evident that the
performance expectations of the manufac-
turer are more than the instruments will
allow, the evaluation can be stopped be-
fore too much time has been invested or
too much expense incurred. Furthermore,
this step can be completed quickly.
Step 8—Develop (if necessary) a re-
lationship between the leak and the
output of the measurement system, if the
relationship between the leak and the out-
put of the measurement system (i.e., be-
tween the signal and the noise) is known
or has been supplied by the manufacturer
and no direct estimate of the signal-
plus-noise histogram at the EPA-specified
leak rate has been made as part of this
protocol, experiments must be conducted
to verify the relationship. This step is not
necessary if the test matrix requires 25
tests at the EPA-specified leak rate (i.e.,
developing the signal-plus-noise histogram
with the direct approach).
Step 9—Develop a histogram of the
noise. A histogram of the noise under the
temperature conditions specified in Step 3
for the pipeline system specified in Step 6
must be developed. This histogram, which
is needed to estimate the probability of
false alarm, is generated from one or more
pipeline tests, conducted according to the
manufacturer's protocol, for each condi-
tion given in Step 3. If the system uses a
multiple-test procedure, two histograms are
required. The performance of the system,
which includes the entire multiple-test se-
quence, is generated from the data ob-
tained from the test that is used to
determine whether the pipeline is leaking
(in many instances these are the data from
the last test in the sequence). Step 9 is the
heart of any evaluation. Once the histo-
gram of the noise is known and either the
relationship between the signal and the
noise is known or a histogram of the
signal-plus-noise has been developed, the
performance of the system can be esti-
mated.
Step 10—Develop a histogram of the
signal-plus-noise. A histogram of the
signal-plus-noise for each leak rate at which
the system will be evaluated and under the
same conditions used to generate the noise
histogram must be developed. If system
uses a multiple-test procedure, two histo-
grams are required. The performance of
the system, which includes the entire
multiple-test sequence, is generated from
the data obtained from the test that is used
to determine whether the pipeline is leak-
ing (in many instances these are the data
from the last test in the sequence). This
histogram is needed to estimate the prob-
ability of detection. It may be a simple
matter to generate the histogram, or it may
involve significant effort. The histogram of
the signal-plus-noise may be measured
directly for each leak rate of interest by
developing a histogram of the test results
when a leak of a given magnitude is
present. As an alternative, a model that
gives the relationship between the signal
and the noise may be developed and vali-
dated experimentally. If the relationship
between the signal and noise is known,
the noise histogram can be used to esti-
mate the signal-plus-noise histogram. This
relationship can be difficult to develop un-
less all sources of noise during the test are
compensated for (or unless they are small).
A model is required if one wants to know a
system's performance at many leak rates
that are different from those specified in
the EPA regulation.
Step 11—Determine the system's
sensitivity to trapped vapor. The sensi-
tivity of the leak detection system to vapor
trapped in the pipeline system must be
determined. To this end, three special leak
detection tests will be performed. In each
test, a specific amount of vapor, unknown
to the tester, will be introduced into the line
by means of an apparatus especially de-
signed for this purpose and described in
the final report. These three tests will be
intermixed with the other 25.
Step 12—Conduct the performance
analysis. The performance of the system
in terms of PD at the EPA-specified leak
rate and in terms of PFA is then calculated.
The protocol is designed so that the PD
and PFA of the system are determined with
the manufacturer's threshold at the .leak
rate and test pressure specified by the
EPA regulation (i.e., 0.1, 0.2, or 3 gal/h). If
the evaluation is not done at the pressure
specified by the EPA, a method is given to
calculate an equivalent leak rate at what-
ever pressure is used. The protocol pro-
vides a summary sheet to be used in
reporting a variety of other performance
estimates so that the performance cari be
compared to that of other leak detection
systems. If a system uses a multiple-test
procedure, the protocol requires a second
performance estimate based on noise and
signal-plus-noise data from the first test of
the multiple-test sequence.
Step 13—Report the results. The fi-
nal step is to report the results of the
evaluation in a set of standardized forms
found in an appendix to the final report.
With the information provided in these
forms, the evaluation can be independently
reviewed and verified.
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Reporting the Results
One of the appendices of the complete
final report contains a standard form on
which the results of the evaluation can be
summarized. The performance character-
istics of the instrumentation, the estimates
of the system's performance in detecting
leaks in the ambient environment, and the
sensitivity of the system to trapped vapor
are summarized in a set of tables. The test
conditions and pipeline systems to which
the detector is applicable are also pre-
sented. Seven attachments to the form
give additional details about the system
and the evaluation. With the data and in-
formation provided in these attachments,
all of the results of the evaluation can be
independently reviewed and verified. The
seven attachments include:
• a description of the system
• a summary of its performance
• a summary of the configuration'of the
pipeline system (s)
• a summary of product temperature
conditions
• a summary of leak tests
• a summary of trapped vapor tests
• a summary of test results used to
check the relationship supplied by the
manufacturer for combining the signal
and the noise.
The full report was submitted in fulfill-
ment of Contract No. 68-03-3409 by Vista
Research, Inc., under the sponsorship of
the U.S. Environmental Protection Agency.
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Joseph W. Maresca, Jr., Robert M. Smedfjeld, Richard F. Wise, and James W. Starr
are with Vfefa Research, Inc., Mountain View, CA 94042.
Anthony N. Tafurl is the EPA Project Officer (see below).
The complete report, entitled "Standard Test Procedures for Evaluating Leak Detection
Methods: Pipeline Leak Detection Systems," (Order No. PB91-106245/AS; Cost:
$23.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-90/050
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