|
Certification |
Leak rate of 0.1 gph with PD = >99% and PFA = <1%.
The US EPA has not set a minimum detectable leak rate for large diameter
pipeline systems (airport hydrant systems) at the time of this evaluation. |
|
Leak Threshold |
A pipeline system should not be declared tight when a
confirmable level of chemical tracer in the sample collected exceeds the
background level. |
|
Applicability |
Gasoline, diesel, aviation fuel, fuel oil #4, waste oil. |
|
Pipeline Capacity |
Not limited by capacity.
Pipeline segments up to 1500 feet in length may be covered by an individual
test sample collected continuously along this length. |
|
Waiting Time |
Ranges from 1 to 6 days after tracer is added to the product
in the pipeline.
All releases at a depth of 5 feet in non-engineered backfill were detected
within 1 day after the start of the test. All releases at a depth of 10
feet were detectable 6 days after the start of the test.
Leak simulations conducted at the depth of the pipeline can be used to
validate test parameters such as soil permeability and waiting period.
For very large pipeline systems, several days or weeks may be required to
circulate tracer-labeled product through all parts of the pipeline.
Waiting time begins after the tracer has reached the portions of the
pipeline being tested. |
|
Leak Simulations |
Leak simulations are the release of surrogate tracer into the
soil or backfill at the depth of the pipeline to evaluate the migration of a
tracer and the sensitivity of the test under on-site sub-surface conditions.
Sub-surface conditions throughout the test area must be at least as
favorable as those at the leak simulation location in order to use the
results. |
|
Tracer Dosage |
Dosage of tracer is based on pipe capacity and frequency and
volume of pipe use according to manufacturer's recommendations.
Tracer-labeled product must be circulated through the pipeline before test
period begins.
Pressurized pipeline must be brought up to operating pressure or operated on
a daily basis. |
|
System Features |
Pipeline must be accurately located to ensure that sampling
activity is within the zone of influence of the tracer.
Sampling is conducted using a small metal sled that is pulled on the ground
above the pipeline being tested. |
|
Comments |
The tester may determine that pre or post testing is needed
to establish the background level of tracer in the soil.
Due to the vapors being collected at the surface, testing can be affected by
extreme windy conditions.
High winds will generally cause a reduction in the amount of tracer from a
release that is collected in the test sample.
The presence of a layer of water saturated soil, that is also frozen, above
the location where a leak may exist, may impede the transport of the tracer
labeled product into the sampling zone.
Groundwater surrounding the pipeline may limit effectiveness of test method
(e.g. when applied to pipelines containing water-miscible products or
products whose specific gravity is greater than 1).
Leak simulations performed at the depth of the pipeline along sections of
the pipeline below the water table or below saturated, frozen soil allow for
validation of the method in these conditions. |
