Issue Date: August 9, 2001
Revision Date: December 21, 2005
Varec,
Inc.
(originally listed as
Coggins Systems, Inc. and later as Endress + Hauser Systems
and Gauging)
Fuels
Manager and Remote Terminal Unit RTU/8130
(MTS Magnetostrictive Probe)
BULK
UNDERGROUND STORAGE TANK LEAK DETECTION METHOD (50,000 gallons
or greater)
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Certification
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Leak
rate is proportional to product surface area (PSA).
For tanks with PSA of 616 ft², leak rate is 0.2 gph with
PD = 96.4% and PFA = 3.6%
For other tank sizes, leak rate equals [(PSA in ft² ÷
616 ft²) x 0.2 gph].
Example:
For a tank with PSA = 900 ft²; leak rate = [(900 ft² ÷
616 ft²) x 0.2 gph] = 0.29 gph.
Leak rate may not be scaled below 0.2 gph.
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Leak
Threshold
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Leak
threshold is proportional to product surface area (PSA).
For tanks with PSA of 616 ft², leak threshold is 0.1 gph.
For other tank sizes, leak threshold equals [(PSA in ft²
÷ 616 ft²) x 0.1 gph].
Example:
For a tank with PSA = 900 ft²; leak threshold = [(900
ft² ÷ 616ft²) x 0.1 gph] = 0.1gph.
A tank system should not be declared tight if the test
result indicates a loss or gain that equals or exceeds
the calculated leak threshold.
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Applicability
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Gasoline,
diesel, aviation fuel.
Other liquids may be tested after consultation with the
manufacturer.
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Tank
Capacity
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Use
limited to single field-constructed vertical tanks 50,000
gallons or greater.
Maximum product surface area (PSA) is 924 ft². Product
must be at full operating level.
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Waiting
Time
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Minimum
of 4 hours, 26 minutes after delivery or dispensing.
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Test
Period
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Minimum
of 24 hours.
There must be no dispensing or delivery during test.
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Temperature
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Average
for product is determined by a minimum of 5 resistance
temperature detectors (RTDs).
Product temperature change during test should not exceed
0.72 degrees F.
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Water
Sensor
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Must
be used to detect water ingress. Minimum detectable water
level in the tank is 0.238 inch.
Minimum detectable change in water level is 0.0017 inch.
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Calibration
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Probe
must be checked and, if necessary, calibrated in accordance
with manufacturer's instructions.
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Comments
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Tests
only portion of tank containing product.
As product level is lowered, leak rate in a leaking tank
decreases (due to lower head pressure).
Consistent testing at low levels could allow a leak to
remain undetected.
Leak Manager uses PC-based software to process probe data.
Remote Terminal Unit (RTU/8130) contains software embedded
in a CPU housed in a stand-alone console. Evaluated in
a nominal 50,000 gallon vertical underground tank with
product surface area (PSA) of 616 ft².
The maximum product level in the tank during test was
65% (32,500 gallons).
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