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Issue Date: December 5, 2002
Engineering
Design Group
EDG
XLD 2000 Plus (Revision 1.02) Leak Detection System
(MTS DDA 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 12,074 ft², leak rate is 1.92 gph
with PD = 95% and PFA = 5%.
For other tank sizes, leak rate equals [(PSA in ft² ÷
12,074 ft²) x 1.92 gph].
Example: For a tank with PSA = 1,260 ft²; leak rate =
[(1,260 ft² ÷ 12,074 ft²) x 1.92 gph] = 0.2 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 12,074 ft², leak threshold is 0.96
gph
For other tank sizes, leak threshold equals [(PSA in ft²
÷ 12,074 ft²) x 0.96 gph].
Example: For a tank with PSA = 1,260 ft²; leak threshold
= [(1,260 ft² ÷ 12,074 ft²) x 0.96 gph] = 0.1 gph.
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, fuel oil #4.
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-walled
tanks having a capacity of 50,000 to 2,100,000 gallons
Minimum product surface area (PSA) is 1260 ft².
Maximum product surface area (PSA) is 12,076 ft².
Performance not sensitive to product level.
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Waiting
Time
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Minimum
of 30 hours, 18 minutes after delivery or transfer.
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Test
Period
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Minimum
of 40 hours, 12 minutes.
There must be no delivery, transfer, or dispensing during
test.
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Temperature
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Average
for product is determined by five resistance temperature
detectors (RTDs)
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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 2.655 inches.
For tanks with a PSA of 12,076 ft² and containing 2.665
inches of water, system takes 52.7 hours to detect a 0.20
gph water ingress rate.
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Calibration
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System
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. Evaluated in nominal 2,100,000 gallon
tank with PSA of 12,076 ft² (124 feet in diameter).
If product temperature change exceeds 1.8 degrees F during
test, test will abort.
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Engineering
Design Group, Inc.
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Evaluator:
Ken Wilcox Associates
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800
Meridian Tower
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Tel:
(816) 443-2494
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5100
E. Skelly Drive
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Date
of Evaluation: 11/16/01
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Tulsa,
OK 74135
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Tel:
(918) 628- 7100
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