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)
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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