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Issue Date: July 18, 2013
Purpora Engineering, Inc.
Alert 8200 Series Sonde
NON-VOLUMETRIC TANK TIGHTNESS TEST METHOD (VACUUM)
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Certification
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Leak rate of 0.1 gph with PD = 100% and PFA = 0%. |
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Leak
Threshold
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A tank system should not be declared tight if the ratio of the ultrasonic signal (when the tank is under vacuum) to the background signal (prior to evacuation) equals or exceeds 1.5 for either 12 kHz or 25 kHz frequency band.
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Applicability
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Gasoline, diesel, aviation fuel, fuel oil #4, waste oil.
Other liquids may be tested after consultation with the manufacturer.
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Tank Capacity
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Maximum of 30,000 gallons.
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Waiting Time
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None between delivery and testing.
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Test Period
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2 minutes reference plus 2 minutes test.
Test data are acquired and recorded by system's computer.
There must be no dispensing or delivery during test.
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Test Pressure
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Minimum of -0.5 psi to a maximum of -2 psi.
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Temperature
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Acoustic/ultrasonic and background signals are independent of product temperature.
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| Groundwater |
Groundwater level in tank excavation backfill must be determined by observation well or soil probe in tank excavation backfill.
If groundwater level in tank excavation backfill is above bottom of tank or the groundwater level in the tank excavation backfill has not been determined, this method cannot be used. |
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Comments
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Method can also be used on double wall tanks to test the primary tank where a dry interstice is present.
Microphone was 25 ft. away from leak source during evaluation.
Although not tested on completely empty tanks, a third party acoustics specialist as certified the device is equally effective when tanks are empty as when tanks contain product.
Test may be inconclusive if there is high background noise.
Vacuum test method may not be effective in some tank excavation backfill (such as clay) because it may plug holes in tank.
More than 4 psi pressure differential across thank wall at any location could damage tank
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| Purpora Engineering, LLC |
Evaluator: Ken Wilcox Associates |
| P.O. Box 80265 |
Tel: (816) 443-2494
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| Saukville, WI 53080 |
Date of Evaluation: 03/19/13 |
| Tel: (800) 352-2011 |
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| E-mail: sat@purporaengineering.com |
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| URL: www.purporaengineering.com |
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