Issue Date:  July 18, 2013

Purpora Engineering, Inc.

Alert 8200 Series Sonde Ullage



Leak rate of 0.1 gph with PD = 100% and PFA = 0%.

Leak Threshold

A tank system should not be declared tight if the ratio of the ultrasonic signal (when the tank is under pressure or vacuum) to the background signal (prior to pressurization or evacuation) equals or exceeds 1.5 for either 12 kHz or 25 kHz frequencey band.


Gasoline, diesel, aviation fuel, fuel oil #4, waste oil. 

Tank Capacity

Maximum ullage volume of 30,000 gallons.

Waiting Time

None between delivery and testing if test is conducted after an underfill tank tightness test.

Test Period

Minimum of 5 minutes. 
Test data are acquired and recorded by system's computer.
There must be no dispensing or delivery during test.

Test Pressure

Net pressure of 2 psi or vacuum of 1.5 psi must be maintained in ullage.
Pressure or vacuum must be maintained in the tank with a loss of less than 0.4 psi.


Acoustic/ultrasonic and background signals are independent of product temperature.


Depth to groundwater in tank excavation backfill must be determined, in order to correctly calculate pressure/vacuum levels.


Manifolded tank systems must be isolated prior to test.  
Tests only ullage portion of tank. 
Product-filled portion of tank must be tested using an underfill test method. 
Vibration due to nearby equipment or dripping condensation may interfere with test. 
Microphone was located 25 feet away from leak source during evaluation. 
Vacuum test method may not be effective in some tank excavation backfill (such as clay) because it may plug holes in tank. 
If soil is saturated with product, air or water ingress may not be detected by vacuum test. A well point in the tank excavation backfill may help identify presence of this condition.



Purpora Engineering Inc.

Evaluator:  Ken Wilcox Associates

658 North Progress Drive

Tel:  (816) 443-2494

Saukville, WI 53080

Dates of Evaluation:  03/19/13

Tel:  (262) 536-4081







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