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Recommended Practices for the Testing and Verification of Spill, Overfill, Leak Detection and Secondary Containment Equipment at UST Facilities For tight-wrap tanks, use the test method in this CAUTION : Use only an air-0perated vacu- section. um source or a vacuum pump powered by an explosion-proof motor. Vacuum pumps 4.2.6 Fiberglass Tanks . Determine if the inter- with electric motors that are not explo- stitial space is a "tight-wrap" design or a " 110% sion-proof may ignite flammable vapors . containment" design. Either type of fiberglass tank If a portable air compressor is used, it may use this test or the latest version of Fiberglass should be located at least 20 feet away Tank & Pipe Institute ' s (FTPI) RP 2007 , Field Test from the venturi•eductor or outside any Protocol for Testing the Annular Space of Installed Class 1, Division 1 area . 4 .2.4 Preparation . The procedures in this sec- tion are general in nature and reflect the suggested vacuum levels and hold times for testing tank r secondary containment areas. Consult tank mann- - facturer and authority having jurisdiction (AHJ) 1 . guidelines before performing these tests , as their n requirements may differ. Determine if there is liquid present in the intersti- tial space. If liquid is found, determine if the fluid °s is water or product, and remove it to the extent . � ti practicable. FIGURE 4-3 . The vacuurn •gauge and control valve used The hydrostatic pressure from a high water table for tank interstitial testing. imposes inward pressure on the outer wall of a UST. Applying a vacuum to the interstitial space of the tank creates additional pressure on the outer wall. These combined forces can damage the secondary tank wall when there is a large defined space between the primary and secondary tanks . Consequently, to prevent damage to the tank, it is important to observe the water table and associated recommended vacuum levels when testing . l � Vent the primary tank to atmosphere during the test. N i In some installations, the tank interstitial space may be vented to minimize the buildup of conden- sation. In these cases , seal off any vent lines to the ` tank interstitial space prior to testing. Determine the volume of the tank. This informa- _ tion is available from facility records or the auto- matic tank gauge (ATG) readout. r 4. 2. 5 Steel Tanks . Determine if the interstitial space is a "tight-wrap" design or a " 110% contain- A ment" design . Tanks with a 110 % containment design should use the latest version of Steel Tank Institute' s (STI) R012, Reconunended Practice for Interstitial Tightness Testing of Existing Under- FIGURE 44. The plumber's plug provides a leak-tight ground Double Wall Steel Tanks for testing . connection to draw a vacuum on the tank interstitial spa ce. pei . org 0