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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-operated 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 I , Division 1 area . - 7 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 \` ' secondary containment areas . Consult tank manu- facturer and authority having jurisdiction (AHJ) _ guidelines before performing these tests , as their requirements may differ. ; Determine if there is liquid present in the intersti- ` tial space . If liquid is found , determine if the fluid is water or product, and remove it to the extent 4 practicable . FIGURE 4-3 . The vacuum 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 . Vent the primary tank to atmosphere during the I F test. 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 . 4. 2 . 5 Steel Tanks . Determine if the interstitial space is a "tight-wrap" design or a " 110 % contain- ment" design . Tanks with a 110% containment 00 design should use the latest version of Steel Tank _ _ Institute ' s (STI) RO12, Recommended Practice for Interstitial Tightness Testing of Existing Under- FIGURE 44 . The plumber 's plug provides a leak4ight ground Double Wall Steel Tanks for testing . connection to draw a vacuum on the tank interstitial space. pei . org O