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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 exploslon-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. �1 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 e secondary containment areas. Consult tank manu- facturer and authority having jurisdiction (AHJ) guidelines before performing these tests, as their requirements may differ. Detennine 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 ;�• practicable. FIGURE 43. 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 Y} recommended vacuum levels when testing. Vent the primary tank to atmosphere during the test. �- In some installations, the tank interstitial space fes' 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 design should use the latest version of Steel Tank Institute's(STI) R012,Recommended Practice for Interstitial Tightness Testing of Existing Under- FIGURE 4-4. 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