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/ PEURP1200-12 <br /> 4.2.4 Preparation. The procedures in this sec- 4.2.7 Test Equipment. Test equipment shall <br /> tion are general in nature and reflect the suggested include: <br /> vacuum levels and hold times for testing tank . a vacuum-generating device that can be used in <br /> secondary containment areas. Consult tank manu- a Class I,Division 1 area capable of pulling 15 <br /> faciurer and authority having jurisdiction (Alin inches of mercury (Hg)vacuum; <br /> guidelines before performing these tests as their <br /> requirements may diger. • an automatic vacuum shutoff valve or vacuum <br /> regulator(The shutoff valve can be set to close at <br /> Determine if there is liquid present in the intetsti- a predetermined safe level, preventing the pos- <br /> tial space.If liquid is found,determine if the fluid <br /> is water or product, and remove it to the extent <br /> practicable. <br /> I � <br /> The hydrostatic pressure from a high water table <br /> imposes inward pressure on the outer wall of a <br /> UST. Applying a vacuum to the interstitial space <br /> of the tank creates additional pressure on the outer <br /> wall. These combined forces can damage the <br /> secondary tank wall when there is a large defined <br /> space between the primary and secondary tanks. <br /> Consequently, to prevent damage to the tank,it is <br /> important to observe the water table and associated •�': x <br /> recommended vacuum levels when testing. ' <br /> Vent the primary tank to atmosphere during the FIGURE 43. The vacuum gauge and control valve used <br /> for tank Interstitial testing. <br /> test. <br /> In some installations, the tank interstitial space <br /> maybe vented to min;mirr the buildup of conden- <br /> sation.In these cases,seal off any vent lines to the <br /> tank interstitial space prior to testing. <br /> Determine the volume of the tank. This mforma- <br /> tion is available from facility records or the auto- <br /> matic tank gauge(ATC)readout. <br /> 4.2.5 Steel Tanks. Determine if the interstitial <br /> space is a"tight wrap"design or a"110%n contain- r . <br /> Ment" design. Tanks with a 110% containment <br /> design should use the latest version of Steel Tank <br /> Institute's (STI) Recommended Practice R012, <br /> Recommended Practice for Interstitial Tightness <br /> Testing of Existing Underground Double Wall Steel <br /> Tanks for testing. <br /> For tight wrap tanks, use the test method in this <br /> section. <br /> 4.2.6 Fiberglass Tanks. Determine if the inter- <br /> stitial space is a "tight wrap„ design or a "110% <br /> containment'design Either type of fiberglass tank 4 _� <br /> may use this test, or the latest version of Fiber- <br /> glass Tank & Pipe Institute's, Field Test Protocol <br /> for Testing the Annular Space of Installed Under- FIGURE 44. The plumber's plug provides a leak-tight <br /> ground Fiberglass Double and Piple-wall Tanks connection to draw a vacuum on the tank Interstitial <br /> with Dry Annular Space, FT&fl 4/01/07. space. <br /> Qpei.org <br />