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IM PEI/RP1200-12 <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 1, Division 1 area capable of pulling 15 <br /> facturer and authority having jurisdiction (AHJ) inches of mercury (Hg)vacuum, <br /> Lwidelines before performing these tests as their <br /> requirement%may differ. • 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 intersti- 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 /> W. <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. ti ` <br /> w' <br /> Consequently, to prevent damage to the tank, it is <br /> important to observe the water table and associated <br /> recommended vacuum levels when testing. �' J <br /> Vent the primary tank to atmosphere during, the RGURE 4-3. The vacuum gauge anti control valve useu <br /> test. for tank interstitial testing. <br /> In some installations. the tank interstitial space <br /> may be vented to minimize 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 informa- <br /> tion is available from facility records or the auto- <br /> matic tank gauge (AT(3) readout. r <br /> 4.2.5 Steel Tanks. Determine if the interstitial <br /> space is a"tight wrap"design or a"I 1019/c contain- ,,10 <br /> merit" design. Tanks with a I109h, containment <br /> design should use the latest version of Steel Tank <br /> Institute's (STI) Recommended Practice R012, <br /> Recommetuled 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 "1105 <br /> containment"design. Either type of fiberglass tank <br /> may use this test. or the latest version of Fiber- <br /> glass Tank & Pipe Instirute's, Field Test Pmtocol <br /> for Testing the Annular Sprue of Installed lJnder- FIGURE 4-4. The plumber's plug provides a leak-tight <br /> ground Fiberglass Double and Trifle-wall Tanks connection to draw a vacuum on the tank interstitial <br /> with Dry Annular Space. FT&P14/01/07. space. <br /> 0 pei.Wo <br />