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PEIJRP1200 - 12 <br /> 4. 2 . 4 Preparation . The procedures in this scc- 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 <br /> • a vacuum- �eneratin � device that can be used in <br /> secondary containment areas . Consult tank mane- a Class I, Division 1 area capable of pulling 15 <br /> facturer and authority having jurisdiction (AHJ ) inches of mercury (Hg) vacuum; <br /> L" before performing these tests as their <br /> requirements 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 /> The hydrostatic pressure from a high water table t <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 � w <br /> t <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 ` " r <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 /> tests <br /> 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- N <br /> tion is available from facility records or the auto- <br /> inatic tank gauge (ATG) readout. <br /> 4. 2 . 5 Steel Tanks . Determine if the interstitial <br /> space is a "tight wrap" design or a " 110% contain- ` <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 Y <br /> Testing of E.Wsting Underground Double Wall Steel <br /> Tanks for testing. <br /> For tight wrap tanks , use the test method in this <br /> section . <br /> � x <br /> 4. 2 . 8 Fiberglass Tanks . Determine if the inter- <br /> stitial space is a "tight wrap" design or a " 110°h " <br /> containment" design . Either type of fiberglass tank -` <br /> may use this test, or the latest version of Filler- v <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 Triple - wall Tanks connection to draw a vacuum on the tank interstitial <br /> with A&vAnnular Space, FT& PI 4/01 /07 . space. <br /> Qpei . org <br />