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PEURP1200-12 _ 4.2.4 Preparation. The procedures in this sec- 4.2.7 Test Equipment. Test equipment shall tion are general in nature and reflect the suggested include: vacuum levels and hold times for testing tank e a vacuum-generating device that can be used in secondary containment areas. Consult tank manu- a Class I,Division 1 area capable of pulling 15 facturer and authority having jurisdiction (AH.I) inches of mercury (Hg)vacuum; guidelines before performing these tests as their requirements may differ. an automatic vacuum shutoff valve or vacuum regulator(The shutoff valve can be set to close at Determine if there is liquid present in the intersti- a predetermined safe level, preventing the pos- tial space. If liquid is found, determine if the fluid is water or product, and remove it to the extent practicable. The hydrostatic pressure from a high water table imposes inward pressure on the outer wall of a F 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 s.y important to observe the water table and associated recommended vacuum levels when testing. Vent the primary tank to atmosphere during the FIGURE 43. The vacuum gauge and control valve used for tank interstitial testing. 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. ^ r 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 y>� 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) Recommended Practice R012, Recommended Practice for Interstitial Tightness Testing of Existing Underground Double Wall Steel Tanks for testing. For tight wrap tanks, use the test method in this section. 4.2.6 Fiberglass Tanks. Determine if the inter- stitial space is a "tight wrap" design or a "110% •- containment"design.Either type of fiberglass tank may use this test, or the latest version of Fiber- glass Tank & Pipe Institute's, Field Test Protocol for Testing the Annular Space of Installed Under- FIGURE 4.4. The plumber's plug provides a leak-tight ground Fiberglass Double and Triple-wall Tanks connection to draw a vacuum on the tank Interstitial with Dry Annular Space, FT&PI 4/01/07. space. 0 pei.org