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TECHNICAL SPECIFICATIONS <br /> USING NSS 37E EPDXY/FRF TANK LININGS <br /> PAGE 3 <br /> 2. PURGING THE TANK OF FLAMMABLE VAPORS <br /> A. The tank is to be isolated from any flammable vapor source <br /> before work begins . Tanks that are manifolded together <br /> create a prevalent danger in that explosive vapors can <br /> infiltrate a tank after it has been purged. Submersible <br /> pumps must be removed and openings plugged. Lines that may <br /> be common to other storage tanks, such as suction, syphon <br /> and vent lines , are to be blanked. The CONTRACTOR must be made <br /> aware that it is common practice to manifold vent lines at <br /> locations where the tanks have been adapted for vapor <br /> recovery. <br /> B. The tank shall be purged of flammable vapors by use of an <br /> air mover constructed of light gage metal of the venturi <br /> (jet) type, or low pressure blower. Air movers located in <br /> the possible path of vapor travel shall be driven by steam, <br /> air or explosion proof electric motors . The apparatus used <br /> to inject the air is to be bonded to the tank. <br /> C. Purging is to continue as long as the test show vapors in <br /> the flammable range are contained in the tank. <br /> D. Tests for flammable vapors are to be made with a <br /> Combustible Gas Indicator, immediately before cutting or <br /> drilling and frequently during the course of the work. <br /> Vapor samples are to be taken in the excavation and at the <br /> top, middle and bottom of the tank at each testing. It is <br /> essential that the operator using the indicator be well <br /> schooled in its use and that he perform the checks recom- <br /> mended by the manufacturer to insure the instrument is in <br /> proper working order prior to the start of each shift. <br /> E. Hot work, such as drilling or cutting, shall not be <br /> performed when flammable vapors are indicated in the <br /> excavation or in the tank. Combustable Gas Indicator <br /> readings above 20 Lower Explosion Limit (LEL) are to be <br /> considered explosive. <br /> 2. OPENING THE TANK <br /> After it is determine that a safe atmosphere has been <br /> established, the tank may be opened. If cutting and drilling <br /> are necessary, the tools are to be air operated or run by <br /> explosion proof electric motors and bonded to the tank. <br />