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0 0 <br /> another suitable openings in the top of the tank. from obstructions. Vacuum in the tank must not <br /> Pump motors and hoses must be properly exceed V = (1/2 D + h) x 0.88 Hg/ft and never <br /> grounded to prevent electrostatic ignition to exceed 5.3"HG. <br /> hazards. In some cases, it may be necessary to <br /> pump a small quantity of water into the tank <br /> through a grounded conductive pipe that is in V=vacuum in inches mercury, <br /> contact with the bottom of the tank to float D=tank diameter in feet,and <br /> product from a low spot so that it can be h = the maximum recommended burial <br /> pumped from the tank. depth in feet, but not less than 3 feet to <br /> the top of the tank. <br /> A5.2.3 PURGING(VAPOR FREEING) 2) A diffused air-blower (see Figure 2) shall <br /> have the air-diffusing pipe properly grounded to <br /> A5.2.3.1 The tank shall be thoroughly purged prevent the possibility of static electricity <br /> with air to remove flammable vapors. The generation and discharge. Fill (drop) tubes may <br /> concentration of flammable vapors in a tank be removed to insure proper diffusion of air. <br /> may go through the flammable range before a The air supply shall be from a compressor <br /> safe atmosphere is obtained. Precautions shall which has been checked to ensure a clean air <br /> be taken to eliminate the possibility of the supply free from volatile vapors. The vent shall <br /> discharge of static electricity or other sources of be inspected to insure it is free from <br /> ignition during vapor freeing procedures. Prior obstructions. Air pressure in the tank must not <br /> to removing a manway or performing any hot exceed 5 psig. <br /> work, the tank shall be vapor tested to insure <br /> that a safe atmosphere has been established as <br /> described in section A6. 1. <br /> (3) A fan type air blower shall be used to blow <br /> air into the tank through the fill opening. The <br /> fan shall be driven by compressed air or a Class <br /> A5.2.3.2 Purging vapors from the tank may be I, Division 1, Group D explosion proof electric <br /> accomplished by one of 3 methods listed below motor. The fan and drop tube shall be properly <br /> or other acceptable industry practices: grounded to prevent the possibility of a static <br /> electric discharge. Fill (drop) tubes may be <br /> removed. The tank vent shall be inspected to <br /> make sure it is free from obstructions. Air <br /> pressure in the tank must not exceed 5 psig. <br /> 1) An eductor-type air mover (see Figure 1), <br /> usually driven by compressed air, shall be <br /> properly grounded to prevent the possibility of <br /> static electricity generation and discharge. A5.2.4 TESTING FLAMMABLE VAPOR <br /> When using this ventilation method, the vapors CONCENTRATIONS. <br /> shall be drawn from the bottom of the tank. For <br /> tanks equipped with fill (drop) tubes, tubes shall <br /> not be removed. An extension attached to the NOTE: Some solvents may impose health risks <br /> air mover shall be used to discharge vapors a due to exposure despite the presence of <br /> minimum of twelve (12) feet above grade. The adequate oxygen and readings of 10%LFL or <br /> vent line shall be checked to insure it is free <br /> 1�. <br />