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0 0 <br /> lower.Entry personnel are to be adequately the bottom, middle, and upper portions of the <br /> trained in the recognition of such hazards. tank with the blower off. Once vapor readings <br /> of 10 percent (10) or less of the lower <br /> flammable limit (LFL) have been obtained <br /> A5.2.4.1 An important phase of the operation is within the tank, additional vapor readings shall <br /> the testing for flammability of the vapor in the be taken at the vent riser to confirm tank vapor <br /> excavated area first and then in the tank. Tests <br /> for flammable vapor concentrations shall be readings with the blower on. Vapor readings of <br /> 10 percent (.1%) or less of the lower flammable <br /> made with a combustible gas indicator which is limit (LFL) shall be obtained in the tank and <br /> properly calibrated on hexane in air or other vent prior to proceeding to tank opening <br /> suitable gas appropriate for the stored product procedures of section A6.0. <br /> and thoroughly checked and maintained in <br /> accordance with manufacturer's instructions. <br /> Persons responsible for testing must be trained <br /> and thoroughly familiar with the use of the A6.0 OPENING THE TANK. <br /> instrument and interpretation of the instrument's <br /> readings. The instrument, unless the instrument <br /> is a continuous read model, shall be purged with WARNING: A CUTTING TORCH OR <br /> fresh air after each reading. ABRASION CUTTING WHEEL SHALL NOT <br /> BE USED ON A TANK UNTIL THE TANK <br /> HAS BEEN CLEANED AND <br /> SANDBLASTED TO WHITE METAL. <br /> A5.2.4.2 When using an eductor-type air <br /> mover,tests shall be performed through a probe <br /> hole provided in the side of the eductor see <br /> Figure 1, Detail 1-A, with the air mover on. To <br /> insure accurate vapor readings, the probe shall A6.1 Immediately prior to opening, vapor <br /> be located prior to the mixing of compressed readings shall be taken as described in section <br /> air within the eductor. The drop tube shall not A5.2.4. If vapor readings indicate the vapor <br /> be removed when using the probe hole for vapor concentration is at 10 percent (.10) or less of <br /> testing to ensure that vapors are drawn off the the lower flammable limit (LFL), the manway <br /> bottom of the tank. Readings of 10 percent (1) cover may be unbolted and removed or, if no <br /> or less of the lower flammable limit (LFL) manway exists, an access opening shall be cut <br /> within the probe hole shall be obtained prior to in the top of the tank with the minimum <br /> proceeding to the tank opening procedures of dimensions of 22 inches by 22 inches. Vapor <br /> A6.0. readings shall be performed as determined <br /> necessary by the qualified person throughout <br /> the opening process to ensure that a safe <br /> atmosphere is maintained. The tank section to <br /> be removed should be marked with chalk. A <br /> A5.2.4.3 When using a diffused air blower or hole shall be drilled with an air driven drill at <br /> fan air blower, tests shall be performed by one corner of the section to be removed using <br /> placing the combustible gas indicator probe into lubricating oil or other appropriate measure to <br /> an opening on the top of the tank. If the fill reduce friction,heat,and possible sparks. <br /> opening is used for testing, the drop tube shall <br /> be removed.Vapor readings shall be taken at <br /> 14 <br />