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B. The tank shall be purged of flammable vapors by use of an air mover constructed <br />of light gauge metal of the venturi (jet) type, or low pressure blower. Air movers <br />located in the possible path of vapor travel shall be driven by steam, air or <br />explosion proof electric motors. The apparatus used to inject the air is to be <br />bonded to the tank. <br />C. Purging is to continue as long as tests show vapors in the flammable range are <br />contained in the tank. <br />D. Tests for flammable vapors are to be made with a Combustible Gas Indicator, <br />immediately before cutting or drilling and frequently during the course of the <br />work. Vapor samples are to be taken in the excavation and at the top, middle and <br />bottom of the tank at each testing. It is essential that the operator using the <br />indicator be well schooled in the use of the Combustible Gas Indicator and that he <br />perform the checks recommended by the manufacturer to insure that the <br />instrument is in good condition prior to the beginning of each work day. <br />E. Hot work, such as drilling or cutting, shall not be performed when flammable <br />vapors are indicated in the excavation or in the tank. Combustible Gas Indicator <br />readings above 20 Lower Explosion Limit (LEL) are to be considered explosive. <br />III. OPENING THE TANK <br />Afler it is determined that a sate atmosphere has been established, the tank may <br />be opened. If cutting and drilling are necessary, the tools are to be air operated or <br />run by explosion proof electric motors and bonded to the tanks. <br />IV. CLEANING AND SURFACE PREPARATION <br />A. Employees entering the tank and those handling tank sludge, will be fully <br />clothed so that arms, legs, head and torso are protected from contact with the <br />tank residue and the coating resins and shall wear oil and water resistant boots <br />and gloves. In addition, protective respiratory equipment providing positive air <br />pressure, in a full facepiece mask, will be worn by those entering the tank before <br />and during bottom sediment and water removal, sandblasting and removal of <br />residue and during the coating application. Protective equipment shall be <br />provided, used and maintained in a sanitary and reliable condition. Persons <br />harnesses tand safety lines and standby emplirators are oyees villtlbe avl be ailable, who are d with fety <br />Communicatable of ions shall be maintaom ined between the workers and stand -bye tank, in the event of an <br />employees. <br />B. Inspection of the interior may be made with one of several forms of internal <br />inspection lamps or fldshlights approved for Class 1, Division I, Group D, hazard <br />locations, or a mirror may be used to reflect light into the container. <br />C. Pumps used for the removal of bottom sediment and water- shall be explosion <br />proof. Shovels used to remove solid sludge shall be of the non-ferrous or <br />sparkproof type. <br />D. The interior tank surfaces are to be sandblasted to a while -petal finish. The <br />shovels used to remove the residue shall be sparkproof as in 1V. C., above. All <br />Corrosion, scale, sand and dirt must be removed. Sandblasting, revoval of sand <br />and scale and wiping, are to be scheduled for one continuous operation. <br />E. Holes are to be located and plugged with boiler plugs, base resin, trowel materialand <br />smooth,trounded,tcogered surface for betterlapplicat un of the spray coat. a w <br />