Document dnkNEGjGQOm5L2ZBp2MbQQqaB

Flammable and Combustible Liquids Forced ventilation may be required in many cases where repair work is to be done inside a tank Where fumes develop from welding or other repair work, mechanical air movers should be used or the workmen should wear fresh air hose masks On a large tank, a door sheet or sheets may be removed for ventila tion after the tank has been made gas free The opening also can be used to expedite removal of sediment and to increase illumina tion If a tank has been closed for some time, there may he a deficiencv of oxygen due to rusting (oxidation) of the metal of the tank In that case, no one should enter the tank without a supplied air mask or, for a relatively brief stay, a self-contained or self-generating breathing apparatus Cleaning aboveground tanks Here m step-by-step form is a summary of a typical procedure for cleaning tanks that have contained flammable or combustible liquids 1 Remove all sources of ignition (matches, open flames, smoking, gas engines, weld ing, exposed electrical wiring and equip ment) from the vicinity of the tank 2 Empty the tank by pumping, draining, and floating tank contents with water, introducing the water through fixed tank connections 3 Disconnect and blank all product, steam smothering, foam, and similar lines Do not rely on valves 4 Open all manholes and allow the tank to air thoroughly Ventilate or steam the tank for the number of hours required by its size If steam is used, cool and ventilate afterward 5 Have available the required personal pro tective equipment fresh air hose masks, approved flashlights, safety belts and life lines, rubber boots and gloves 6 If light is needed, use only flashlights or electric lanterns approved for combusti ble atmospheres by Underwriters' Lab oratories, Inc 7 Test for vapor content with a combustible gas indicator For entering the tank be fore it tests vapor-free, wear a fresh air hose mask, air supply tanks, and safety belt and lifeline if the tank atmosphere contains more than the maximum accept able concentration of the vapor Have ample help available outside for the number of men inside 8 If a storage tank has contained leaded gasoline subsequent to its last thorough cleaning, follow instructions of suppliers of tetraethyl lead 9 Bond steam, lines and water wash nozzles to the tank 10 Wash sludge, sediment, and scale from the tank through the dram or remove it with a pump Flush out well and over flow the tank with water if necessary 11 Make a gas test and, if the tank is found vapor-free, check conditions inside the tank before issuing an OK for the work Otherwise, clean and ventilate further as required 12 Continue ventilation for duration of the work m the tank, and make periodic tests for the presence of gases or vapors as the work progresses Ventilation by air instead of steaming is used more widely where deposits of iron sulfide are not present and where a source of power supply for mechanical air removers is available Special precautions are required for the servicing of tanks which contain pyro phoric iron sulfide (See the API accident prevention manual. Cleaning Petroleum Stor age Tanks, listed in "References ") Cleaning small tanks and containers General precautions Work on containers that have held flammable or combustible liquids or gases shall be supervised by a trained foreman capable of maintaining a high degree of safe operations If the con tainer has held such unstable compounds as nitrocellulose, pyroxylin solutions, nitrates, chlorates, perchlorates, or peroxides, which may mean that it contains enough oxygen to support combustion, special precautions should be taken Contact the manufacturer or supplier for specific information regarding 1038