Document QN4BMKLRXYjJwG0KzZ7Beqm4

FLAMMABLE AND COMBUSTIBLE LIQUIDS Fig 32-16. Before cleaning a tank, work man should be properly equipped and in structed, ond have dear means of escape. Sandblasting equipment should be bonded to prevent static sparks Use of power chipping tools and nvet busters should be suspended while flammable vapors from tanks may be present in the area Nozzles on steam lines used to free tanks of vapor should be bonded to the tank shells to pre vent static accumulation Motor trucks, gas engines, open flames, and portable electric equipment should be kept a safe distance from the tank being cleaned Protective equipment Although full details on personal protec tive equipment can be found in Chapter 36, it is well to discuss specifics concerning tank cleaning here It is considered good practice to wear watertight rubber boots, thoroughly cleaned and in good condition, for tank cleaning It is advisable to wear rubber or imperme able gloves, but if work does not permit their use, a protective cream recommended for the exposure should be used In an at mosphere which is dangerously irritant or corrosive to the skin, a complete outfit of impervious clothing must be worn Supplied air hose masks with blowers and safety harnesses with life lines, or self-con tained or self-generating breathing apparatus should be worn by men entering tanks unless the person m charge has determined that the vapor concentration is at or below the thres hold limit value (see Chapter 40, "Industrial Toxicology") and that no oxygen deficiency exists Some companies will permit a canister type gas mask with an approved canister to be used in the presence of petroleum vapors when the vapor concentration is over 0 1 per cent but less than 0 5 per cent and the exposure is short Canisters approved by the Bureau of Mines give protection against up to 2 per cent of gas It is important that there always be sufficient oxygen pres ent when a canister type mask is used If a test of the tank shows it to be defi cient in oxygen, whether or not it is other wise immediately hazardous to life, a com pressed-air type of self-contained breathing apparatus, or self-generating or air supplied mask should be used Fit of the facepiece should be carefully checked before the work man enters the tank If the environment contains a substance that is dangerously ir ritant or corrosive to the skin (lead tetra ethyl, for example), the breathing apparatus may be supplemented by complete attire of impervious clothing Some medical authorities advise that in dividuals with broken eardrums not work in vapor-laden atmospheres, because no mask will protect these abnormal openings The supplied fresb-air hose mask with blower is generally the best type of respira tory equipment for continuous use in tank interior operations Proper procedures Wherever possible, best practice is to do the washing from outside the manhole until the vapor concentration has been reduced to or below the threshold limit value for the vapor An individual making tests with a com bustible gas indicator should be thoroughly familiar with the instrument and be satis fied that it is in proper working order Tests should not be made m the presence of steam A worker should not be allowed to enter 32-26