(d) A combustible solid; i.e., finely divided particles which may be
present in the form of an explosive dust cloud.
b. Preparing the container for cleaning.
(1) In cleaning do not use chlorinated hydrocarbons, such as
trichloroethylene or carbon tetrachloride. The materials may be decomposed by the
heat or radiation from welding or cutting to form phosgene.
(2) Disconnect or remove from the vicinity of the container all sources of
ignition before cleaning is started.
(3) Personnel cleaning the container must be protected against harmful
exposure.
(4) If practical, move the container into the open.
When indoors make sure
the room is well ventilated.
(5) Empty and drain the container thoroughly, including all internal
piping, traps, and standpipes. Removal of scale and sediment may be facilitated by
scraping, hammering with a nonferrous mallet, or by using a nonferrous chain as a
scrubber. Do not use any tool which may spark and cause flammable vapors to
ignite. Dispose of the residue before starting to weld or cut.
(6) Identify material for which the container was used; determine its
flammability and toxicity characteristics. If the substance previously held by the
container is not known. assume that the substance is flammable, toxic, and
insoluble in water.
(7) Cleaning a container that has held combustibles is necessary in all
cases before any welding or cutting is done. This cleaning may be supplemented by
filling the container with water or by using an inert gas both before and during
such work.
(8) Treat each compartment in a container having two or more compartments
in the same manner, regardless of which compartment is to be welded or cut.
c. Methods of precleaning containers having held flammable liquids.
(1) It is very important for the safety of personnel to completely clean
all tanks and containers which have held volatile or flammable liquids of all
dangerous fumes. Safety precautions cannot be overemphasized of the dangers
involved when these items are not thoroughly purged prior to the application of
heat-especially an open flame.
(2) Accepted methods of cleaning. The various methods of cleaning these
containers follow. However, the steam cleaning and automotive exhaust methods are
considered, by military personnel, to be the safest and easiest methods of purging
these containers.
d. Automotive exhaust method of cleaning.
(1) Completely drain the container of all fluid.
(2) Fill the container at least 25 percent full of a solution of hot soda
or detergent (1 lb-per gallon of water) and rinse it sufficiently to insure that
the inside surface is thoroughly flushed.
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