Page 276 - Introduction to Marine Engineering

250 Fire fighting and safety

and oxygen necessary for a fire or explosion are shown. By keeping the
tank atmosphere outside of the flammable limits, no fire or explosion
can occur. It is usual practice to inert the tank atmosphere by displacing
the oxygen with an inert gas and thus effectively prevent a fire or
explosion. The inert gas producing systems have already been
described.

Training and awareness
Where is the nearest fire extinguisher? What type is it? How is it
operated? At any position in the ship these questions should be asked
and answered. Knowing how to operate any extinguisher just by looking
at it will indicate some degree of training and an awareness of the fire
defences.
Fire drills are often referred to as 'Board of Trade Sports', but they
merit a more sober attitude than they receive. Practices are useful and
should be seriously undertaken. Equipment should be tried and tested
to ensure that it works and is ready when needed. Regular maintenance
should take place on extinguishers, fire pumps, hydrants, hoses, etc. All
engineers should be familiar with recharging and overhauling extin-
guishers and those in charge should make sure it is regularly done. The
statutory surveys do much to ensure that equipment is ready for use but
the one year period between leaves a lot of time for neglect.

Breathing apparatus
Many fire fighting situations may require the use of some form of
breathing apparatus. The use of such equipment will ensure a supply of
oxygen to the wearer so that he can perform his particular tasks in safety.
Two basic types are in use—the smoke helmet and the self-contained
unit using air cylinders.
The smoke helmet arrangement uses a helmet which covers the head
and is connected to an air hose. A hand operated pump or bellows
supplies the air. A system of signals between user and supplier must be
arranged to ensure safe, correct operation.
The self-contained unit consists of one or two cylinders of compressed
air kept in a harness which is carried on the back (Figure 13.16). The
high pressure air is fed through a reducing valve and then to a demand
valve. The demand valve is fitted into a face mask and supplies air to
meet the breathing requirements of the wearer. A non-return valve
permits breathing out to atmosphere. A warning whisde sounds when
the air pressure falls to a low value. A standard cylinder will allow for
about 20 to 30 minutes' operation.