Page 268 - Introduction to Marine Engineering

Fire fighting and safety 243

times the quantity of foam. The generator blows air through a net
sprayed with foam concentrate and water. The vastly expanded foam is
then ducted away to the space to be protected. The foam is an insulator
and an absorber of radiant heat; it also excludes oxygen from the fire.

Carbon dioxide flooding
A carbon dioxide flooding system is used to displace the oxygen in the
protected space and thus extinguish the fire. The carbon dioxide is
stored as a liquid under pressure in cylinders.
The volume of space to be protected determines the number of
cylinders required. A common battery of cylinders may be used to
protect both cargo holds and machinery space.
The cargo space system is normally arranged for smoke detection,
alarm and carbon dioxide flooding (Figure 13,12).
Small air sampling pipes from the individual cargo holds are led into a
cabinet on the bridge. Air is drawn from each hold by a small fan and
each pipe is identified for its particular hold. If smoke is drawn into the
cabinet from one of the holds it will set off an alarm. The smoke is also
passed into the wheelhouse where it can be detected by personnel on
watch.
The location of the fire can be identified in the cabinet and the hold
distribution valve below the cabinet is operated. This valve shuts off the
sampling pipe from the cabinet and opens it to the carbon dioxide main
leading from the cylinder battery. A chart will indicate the number of

Fan motor box
C0 2 room Diverting valve Wheelhouse top

Smoke detection cabinet
in wheelhouse
Low pressure
suction lines

High pressure C0 2
suction lines
Combined smoke collector
^x-'and discharge head

s 2 s j a s a
T ween deck
CO 2 nozzles in engine room

Hold

W^^^>^^
Figure 13.12 Carbon dioxide detection and flooding system