Page 263 - Introduction to Marine Engineering

238 Fire fighting and safety

equipment. The carbon dioxide extinguisher is not permitted in the
accommodation since, in a confined space, it could be lethal.

Dry powder extinguishers
The outer container contains sodium bicarbonate powder. A capsule of
carbon dioxide gas is located beneath a plunger mechanism in the
central cap (Figure 13.7). On depressing the plunger the carbon dioxide
gas forces the powder up a discharge tube and out of the discharge
nozzle.
The dry powder extinguisher can be used on all classes of fire but it
has no cooling effect. It is usually located near electrical equipment in
the machinery space and elsewhere on the ship.

Maintenance and testing
All portable extinguishers are pressure vessels and must therefore be
regularly checked.
The soda-acid and foam extinguisher containers are initially tested to
25 bar for five minutes and thereafter at four-yearly intervals to 20 bar.

Plunger
mechanism

Safety
cup

Nozzle

Figure 13.7 Dry powder extinguisher