174: NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE
the burning oil to spread by washing it into corners or into adjacent
compartments, hence the reason for spraying the water on an oil fire.
Firefoam is contained in portable cylinders, and when discharged
at the spot it froths, spreads, envelops the surfaces, smothers the flames
it comes in contact with and prevents the ignited oil from overflowing
into other compartments.
Fixed Fire Extinguishing Systems usually consist of a battery of
cylinders filled with carbon dioxide gas (C02) at a pressure round about
900 Ihs. to the square inch. A system of pipes leads from the
cylinders to the various compartments and cargo spaces, by way of the
wheelhouse as a rule, where a detecting cabinet is fitted.
In the Lux-Rich' system a partial vacuum is maintained in the
chamber of the cabinet by a small exhauster, the suction of which
continuously draws ail samples from all compartments of the ship,
one pipe being fitted for each cargo space. Smoke, drawn from a
tube in the detecting cabinet, is the warning that tells of the existence
of fire in a particular compartment, and a lighting arrangement makes
the slightest amount of smoke strikingly visible to anyone in the wheel-
house, a further warning being given by the smell of the exhaust air
flowing from the vacuum chamber.
When fire is detected the extinguishing gas from the cylinders is
introduced into the detection pipe by means of a three-way valve. The
valve shuts ofl the air flowing up from the cargo spaces to the detec-
tor and connects the holds with the carbon dioxide which flows direct
from the cylinders along the same pipe, the gas on emerging from the
pipe into the hold expands rapidly and penetrates into crevices and the
inaccessible places, thus flooding the burning compartment with the
released gas and smothering the flames or smouldering mass.
In both the Clayton and the Harper systems the gas is pumped
into the cargo spaces and these systems may also be used for fumigating
the ship.
5. What would you do in the event of fire breaking out, the ship being
at sea?
Give the particular alarm signal as recognised on board the ship,
usually a succession of 6 short blasts followed by 1 long blast on the
whistle. Treat the fire as a serious one from the very first. All fires,
like human beings, begin in a small way. Try to locate the source of
the fire; hands to stations and couple up the hoses.
H the fire can be got at and is found to be small, turn on a fire