Direct attack of fire
Whenever somebody discovers a fire on board ship, the
first thing for him to do is to alert people so that more help
available. At the same time, with a portable fire extinguisher
he has to quickly
make use of it to put out the fire.
However, with the volatile and highly
combustible nature of some cargo or fuel, very often the fire
will spread quickly. Portable fire extinguishers will then become
no match for these types of fire.
Probably the most vulnerable place for
fire to start will
be the engine room. As we have seen in another page, the
triangle is ever present in the engine room. There are
plentiful supply of combustibles, strong heat source and of
course, oxygen in the air, or even in gas cylinders.
Having to deal with these types of big
or medium sized fires is therefore a strong possibility. Short
of the last resort of flooding the whole engine with carbon
dioxide, or foam or even water sprays, which, incidentally
will mean massive destruction of the machinery in the engine
room, the ship's officers and engineers must know what to do
if such a fire occur on board.
Usually, they will split into 2 teams.
One team will go directly to attack the fire and try to bring
it under control. Another team will do boundary cooling to
prevent the heat from one compartment to travel to another
compartment thereby spreading to the whole ship.
A most likely scenario will have the
engine personnel attacking the fire at the source, (most
likely to be in the engine room) and the deck personnel doing
the boundary cooling from the deck or cargo hold.
For those people who are directly
attacking the fire, they have to protect themselves from the
tremendous radiant heat of the fire while at the same time try
to cool down the fire by water jets.
The attacking team therefore has to
approach the fire in two groups. One group will adjust their
hose nozzles to form a spray pattern, also called "water wall"
while another group will follow behind the water wall (and so
be protected from the radiant heat) with jet nozzles that can
be directed to the seat of the fire.
As the pressure from the hoses are very
strong, they will need at least 2 persons for one group in
order to control the hoses.
On some ships, foam liquid could be
mixed with the water in order to fight oil fires effectively.
The action of foam is to blanket and starve the fire of
oxygen. If water is used alone it must be used carefully in
order not to worsen the spread the fire. This is because oil
floats on water and the burning oil may thus spread with the
water flooding the place.
The action of water in extinguishing the
fire is by cooling. Sometimes it is better to break up the
water jet by shooting above the fire and letting the water
drop and cool down the fire in a fine mist.
When people are attacking the fire so
closely, some way has to be made to divert all the smoke away
from the firefighters. Most likely, some manhole, window or
skylight will have to be opened up away from the firefighters.
In such incidents of fire, the quick-closing valves for all the oil tank outlets will be
closed remotely from the deck. This is to prevent adding more
fuel to the fire.
The fire fighting water piping installations
on board ship will also have isolating valves that can be used
to isolate certain portions that have been damaged by the
fire. By closing these valves to the damaged portion of the
piping, the pressure of the hoses can be maintained.
Even when there is a blackout caused by
fire damage to electrical cables or generator sets, there is
still an emergency fire pump driven by diesel engine available. This
pump unit is usually located far away from the engine room,
usually near the steering room at the stern of the ship. The
engineers can start this pump engine by manual cranking.
With all these carefully thought out
system in place and well-trained personnel, most medium-sized
fire could be put under control and extinguished.
However, if these fail, there is no
other choice but to do a total flooding of the engine room.
This is the last choice because if this fails to extinguish
the fire, there is no second chance left.
Total flooding of carbon dioxide system usually means getting all
personnel out of the engine room, closing all the doors,
skylights, ventilation fans, openings and discharging carbon
dioxide gas into the engine room space... and waiting
patiently. Patient enough not be tempted to open the door to
look inside. There is a good reason for this. Once a door is
opened, oxygen will enter and the fire may start again and
there is no more carbon dioxide left to flood again.
The pictures show personnel being
trained to use water wall spray to protect against the radiant
heat of the fire