Describe how the engine room of a motor ship is ventilated. Give reasons for the
ventilation of diesel engine rooms. What provision is made to prevent moisture from entering
through the ventilation system and what would be the effects of too much moisture getting
carried in the machinery spaces?
Ventilation can be defined as the movement of air from outside the ship to inside of the ship, or
from the inside of the ship to the outside of the ship. Ventilation systems can be broken down
into two parts air supply and exhaust.
The air supply system consist of weather intake, centrifugal fans, and duct work through the
engine room so positioned that the entire engine room is supplied with fresh air. The exhaust
system consists of a hood or canopy and exhaust or extraction fans, ductwork, and a weather
opening. In the case of exhaust air they can be extracted from the engine room by pressure
difference. They will rise through the engine room and escape through the funnel.
In the supply air system air is drawn in through the air inlet vent by the centrifugal fans and
pushed through the duct work to the engine room spaced. The supply fans are usually two
speeds because less air flow may be required in the heating season. Each of the duct holds may
be fitted with cut off shutters to cut air flow to any space it is not required. The ventilation air
intake parts are fitted with fire dampers to cut off are supply in case of fire and fans have
remote shut offs outside the engine room for use in case of fires.
With the increase in generator capacity on board ships the fans are able to produce higher
pressure of ventilation in the engine room of a ship is to supply the air necessary for the
operation of the engines and possible boiler, also to remove contaminants and heat generated
by the running machinery. The air supply is used for cooling the spaces and machinery in the
space and make the spaces somewhat comfortable for working.
With the introduction of heating and air conditioning the engine room can be very live able in
hot and cold weather. To reduce a large flow of moisture through the ventilation system,
provisioned must be made. Most ships have filters installed in the system to absorb the
moisture. The ductwork may be provided with drains and if a build up of moisture is large
enough it can be drained. In more modern ships an air dryer will be fitted in the system. the end
of the ductwork opening are designed to not blow on electric motors or electric equipment. If
there was too much moisture in the machinery space its biggest effect would-be on the
electrical equipment. Moisture is a very good conductor of electricity, therefore an electric
equipment exposed to moisture will most likely overheat causing a breakdown in insulation on
the wiring forming a short of ground. This may cause fuses to blow or the electrical equipment
to burn out. Engine should also be vented because of gases escaping from the engines. These
gases can be very harmful to humans.