A boiler in one form or another will be found on every type of ship. Where the main machinery is steam powered, one or more large watertube boilers will be fitted to produce steam at very high temperatures and pressures. On a diesel main machinery vessel, a smaller (usually firetube type) boiler will be fitted to provide steam for the various ship services. Even within the two basic design types, watertube and firetube, a variety of designs and variations exist.
A boiler is used to heat feed water in order to produce steam. The
energy released by the burning fuel in the boiler furnace is stored (as
temperature and pressure) in the steam produced. All boilers have a
furnace or combustion chamber where fuel is burnt to release its energy.
Air is supplied to the boiler furnace to enable combustion of the fuel to
take place. A large surface area between the combustion chamber and
the water enables the energy of combustion, in the form of heat, to be
transferred to the water.
A drum must be provided where steam and water can separate. There
must also be a variety of fittings and controls to ensure that fuel oil, air
and feedwater supplies are matched to the demand for steam. Finally
there must be a number of fittings or mountings which ensure the safe
operation of the boiler.
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