Boiler Terms

Shell: The shell of a boiler consists of one or more steel plates bents into a
cylindrical form and riveted or welded together. The shell ends are closed with
the end plates.

Setting: The primary function of setting is to confine heat to the boiler and form a passage for gases. It is made of brick work and may form the wall of furnace
and the combustion chamber. It also provides support in some type of
boilers(eg. Lancashire boiler).

Grate. It is the platform in the furnace upon which fuel is burnt and it is made of cast iron bars. The bars are so arranged that air may pass on to the fuel for
combustion. The area of the grate on which the fire rests in a coal or wood fired
boiler is called grate surface.

Furnace. It is a chamber formed by the space above the grate and below the
boiler shell, in which combustion takes place. It is also called fire-box.
Water space and steam space: The volume of the shell that is occupied by the
water is termed water space while the entire shell volume less the water and
tubes space is called steam space.

Mountings. The items such as stop valve, safety valves, water level gauges,
fusible plug, blow off cock, pressure gauges, water level indicator etc. are
termed as mounting and boiler can not work safely without them.

Accessories: The items such as super heaters, economizers, feed pumps etc.
are termed as accessories and they form integral part of the boiler. They increase
the efficiency of the boiler.

Water Level: The level at which water stands in the boiler is called water level.
The space above the water level is called steam space.

Foaming: Formation of steam bubbles on the surface of boiler water due to high
surface tension of the water.

Scale: A deposit of medium to extreme hardness occurring on water heating
surface.

Blowing off: The removal of the mud and other impurities of water from the
lowest part of the boiler is termed as ‘blowing off’. This is accomplished with the
help of blow off cock or valve.

Lagging: Blocks of asbestos or magnesia insulation wrapped on the outside of a
boiler shell or steam piping.

Refractory: A heat insulation material, such as fire brick or plastic fire clay, used for such purposes as lining combustion chambers.