Saturday, January 22, 2011

CrazyEngineers Forum - Mechanical & Civil Engineering

CrazyEngineers Forum - Mechanical & Civil Engineering

Boiler Terms

Posted: 22 Jan 2011 04:04 AM PST

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.

Classification of boilers

Posted: 22 Jan 2011 03:59 AM PST

Classification

1.Horizontal, Vertical or Inclined Boiler.

If the axis of the boiler is horizontal,the boiler is called horizontal, if the axis is vertical, it is called verticalboiler and if the axis is inclined it is called as inclined boiler.The parts of horizontal boiler is can be inspected and repaired easily but it occupies more space.The vertical boiler occupies less floor area.

2.Fire Tube and Water Tube

In the fire boilers, the hot gases are inside the tubes and the water surrounds the tubes.
Examples: Cochran, Lancashire and Locomotive boilers.
In the water tube boilers, the water is inside the tubes and hot gases surround them.
Examples: Babcock and Wilcox,
Stirling, Yarrow boiler etc.

3.Externally Fired and Internally Fired

The boiler is known as externally fired if the fire is outside the shell.
Examples: Babcock and Wilcox boiler,Stirling boiler etc.
In case of internally fired boilers, the furnace is located inside the shell.
Examples: Cochran, Lancashire boiler etc.

4.Forced circulation and Natural Circulation

In forced circulation type of boilers, the circulation of water is done by a
forced pump.
Examples: Velox,Lamomt,Benson Boiler etc.
In natural circulation type of boilers, circulation of water in the boiler takes
place due to natural convention currents produced by the application of
heat.
Examples: Lancashire, Babcock and Wilcox boiler etc.

5.Higher Pressure and Low Pressure Boilers
The boiler which produce steam at pressures of 80 bar and above are
called high pressure boilers.
Examples: Babcock and Wilcox, Velox,Lamomt,Benson Boiler etc.
The boilers which produce steam at pressure below 80 bar are called low
pressure boilers.
Examples: Cochran, Cornish, Lancashire and Locomotive boiler etc.

6. Stationary and Portable

• Primarily, the boilers are classified as either stationary or mobile.
• Stationary boilers are used for power plant steam, for central station utility
power plants, for plant process steam etc.
• Mobile boilers or portable boilers include locomotive type, and other small
units for temporary use at sites.

7. Single Tube and Multi Tube Boiler

The fire tube boilers are classified as single tube and multi-tube boilers,
depending upon whether the fire tube is one or more than one.
Examples: Cornish ,simple vertical boiler are the single tube boiler and rest
of the boilers are multi-tube boiler.
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