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WATERTUBE boiler components

Steam Drum

The steam drum is located at the top of the boiler to provide an upper reservoir forthe water covering the generating tube bank. Water is distributed from the steam

drum to the lower drums and headers by pipes called downcomers. Generated

steam is also collected and is separated from the water in the steam drum. Boilersare also equipped with safety valves to relieve excessive pressure. The valves are

located on the steam drum and superheater outlet. They are designed to relieve

sufficient pressure to safely steam the boiler at 1!" with boiler steam stop

valves closed.

Water Drum

#t provides for the distribution of water. $ntering it from the %owncomers& to the

screen and generating tubes and in some cases to the water wall headers. #t alsoprovides a space for the accumulation of suspended solids which may be

precipitated from the boiler water. The blow down connection enables these to be

blown out as required.

Headers

'ocated along the furnace sidewall and rearwall. These lower and upper headersperform a similar duty to that of the drums& it connects the wall tubes as well to

the to the steam and water drums. #t distributes water to the sidewall tubes andprovides another blowdown point for sludge removal.

Downcomers

These are large diameter pipes connecting the steam drum with the water drum

and lower headers to ensure proper circulation by delivering water from the steam

drum to the water drum and lower headers. The downcomers are located betweenthe inner and outer air casing to protect them from the direct radiant heat of the

furnace.

Risers

These consist of numerous small diameter tubes placed in the main flow of hotgases& so forming a large heat exchanger surface. The generation of the steam

takes place mainly by convection.

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Screen Tubes

These are placed ad(acent to the furnace& so receiving heat from the flametogether with the heat from the hot gases leaving the furnace. Therefore they need

a relatively large diameter to keep the ratio of steam to water low enough to

prevent overheating. The duty of the screen tubes is to protect the )uperheatertubes from the direct radiant heat of the furnace flame.

Sootblowers

*perated by steam or compressed air. They act to blow away soot and theproducts of combustion from the tube surfaces.

Economizer

The economi+er is a multi,pass heat exchanger located above the main generating

bank at the base of the exhaust stack& so that combustion gas will give up a lot of

its remaining heat to the incoming feedwater before passing out the exhaust stackThe incoming feedwater absorbs about 1!!,!!- sensible heat from the exhaust

gases. -ins are installed on the economi+er tubes to increase the heating surface

area further& helping to increase efficiency.