BOILERS

Mechanical Science Volume 2 of 2
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BOILERS DOE-HDBK-1018/2-93 Miscellaneous Mechanical Components BOILERS Boilers are commonly used at large facilities to act as primary or backup steam sources. The source of heat that generates the steam varies, but the basic operation of the boiler is the same. This chapter will summarize the operation of a boiler. EO 1.7 DESCRIBE the basic operation of a boiler. EO 1.8 IDENTIFY the following components of a typical boiler: a. Steam drum d. Downcomer b. Distribution header(s) e. Risers c. Combustion chamber Introduction The primary function of a boiler is to produce steam at a given pressure and temperature. To accomplish this, the boiler serves as a furnace where air is mixed with fuel in a controlled combustion process to release large quantities of heat. The pressure-tight construction of a boiler provides a means to absorb the heat from the combustion and transfer this heat to raise water to a temperature such that the steam produced is of sufficient temperature and quality (moisture content) for steam loads. Boilers Two distinct heat sources used for boilers are electric probes and burned fuel (oil, coal, etc.) This chapter will use fuel boilers to illustrate the typical design of boilers. Refer to Figure 9 during the following discussion. The boiler has an enclosed space where the fuel combustion takes place, usually referred to as the furnace or combustion chamber. Air is supplied to combine with the fuel, resulting in combustion. The heat of combustion is absorbed by the water in the risers or circulating tubes. The density difference between hot and cold water is the driving force to circulate the water back to the steam drum. Eventually the water will absorb sufficient heat to produce steam. Steam leaves the steam drum via a baffle, which causes any water droplets being carried by the steam to drop out and drain back to the steam drum. If superheated steam is required, the steam may then travel through a superheater. The hot combustion gasses from the furnace will heat the steam through the superheater's thin tube walls. The steam then goes to the steam supply system and the various steam loads. ME-05 Rev. 0 Page 14

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