CHAPTER 2BOILERS TEXT 1
TEXT A boiler is used to heat feedwater in order to produce steam. There are watertube and firetube boilers. All boilers have a furnace or combustion chamber where fuel is burnt to release its energy, A drum must be provided where steam and water can separate. Finally there must be a number of fittings which ensure safe operation of the boiler. The feedwater enters the boiler where it is heated and becomes steam The feedwater circulates from the steam drum to the water drum and is heated in the process. Some of the feedwater passes through the tubes surrounding the furnace, where it is heated and returns to the drum. Large - bore downcomer tubes pass outside of the furnace and join the steam and water drums. They are used to circulate feedwater between the drums. The steam is produced in a steam drum and may be drawn off for use from here. The steam may also pass to a superheater which is located within the boiler. The hot gases produced in furnace heat the feedwater, produce steam and superheat the steam from the boiler drum. The gases then pass over an economiser through which the feedwater passes before it enters the boiler. (1100)
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