What Are The Boiler Accessories

A complete boiler system requires a variety of equipment, then what are these boiler accessories and their function?

Air preheater: The function of air preheater is to increase the temperature of air before enters the furnace. It is generally placed after the economizer so the flue gases on one side and air on other. It preheats the to be supplied to the furnace, pre-heated air accelerates the combustion and facilitates the burning of coal.

Economizer: It is a device in which the waste heat of the flue gases is utilized for heating the feed water. To recover some of heat being carried over by exhaust gases. This heat is used to raise the temperature of feed water supplied to the boiler. Advantages of using Economizer: Evaporative capacity of boiler is increased. Overall efficiency of the plant is increased. If the boiler is fed with cold water it may results in chilling the boiler metal. The temperature range between various parts of the boiler is reduced which results in reduction of stresses due to unequal expansion.

Super-heater: Super -heater is a device which increase the temperature of the steam above its saturation point. The steam generated above the surface of water is always wet which causes erosion of turbine blades, pipes etc. So that super heated air is required and therefore we use super-heater in boiler.
Advantages of super-heater: Erosion of turbine blade is eliminated. Thermal efficiency of steam plant is increased. Steam consumption is reduced.

Steam separator: Steam separator removes the suspended water particles from the steam. Steam is collected from a boiler may be wet, dry or super-heated, but many case steam become wet due to loss of heat during passing through steam pipe. The use of wet steam in an engine or turbine is not economical. so there is need to separate the water partials from the steam.

Feed pump: It is used to feed the water into the boiler under pressure through feed check valve. It is a device of boiler used to supplied proper amount of water at least equal to that evaporated in the boiler.

Safety valve: It is used to relieve pressure and prevent possible explosion of a boiler.

Water level indicators: They show the operator the level of fluid in the boiler, also known as a sight glass, water gauge or water column.

Bottom blowdown valves: They provide a means for removing solid particulates that condense and lie on the bottom of a boiler. As the name implies, this valve is usually located directly on the bottom of the boiler, and is occasionally opened to use the pressure in the boiler to push these particulates out.

Continuous blowdown valve: This allows a small quantity of water to escape continuously. Its purpose is to prevent the water in the boiler becoming saturated with dissolved salts. Saturation would lead to foaming and cause water droplets to be carried over with the steam – a condition known as priming. Blowdown is also often used to monitor the chemistry of the boiler water.

Automatic blowdown/continuous heat recovery system: This system allows the boiler to blowdown only when makeup water is flowing to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the makeup water. No flash tank is generally needed as the blowdown discharged is close to the temperature of the makeup water.

Hand holes: They are steel plates installed in openings in "header" to allow for inspections & installation of tubes and inspection of internal surfaces.