Maintaining an industrial boiler during shutdown time is mainly to prevent boiler corrosion, especially for large scale circulating fluidized bed boiler or water tube boilers. During the shutdown time, the heating surface of boiler absorbs the moisture in the air to form a water film. The oxygen in water film reacts with furnace of boiler and forms iron rust to corrode the boiler. When the boiler operates, the high temperature will accelerate corrosion, which may greatly reduced the service life of boiler, even seriously reduce the strength of steel and cause the occurrence of a major explosion. Therefore, a good maintenance during shutdown period is an important measure to ensure the safe operation of boilers and extend the service life of the boiler. The widely used methods to maintain the boiler are as follows:
Maintain boiler with pressure method
Maintain boiler with pressure method is generally used for the shutdown time of boiler is less than a week, such as some steam boilers in industries. The pressure of boiler should be between 0.05-0.1MPa, and the temperature of boiler water should be slightly higher than 100 degrees. In such a circumstance, boiler water is free of oxygen and the air is keep out of the drum. Then the boiler could be protected effectively.
Maintain boiler with wet method
Maintain boiler with wet method is generally used for the shutdown time of boiler is less than one month. After shutting down the boiler, the water in the boiler should be discharged, then remove scale and soot, close all valves. Then softened water is added into boiler to the lowest water level, and inject special alkaline protection fluid into the boiler. Besides, switch on the feed boiler valve until the water comes out of the air valve. Then close the air valve and the feed water valve to make a water circulation in boiler so that the water has a same concentration throughout the boiler. Regularly firing the boiler to keep the boiler surface dry is also necessary.
Maintain boiler with dry method
Maintain boiler with dry method is generally used for the shutdown time of boiler is more than one month., especially for the central heating boilers that stop used for heating hot water in summer time. After shutting down the boiler, the water in the boiler should be discharged, then remove scale and soot, close all valves. If the boiler room is wet, a regularly firing the boiler or some desiccant to keep the boiler surface dry is also necessary. We should also check for corrosion and timely replace the desiccant every two weeks.
Maintain boiler with gas method
Maintain boiler with gas method is generally used for the shutdown time of boiler is long. The nitrogen and ammonia are injected into the boiler from the highest point of the boiler and maintain the pressure between 0.05-0.1MPa, then the air in boiler is forced out, while the gas in furnace is alkaline and corrosion of boiler is prevented.
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