After the boiler is out of service, if the inner surface of the pipe is moist and the outside air enters, it will cause the oxidation corrosion of the metal on the inner surface. 

To prevent this kind of corrosion, the boiler should be maintained after stopping. For different furnace shutdown, there are the following maintenance methods:

1, steam pressure method antisepsis stop standby time not more than 5 days, can use this method. After the boiler stops providing steam to the outside, all holes and doors should be closed to reduce heat loss, slow down steam pressure drop and maintain drum pressure above 0.5mpa. When the drum pressure is lower than 0.5mpa, it shall be ignited to boost the pressure, or the steam heating device in the adjacent furnace shall be used to maintain the steam pressure.

2, feed water overflow method anticorrosive stop after the furnace into standby or treatment of non-pressure parts defects, stop using time of about 30 days, can be used this method. When the steam pressure drops to 0.5-1.0mpa after stopping the furnace, the superheater outlet header flows upstream in reverse direction until the sampling door at the highest point of the boiler overflows, and the overflow water is controlled at 50-200l /h. During the anti-corrosion period, special personnel should be set to monitor and keep the pressure of steam drum within the prescribed range to prevent pressure from changing too much.

3, ammonia liquid antisepsis stop the furnace standby time is long, can use this method. After shutdown, close all valves connected to the public system, fill the boiler with water and inject ammonia. Control the ammonia concentration range of pot water: prepared with condensate or desalted water is 500-600mg /L; 800 -- 1000mg/L when prepared with softened water.

4, boiler waste heat drying method after the shutdown of all the hole door, reduce heat loss, high pressure boiler in the pressure drop to 0.5 -- 0.8mpa, the pot water drain, the use of waste heat will be heated surface of the inner surface drying. Or use adjacent furnace hot air drying, and then close all valves. This method is suitable for protecting the boiler during overhaul.

5, desiccant method when the boiler needs long-term standby use this method. After stopping the furnace and drying, put the desiccant into the drum and close all the valves. The desiccant absorbs the moisture inside the heating surface of the boiler and keeps the inner surface dry.