If the boiler is not used for more than one week, the nitrogen protection should be adopted.
--- After shutdown, the nitrogen should be filled into the boiler if the drum pressure is reduced to 0.3MPa. Under the condition that the nitrogen pressure is maintained to be within 0.3MPa to 0.5MPa, the water drainage door should be opened. And they should be all shut off until the boiler water is totally discharged by the use of nitrogen.
--- The steam water system should be overall checked, close the air valves, the drainage valve, the sewage valve, the feedwater pipeline, the main steam pipeline and its drainage valves tightly, make sure that the nitrogen system is very tight.
--- During the nitrogen protection period, make sure that the nitrogen pressure should be more than 0.03MPa (on gauge) and the nitrogen purity should be more than 98%.