Guide: ①Drying method After the boiler is out of service, when the boiler water temperature drops to 100～120℃, the water will be discharged (the hot furnace is discharged), and the air discharge valve will be opened at the same time. After the water is exhausted, use

　　① Drying method

　　After the boiler is out of service, when the boiler water temperature drops to 100～120℃, it will start to discharge water (heat furnace water discharge), and open the air discharge valve at the same time. After the water is exhausted, use the residual heat in the furnace to dry the metal surface in the pot. If it is not repaired, it is best to close all external connecting valves after the furnace is cold.

This method is only applicable to the anti-corrosion of the boiler during maintenance or short-term shutdown (within a week).

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　　② Nitrogen filling method

　　After stopping the furnace, drain the pot of water and fill the tube side with nitrogen with a purity of 99% and above. When filling nitrogen, all valves of the boiler water vapor system should be closed and tightly leak-proof. The nitrogen pressure should be maintained above 0.05 MPa gauge pressure. During the period of nitrogen filling protection, the pressure of nitrogen in the boiler water and steam system should be constantly monitored. If there is a drop, it is necessary to find and eliminate leaks and add nitrogen to maintain the specified pressure.

　　If nitrogen can be added in time during the nitrogen protection period to maintain the specified pressure, this method can be applied to long-term shutdown of the boiler (more than three months) or protection in cold areas to prevent the boiler from freezing due to freezing. When restarting, nitrogen can be directly discharged into the atmosphere.

　　③ Desiccant method

　　After the boiler is stopped, the water in the boiler can be drained. A hot boiler can be used to drain the water, and the metal surface in the boiler can be dried by the residual heat in the boiler. After the boiler is cooled, a certain amount of desiccant with a certain water absorption capacity is placed in each cubic meter of the boiler volume (Such as anhydrous calcium chloride, silica gel, quicklime, etc., the amount is about 1-3kg/m3), put it into a special small container and put it on the side of the boiler tube. It can be put into the header through the boiler inspection hole or the main steam pipe seat, but make sure that the desiccant can be taken out when the boiler is restarted. During the protection period, the boiler should be kept in a closed state, and the desiccant should be inspected and replaced regularly (for example, every other month).

　　This method is simple and convenient to operate, and can be used for long-term shutdown of the boiler (more than three months) or protection in cold areas to prevent the boiler from freezing due to freezing. When restarting, remove the desiccant and rinse the boiler.

　　④ Maintaining water supply pressure method

　　When the boiler is out of service, fill the boiler with feed water that has undergone deoxygenation treatment, and close all valves to prevent air from entering the boiler. During the protection period, use the feed water pump to control the pressure in the pot to be above 0.3MPa gauge pressure, and always check the oxygen content in the pot water. If it exceeds the standard, replace the pot water. This law can be applied to protection within one month. If sodium sulfite is added to the pot water at the same time and the excess amount is maintained at 5-10 mg/L, this method can be applied to the protection within three months.

When applying this method in cold areas, take anti-freezing measures to avoid damage to the equipment

　　⑤ Vapor phase corrosion inhibitor method

　　Vapor phase corrosion inhibitors mainly include inorganic ammonium salts and organic amines, such as diammonium hydrogen phosphate, urotropine, ammonium benzoate, and cycloethylamine carbonate. The method of use is simple and basically the same as the desiccant method. Use a hot furnace to discharge water. After the furnace is cooled, the selected one or two vapor phase corrosion inhibitors are put into a small cloth bag and placed on the side of the boiler tube at a dosage of 50-100g/m3. It can be put into the header through the boiler inspection hole or the main steam pipe seat, but the bag can be taken out when the boiler is restarted. During the protection period, the boiler should be kept in a closed state.

　　If the sealing is good, the protection period can reach about three months, which is suitable for long-term shutdown of the boiler or protection in cold areas to prevent the boiler from freezing due to freezing.

The shutdown maintenance of the gas steam boiler can be done according to your actual needs. We recommend the dry maintenance method, which is more worry-free and the maintenance time will be longer.