With the development of social economy, the use of valves is more and more extensive. There are many kinds of valves used in the pipeline, with different structures, and they are the most easily damaged pipeline accessories. The maintenance of each valve should be carried out according to the specific structure. There are many kinds of valves used in the pipeline, with different structures, and they are the most easily damaged pipeline accessories, and the maintenance of each valve.

1. The maintenance valve body and bonnet of the valve body and bonnet are the most external closed shell of the valve, which are used to bear the pressure of the medium, the additional force during operation, the weight of other parts of the valve, and the tightening force of the flange or thread at the joint. The valve body and bonnet are required to have certain strength and rigidity. Their damage is mainly caused by the local defects caused by the medium corrosion, erosion and mechanical damage. Or if the wall is thinned due to erosion, which affects their strength and rigidity, it cannot be repaired and should be replaced.

During maintenance, the water pressure strength test shall be carried out for the valve body and bonnet first, and then the tightness shall be inspected with water, compressed air, kerosene or other media. Generally, repair welding method shall be adopted for the defects of valve body and bonnet, and the corresponding welding rod and welding process shall be selected according to the different materials. The defective metal shall be cleaned before repair welding, and the inspection and repair shall be carried out after repair welding, and the stress shall be eliminated.

2. The maintenance of the packing chamber includes the replacement of the packing and the inspection and repair of the packing box. When selecting the packing, the service conditions and medium conditions must be considered. Generally speaking, the oil-borne asbestos packing is suitable for the air, steam, water and heavy oil products of a certain temperature. The graphite asbestos packing can be used under the conditions of high temperature and pressure, especially the graphite asbestos packing with steel wire has better pressure resistance. Asbestos and lead packing can be used for medium with high temperature and constant temperature change. PTFE asbestos packing or PTFE braiding can be used for medium with strong corrosion.