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

1. Maintenance of valve body and bonnet the valve body and bonnet are the closed shell outside the valve to bear the pressure of medium, additional force during operation, weight of other parts of the valve, and tightening force of flange or thread at the joint The valve body and valve cover are required to have certain strength and rigidity. Their damages are mainly local defects caused by medium corrosion, erosion and mechanical damage. When the wall is thinned due to corrosion or erosion and their strength and rigidity are affected, they cannot be repaired and should be replaced.
 

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

2. Maintenance of packing chamber The maintenance of packing chamber includes the replacement of packing and the inspection and repair of stuffing box. When selecting packing, the service conditions and medium conditions must be considered. Generally speaking, oil impregnated asbestos packing is suitable for air, steam, water and heavy oil products with a certain temperature. Graphite asbestos packing can be used under high temperature and high pressure conditions, especially the graphite asbestos packing with steel wire has better pressure resistance. High temperature and constant temperature are the main reasons The changing medium can be packed with asbestos and lead. The strong corrosive medium can be packed with asbestos or woven with polytetrafluoroethylene.

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