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In the pipeline used in a wide variety of valves, different structures, but also the most vulnerable pipe accessories, maintenance of each valve should be based on the specific structure of the valve used in the pipeline a wide variety of structures Different, but also the most vulnerable pipeline annex, for each valve overhaul, should be based on the specific structure. 1: Body and bonnet inspection The valve body and bonnet are the outermost enclosed housings of the valve to withstand medium pressure, additional forces during operation, weight of other parts of the valve, and the tightness of the flange or thread at the connection The valve body and bonnet require a certain degree of strength and stiffness, their damage is mainly caused by medium corrosion, erosion and mechanical damage caused by local defects, when corrosion or erosion caused by wall thinning, and even affect their strength And stiffness, it can not be repaired and should be replaced. Overhaul, the valve body and bonnet should be first hydraulic pressure test, and then water, compressed air, kerosene or other media to test its tightness. Body and bonnet defects Generally use the method of welding, according to the material of the different selection of the corresponding welding rod and welding process. Welded metal defects before cleaning should be cleaned, repaired after welding should also be checked and eliminate stress. 2: Overhaul of the stuffing room includes replacement of stuffing and inspection and repair of stuffing box parts. When using stuffing, the condition of use and the condition of the medium must be considered. In general, asbestos packing is suitable for a certain temperature Air, steam, water and heavy oil products Graphite asbestos packing can be used under high temperature and pressure conditions, especially wire with graphite asbestos packing pressure is better.High temperature and temperature changes of the medium can be asbestos plus lead packing. Strong corrosive media can be used to invade PTFE asbestos packing or PTFE woven.