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1. General requirements 1.1 Valve specifications and categories should be consistent with the requirements of the pipeline design documents. 1.2 The type of valve should be marked on the basis of the national standard number requirements. If the enterprise standard, should indicate the relevant description of the model. 1.3 The working pressure of the valve, the required working pressure ≥ pipe, without affecting the price under the premise of the valve can withstand the working pressure should be greater than the actual pipeline pressure; valve off any side should be able to withstand 1.1 times the valve pressure Value without leakage; valve open condition, the valve body should be able to withstand the pressure twice the valve requirements. 1.4 valve manufacturing standards should be based on the national standard number, if the enterprise standards, procurement contracts should be accompanied by corporate documents. 2. Valve Qualities 2.1 Body material, ductile iron should be based, and indicate the grades and the actual physical and chemical testing of cast iron. 2.2 stem material, and strive to stainless steel stem (2CR13), large-diameter valve should also be stainless steel embedded valve stem. 2.3 nut material, the use of cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the stem. 2.4 stem bushing material, the hardness and strength should not be greater than the stem, and in the water soaking conditions with the stem, the valve body does not form electrochemical corrosion. 2.5 sealing surface material: ①different types of valves, sealing methods and material requirements vary; ② ordinary wedge gate valve, copper ring material, fixing methods, grinding methods should be described; ③ soft seal gate valve, valve lining rubber material Of the physical and chemical and health testing data; ④ butterfly valve should be marked on the sealing material on the valve body and sealing material on the disc; their physical and chemical testing data, especially the rubber hygiene requirements, anti-aging properties, wear resistance; NBR and EPDM rubber, non-doped with recycled rubber. 2.6 Stem packing: ①Because of the valve in the pipe network, it is usually not frequent to open or close, requiring the packing to be inactive within a few years, the packing is not aged, and the sealing effect will be maintained for a long time. ② The valve shaft packing should withstand frequent opening and closing , The sealing effect of good; ③ In view of the above requirements, the valve shaft filler for life or do not change for more than ten years; ④ packing to be replaced, the valve design should be considered under water pressure conditions to replace the measures. 3. Transmission Gearbox 3.1 Material and internal and external anti-corrosion requirements of the body and the same principle. 3.2 boxes should be sealed, the box assembly can withstand 3 meters of water column status soak. 3.3 Box opening and closing limit device, the adjustment nut should be in the box or set in the box, but need special tools to work. 3.4 Transmission structure design is reasonable, when opening and closing can only drive the valve shaft to rotate, do not make it move up and down, transmission components bite moderation, do not produce separation and sliding with load hoist.