Pneumatic valve: with compressed air driven valve. Pneumatic valve procurement only a clear specification, type, pressure to meet the procurement requirements of the practice in the current market economy environment is imperfect. Because the pneumatic valve manufacturers in order to compete for products, each in the design of pneumatic valve under the concept of a unified, innovative, formed their own corporate standards and product personality. Therefore, pneumatic valve procurement more detailed technical requirements, and manufacturers to obtain consensus, as a pneumatic valve procurement contract annex is necessary. 1. General requirements 1.1 Pneumatic valve specifications and categories should be consistent with the requirements of the pipeline design documents. 1.2 Pneumatic valve model should be marked on the basis of GB number requirements. If the enterprise standard, should indicate the relevant description of the model. 1.3 Pneumatic valve working pressure, 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; pneumatic valve closed condition on either side should be able to withstand 1.1 times the valve Work pressure value without leakage; valve open condition, the valve body should be able to withstand the double valve pressure requirements. 1.4 Pneumatic valve manufacturing standards should be based on the national standard number, if the corporate standards, procurement contracts should be accompanied by corporate documents. 2. Pneumatic valve quality 2.1 body material, ductile iron should be based, and indicate the grades and cast iron actual physical and chemical testing data. 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 ①pneumatic valve types, 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; Buna nitrile rubber metallurgical? Cellulite? Carried out under the jurisdiction of the fans? Hypoallergenic? Skeleton? 2.6 valve shaft packing ①pneumatic valve in the pipe network, usually open and close infrequently, requiring filler in a few years inactivity, The packing is not aging, long-term to maintain the sealing effect; ② valve shaft packing should also withstand frequent opening and closing, the sealing effect of the good; ③ In view of the above requirements, valve shaft packing for life or do not change for more than ten years; If replacement is required, the design of the pneumatic valve should consider measures that can be replaced under water pressure conditions. 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. 3.5 Variable speed transmission box and valve shaft seal can not be connected into a whole without leakage, otherwise there should be reliable anti-stringing measures. 3.6 box body without debris, the gear occlusion should have grease protection. 4. Pneumatic valve operating mechanism 4.1 Pneumatic valve opening and closing direction of operation, should be closed clockwise. This article Keywords: Pneumatic valve
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