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 of pneumatic valve manufacturers in order to compete for products, each in the pneumatic valve unified design concept, To carry out different innovations, 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. 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. Pneumatic valve material 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; NBR and EPDM rubber, non-doped with recycled rubber. 2.6 Stem packing ①Due to the pneumatic valve in the pipe network, it is usually not frequent to open and close, requiring the packing to be inactive within a few years, the packing is not aged, and the sealing effect is maintained for a long time. ② The valve shaft packing should withstand frequent opening and closing , The sealing effect of good; In view of the above requirements, the valve shaft filler for life or do not change for more than ten years; If the filler needs to be replaced, pneumatic valve design should be considered under water pressure conditions to replace the measures. Transmission gear box 3.1 Material and internal and external corrosion protection requirements and the same body 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. Pneumatic valve operating mechanism 4.1 Pneumatic valve opening and closing direction of operation, should be closed clockwise. 4.2 As the pipe network of pneumatic valves, often manual opening and closing, opening and closing speed should not be too much, that is, large-diameter valves should be within 200-600 turn. 4.3 In order to facilitate a person's opening and closing operation, under plumbing conditions, the maximum opening and closing torque should be 240N-m. 4.4 Pneumatic valve opening and closing operation end should be square tenon, and size standardized, and facing the ground, so that people from the ground can be directly manipulated. Valves with wheels are not suitable for underground pipe networks. 4.5 Pneumatic valve opening and closing of the display plate ①pneumatic valve opening and closing of the scale line should be cast in the gearbox cover or switch the direction of the display after the shell, all toward the ground, the scale brush phosphor to show Eye-catching; ② indicates that the material of the needle plate can be used in the case of better management of stainless steel plate, otherwise painted steel, do not use aluminum production; ③ indicating needle needle eye-catching, fixed firmly, once the opening and closing adjustment is accurate, should Rivet lock. 4.6 If the pneumatic valve is deeply buried, the operating mechanism and the display panel should be provided with extension rod facilities when the distance to the ground is ≥1.5m, and should be fixed firmly so that people can observe and operate from the ground. In other words, pipe network valve opening and closing operation, should not go down to work. More keyword search: Pneumatic valve