Valve procurement process must refer to eight factors
April 07 14:02:50, 2021
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 valve manufacturer in order to compete for the product, each in the valve under the concept of a unified design, different innovations, formed their own corporate standards and product personality. Therefore, when the valve procurement more detailed technical requirements, and manufacturers to obtain consensus, as the annex to the valve procurement contract is necessary. 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 Physical and chemical and health testing data; ④ butterfly valves 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; Clear rubber and EPDM rubber, non-doped with recycled rubber. 2.6 Valve shaft packing ①Because the valve in the pipe network is usually not open and close frequently, it is required that the packing should not be activated within a few years and the packing should not be aged, and the sealing effect should be maintained for a long time. ② The valve shaft packing should withstand frequent opening and closing , The sealing effect of the good; ③ In view of the above requirements, the valve shaft filler for life or do not change for more than ten years; ④ filler to be replaced, the valve design should be considered under pressure to replace the measures. 3. Transmission Gearbox 3.1 Material and the 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 valve operating mechanism 4.1 valve opening and closing direction of operation, should be closed clockwise. 4.2 Due to the valve in the pipe network, often manual opening and closing, opening and closing speed should not be too much, that is, large-diameter valves should also 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 Valve opening and closing operation end should be square tenon, and size standardization, and facing the ground, so that people can directly operate from the ground. Valves with wheels are not suitable for underground pipe networks. 4.5 degree of opening and closing of the valve display ①valve 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 on the phosphor to show eye-catching; ② indicating the material of the needle plate in the management of better use of stainless steel plate, or painted steel, do not use aluminum production; ③ indicating needle needle eye-catching, fixed firmly, once the opening and closing adjustment is accurate, should be rivets locking. 4.6 If the valve buried deeper, the operating mechanism and the display panel from the ground distance ≥ 1.5m, should be equipped with additional rod facilities, and fixed firmly, so that people from the ground to observe and operate. In other words, pipe network valve opening and closing operation, should not go down to work. 5. Valve performance testing 5.1 Valve batch manufacturing a certain specification, the authority should be entrusted to the agency for the following performance testing: ①valve opening and closing under pressure conditions; ② Under the pressure conditions, to ensure that the valve is closed tight Of the continuous opening and closing times; ③ valve in the pipeline water flow resistance coefficient of the test. 5.2 The valve should be tested at the factory as follows: ①When the valve is in the open condition, the valve body shall withstand the internal pressure twice the pressure value of the valve; ② Under the closed condition of the valve, both sides shall withstand 1.1 times the valve working pressure , No leakage; but the metal seal butterfly valve, the leakage value is not greater than the relevant requirements. 6. Inside and outside the valve anti-corrosion 6.1 The body (including the gear box) inside and outside, the first shot blasting sand rust, and strive to electrostatic spray powder non-toxic epoxy resin, the thickness of 0.3mm above. Extra-large valve electrostatic spraying non-toxic epoxy resin difficulties, should also be brushing, spraying similar non-toxic epoxy paint. 6.2 All parts of the valve body and the valve plate require full corrosion protection. On the one hand, it will not be eroded in the water and will not cause electrochemical corrosion between the two metals. On the other hand, the smoothness of the surface reduces the resistance to over-water flow. 6.3 Anticorrosive epoxy resin or paint the body of the health requirements, there should be the corresponding authority of the test report. Chemical and physical properties should also meet the relevant requirements. 7. Valve packaging and transportation 7.1 should be set on both sides of the light blocking plate solid seal. 7.2, small-caliber valves should be tied with straw, and transported by container mode is appropriate. 7.3 Large diameter valve also has simple wooden frame solid packaging, in order to avoid collision damage during transportation. 8 valve factory instructions The valve is a device, the factory manual should be marked with the following relevant data: Valve Specifications; Model; Working pressure; Manufacturing standards; Body material; Stem material; Sealing material; Stem packing material; Stem Shaft Set of materials; inside and outside anti-corrosion materials; Start the direction of operation; Revolutions; Opening and closing torque under conditions of work pressure; Factory name; Date of manufacture; Factory number; Weight; Diagram shows the overall length, width and height control dimensions; valve flow resistance coefficient; the number of effective opening and closing; the valve factory inspection of the relevant data and installation, maintenance precautions and so on.