Pneumatic check valve role:
The main function of the pneumatic check valve is to prevent backflow of the medium in the pipe. Bottom valve and duckbill valve is also part of the check valve system. Check valve can be divided into lift, swing Kai, butterfly three. Lifting and can be divided into vertical and horizontal two kinds, lifting structure is moving along the axis. Swing type can be divided into single-valve, double-valve and multi-valve three, swing-type structure is rotated according to the center of gravity. Butterfly structure for the through-flow channel. Check valve opening and closing is dependent on the flow of media to open and close their own. Check valves are automatic valve products, check valves only allow medium to flow in one direction of the pipeline used to prevent the phenomenon of medium reflux. Its use of a wide range of applicable caliber, a variety of media, power station high-pressure system.
Pneumatic check valve general requirements:
1, the production of pneumatic valve specifications and categories should be consistent with the requirements of the pipeline design documents.
2, pneumatic valve model should be marked on the basis of the national standard number requirements. If the enterprise standard, should indicate the relevant description of the model.
3, the working pressure of pneumatic valve, the working pressure of ≥ pipeline, without affecting the price under the premise of the valve can withstand the working pressure should be greater than the actual working pressure pipeline; pneumatic valve closed condition on either side should be able to withstand 1.1 times Valve pressure value without leakage; valve open condition, the valve body should be able to withstand the pressure twice the valve requirements.
4, pneumatic valve manufacturing standards should be based on the national standard number, if the enterprise standards, procurement contracts should be accompanied by corporate documents.
Pneumatic check valve
Pneumatic check valve material:
1, the body material, ductile iron should be based, and indicate the grades and the actual physical and chemical testing of cast iron.
2, stem material, and strive to stainless steel stem (2CR13), large-diameter valve should also be stainless steel embedded valve stem.
3, nut material, the use of cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the stem.
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.
5, the sealing surface of the material:
① different types of pneumatic valves, sealing methods and material requirements vary;
② ordinary wedge gate valve, copper ring material, fixed way, grinding methods should be described;
③ soft seal gate valve, valve lining rubber material physical and chemical and health testing data;
④ butterfly valve should be marked on the valve body sealing surface material and the sealing material on the disc; their physical and chemical testing data, especially the rubber hygiene requirements, anti-aging properties, wear resistance;
6, valve shaft packing:
① due to the pneumatic valve in the pipe network, it is usually not frequent opening and closing, requiring the filler does not move within a few years, the filler is not aging, long-term 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, the valve shaft filler for life or do not change for more than 10 years;
④ If the packing needs to be replaced, the pneumatic valve design should consider the measures that can be replaced under the condition of water pressure.
Variable speed gearbox:
1, the cabinet material and internal and external corrosion requirements and the same principle of the valve body.
2, the box should be sealed, the box assembly can withstand 3 meters water column status soak.
3, the opening and closing limit on the box device, the adjustment nut should be in the box or located outside the box, but need special tools to work.
4, Transmission structure design is reasonable, when opening and closing can only drive the valve shaft to rotate, not to make it move up and down, transmission parts bite moderately, do not produce separation and slipping with load hoist.
5, variable speed transmission box and the valve shaft seal can not be connected into a whole without leakage, otherwise there should be reliable anti-stringing measures.
6, no debris inside the box, the gear occlusion should have grease protection.
Pneumatic check valve operating mechanism:
1, Pneumatic valve opening and closing direction of operation, should be closed clockwise.
2, due to the pneumatic 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 be within 200-600 turn.
3, in order to facilitate a person's opening and closing operations, the plumbing pressure conditions, the maximum opening and closing torque should be 240N-m.
4, pneumatic valve opening and closing operation side 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.
5, pneumatic valve opening and closing of the display panel
① pneumatic valve opening and closing of the scale line, should be cast in the gearbox cover or switch the direction of the display panel after the shell, all toward the ground, the scale brush on the phosphor to show the eye-catching
② indicating the material of the needle plate in the management of better available stainless steel plate, otherwise painted steel, do not use aluminum production;
③ indicates needle plate eye-catching, fixed firmly, once the opening and closing adjustment is accurate, should rivet lock.
6, If the pneumatic valve is buried deeply, when the operating mechanism and display panel are more than 1.5m away from the ground, it shall be provided with extension bar facilities which are fixed and firm 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.
Pneumatic check valve performance testing:
1, the valve manufactured in a batch size, the authoritative agencies should be commissioned to test the following properties:
① valve opening and closing moment under the conditions of work pressure;
② in the working pressure conditions, to ensure that the valve closed tight opening and closing times;
③ valve in the pipeline under the water flow resistance coefficient of detection.
2, the valve should be carried out in the factory the following test:
① valve in the open condition, the valve body pressure should withstand twice the pressure test;
② closed the valve, both sides were 1.1 times the valve pressure, no leakage; but the metal seal butterfly valve, the leakage value is not greater than the relevant requirements.
Pneumatic check valve inside and outside corrosion:
1, the valve body (including variable speed transmission 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.
2, all parts of the valve body and the valve plate requires a full anti-corrosion, on the one hand soaked in water will not rust, electrochemical corrosion between the two metals does not produce; two smooth surface to reduce the water resistance.
3, the body of the anti-corrosion epoxy resin or paint the health requirements, there should be the corresponding authority of the test report. Chemical and physical properties should also meet the relevant requirements.
Pneumatic check valve packaging and transportation
1, the valve should be set on both sides of the light blocking plate seal.
2, medium and small-diameter valves should be tied with straw, and transport by container is appropriate.
3, large-diameter valves are also simple wooden frame solid packaging, in order to avoid collision damage during transport.
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