The procurement needs to pay attention to the standard problem of pneumatic valve procurement valve technical requirements of the valve
In the world usually pneumatic valves are a unified standard, so buyers are more convenient and secure procurement. But in the domestic pneumatic valve although there are national standards, but due to different market requirements, domestic manufacturers in order to meet customer needs, each manufacturer according to the national standard on the basis of the corresponding changes and innovation to adapt to the better use of pneumatic valves in different environments.
So here to remind the vast number of buyers, we must according to the needs of the site, detailed specifications and requirements when purchasing, and manufacturers negotiate the requirements of pneumatic valves and marked clearly in the contract attachment: for example, the pressure is greater than the number of times of pipeline pressure, normally open or normally closed state can bear the pressure value. Of course, manufacturers will also put their own innovation or non – target specifications to tell customers for reference.
The technical requirements of valve procurement valve working pressure, requirements ≥ pipeline working pressure, under the premise of not affecting the price, the valve can withstand the working pressure should be greater than the actual working pressure of the pipeline; Any side of the closed valve 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 requirements of two times the valve pressure. If the valve is buried deep, operating mechanism and display disk from the ground distance ≥1 5m, should be equipped with a lengthening rod facility, and fixed firmly, so that people from the ground observation and operation. That is to say, the valve opening and closing operation in the pipe network is not suitable for well operation.
1 General Requirements
1.1 Valve specifications and categories shall conform to the requirements of pipeline design documents.
1.2 The valve model shall indicate the national standard numbering requirements. If the enterprise standard, should indicate the relevant description of the model.
1.3 The working pressure of the valve shall be ≥ the working pressure of the pipeline. Under the premise of not affecting the price, the working pressure that the valve can bear shall be greater than the actual working pressure of the pipeline; Any side of the closed valve 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 requirements of two times the valve pressure.
1.4 For the valve manufacturing standard, the national standard number should be specified. If it is the enterprise standard, the enterprise document should be attached to the purchase contract.
2 Valve material
2.1 Valve material, as gray cast iron pipe is gradually not recommended, the valve body material should be mainly ductile cast iron, and mark the brand
And the actual physical and chemical test data of castings.
2.2 Stem material, strive to stainless steel stem (2CR13), large diameter valves should also be stainless steel embedded stem.
2.3 The nut is made of cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem.
2.4 The hardness and strength of the valve stem bushing material shall not be greater than the valve stem, and there shall be no electrochemical corrosion with the valve stem and valve body under the condition of water immersion.
2.5 Material of sealing surface
(1) Different types of valves, sealing methods and material requirements;
② Common wedge gate valve, copper ring material, fixing way, grinding way should be described;
③ Physical, chemical and health test data of soft seal gate valve and valve plate lining rubber material;
(4) The butterfly valve should indicate the sealing surface material on the valve body and the sealing surface material on the butterfly plate; Their physical and chemical test data, especially rubber health requirements, aging resistance, wear resistance; Usually adopt butadiene rubber and EPDM rubber, it is strictly prohibited to mix with recycled rubber.
2.6 Valve shaft packing
(1) Because the valve in the pipe network is usually opened and closed infrequently, the packing is not active in a few years, the packing is not aging, and the sealing effect is maintained for a long time;
(2) Valve shaft packing should also withstand frequent opening and closing, sealing effect is good;
(3) In view of the above requirements, the valve shaft packing should not be replaced for life or more than 10 years;
④ If the packing needs to be replaced, the valve design should consider the replacement measures under the condition of water pressure.
3 Variable speed transmission box
3.1 The material and internal and external anticorrosion requirements of the box body are consistent with the principle of the valve body.
3.2 The box body should be sealed and can withstand soaking of 3m water column after assembly.
3.3 The adjusting nuts of the opening and closing limiting device on the box should be in the box.
3.4 Reasonable transmission structure design, opening and closing can only drive the valve shaft rotation, do not make it move up and down, moderate transmission parts bite, do not produce load when opening and closing separation slip.
3.5 The sealing place of the gearbox and valve shaft shall not be connected into a leak-free whole.
3.6 There is no sundry matter in the box, and the gear occlusal part should be protected by grease.
4. Operating mechanism of valve
4.1 The opening and closing direction of the valve during operation shall be closed clockwise.
4.2 Because the valves in the pipe network are often opened and closed manually, the opening and closing revolutions should not be too much, even the large diameter valves should also be within 200-600 revolutions.
4.3 In order to facilitate one person’s opening and closing operation, under the condition of plumber pressure, the maximum opening and closing torque should be 240m-m.
4.4 Valve opening and closing operation end shall be square tenon, standardized size, and face the ground, so that people can directly operate from the ground. The valve with wheel is not suitable for underground pipe network.
4.5 Display panel of valve opening and closing degree
(1) The scale line of the opening and closing degree of the valve should be cast on the gearbox cover or the shell of the display plate after the conversion direction, all facing the ground, and the scale line should be brushed with phosphor to show eye-catching;
(2) The material of the indicator plate needle can be used in the case of better management of stainless steel plate, otherwise painted steel plate, do not use aluminum skin production;
The indicator disk needle eye-catching, fixed firmly, once the opening and closing adjustment is accurate, should be locked with rivet.
4.6 If the valve is buried deep and the distance between the operating mechanism and the display plate and the ground is greater than or equal to 15 m, the extension rod facility should be provided and fixed firmly, so that people can observe and operate from the ground. That is to say, the valve opening and closing operation in the pipe network is not suitable for well operation.
5. Performance test of valves
5.1 When the valve of a certain specification is manufactured in batch, the following performance should be tested by a perfect mechanism:
① Opening and closing torque of valve under working pressure condition;
(2) Under the working pressure condition, can ensure that the valve closed tightly continuous opening and closing times;
③ The detection of flow resistance coefficient of valve under the condition of pipeline water transmission.
5.2 The valve shall be tested as follows before leaving the factory:
(1) The valve in the open condition, the valve body should bear the internal pressure detection of the valve working pressure value twice;
(2) Valve in closed condition, both sides respectively bear 1 times the valve working pressure value, no leakage; But the metal seal butterfly valve, leakage value is not greater than the relevant requirements.
6. Internal and external anticorrosion of valve
6.1 The inside and outside of the valve body (including the variable speed transmission box), the first thing should be shot blasting, sand cleaning and rust removal, and strive to electrostatic spraying powder non-toxic epoxy resin, the thickness of more than 0 3mm. When electrostatic spraying non-toxic epoxy resin is difficult for oversized valves, similar non-toxic epoxy paint should also be brushed and sprayed.
6.2 The inside of the valve body and all parts of the valve plate require perfect anticorrosion. On the one hand, it will not rust when soaked in water, and there will be no electrochemical corrosion between the two metals; Two aspects of smooth surface to reduce water resistance.
6.3 For the sanitary requirements of the anticorrosive epoxy resin or paint in the valve body, the corresponding inspection report of the ** organ shall be provided. Chemical and physical properties should also meet the relevant requirements.
7. Valve packing and transportation
7.1 Light plugging plates shall be installed on both sides of the valve.
7.2 Medium and small diameter valves should be tied with straw ropes and transported in containers.
7.3 Large diameter valves are also equipped with simple wooden strip frame retaining package to avoid damage during transportation.
Valves are equipment, and the following relevant data should be marked in the factory manual: valve specifications; Model number; Working pressure; Manufacturing standards; Valve body material; Stem material; Sealing material; Valve shaft packing material; Valve stem sleeve material; Internal and external anticorrosive material; Operation start direction; Revolutions; Opening and closing moment under working pressure; The name of the manufacturer; Date of delivery; Factory number; Weight; Connecting flange aperture, hole number, center hole distance; The control dimensions of overall length, width and height are indicated in graphic form; Valve flow resistance coefficient; Effective opening and closing times; Valve factory test data and installation, maintenance precautions, etc.
Post time: Jan-07-2023