1. General requirements
1.1 The specifications and categories of pneumatic valves should meet the requirements of pipeline design documents.
1.2 The model of the pneumatic valve should indicate the requirements of the national standard number. If it is an enterprise standard, the relevant description of the model should be indicated.
1.3 The working pressure of the pneumatic valve is required to be greater than or equal to the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can withstand should be greater than the actual working pressure of the pipeline; any side of the pneumatic valve should be able to withstand 1.1 times the valve when it is closed. Working pressure value without leakage; when the valve is open, the valve body should be able to withstand twice the working pressure of the valve.
1.4 For the manufacturing standard of pneumatic valve, the national standard number should be stated. If it is an enterprise standard, the enterprise document should be attached to the purchase contract.
2. Standard quality of pneumatic valve
2.1 The material of the valve body should be mainly ductile iron, and the grade and actual physical and chemical testing data of the cast iron should be indicated.
2.2 The material of the valve stem should be made of stainless steel stem (2CR13). Large-diameter valves should also be stainless steel embedded valve stems.
2.3 The nut is made of cast aluminum brass or cast aluminum bronze, and its hardness and strength are greater than those of the valve stem.
2.4 The hardness and strength of the valve stem bushing shall not be greater than that of the valve stem, and there shall be no electrochemical corrosion with the valve stem and valve body under water immersion.
2.5 Material of sealing surface
①The types of pneumatic valves are different, and the sealing methods and material requirements are different;
② For ordinary wedge gate valves, the material, fixing method and grinding method of the copper ring should be explained;
③Physicochemical and hygienic testing data of soft sealing gate valve and valve plate rubber lining material;
④The butterfly valve should be marked with the material of the sealing surface on the valve body and the material of the sealing surface on the butterfly plate; their physical and chemical test data, especially the hygienic requirements of rubber, anti-aging performance, and wear resistance;
2.6 Valve shaft packing
①Because the pneumatic valves in the pipe network are usually opened and closed infrequently, the packing is required to be inactive for several years, and the packing will not age, so that the sealing effect can be maintained for a long time;
②The valve shaft packing should also have good sealing effect when it is subjected to frequent opening and closing;
③ In view of the above requirements, the valve shaft packing shall not be replaced for life or more than ten years;
④ If the packing needs to be replaced, the design of the pneumatic valve should consider the measures to be replaced under the condition of water pressure.
3. Variable speed gearbox
3.1 The box material and internal and external anti-corrosion requirements are consistent with the valve body principle.
3.2 The box body should have sealing measures, and the box body can withstand the immersion of 3 meters of water column after assembly.
3.3 For the opening and closing limit device on the box, its adjusting nut should be inside the box or outside the box, but it needs special tools to work.
3.4 The design of the transmission structure is reasonable. When opening and closing, it can only drive the valve shaft to rotate, not to make it move up and down.
3.5 The transmission case and the valve shaft seal should not be connected to form a leak-free whole, otherwise there should be reliable anti-leakage measures.
3.6 There is no debris in the box, and the gear occlusion part should be protected by grease.
4. Operating mechanism of pneumatic valve
4.1 The opening and closing direction of the pneumatic valve should always be closed clockwise.
The above four points are the basic knowledge of pneumatic valves shared with you today. I think everyone has a certain understanding of the basic knowledge of pneumatic valves after reading them.