• General requirements for pneumatic check valves

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General requirements for pneumatic check valves

  • 04 22, 2019
1. The specifications and categories of pneumatic valves produced should meet the requirements of the pipeline design documents.

2.  The model of the pneumatic valve should be indicated, according to the national standard number.  If it is an enterprise standard, the relevant description of the model should be indicated.

3. The working pressure of the pneumatic valve requires ≥ the working pressure of the pipeline. Under the premise of not affecting the price, the working pressure of the valve should be greater than the actual working pressure of the pipeline; any side of the pneumatic valve under closing condition should be able to withstand 1.1 times the working pressure of the valve without leakage; when the valve is open, the valve body should be able to withstand twice the working pressure of the valve.

4. Pneumatic valve manufacturing standards should be indicated in accordance with the national standard number. If it is an enterprise standard, the company's documents shall be attached to the procurement contract.

Pneumatic check valve material:
4.1 The body material should be made of ductile iron, and the grade and the actual physical and chemical testing data of the cast iron should be indicated.
4.2 Valve stem material: it is best to use stainless steel valve stem (2CR13), and a large diameter valve should also have a stainless steel embedded valve stem.
4.3 Nut material: cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than that of the valve stem.
4.4 The stem bushing material should have a hardness and strength not greater than that of the valve stem, and it will not form electrochemical corrosion with the valve stem and valve body under water immersion conditions.

5. Material of sealing surface:
5.1 Sealing methods and material requirements are different according to the type of the pneumatic valves;
5.2 For ordinary wedge gate valve, the material, fixing method and grinding method of the copper ring should be explained;
5.3 For soft sealed gate valves, the physical and chemical testing data and health inspection data of valve plate lining material;
5.4 For butterfly valves, the sealing surface material on the valve body and the sealing surface material on the butterfly plate should be indicated; as well as their physical and chemical testing data, especially the hygienic requirements of rubber, anti-aging performance and wear resistance; it is forbidden to use reclaimed rubber.

6. Valve shaft packing:
6.1 Because the pneumatic valves in the pipe network are usually opened and closed infrequently, the fillers are required to be inactive for several years, the fillers are not aged, and the sealing effect is maintained for a long time;；
6.2 The valve shaft packing should also be well sealed when subjected to frequent opening and closing;
6.3 In view of the above requirements, the valve shaft packing is intended to be replaced for a lifetime or not replaced for more than ten years;
6.4 If the packing needs to be replaced, the design of the pneumatic valve should take into account the measures for replacement under water pressure.

General requirements for pneumatic check valves
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