What is a pneumatic valve

When purchasing pneumatic valves, it is not perfect in the current market economy environment that only the specification, category and working pressure are specified to meet the purchasing requirements. For the sake of product competition, the manufacturers of pneumatic valves carry out different innovations under the concept of unified design of pneumatic valves, forming their own enterprise standards and product personality. Therefore, it is very necessary to put forward the technical requirements in detail when purchasing the pneumatic valve and reach a consensus with the manufacturer as an attachment of the pneumatic valve purchase contract.

1. General requirements

1.1 the specification and category of pneumatic valve shall meet the requirements of pipeline design documents.

1.2 the model of pneumatic valve shall indicate the number requirements of national standard. If it is an enterprise standard, the relevant description of the model shall be indicated.

1.3 the working pressure of pneumatic valve is required to be ≥ the working pressure of the pipeline. On 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 pneumatic valve under the closed condition shall be able to bear 1.1 times the working pressure of the valve without leakage; under the open condition of the valve, the valve body shall be able to bear twice the working pressure of the valve.

1.4 the manufacturing standard of pneumatic valve shall indicate the national standard number. If it is an enterprise standard, the procurement contract shall be attached with the enterprise document.

2. Standard quality of pneumatic valve

2.1 the valve body material shall be mainly nodular cast iron, and the brand and actual physical and chemical test data of cast iron shall be indicated.

2.2 the material of valve rod shall be stainless steel (2Cr13), and the large-diameter valve shall also be stainless steel embedded valve rod.

2.3 the nut is made of cast aluminum brass or cast aluminum bronze, and its hardness and strength are greater than that of the valve rod.

2.4 the hardness and strength of the material of the valve rod bushing shall not be greater than that of the valve rod, and it shall not form electrochemical corrosion with the valve rod and valve body under the condition of water immersion.

2.5 material of sealing surface

① There are different types of pneumatic valves, different sealing methods and material requirements;

② For ordinary wedge gate valve, the material, fixing method and grinding method of copper ring shall be specified;

③ Physical, chemical and sanitary test data of soft seal gate valve and valve plate rubber lining material;

4. The butterfly valve should mark the material on the sealing surface of the valve body and the material of the sealing cover on the butterfly plate; their physical and chemical test data, especially the hygienic requirements, anti-aging and wear-resisting properties of the rubber, usually use NBR and three ethylene propylene rubber, and so on, and strictly prohibit the addition of reclaimed rubber.

2.6 shaft packing

① As the pneumatic valve in the pipe network is usually opened and closed infrequently, it is required that the packing will not be active for several years, and the packing will not age, so as to maintain the sealing effect for a long time;

② The packing of valve shaft should also bear the good sealing effect when it is opened and closed frequently;

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 pneumatic valve design shall consider the replacement measures under the condition of water pressure.