Source: Internet Release Date: 2009/10/14
1. General requirements
1.1 The valve specifications and categories should meet the requirements of the pipeline design documents.
1.2 The valve model should be marked with the national standard number requirements.If it is a corporate standard, the relevant description of the model should be indicated.
1.3 The working pressure of the valve is required to be greater than or equal to the working pressure of the pipeline. The working pressure that the valve can withstand should be greater than the actual working pressure of the pipeline without affecting the price; any side of the valve should be able to withstand 1.1 times the working pressure of the valve when the valve is closed. Value without leakage; when the valve is open, the valve body should be able to withstand twice the valve working pressure.
1.4 The valve manufacturing standard should state the national standard number on which it is based. If it is a corporate standard, the purchase contract should be accompanied by corporate documents.
2. Valve standard quality
2.1 The material of the valve body should be mainly ductile iron, and the grade and actual physical and chemical test data of the cast iron should be indicated.
2.2 Stem material, strive for stainless steel stem (2CR13), large diameter valves should also be stainless steel embedded stems.
2.3 The nut material is made of cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem.
2.4 The material of the valve stem bushing shall have a hardness and strength not greater than that of the valve stem, and it shall not form electrochemical corrosion with the valve stem and valve body under the condition of water immersion.
2.5 Material of sealing surface: ①Valve types are different, sealing method and material requirements are different; ②Common wedge gate valve, copper ring material, fixing method, and grinding method should be explained; ③Soft sealing gate valve, valve plate lining material The physical, chemical and sanitary testing data of the butterfly valve; ④The butterfly valve should indicate the sealing surface material on the valve body and the sealing surface material of the butterfly plate; their physical and chemical testing data, especially the hygienic requirements, anti-aging performance, and wear resistance of rubber; usually used NBR and EPDM rubber are strictly prohibited from mixing with reclaimed rubber.
2.6 Valve shaft packing: ①As the valves in the pipe network are usually opened and closed infrequently, the packing is required to be inactive for several years, and the packing does not age, and the sealing effect is maintained for a long time; ②The valve shaft packing should also be subjected to frequent opening and closing In view of the above requirements, the valve shaft packing should not be replaced for life or more than ten years; ④If the packing needs to be replaced, the valve design should consider the measures that can be replaced under water pressure.
3. Variable speed transmission box
3.1 The material of the box body and the internal and external anti-corrosion requirements are consistent with the principle of the valve body.
3.2 The box body should have sealing measures, and the box body can withstand 3 meters of water column immersion after assembly.
3.3 The adjustment nut of the opening and closing limit device on the box body should be inside or outside the box, but special tools are required for operation.
3.4 The design of the transmission structure is reasonable. It can only drive the valve shaft to rotate when opening and closing, without causing it to move up and down, and the transmission parts will bite properly, and there will be no separation and slippage when opening and closing with load.
