Standard quality of pneumatic gate valve
1) The valve body is made of nodular cast iron, cast steel and stainless steel. The 316L is mainly marked with cast iron brand and actual physical and chemical testing data.
2) The valve stem shall be made of stainless steel (2) CR13). Large diameter valves shall also be stainless steel embedded valve stems.
3) Cast aluminum brass or cast aluminum bronze is made of nut material, and its hardness and strength are greater than those of the valve stem.
4) The hardness and strength of the valve stem bushing material shall not be greater than that of the valve stem, and the valve body will not form electrochemical corrosion when immersed in water.
5) Material of sealing surface
① Different types of pneumatic valves require different sealing methods and materials;
② General wedge gate valve, copper ring material, fixing method and grinding method;
③ Physical, chemical and sanitary testing data of soft seal gate valve and valve plate rubber lining material;
④ The sealing surface materials on the valve body and butterfly plate shall be marked for butterfly valves; The physical and chemical testing data, especially the hygienic requirements, aging resistance and wear resistance of rubber; Nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) are commonly used to mix recycled rubber.
6) Valve shaft packing
① As the pneumatic valve in the pipe network is usually closed infrequently, it is required that the filler should not be active for several years, and the filler should not be aged, so as to maintain the sealing effect for a long time;
② When withstanding frequent switching, the valve shaft packing shall also have a good sealing effect;
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 shall consider the replacement measures under water pressure.
Transmission case
1) The box material and internal and external anti-corrosion requirements are consistent with the valve body principle.
2) The box shall be provided with sealing measures, and the box can withstand immersion of 3m water column after assembly.
3) The adjusting nut of the opening and closing limit device on the box shall be located inside or outside the box, but it can only be operated with special tools.
4) The design of transmission structure is reasonable. When switching, the valve shaft can only be driven to rotate, instead of moving it up and down. The transmission parts are engaged properly, so that separation and slipping will not occur when switching on load.
5) The gearbox and the valve shaft seal shall not be connected as a whole without leakage, or reliable measures against string leakage shall be taken.
6) There are no sundries in the box, and the gear engagement part should be protected by grease.
