Procurement pneumatic valve eight tips

pneumatic valve procurement only clear specification, category, work pressure meet the requirements of the practice, in the current market economy environment is not perfect. Because pneumatic valve manufacturer to product competition, each are unified in the pneumatic valve design conception, for different innovation, formed their own enterprise standards and product personality.
so on pneumatic valve procurement detailed technical requirements, coordination with manufacturer agreement, procurement contract as pneumatic valves accessories is very necessary.
general requirements: pneumatic valve specifications and categories, should accord with the requirement of pipe design documents. Pneumatic valve type shall be marked according to gb code requirements. If the enterprise standards, should indicate the type of relevant specification. Pneumatic valve working pressure and requirement of pipe or work pressure, without affecting the price under the premise of pneumatic valve can withstand work pressure should be greater than pipeline of actual work.
the any side of the pneumatic valve closed condition should be able to withstand times working pressure pneumatic valve value without leakage; Pneumatic valve open conditions, the body should be able to withstand 2 times the work pressure of the pneumatic valve requirements. Pneumatic valve manufacturing standards, should be according to gb code, if the enterprise standards, on the purchase order file should be attached to the enterprise.
pneumatic valve standard quality: body material, should give priority to with nodular cast iron, and indicate the brand and cast iron is the actual physical and chemical testing data; Pneumatic valve stem material, and strive to stainless steel pneumatic valve stem ( CR, large diameter pneumatic valves should also be embedded package of stainless steel stem; Nut material, the use of cast aluminum bronze, brass or aluminum and the hardness and strength is greater than the pneumatic valve rod; Pneumatic valve stem bushing material, its hardness and strength shall be no greater than the pneumatic valve stem, and soaking in the water condition and pneumatic, pneumatic valve stem don't form the electrochemical corrosion.
the sealing surface material: (1) pneumatic valves have different categories, different sealing methods and material requirements; (2) general pneumatic wedge gate valve, the material of copper ring, fixed way and grinding way shall specify; (3) pneumatic soft sealing gate valve, pneumatic valve plate rubber lining material physical chemistry and health testing data; (4) butterfly pneumatic valve pneumatic sealing surface on the valve body material and butterfly plate must be marked on the sealing surface material; Their physical and chemical testing data, especially the health requirements of rubber, ageing resistance, wear resistance; Usually use nitrile butadiene rubber and epdm and so on, it is strictly prohibited to mixed with reclaimed rubber.
pneumatic valve shaft packing: (1) due to pipe network in pneumatic valve, usually open/close not frequent, packing in a few years no activity, the packing is not aging, long sealing effect; (2) pneumatic valve shaft packing should also be under the frequent opening and closing, good seal effect; (3) in view of the above requirements, the pneumatic valve shaft packing to lifetime don't change or more than ten years will not be changed; (4) packing if need to change, the pneumatic valve design should be considered to have the water pressure under the condition of change of measures.