Procurement of anti-corrosion valves to consider the necessary procurement only clear specifications, categories, work pressure to meet the procurement requirements of the practice, in the current market economy is not perfect. Because the valve manufacturers in order to product competition, each in the valve under the concept of unified design, different innovations, the formation of their own corporate standards and product personality. Therefore, in the valve procurement more detailed technical requirements, and manufacturers to coordinate to achieve consensus, as an annex to the valve procurement contract is very necessary.
- General requirements
1.1 Valve specifications and categories, should be in line with the requirements of the pipeline design documents.
1.2 The model number of the valve should be indicated based on the national standard number requirements. If it is a corporate standard, the relevant description of the model should be indicated.
1.3 valve working pressure, required ≥ the working pressure of the pipeline, without affecting the price of the premise that the valve can withstand the pressure should be greater than the actual pressure of the pipeline; valve closed condition of any side should be able to withstand 1.1 times the valve pressure value without leakage; valve open condition, the valve body should be able to withstand two times the valve pressure requirements.
1.4 valve manufacturing standards, should be based on the national standard number, if it is a corporate standard, the procurement contract should be attached to the corporate documents.
- Valve standard quality
2.1 valve body material, should be mainly ductile iron, and specify the grade and the actual physical and chemical test data of cast iron.
2.2 Valve stem material, strive to stainless steel stem (2CR13), large diameter valves should also be stainless steel embedded stem.
2.3 Nut material, using cast aluminum brass or cast aluminum bronze, and hardness and strength are greater than the stem.
2.4 Stem bushing material, its hardness and strength should be no greater than the stem, and in the case of water immersion and the stem, the body does not form electrochemical corrosion.
2.5 sealing surface material: ① valve categories vary, sealing methods and material requirements vary; ② ordinary wedge gate valve, copper ring material, fixing method, grinding method should be described; ③ soft seal gate valve, valve plate rubber lining material physicochemical and health testing data; ④ butterfly valve should indicate the sealing surface material on the valve body and the sealing surface material on the butterfly plate; their physicochemical testing data, especially the rubber health requirements The material of the sealing surface on the valve body and the material of the sealing surface on the butterfly plate; their physicochemical test data, especially the health requirements of the rubber, anti-aging performance, wear resistance; usually use nitrile rubber and EPDM rubber, etc., is strictly prohibited to mix with recycled rubber.
2.6 spool packing: ① due to the valve in the network, usually open and close infrequently, the packing is not required in a few years, the packing is not aging, long-term sealing effect; ② spool packing should also be subject to frequent opening and closing, the good sealing effect; ③ in view of the above requirements, the spool packing strive not to change for life or more than ten years without replacement; ④ packing if you need to replace, the valve design should consider the water pressure conditions replacement measures.
- Variable speed transmission box
3.1 Box material and internal and external anti-corrosion requirements and the principle of the valve body consistent.
3.2 The box body should be sealed, the box body can withstand the immersion of 3 meters of water column condition after assembly.
3.3 The opening and closing limit device on the box, its adjustment nut should be in the box or located outside the box, but special tools are required to work.
3.4 Drive structure design is reasonable, open and close can only drive the valve shaft rotation, not to make it up and down, the drive parts bite moderate, not to produce a load open and close when the separation of slippage.
3.5 Variable speed transmission box and valve shaft seal can not be connected into a leak-free whole, otherwise there should be a reliable anti-string leakage measures.
3.6 No debris in the box, gear bite parts should be protected by grease.
- Valve operating mechanism