The practice of only specifying specifications, categories, and pressures to meet the procurement requirements when purchasing electric ball valves is imperfect in the current market economy environment. For the sake of product competition, electric ball valve manufacturers have carried out different innovations under the concept of unified design of electric ball valves, forming their own corporate standards and product individualities. Therefore, it is very necessary to make detailed technical requirements when purchasing electric ball valves, and coordinate with the manufacturers to reach a consensus. It is very necessary as an attachment to the electric ball valve purchase contract.

　　 1. General requirements

　　1.1 The specifications and categories of electric ball valves shall meet the requirements of the pipeline design documents.

　　1.2 The model of electric ball valve should be marked with the national standard number requirement. If it is a corporate standard, the relevant description of the model should be indicated.

1.3 The working pressure of the electric ball valve is required to be ≥ the working pressure of the pipeline. Under the premise of not affecting the price, the working pressure of the electric ball valve should be greater than the actual working pressure of the pipeline; any side of the electric ball valve should be able to withstand 1.1 times when it is closed The working pressure of the electric ball valve does not leak; when the electric ball valve is open, the valve body should be able to withstand the requirement of twice the working pressure of the electric ball valve.

　　1.4 Electric ball valve manufacturing standards should state the number of the national standard on which it is based. If it is a corporate standard, the purchase contract should be accompanied by corporate documents.

　　2. Variable speed transmission box

　　2.1 Box body material and internal and external anti-corrosion requirements are consistent with the valve body principle.

　　2.2 The box body should have sealing measures, and the box body can withstand 3 meters of water column immersion after assembly.

　　2.3 For the opening and closing limit device on the box body, the adjusting nut should be inside or outside the box, but special tools are required for operation.

　　2.4 The transmission structure is designed reasonably. 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 it will not cause separation and slippage when opening and closing with load.

　　2.5 The variable-speed transmission box and the valve shaft seal cannot be connected as a leak-free whole, otherwise reliable leakage prevention measures should be taken.

　　2.6 There is no debris in the box, and the gear bite part should be protected by grease.

　　3. Standard quality of electric ball valve

　　3.1 The valve body material should be mainly ductile iron, and the grade and actual physical and chemical test data of the cast iron should be indicated.

　　3.2 stem material, strive for stainless steel stem (2CR13), large-caliber electric ball valve should also be stainless steel embedded stem.

　　3.3 The nut material is made of cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem.

　　3.4 The material of the stem bushing should have a hardness and strength not greater than that of the stem, and it should not form electrochemical corrosion with the stem and valve body under water immersion.

3.5 Material of sealing surface: ① Electric ball valve has different types, sealing method and material requirements; ② Ordinary wedge gate valve, copper ring material, fixing method, and grinding method should be explained; ③ Soft sealing gate valve, valve plate lining rubber Material physical and chemical and sanitary test data; ④Butterfly valves should indicate the sealing surface material on the valve body and the sealing surface material of the butterfly plate; their physical and chemical test data, especially the hygienic requirements, chemical properties, and wear resistance of rubber; usually used For nitrile butadiene rubber and EPDM rubber, it is strictly forbidden to mix with reclaimed rubber.

3.6 Valve shaft packing: ①Because the electric ball valve in the pipe network is usually opened and closed infrequently, the packing is required to be inactive for several years, 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. When closed, the sealing effect is good; ③In view of the above requirements, the valve shaft packing should not be changed or replaced for more than ten years; ④If the packing needs to be replaced, the electric ball valve design should consider the measures that can be replaced under the condition of water pressure.