Necessary technology of valve procurement

When purchasing valves, it is not perfect in the current market economy environment that only the specification, category and working pressure are specified to meet the purchasing requirements. Because for the competition of products, valve manufacturers carry out different innovations under the conception of unified valve design respectively, forming their own enterprise standards and product personalities. Therefore, it is very necessary to put forward the technical requirements in detail when purchasing the valve and reach a consensus through coordination with the manufacturer as the attachment of the purchase contract of the valve.

1. General requirements

1.1 specifications and categories of valves should meet the requirements of pipeline design documents.
1.2 The model number of the valve should be indicated according to the national standard number requirements. If it is an enterprise standard, the relevant specifications 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. On the premise of not affecting the price, the working pressure that the valve can bear should be greater than the actual working pressure of the pipeline; when the valve is closed, any side should be able to bear 1.1 times the valve pressure without leakage; when the valve is open, the valve body should be able to bear the requirement of double the valve pressure.
1.4 The standard of valve manufacturing should state the national standard number on which it is based. If it is Enterprise Standard, Enterprise documents should be attached to the procurement contract.

2. Valve standard quality
2.1 The material of the valve body should be mainly the graphite cast iron, and the brand and the actual physical and chemical test data of the cast iron should be marked.
2.2 The material of the valve stem, strive for stainless steel valve stem (2CR13), and the large caliber valve should also be stainless steel embedded valve stem.
2.3 nut material, using cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem.
2.4 The hardness and strength of the valve stem bushing material should not be greater than that of the valve stem, and it will not form electrochemical corrosion with the valve stem and the valve body under the condition of soaking in water.
2.5 material of sealing surface
① Different types of valves, different sealing methods and material requirements;
② The material, fixing method and grinding method of common wedge gate valve and copper ring should be illustrated;
③Physical chemistry and health detection data of soft seal gate valve and valve plate rubber material;
④ Butterfly valve should indicate the material of the sealing surface on the valve body and the material of the sealing surface on the butterfly plate; their physical and chemical testing data, especially the hygiene requirements, anti-aging performance and wear-resisting performance of rubber; usually use Ding Qing rubber and ethylene glycol rubber, etc., and it is forbidden to add recycled rubber.
2.6 valve shaft stuffing
① Because the valves in the pipe network usually start and close infrequently, it is required that the stuffing will not move within several years, and the stuffing will not be aging, so as to keep the sealing effect for a long time; ② the valve shaft stuffing should also bear the good sealing effect when it is frequently opened and closed;
③In view of the above requirements, the valve shaft stuffing tries not to be replaced for a lifetime or for more than ten years; ④if the stuffing needs to be replaced, the valve design should consider the replacement measures under the condition of water pressure.

3. Variable speed transmission box

3.1 The material and anti-corrosion requirements of the box body are in accordance with the principles of the valve body.
3.2 The Box body should have sealing measures. After assembling, the box body can withstand soaking under the condition of 3 meters water column.
3.3 for the opening and closing limit device on the box body, its Adjusting nut should be inside or outside the box, but it can only work with special tools.
3.4 The design of transmission structure is reasonable. When it is on and off, it can only drive the valve shaft to rotate, not to make it move up and down. The drive parts are properly bitten and do not produce separation and sliding when it is on and off with load.
3.5 Variable Speed transmission box and valve shaft seal should not be connected into a leak-free entirety, otherwise there should be reliable leakage prevention measures.
3.6 there is no sundries in the box, and there should be lubricating grease in the gear bite part