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1. Conventional valves include butterfly valves, gate valves, ball valves and stopcock valves. The range of valves used in the water supply pipe network should be considered in the selection.

2. In order to reduce the depth of the pipeline's soil covering, generally larger diameter pipelines are equipped with butterfly valves; the main disadvantage of butterfly valves is that the butterfly plate occupies a certain cross section of the water and increases a certain head loss;

3. If it has little effect on the depth of soil covering, strive to choose gate valves; the height of the electric gate valve large-diameter vertical gate valve affects the soil covering depth of the pipeline, and the length of the large-diameter horizontal gate valve increases the horizontal area occupied by the pipeline and affects the arrangement of other pipelines £»

4. The casting and processing of ball valves and plug valves are difficult and expensive, and they are generally suitable for small and medium-diameter pipelines. Ball valves and plug valves maintain the advantages of single gate valve, small water flow resistance, reliable sealing, flexible action, and convenient operation and maintenance. The plug valve also has similar advantages, but the cross-section of the water is not a perfect circle.

5. In recent years, due to the improvement of casting technology, the use of resin sand casting can avoid or reduce mechanical processing, thereby reducing costs. Therefore, the feasibility of ball valves for large-diameter pipelines is worth exploring. As for the demarcation line of the size of the caliber, it should be divided according to the specific conditions of each region.

6. At present, the valve market has developed soft-seal gate valves. This new type of gate valve has several differences in the traditional wedge or parallel double gate valve:

7. The valve body and bonnet of the soft-sealed gate valve are cast by precision casting, forming one time, no mechanical processing is required at all, and the sealing copper ring is not used, which saves non-ferrous metals;

8. There is no pit at the bottom of the soft seal gate valve, no slag accumulation, and the failure rate of the gate valve opening and closing is low;

9. The size of the soft-seal rubber-lined valve plate is uniform, and the interchangeability is strong.

Therefore, the soft seal gate valve will be the development direction of the gate valve, and it is also a kind of valve that the pipeline water supply industry is willing to accept. When opening or closing the soft-seal gate valve, do not close it too tightly, as long as it achieves the water-stop effect, otherwise it will not be easy to open or peel off the lining.

10. Most of the butterfly valves used in the pipeline water supply industry are soft-sealed butterfly valves. In view of the easy damage of the rubber ring during the installation process of the butterfly valve, which affects the sealing performance, many manufacturers have introduced metal-sealed butterfly valves instead of rubber-sealed butterfly valves. The metal-sealed butterfly valve generally adopts an eccentric structure due to the small elasticity of the sealing element, and it is more reasonable to use a three-dimensional eccentric structure in particular.