Since 2010, many domestic valve manufacturers have developed soft-sealed gate valves. Compared with the traditional type or parallel-type double-gate gate valves, the gate valves have the following characteristics: 1. The valve body and bonnet of the soft-sealed gate valve are precision cast. Casting, one-shot molding, no longer mechanical processing, no sealing copper ring, saving non-ferrous metals; 2, no soft pit seal valve bottom without pits, no accumulation of slag, low failure rate of gate valve opening and closing; 3, soft seal rubber The valve plate is uniform in size and interchangeable. 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 water supply industry is willing to adopt. When opening and closing the soft seal gate valve, do not close it too much, as long as the water stop effect is achieved, otherwise it will not be easy to open or the rubber stripping. Most of the butterfly valves used in the water supply industry are soft-sealed butterfly valves. For the butterfly valve during the installation process, the rubber ring is easily damaged, which affects the sealing performance. Many manufacturers have introduced metal sealing butterfly valves instead of rubber ring sealing butterfly valves. Due to the small elasticity of the seal, the metal sealing butterfly valve generally adopts an eccentric structure, and it is more reasonable to use a three-dimensional eccentric structure.
Valves have butterfly valves, gate valves, ball valves and plug valves, and the range used in the water supply network is different. In order to reduce the depth of the soil covering the pipeline, the butterfly with a larger diameter is generally equipped with a butterfly valve; the impact on the depth of the soil is not large, and the gate valve is selected; the casting and processing of the ball valve and the plug valve are difficult and expensive, and are generally applicable to small and medium-sized pipes. In recent years, due to the improvement of casting technology, the resin sand casting method can avoid or reduce the mechanical processing, thereby reducing the cost. Therefore, the feasibility of the ball valve for the large diameter pipe is worth exploring. As for the dividing line of the size of the caliber, it should be divided according to the specific circumstances. The main disadvantage of the butterfly valve is that the butterfly plate occupies a certain cross-section of the water and increases the loss of the head; although the gate valve does not have this problem, the height of the large-diameter vertical gate valve affects the depth of the soil, and the length of the large-diameter horizontal gate valve increases. Pipes occupy a horizontal area, affecting the arrangement of other pipelines; ball valves and plug valves maintain the advantages of single valve gate, small water flow resistance, reliable sealing, flexible operation, and convenient operation and maintenance. Plug valves also have similar advantages, except that the cross section of the water is not a perfect circle.