In order to achieve zero leakage inside and outside the valve seal, save energy, protect the environment and improve work efficiency, the valve must have a reliable sealing performance. The sealing parts of the valve mainly include the contact between the two sealing surfaces of the opening and closing member and the valve seat, the contact between the valve stem and the valve cover, the sealing position of the valve stem, the gasket contact between the valve body and the valve cover, and the like. Among them, the opening and closing parts and valve seat leakage between the two sealing surfaces is called the valve's internal leakage, and the valve stem and valve cover, valve stem seal and the valve cover sealing surface leakage between the leakage as the valve. Valve leakage will affect the ability of the valve to cut off the medium. Leakage of the valve will result in the loss of transport medium or pollute the environment, causing serious accidents in severe cases. For flammable, toxic or radioactive medium, the valve leakage phenomenon is even more not allowed to happen. Valve sealing performance is a measure of the quality of the valve an important technical indicators, the national standard on the steel gate valve and the valve on the technical requirements of the seal developed the relevant provisions. The sealing effect of the steel gate valve and the stop valve is related to many aspects such as valve material, processing equipment, tooling manufacturing, heat treatment, processing technology, shape tolerance and part machining precision, and a certain technology can not meet the design requirements Will directly affect the effect of the seal (the valve seal shown in Figure 1 3 to 4 parts). According to the relevant standards, the valve seal should have a conical or spherical sealing structure. However, the conical or spherical sealing structure has some unfavorable factors relative to the planar sealing structure, such as the friction phenomenon of the sealing surface, the difficulty of maintenance, the high processing difficulty and the increase of the production cost. The result is an increase in production costs and a lack of competitiveness of the product. At the same time, the valve sealing performance is also difficult to meet the standard technical requirements, often after several sealing performance test will fail. Aiming at the problems existing in the conical and spherical sealing surfaces and the performance analysis based on the actual working conditions of the valve, the principle of the flat sealing of the valve disc is adopted in the design of the sealing on the valve. The valve stem and the bonnet are originally made of conical Upper sealing surface improved to flat contact mode. Valve stem and the cover of the plane contact with the seal generally not affected by equipment accuracy, tooling accuracy and shape with the impact of parts tolerances, simple structure, easy processing, bonnet sealing parts only after finishing welding can meet the design requirements. After the valve stem is finished, the head of the valve stem is heated to the quenching temperature, air-cooled to room temperature, and the fine car can be assembled after sealing the plane. Valve seal test a pass rate of 100%, its service life can also be achieved with the same number of valve opening and closing, but also more convenient to repair. Stainless steel valve stem and valve cover materials are generally the same austenitic material, the two tend to stick after the contact pressure, the valve cover as far as possible not to use the upper cone sealing form. Sealing holes can be machined in the lower part of the filler hole of the valve cover. The use of a cone on the valve stem and a Teflon conical seal as a seal pair makes this structure ideal for use in corrosive media. Open the valve, the opening and closing pieces should be in place, so that the seal should play its due function. But it is noteworthy that the force should be light and modest, not too big too fast, so as not to scratch the sealing surface, extend the life of the seal on the valve to prevent the valve leakage caused by the harm. Practice has proved that the valve seal on the use of planar design and cone sealing form compared to the machining equipment and process equipment requirements are relatively low, whether small-scale operations or mass production, can reduce production costs, Improve work efficiency, and have a positive meaning to stabilize product quality and ensure the safe operation of supporting facilities. This article keyword search: valve supply information