Sealing performance Valve sealing performance refers to the sealing of the valve to prevent leakage of the ability of the media, it is the valve of the most important technical performance indicators. There are three parts of the valve seal: opening and closing parts and valve seat seal between the two contacts; filler and the stem and packing box with the Department of the valve body and the valve cover connections. One of the leaks is called leakage before, which is commonly referred to as lax, it will affect the ability of the valve to cut off the medium. For cut-off valves, internal leakage is not allowed. After the two leaks called leakage, that is, the medium leaked from the valve to the valve. Leakage will result in material loss, pollute the environment, serious accidents will result. For flammable, toxic or radioactive media, leakage is even more not allowed, so the valve must have a reliable sealing performance. Flow medium through the valve will produce pressure loss (both before and after the valve pressure difference), that is, the valve on the flow of media have a certain resistance, the media to overcome the resistance of the valve will consume some energy. From the energy conservation considerations, the design and manufacture of valves, to minimize the resistance of the valve on the flow medium. Opening and Closing Force and Opening and Closing Moment The opening and closing force and opening and closing torque refer to the force or torque that must be applied when the valve is opened or closed. Close the valve, the need to make the opening and closing seat and the seat between the two sealing surface to form a certain seal than the pressure, but also to overcome the valve stem and packing between the stem and nut thread between the stem end of the bearing and Other friction parts of the friction, which must impose a certain closing force and closing torque, the valve opening and closing process, the required opening and closing force and opening and closing torque is changing, the maximum value is in the closure of the final instantaneous or open The initial instant. When designing and manufacturing valves, they should strive to reduce their closing force and closing torque. Opening and closing speed Opening and closing speed is used to complete the valve to open or close the action required to represent. General opening and closing of the valve speed is not strictly required, but some conditions on the opening and closing speed has special requirements, if any requirements quickly open or close to prevent accidents, and some require slow closure to prevent water hammer and so on, This should be considered when choosing the type of valve. Motion Sensitivity and Reliability This is the degree to which the valve responds sensitively to changes in media parameters. The function sensitivity and reliability of valves with specific functions such as valves, pressure relief valves, regulating valves and other valves used to adjust the media parameters as well as safety valves and steam traps are very important technical performance indicators. It shows the durability of the valve life is an important performance indicators of the valve, and has great economic significance. Usually to ensure the sealing requirements of the opening and closing times that can also be used to represent the time.