1. Sealing performance
The sealing performance of the valve refers to the ability of the sealing part of the valve to prevent the leakage of the medium, which is the most important technical performance index of the valve. The valve has three sealing parts: the contact between the opening and closing part and the sealing surface of the valve seat; the packing and the valve stem and the stuffing box are matched; the body to the hood joint. Leakage at the front of the valve is called internal leakage, which is usually called looseness of closure, which will affect the ability of the valve to block the medium. For shut-off valves, internal leakage is not allowed. The latter two kinds of leakage are called external leakage, that is, the leakage of the medium from the valve to the valve. Leakage can cause material loss, pollute the environment, and even cause serious accidents. For flammable, explosive, toxic or radioactive media,
After the medium flows through the valve, there will be a pressure difference between the front and back, which makes the valve produce a certain resistance to the flow of the medium. The medium that overcomes the resistance of the valve will consume a certain amount of energy. Therefore, when designing and manufacturing the valve, the resistance of the valve to the flow of the medium should be minimized , Reduce energy loss.
3. Hoisting force and moment
Opening and closing forces and moments are the forces or moments that must be applied to open or close the valve. When closing the valve, it is necessary to make the sealing pressure between the opening and closing part and the two sealing surfaces, but also to overcome the friction of the valve stem and the friction of other parts. Therefore, the valve must apply a closing force during the opening and closing process. And the closing torque, so the design and manufacture of the valve should strive to reduce the closing force and closing torque.