Technical performance to pay attention to when choosing pneumatic valve

1. Sealing performance. The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent the leakage of the medium, which is an important technical performance index of the valve. There are three sealing parts of the valve: the contact between the opening and closing parts and the two sealing surfaces of the valve seat; the matching place between the packing and the valve stem and the stuffing box; the connection between the valve body and the bonnet. The leakage in the former part is called internal leakage, which is commonly referred to as lax closure, which will affect the ability of the valve to cut off the medium. For shut-off valves, internal leakage is not allowed. The leakage in the latter two places is called external leakage, that is, the medium leaks from the inside of the valve to the outside of the valve. External leakage will cause material loss, pollute the environment, and even cause accidents in severe cases. For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.

2. Flow medium. After the medium flows through the valve, there will be a pressure difference between the front and back, so that the valve has a certain resistance to the flow of the medium, and the medium consumes a certain amount of energy to overcome the resistance of the valve. Therefore, when designing and manufacturing the valve, it is necessary to reduce the flow of the valve as much as possible. The resistance of the medium reduces the loss of energy.

3. Opening and closing force and opening and closing torque. Opening and closing force and opening and closing torque refer to the force or torque that must be exerted by the valve to open or close. When closing the valve, it is necessary to form a certain sealing specific pressure between the opening and closing parts and the two sealing surfaces of the hair seat, and at the same time to overcome the friction between the valve stem and other frictional parts. Therefore, the valve must be opened and closed during the opening and closing process. Closing force and closing torque, so the valve should be designed and manufactured to reduce its closing force and closing torque.

4. Opening and closing speed. The opening and closing speed is expressed by the time required for the valve to complete an opening or closing action. Generally, there are no strict requirements for the opening and closing speed of the valve, but some working conditions have special requirements for the opening and closing speed. Some require rapid opening or closing to prevent accidents, and some require slow closing to prevent water hammer, etc. This should be taken into account when selecting the valve type.

5. Service life. It indicates the durability of the valve, is an important performance indicator of the valve, and has great economic significance. It is usually expressed by the number of times of opening and closing that can ensure the sealing requirements, and it can also be expressed by the use time.