1. Sealing performance. The sealing performance of the […]
1. Sealing performance. The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent medium leakage, and it is the most 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 of the packing and the stem and stuffing box; the connection place of the valve body and the bonnet. The leak in the previous one is called internal leakage, which is usually called the tightness, which will affect the ability of the valve to cut off the medium. For cut-off valves, internal leakage is not allowed. The leakage in the last two places is called external leakage, that is, the medium leaks from 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. Flowing medium. After the medium flows through the valve, there will be a pressure difference before and after, which makes the valve have a certain resistance to the flow of the medium. The medium consumes a certain amount of energy to overcome the resistance of the valve. Therefore, when designing and manufacturing the valve, the valve should be reduced as much as possible. The resistance of the medium reduces energy consumption.
3. Opening and closing force and opening and closing torque. The opening and closing force and opening and closing torque refer to the force or torque that must be applied to open or close the valve. When closing the valve, a certain sealing specific pressure needs to be formed between the opening and closing parts and the sealing surfaces of the hair seat, and at the same time, the friction between the valve stem and other friction parts must be overcome. Therefore, during the opening and closing process, a certain amount of pressure must be applied Closing force and closing torque, so when designing and manufacturing valves should strive to reduce their 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 is no strict requirement on the opening and closing speed of the valve, but some working conditions have special requirements on the opening and closing speed. If there is a requirement to quickly open or close, to prevent accidents, some require slow closing to prevent water hammer, etc., This should be considered when selecting the valve type.
5. Service life. It represents the durability of the valve, is an important performance index of the valve, and has great economic significance. It is usually expressed by the number of openings and closings that can guarantee the sealing requirements, and can also be expressed by using time.