1. Sealing performance

The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent medium leakage. 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; Matching of packing with valve stem and stuffing box; The connection between valve body and bonnet. The first leakage is called internal leakage, which is commonly referred to as lax closing, which will affect the ability of the valve to cut off the medium. For block valves, internal leakage is not allowed. The leakage at the latter two places is called external leakage, that is, the medium leaks from inside the valve to outside the valve. External leakage will cause material loss, pollute the environment, and even cause accidents in serious cases. For flammable, explosive, toxic or radioactive media, external 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 between the front and back, so that the valve has a certain resistance to the flow of the medium. In order to overcome the resistance of the valve, the medium will consume a certain amount of energy. Therefore, when designing and manufacturing the valve, it is necessary to reduce the resistance of the valve to the flowing medium as much as possible and reduce the loss of energy.

3. Hoisting force and moment

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, 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 overcome the friction between the valve stem and other friction parts. Therefore, during the opening and closing process of the valve, a certain closing force and closing torque must be applied. Therefore, when designing and manufacturing the valve, we should strive 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 on the opening and closing speed of the valve, but some working conditions have special requirements on the opening and closing speed. For example, some require rapid opening or closing to prevent accidents, and some require slow closing to prevent water hammer, which should be considered when selecting the valve type.

5. Service life

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