6 Characteristics Of Valve
1. Sealing Performance
The sealing performance of valve refers to the ability to prevent the leakage of media at the sealing part of valve, which is the most important technical performance index of valve. There are three sealing parts of the valve: The opening and closing piece and the valve seat between the two sealing surface of the contact; packing and stem and packing letter with the place; valve body and bonnet joint. One of the previous leak is called the internal leak, which is often referred to as the slack, it will affect the ability of the valve to cut off the media. For shutoff valves, internal leakage is not allowed. The last two leakage is called leakage, that is, media leakage from the valve to the valve outside. Leakage will cause material loss, pollution of the environment, serious will also cause accidents. For flammable explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.
2. Flowing Medium
Media flow through the valve will produce pressure loss (both the pressure difference before and after the valve), that is, the valve has a certain resistance to the flow of media, media to overcome the resistance of the valve to consume a certain amount of energy. In order to save energy, it is necessary to reduce the resistance of the valve to the flow medium when designing and manufacturing the valve.
3. Opening And Closing Force And Opening And Closing Moment
Opening and closing force and opening and closing moments are the force or moments that must be exerted to open or close the valve. When the valve is closed, a certain sealing specific pressure needs to be formed between the opening and closing parts and the two sealing surfaces of the engine seat At the same time, to overcome the friction between the valve stem and packing, between the valve stem and nut threads, the valve stem end support and other friction parts, so it is necessary to impose a certain closing force and closing torque, the valve in the open and close process, the required opening and closing force and opening and closing torque are variable, the maximum of which is at the final instant of closing or at the initial instant of opening. Valves should be designed and manufactured to reduce their closing force and closing torque.
4. Opening And Closing Speed
The opening and closing speed is expressed by the time it takes the valve to complete an opening or closing action. Generally, there is no strict requirement for the opening and closing speed of valves, but some operating conditions have special requirements for the opening and closing speed. For example, some require quick opening or closing to prevent accidents, and some require slow closing to prevent water hammer, etc. This should be considered when selecting the valve type.
5. Motion Sensitivity And Reliability
This refers to the valve for the medium parameter changes, make the corresponding response sensitivity. The function sensitivity and reliability of the throttle valve, pressure reducing valve, regulating valve, safety valve and steam trap are very important technical performance indexes.
6. Service Life
It indicates the durability of the Valve, the valve is an important performance indicator, and has great economic significance. Usually to ensure the sealing requirements of the number of times to express, it can also be used to express time.