Performance introduction and service life description of imported valves

Sealing performance
The sealing performance of the valve refers to the ability of the sealing parts 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; the matching place between the filler and the stem and the filling box; and the connecting place between the valve body and the valve cover. The former leakage is called internal leakage, which is commonly referred to as lax closure, and it will affect the ability of the valve to cut off the medium. Internal leakage is not allowed for truncation valves. Leakage at the last two places is called leakage, i.e. medium leaks from inside to outside of the valve. Leakage can cause material loss, pollution of the environment, and serious accidents. For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.

Flow medium
When the medium flows through the valve, it will cause pressure loss (the pressure difference between the front and the back of the valve), that is, the valve has certain resistance to the flow of the medium, and the medium will consume a certain amount of energy to overcome the resistance of the valve. Considering energy saving, when designing and manufacturing valves, the resistance of valves to flow media should be reduced as much as possible.

Opening and closing force and moment
Opening and closing forces and opening and closing moments refer to the forces or moments that must be applied when the valve is opened or closed. When closing the valve, it is necessary to form a certain specific sealing pressure between the opening and closing parts and the sealing surfaces of the seat. At the same time, it is necessary to overcome the friction between the stem and filler, between the threads of the stem and nut, at the end of the stem support and other frictional parts. Therefore, a certain closing force and closing moment must be applied to the valve during the opening and closing process. The required opening and closing force and moment are variable, and the maximum value is at the final closing moment or the initial opening moment. Valves should be designed and manufactured to reduce their closing force and closing moment.

Open-close speed
The opening and closing speed is expressed by the time required for the valve to complete an opening or closing operation. Generally, there is no strict requirement for the opening and closing speed of valves, but some working conditions have special requirements for the opening and closing speed, such as some requirements for quick opening or closing, in order to prevent accidents, some requirements for slow closing, in order to prevent water hammer, etc., which should be considered when selecting valve types.

Action sensitivity and reliability
This refers to the sensitivity of the valve to the change of medium parameters and the corresponding response. For throttle valves, pressure relief valves, control valves and other valves used to regulate medium parameters, as well as safety valves, traps and other valves with specific functions, their functional sensitivity and reliability are very important technical performance indicators.

Service life
It represents the durability of the valve, is an important performance index of the valve, and has great economic significance. Usually, it can be expressed by the number of times of opening and closing that can guarantee the sealing requirements, or by the use time.