Valve related terms

Valve related terms

The following describes the flow medium, opening and closing force and opening and closing torque, opening and closing speed, motion sensitivity and reliability, and service life.  

The sealing performance of the valve refers to the ability of the sealing parts of the valve to prevent the leakage of the medium. It is the most important technical performance index of the valve. There are three sealing parts of the valve: the contact between the sealing surface of the opening and closing parts and the valve seat; the joint of the packing with the valve stem and the stuffing box; the connection between the valve body and the valve cover. The leak in the former place is called endoleak, which is commonly referred to as the lack of tightness, which will affect the ability of the valve to cut off the medium. For shut-off valves, internal leakage is not allowed. The latter two leaks are called external leaks, ie the medium leaks from the valve to the outside of the valve. External leakage can cause material loss, pollute the environment, and cause accidents in severe cases. For flammable, explosive, toxic or radioactive media, external leakage is not allowed, so the valve must have a reliable sealing performance.

When the medium flows through the valve, pressure loss (both pressure difference before and after the valve) is generated, that is, the valve has a certain resistance to the flow of the medium, and the medium consumes a certain amount of energy in order to overcome the resistance of the valve. In terms of energy conservation, when designing and manufacturing valves, it is necessary to reduce the resistance of the valve to the flowing medium as much as possible.

The opening and closing force and the opening and closing torque refer to the force or moment that must be applied when the valve is opened or closed. When closing the valve, it is necessary to form a certain sealing specific pressure between the opening and closing parts and the sealing surface of the bearing seat, and at the same time overcome the between the valve stem and the packing, between the thread of the valve stem and the nut, and at the end of the valve stem and The friction of other friction parts must be applied with a certain closing force and closing torque. During the opening and closing process, the required opening and closing force and opening and closing torque are changed. The maximum value is the final moment or opening of the closing. The initial moment. When designing and manufacturing valves, it is desirable to reduce their closing force and closing torque.

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 for the opening and closing speed of the valve, but some working conditions have special requirements for the opening and closing speed. If some requirements are quickly opened or closed, in case of accidents, some requirements are required to be slowly closed to prevent water hammer, etc. This should be considered when selecting the valve type.

This refers to the sensitivity of the valve to the corresponding changes in the media parameters. For valves with regulating functions such as throttle valves, pressure reducing valves, regulating valves, etc., as well as valves with special functions such as safety valves and traps, the functional sensitivity and reliability are important technical performance indicators.

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

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