The main technical performance of the valve

The main technical performance of the valve:

Flow medium

After the medium flows through the valve, there will be a pressure loss (pressure difference between the valve and the front and rear), that is, the valve has a certain resistance to the flow of the medium, and the medium needs to consume a certain amount of energy to overcome the resistance of the valve. From the viewpoint of energy conservation, when designing and manufacturing valves, the resistance of the valve to the flowing medium should be reduced as much as possible.

Lifting force and opening and closing torque

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

Sealing performance

The sealing performance of the valve refers to the ability of the valve sealing parts to prevent the leakage of the medium. It is the most important technical performance index of the valve. The sealing part of the valve has three parts: the contact between the opening and closing part and the sealing surface of the valve seat; the fitting between the packing and the valve stem and the stuffing box; and the connection between the valve body and the valve cover. The leak in the former is called endoleak, which is usually referred to as lax, and it will affect the ability of the valve to cut off the medium. For the cut-off valve class, endoleaks are not allowed. The last two leaks are called leaks, that is, the medium leaks from the valve to the outside of the valve. Leakage can cause material loss, pollute the environment and cause accidents when severe. For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have a reliable sealing performance.

Motion sensitivity and reliability

This refers to the degree of sensitivity of the valve to changes in the medium's parameters. For valves such as throttling valves, pressure reducing valves and regulating valves that are used to adjust medium parameters, as well as valves with specific functions such as safety valves and steam traps, their functional sensitivity and reliability are very important technical performance indicators.

Open and close speed

The opening and closing speed is represented by the time required for the valve to complete one opening or closing action. Generally speaking, there is no strict requirement on the valve opening and closing speed, but some operating conditions have special requirements for the opening and closing speed. If any of them require quick opening or closing to prevent accidents, some require slow closing to prevent water hammer. This should be taken into account when selecting the type of valve.

Service life

It shows the degree of durability of the valve, is an important performance index of the valve, and has great economic significance. It is usually expressed in terms of the number of opening and closing that can guarantee the sealing requirements. It can also be expressed in terms of use time.