Connection and movement mode of the valve stem

Valve, throttle valve, plunger valve, gate valve, diaphragm valve opening and closing action is achieved through the relative movement of the drive device or hand wheel, valve stem and stem. The valve stem and the valve stem nut are processed with trapezoidal thread or thread, the thread of the screw direction by hand wheel clockwise rotation of the principle to decide.
Movement mode of valve stem
Valve stem nut and valve stem connection with the movement of the way, the valve stem movement usually have the following three kinds: 0 rotating lift type: rotating hand wheel, the valve stem is also followed by rotation and movements, so that the valve opening and closing. Valve stem threads in the valve body and the medium contact, stem nut and valve body (or valve cover) made of a body, commonly used in small caliber valve. Valve stem threads in the external, do not contact with the media, the valve stem screw fixed on the valve cover, the application is very common in the globe valve and throttle valve. The lifting and rotating pole has the advantages of simple structure, reliable application, but on the filler seal, also because its structure high degree is varied, covers an area of a larger space, to a remote control increases the difficulty of:
Lift valve stem: turning the hand wheel, the valve stem only for lifting movement and not rotating, so that the valve is opened and closed. Lift valve stem is widely used in various working conditions of the valve body including the most demanding conditions, high temperature, high pressure, corrosive media, etc.. The valve stem nut is arranged on the upper part of the bracket, so that it is separated from the medium, and the temperature is lower than the temperature of the valve body and the valve cover.
In the case of the valve stem axial force is relatively large, the valve stem nut will produce a large friction torque, so that the valve operation is difficult, in this case, the valve stem nut is installed in the ball bearing thrust ball.
In order to save non-ferrous metals, large diameter valve stem nut can be made into a combination of carbon steel, brass or bronze threaded bushing. Stem threads should be lubricated regularly. In case of lack of lubricant, the valve operation torque increase, and to accelerate the wear of the valve stem.
This only lift does not rotate the valve stem, the sealing of the filler is relatively good. The structure is conducive to remote control. But when the valve is fully open, the valve stem up to a high degree of opening the valve stem nut installation, the valve must have reserved space.
Rotary valve stem: turning the hand wheel, the valve stem only for the rotating movement, so that the valve stem nut to match the gate open or closed.
The only non rotating lifting stem only in the dark bar valve use, the valve stem nut installed at the gate, direct contact with the media, thread by medium erosion, only in the case of large aperture and restricted installation space only using this structure, its height is fixed, is conducive to the remote control.