Working principle of gate valve

Gate valve is one of the more common types of shut-off valves. It is mainly used to cut off the medium in the pipeline. It is usually called a shut-off valve or a blocking valve.

1. Gate valve structure: 

Generally composed of valve body, valve seat, valve stem, wedge, valve bonnet, sealing ring, etc. The opening and closing part of gate valve is wedge, and the movement direction of wedge is perpendicular to the direction of fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled to medium.

2. Working principle: 

When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, rely on the medium pressure to press the sealing surface of the wedge to the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the gate must be forced against the seat by external force to ensure the tightness of the sealing surface. 

The wedge of the gate valve moves linearly with the valve stem, which is called the lifting stem gate valve, also called the rising stem gate valve. Usually there is a trapezoidal thread on the lifting rod, through the nut on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. 

When the valve is opened, when the lift height of the gate is equal to 1:1 times the valve diameter, the fluid passage is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as the mark, that is, the unmovable position, as its fully open position. 

In order to take into account the lock-up phenomenon caused by temperature changes, it is usually opened to the top position, and then rewind 1/2 or 1 circle, as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate. In some gate valves, the stem nut is set on the wedge, and the rotation of the handwheel drives the rotation of the valve stem to lift the gate. This kind of valve is called a rotating stem gate valve, or a non-rising stem gate valve.

More details of gate valves, please go to https://www.mingpinmetals.com/Gate-Valve-pl3117724.html