The opening and closing part of the gate valve is the gate, and the movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used gate valve form a wedge shape. The wedge angle varies with the valve parameters, usually 50, and 2°52' when the medium temperature is not high. When the medium temperature is not high, it is 2°52'.

The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its manufacturability and make up for the deviation of the sealing surface angle during processing. The plate is called an elastic gate. When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, relying on the medium pressure to press the sealing surface of the gate to the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are forced to seal, that is, when the valve is closed, the gate must be forced to the valve seat by external force to ensure the tightness of the sealing surface. The gate of the gate valve moves in a straight line with the valve stem, which is called a lifting rod gate valve, also called a rising rod gate valve. Usually, there is a trapezoidal thread on the lift rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into a linear motion, that is, the operating torque is changed into an operating thrust. When the valve is opened, when the lift height of the gate is equal to 1:1 times the diameter of the valve, the fluid channel is completely unobstructed, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a sign, that is, the position where it cannot be opened, 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 back to 1/2-1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve is determined according to the position of the gate, that is, the stroke. For some gate valves, the valve stem nut is set on the gate plate, and the rotation of the handwheel drives the valve stem to rotate, which makes the gate plate lift. This kind of valve is called a rotating stem gate valve or a dark stem gate valve. , This kind of valve is called rotary stem gate valve or dark stem gate valve.

The disadvantages of gate valves are as follows:

1. It is easy to cause erosion and scratches between the sealing surfaces of the gate valve, and it is difficult to maintain.

2. The gate valve has a large size, requires a certain space when opening, and takes a long time to open and close.

3. The gate valve structure is more complicated.

The gate valve has the following advantages:

1. The fluid resistance of the gate valve is small, and the sealing surface is less brushed and eroded by the medium.

2. The gate valve is more labor-saving to open and close.

3. The medium flow direction of the gate valve is not restricted, and it does not disturb the flow or reduce the pressure.

4. The gate valve has a simple shape, short structural length, good manufacturing process and wide application range.

The types of gate valves can be divided into wedge gate gate valves and parallel gate gate valves according to the configuration of the sealing surface. Wedge gate gate valves can be further divided into: single gate type, double gate type and elastic gate type; parallel gate gate valves can be Divided into single gate type and double gate type. According to the thread position of the valve stem, it can be divided into two types: open stem gate valve and dark stem gate valve.