The gate valve is a gate with a hoist. The movement direction of the gate is perpendicular to the fluid direction. The gate valve can only be fully opened and fully closed, and cannot be adjusted and throttled. The gate valve is sealed by the contact between the valve seat and the gate. Usually, the sealing surface will be overlaid with metal materials to increase the wear resistance, such as overlaying 1Cr13, stl6, stainless steel, etc. The gate has rigid gate and elastic gate. According to the difference of the gate, the gate valve is divided into rigid gate valve and elastic gate valve.

The opening and closing part of the gate valve is the ram, and the movement direction of the ram is perpendicular to the fluid direction. The gate valve can only be fully opened and closed, and cannot be adjusted and throttled. The ram has two sealing surfaces. The two sealing surfaces of the more commonly used Mode RAM valve form a wedge, and the wedge angle varies with the valve parameters, usually 5 °, and 2 ° 52 'when the medium temperature is not high. The gate of wedge gate valve can be made into a whole, which is called rigid gate valve; It can also be made into a ram that can produce slight deformation to improve its processability and make up for the deviation of the angle of the sealing surface in the processing process. This kind of ram is called an elastic ram. When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate valve can be pressed against the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self sealing. Most gate valves are sealed by force, that is, when the valve is closed, the gate must be pressed against 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 also called rising stem gate valve or rising stem gate valve. Generally, there are trapezoidal threads on the lifting rod. Through the nut at 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 lifting height of the ram is equal to 1:1 times the valve diameter, the fluid channel is unblocked, but during operation, this position cannot be monitored. In actual use, the vertex of the valve rod is taken as the mark, that is, the position that cannot be opened is taken as its full open position. In order to consider the locking phenomenon caused by temperature change, it is usually opened to the peak position and then turned back 1/2-1 turn as the fully open valve position. Therefore, the full open position of the valve is determined by the position of the ram, that is, the travel. For some gate valves, the valve stem nut is set on the ram, and the rotation of the hand wheel drives the valve stem to rotate, so as to raise the ram. This kind of valve is called rotary stem gate valve, or Non rising stem gate valve.