The opening and closing parts of the gate valve are the gate plates. The movement direction of the gate plates is perpendicular to the direction of the fluid. The gate valves can only be opened and closed completely, and can not be adjusted or throttled. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used mode gate valves form wedges and wedge angles that vary with the parameters of the valve, usually 5 degrees and 2 52'when the medium is not high. The sluice gate of a wedge valve can be made into a whole, called a rigid gate, or a sluice which can produce a small amount of deformation to improve its craft and make up for the deviation produced by the angle of the sealing surface in the process of processing, which is called an elastic gate.

     When the gate is closed, the sealing surface can be sealed only by the pressure of the medium, that is, the sealing surface of the gate is pressed to the seat of the other side by the pressure of the medium. This is self sealing. Most gate valves are forced to seal, that is, when the valve is closed, to rely on external force to force the gate to the seat to ensure the sealing surface. The gate plate of the gate valve moves in a straight line with the stem, which is called the lift rod gate valve, also known as the open rod gate valve. Usually there are trapezoid threads on the lifting rod. Through the nut at the top of the valve and the guide slot on the valve body, the rotation motion is turned into a straight motion, that is, the operating torque is converted to the operating thrust. When the valve is opened, when the gate lifting height equals 1:1 times the valve diameter, the flow passage is completely unblocked, but in operation, this position can not be monitored. In practical use, the top of the valve stem is taken as the sign, that is, the position of the valve stem which can not be opened is taken as its full open position. In order to consider the locking phenomenon of temperature change, usually open to the vertex position, and then back 1/2-1 turn, as the full open valve position.

     Therefore, the full open position of the valve, according to the position of the gate stroke to determine. Some gate valves, valve stem nuts on the gate, hand wheel rotation to drive the stem rotation, and make the gate lift, this valve is called the rotary bar valve, or the dark rod valve.