Gate valve of the headstock is the gate, the movement direction of the gate and the direction of the fluid perpendicular to the gate valve can only be fully open and full clearance, can not be adjusted and throttling. Gate has two sealing surface, the most commonly used mode gate valve two sealing surface form wedge, wedge-shaped angle with valve parameters, usually 5 °, medium temperature is not high when 2°52 '. Wedge Gate valve can be made into a whole, called a rigid gate, can also be made to produce a small amount of deformation of the gate, in order to improve the process, to make up for the angle of the sealing surface in the processing of the deviation, the gate is called Elastic Gate. 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 is pressed to the other side of the valve seat to ensure the seal of the seal surface by the medium pressure, which is the self sealing. Most of the gate valve is a forced seal, that is, the valve closed, to rely on external forces to force the gate pressure to the seat to ensure the sealing surface of the seal. Gate valve of the gate with the stem for straight line movement, called the lift bar gate Valve, also known as the Ming stem gate valve. Usually on the lifter has trapezoidal thread, through the top of the valve nut and valve body on the guide groove, the rotation of the movement into a straight line movement, that is, the operation torque into operation Thrust. When opening the valve, when the gate lifting height equals valve diameter 1:1 time times, the fluid channel is completely unimpeded, but at run time, this position is unable to monitor. In actual use, it is the vertex of the stem as a sign, that is, the position of the open, as its full opening position. In order to consider the temperature changes in the deadlock phenomenon, usually open to the vertex position, and then back to the 1/2-1 ring, as the position of full opening valve. Therefore, the full open position of the valve, according to the position of the gate is the journey to determine. Some gate valve, the stem nut is located on the gate, the handwheel rotates to drive the stem to rotate, but causes the gate board to ascend, this kind of valve is called the Rotary Pole Gate valve, or is called the Dark pole gate valve.