Is the gate valve opening and closing parts, RAM direction of motion perpendicular to the direction of the fluid, valve can only be fully open and fully closed, can not be adjusted and the throttle. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used gate valve form wedge and wedge angle varies with the valve parameters, usually 5 degrees, and the medium temperature is not high when it is 2 degrees 52'. Wedge gate valve can be made into a whole, called rigid gate, can also be made into a micro deformation of the gate, to improve its technology, make up for the sealing surface angle in the process of processing deviation, this gate is called the flexible ram. When the gate valve closes, the sealing surface can only rely on the medium pressure to seal, that is to rely on the medium pressure to ram the sealing surface to the other side of the valve seat to ensure the sealing surface seal, which is self sealing. Most of the gate valve is forced seal, that is to say, when the valve is closed, the gate should be pressed to the valve seat by external force, so as to ensure the sealing surface sealing. Gate valve with the stem along with linear movement, called lift rod gate valve, also known as gate valve. Usually there is a trapezoidal thread on the lifter, and through the nut at the top of the valve and the guide groove on the valve body, the rotating motion is changed into a straight line motion, that is to say, the operating torque is changed into the operation thrust. When opening the valve, when the gate lift height is equal to 1:1 times of the valve diameter, the fluid channel is completely unblocked, but at the time of operation, this position is unable to monitor. In actual use, the top of the stem is used as a sign, that is, the open position, as its full open position. Temperature changes appear to consider locking phenomenon, usually open to the vertex position, and then rewind 1/2 1 circle, as a fully open valve position. Therefore, the opening position of the valve is determined by the position of the gate. Some gate valve, stem nut is located in the gate, handwheel rotation drive stem rotation, and make the gate lifting, this valve is called rotary rod gate valve, or called dark rod gate valve.