The opening closing part of the gate valve is the gate. The movement direction of the gate valve is perpendicular to the fluid direction. The gate valve can only be fully opened closed, but cannot be adjusted throttled. The ram has two sealing surfaces. The two sealing surfaces of the most commonly used model gate valve form a wedge. The wedge angle varies with the valve parameters, usually 5 ° 2 ° 52 'when the medium temperature is high. The gate of wedge gate valve can be made into a whole, which is called rigid gate; it can also be made into a gate which can produce slight deformation, so as to improve its processability make up for the deviation of sealing surface angle in the processing process. This kind of gate is called elastic gate. When the gate valve is closed, the sealing surface can only be sealed by the medium pressure, that is, the sealing surface of the gate valve is pressed to 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 forced to seal, that is, when the valve is closed, the gate should be forced to the valve seat by external force, so as to ensure the tightness of the sealing surface. Gate valve gate with the stem together for linear movement, known as lifting stem gate valve, also known as rising stem gate valve. Generally, there are trapezoidal threads on the lifting rod. Through the nut on the top of the valve 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 of the valve diameter, the fluid channel is completely unblocked, but in operation, this position cannot be monitored. In actual use, the apex of the valve stem is used as the mark, that is, the position that can be opened is used as its full open position. In order to consider the lock phenomenon of temperature change, usually in the open to the top position, then back 1 / 2-1 circle, as the position of full open valve. Therefore, the full open position of the valve is determined by the position of the ram, that is, the travel. Some gate valves, stem nut is set on the gate, hand wheel rotation drives the stem to rotate, so that the gate is lifted, this kind of valve is called rotating stem gate valve, Non rising stem gate valve.