Operating principle of gate valve

A gate valve is a gate of a hoist. The movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened or closed, and cannot be adjusted or throttled. The gate valve is sealed through the contact between the valve seat and the gate plate. Generally, the sealing surface will be welded with metal materials to increase the wear resistance, such as 1Cr13, STL6, stainless steel, etc. The ram has rigid ram and elastic ram. According to different rams, the gate valve is divided into rigid gate valve and elastic gate valve.



The opening and closing parts of the gate valve are 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 or throttled. The gate has two sealing surfaces. The two sealing surfaces of the more common mode gate valve form wedges, and the wedge angle varies with the valve parameters, usually 5 °. When the medium temperature is not high, it is 2 ° 52 '. The gate of wedge gate valve can be made into a whole, which is called rigid gate; It can also be made into a ram that can produce slight deformation to improve its processability and compensate for the deviation of sealing surface angle during processing. This ram is called 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 plate is pressed to the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is called self sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the gate plate shall be forced to the valve seat by external force to ensure the tightness of the sealing surface. The gate plate of the gate valve moves in a straight line with the valve stem. It is called a rising stem gate valve or a rising stem gate valve. Generally, there are trapezoidal threads on the lifting rod. Through the nut on 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 the operating thrust. When opening the valve, when the lifting height of the ram is equal to 1:1 times of the valve diameter, the fluid channel is smooth, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is taken as the sign, that is, the position that cannot be opened is taken as its full open position. In order to consider the phenomenon of locking due to temperature change, it is usually to open the valve to the top position and then turn back 1/2 － 1 circle as the position of fully opening the valve. Therefore, the full open position of the valve is determined according to the position of the ram, that is, the travel. For some gate valves, the stem nut is set on the gate, and the hand wheel rotates to drive the stem to rotate, thus lifting the gate. This valve is called rotary stem gate valve or non rising stem gate valve.