Knowledge

What is a gate valve?



Principle: The opening and closing part of the gate valve is the gate. The direction of movement of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully open and fully closed, and cannot be adjusted and throttled. The gate has two sealing faces. The two sealing faces of the most common mode gate valves form a wedge shape. The wedge angle varies with the valve parameters, usually 5°, and the medium temperature is not 2°52'. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its processability and make up for the deviation of the sealing surface angle during the machining process. The board is called a resilient shutter. When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the ram is pressed against the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most of the gate valves are forced to seal, that is, when the valve is closed, the external force is forced to press the gate to the valve seat to ensure the sealing of the sealing surface.

           The gate of the gate valve moves linearly with the valve stem, which is called the lift gate valve, also called the open gate valve. Usually there is a trapezoidal thread on the lifting rod, and the rotary motion is changed into a linear motion by the nut at the top end of the valve and the guide groove on the valve body, that is, the operating torque is changed to the operating thrust. When the valve is opened, when the lifting height of the gate is equal to 1:1 times the diameter of the valve, the passage of the fluid is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a mark, that is, the position where the valve is opened, as its fully open position. In order to consider the temperature change, the lock phenomenon occurs, usually at the position of the opening to the apex, and then back to 1/2-1 circle as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the shutter, that is, the stroke. In some gate valves, the stem nut is arranged on the gate plate, and the rotation of the hand wheel drives the valve stem to rotate, and the shutter is lifted. This valve is called a rotary lever gate valve, or a dark rod gate valve.