The working principle of valve

The opening and closing parts of the gate valve are the gate, the movement direction of the gate is perpendicular to the direction of the fluid, the gate valve can only be fully open and closed, can not be adjusted and throttle. The gate has two sealing surfaces, the two sealing surfaces of the most commonly used pattern gate valves form a wedge, the Angle of which varies with valve parameters, usually 5°, and 2°52' when the medium temperature is not high. Wedge gate valves can be made into a single gate, called the rigid gate; It can also be made to produce micro-deformation of the gate, to improve the process, to make up for the Angle of the sealing surface in the process of deviation, this gate is called elastic gate. When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, relying on the medium pressure to press the sealing surface of the gate to the other side of the valve seat to ensure the sealing surface, this is self-sealing. Most gate valves are sealed by force, that is, when the valve is closed, rely on external force to force the gate to the seat, to ensure the sealing surface. The gate valve with the stem of the gate movement in a straight line, called lift rod gate valve, also known as the open rod gate valve. There is usually a trapezoidal thread on the lifting rod, which changes the rotary motion into a straight line through the nut on the top of the valve and the guide groove on the body, that is, the operating torque into the operating thrust. When the valve is opened, when the height of the gate is 1:1 of the valve size, the flow passage is completely free, but this position cannot be monitored during operation. In practice, it is marked by the top of the stem, the unmovable position, as its full open position. To account for temperature changes, locking occurs, usually at the top position, and then back to 1/2-1 turn, as the position of the fully open valve. Therefore, the full open position of the valve is determined by the position of the gate, i.e. the stroke. Some gate valves, the stem nut on the gate, the hand wheel turns to drive the stem to turn, and the gate to lift, this valve is called a rotary stem gate valve, or dark stem gate valve.