Working principle of gate valve

The opening and closing component of the gate valve is the gate, and the movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The gate has two sealing surfaces, and the most commonly used mode is that the two sealing surfaces of the gate valve form a wedge shape. The wedge angle varies depending on the valve parameters, usually 5 °, and when the medium temperature is not high, it is 2 ° 52 '. The gate plate of a wedge gate valve can be made into a whole, called a rigid gate plate; It can also be made into a gate that can produce slight deformation to improve its processability and compensate for the deviation of the sealing surface angle during the processing. This type of gate is called an elastic gate. When the gate valve is closed, the sealing surface can only rely on medium pressure to seal, that is, relying on medium pressure to press the sealing surface of the gate plate towards the other side of the valve seat to ensure the sealing surface, which is self sealing. Most gate valves use forced sealing, which means that when the valve is closed, external force is used to forcefully press the gate plate towards the valve seat to ensure the sealing surface is sealed. The gate plate of a gate valve moves in a straight line with the valve stem, which is called a rising stem gate valve, also known as a rising stem gate valve. Usually, there is a trapezoidal thread on the lifting rod, which transforms the rotating motion into linear motion through the nut at the top of the valve and the guide groove on the valve body, that is, the operating torque is converted into the operating thrust. When opening the valve, when the lifting height of the gate is equal to 1:1 times the valve diameter, the fluid channel is completely unobstructed, but this position cannot be monitored during operation. In actual use, the vertex of the valve stem is used as the mark, that is, the position that cannot be opened, as its fully open position. To consider the phenomenon of lockup due to temperature changes, it is usually done by turning back 1/2 to 1 turn at the top position as the fully open valve position. Therefore, the fully open position of the valve is determined based on the position of the gate, i.e. the stroke. Some gate valves have a stem nut located on the gate, and the handwheel rotates to drive the stem to rotate, causing the gate to lift. This type of valve is called a rotary stem gate valve, or a non rising stem gate valve.