Working Principle of Gate Valve

A gate valve is an opening and closing component that moves perpendicular to the fluid direction. It can only be fully opened and fully closed, and cannot be adjusted or throttled. Gate valves are sealed by the contact between the valve seat and the gate plate, and the sealing surface is usually welded with metal materials to increase wear resistance, such as 1Cr13, STL6, stainless steel, etc. There are rigid gate valves and elastic gate valves. According to the different gate valves, gate valves are divided into rigid gate valves and elastic gate valves.

The opening and closing component of a gate valve is the gate plate, and the direction of movement of the gate plate 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 valve has two sealing surfaces, and the most commonly used mode gate valve has two sealing surfaces that form a wedge shape. The wedge angle varies with the valve parameters, usually 5 °, and 2 ° 52 'when the medium temperature is not high. The gate of a wedge gate valve can be made as a whole, called a rigid gate; 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 be sealed solely by the medium pressure, that is, the sealing surface of the gate is pressed against the valve seat on the other side by the medium pressure to ensure the sealing surface is sealed, which is called self sealing.

Most gate valves use forced sealing, which means that when the valve is closed, external force must be used to forcefully press the gate plate against the valve seat to ensure the sealing performance of the sealing surface. The gate of a gate valve moves in a straight line with the valve stem, which is called a rising stem gate valve or a rising stem gate valve. Usually, there are trapezoidal threads on the lifting rod, which convert rotational motion into linear motion through the nut at the top of the valve and the guide groove on the valve body, that is, convert operating torque into operating thrust. When the valve is opened, 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 a marker, that is, the position where it cannot be opened, as its fully open position.

To consider the phenomenon of locking due to temperature changes, it is usually done by opening the valve to the top position and then reversing it by 1/2-1 turn as the position for fully opening the valve. Therefore, the fully open position of the valve is determined by the position of the gate and the stroke. Some gate valves have the stem nut set on the gate plate, and the handwheel rotates to drive the stem to rotate, thereby lifting the gate plate. This type of valve is called a rotary stem gate valve or a concealed stem gate valve.