Working Principle of Gate Valve
Gate valve is a gate with opening and closing parts. The movement direction of gate is perpendicular to the direction of fluid. Gate valve can only be fully opened and closed, and can not be adjusted and throttled. Gate valves are sealed by contact between the valve seat and gate plate. Metal materials are usually overlaid on the sealing surface to increase wear resistance, such as 1Cr13, STL6, stainless steel, etc. There are rigid gate and elastic gate. According to the difference of gate, gate valves are divided into rigid gate and elastic gate.
The opening and closing part of the gate valve is the gate. The movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and closed, and can not be adjusted and throttled. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used mode gate valves form wedges. The wedge angle varies with the valve parameters, usually 5 degrees, and the medium temperature is 2 degrees 52'. Wedge gate valve can be made into a whole, called rigid gate; it can also be made into a gate that can produce slight deformation to improve its workability and make up for the deviation of sealing surface angle in the process of processing. This kind of gate is called elastic gate. When the gate valve closes, the sealing surface can be sealed only by medium pressure, that is to say, the sealing surface of the gate can be pressed to the seat on the other side to ensure the sealing surface sealing, which is self-sealing. Most gate valves are forced to seal, that is, when the valve closes, the gate must be forced to the seat by external force to ensure the sealing surface. The gate plate of the gate valve moves in a straight line with the stem, which is called the lift bar gate valve, or the open bar gate valve. Usually there are trapezoidal threads on the lifting rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is to say, the operating torque is changed into the operating thrust. When opening the valve, when the gate lifting height is equal to 1:1 times the valve diameter, the flow passage is completely open, but in operation, this position can not be monitored. In practical use, the vertex of the valve stem is used as the sign, that is, the position of the valve stem that is not moving is used as its full open position. In order to consider the locking phenomenon of temperature change, it is usual to turn back 1/2-1 circle at the top position as the position of the fully open valve. Therefore, the full open position of the valve is determined by the position of the gate, that is, the stroke. Some gate valves, stem nuts set on the gate plate, hand wheel rotation to drive the rotation of the stem, and make the gate lift, this valve is called rotary bar gate valve, or dark bar gate valve.