Q
How do gate valves work?
A

Gate valve is a gate with open and close parts, the movement direction of the gate is perpendicular to the direction of the fluid, the gate valve can only be fully open and fully closed, can not be adjusted and throttle.Gate valves are sealed by contact between the seat and gate. Usually, the sealing surface is surfacing welded with metal materials to increase wear resistance, such as surfacing 1Cr13, STL6, stainless steel, etc.The gate has the rigid gate and the elastic gate, according to the gate different, the gate valve is divided into the rigid gate valve and the elastic gate valve.

The opening and closing part of gate valve is the gate, the movement direction of the gate is perpendicular to the direction of the fluid, gate valve can only be fully open and fully closed, can not be adjusted and throttle.The gate has two sealing faces, the two sealing faces of the gate valve in the more common mode form a wedge, the wedge Angle varies with the valve parameters, usually 5°, medium temperature is not high 2°52'.Wedge gate valve gate can be made into a whole, called a rigid gate;It can also be made into a small deformation of the gate, to improve its process, to compensate for the Angle of the sealing surface in the process of the deviation, this kind of gate is called elastic gate.When the gate valve is closed, the sealing surface can be sealed only by the pressure of the medium, that is, the pressure of the sealing surface of the gate to the other side of the seat to ensure the sealing surface, this is self-sealing.Most gate valves are used for forced sealing, that is, when the valve is closed, to rely on external force to force the gate to the seat, in order to ensure the sealing surface of the seal.Gate valve gate with the stem for linear movement, called lifting stem gate valve, also called rising stem gate valve.Usually there is a trapezoidal thread on the lifting rod, through the nut at the top of the valve and the guide groove on the valve body, the rotation movement into a straight movement, that is, the operation torque into the operation thrust.When the valve is opened and the gate is raised to a height equal to 1:1 of the valve size, the flow path is completely clear, but this position cannot be monitored during operation.The actual use of the stem is marked by the apex of the valve, that is, the open position, as its full open position.In order to consider the temperature change of the lock phenomenon, usually open to the vertex position, and then rewind 1/2-1 turn, as the position of the fully open valve.Therefore, the fully open position of the valve is determined by the position of the gate, i.e. the stroke.Some gate valves, the stem nut is on the gate, the handwheel rotation to drive the stem rotation, and the gate lift, this valve is called the rotary stem gate valve, or called the hidden stem gate valve.

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