When the gate valve is closed, the sealing surface can be sealed only by the dielectric pressure, that is, relying only on the dielectric pressure to press the sealing surface of the gate to the seat on the other side to ensure the sealing of the sealing surface, which is self-sealing.
Most gate valves are forced sealed, that is, when the valve is closed, it is necessary to rely on external forces to forcibly push the gate to the seat, in order to ensure the sealing of the sealing surface. Motion mode: The gate of the gate valve moves in a straight line with the stem, also known as the Ming pole 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 rotational motion becomes linear motion, that is, the operating torque into the operation thrust. When opening the valve, when the gate lift height is equal to 1:1 time times the valve diameter, the channel of the fluid is completely smooth, but at run time, this position cannot be monitored. When used in practice, it is marked by the vertex of the stem, that is, the motionless position, as its fully open position. In order to consider the temperature change there is a lock phenomenon, usually in the position of opening to the vertex, and then back to the 1/2-1 ring, as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate (that is, the itinerary). Some gate valve stem nuts are located on the gate, handwheel rotation to drive the stem rotation, and make the gate lift, this valve is called rotary rod gate valve or Dark bar gate valve.
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