The gate valve of the gate valve moves linearly with the valve stem, which is also called a rising stem gate valve. Usually there is a trapezoidal thread on the lifting rod, through the valve nut and the guide groove on the valve body, the rotation is changed into linear motion, that is, the operating torque is changed into operating thrust.
When the valve is opened, when the lift height of the gate is equal to 1:1 times the valve diameter, the fluid passage is unblocked, but this position cannot be monitored during operation.
In actual use, the apex of the valve stem is used as the mark, that is, the unmovable position, as its fully open position. In order to take into account the lock-up phenomenon caused by temperature changes, it is usually opened to the apex 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 (that is, stroke). Some gate valve stem nuts are set on the gate, and the rotation of the handwheel drives the rotation of the valve stem to lift the gate. This kind of valve is called Rotating stem gate valve or dark stem gate valve.
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