The Dark Bar gate valve is also called the Rotary Rod Gate valve (also known as the Dark Rod Wedge gate valve). The stem nut is arranged on the gate, the handwheel rotates to drive the stem to rotate, and the gate is lifted, usually at the bottom of the stem with trapezoidal thread, through the thread at the bottom of the valve and the Guide groove on the disc, the rotational motion becomes linear motion, that is, the operation 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 stroke).
