Soft seal gate valves are divided into two types: open stem soft seal gate valves and concealed stem soft seal gate valves. Usually there is a trapezoidal thread on the lifting rod. Through the nut in the middle of the gate plate and the guide groove on the valve body, the rotational motion is changed into linear motion, that is, the operating torque is changed into the operating thrust. When the valve is opened, when the lift height of the gate plate is equal to 1:1 times of the valve diameter, the fluid channel is completely unobstructed, but during operation, this position cannot be monitored. In actual use, the top of the valve stem is used as a mark, that is, the position that does not open, as its fully open position. In order to consider the locking phenomenon caused by temperature changes, the valve is usually opened to the top position and then retracted 1/2-1 turn as the fully open valve position. Therefore, the fully open position of the valve is determined by the position of the gate (i.e. stroke). This type of valve should generally be installed horizontally in the pipeline.
