Parallel gate valve: A gate valve in which the two sealing surfaces of the gate are parallel to each other and perpendicular to the axis of the valve body channel. The opening and closing parts (gate plates) can be single gate plates or double gate plates with expansion mechanisms. The flow resistance of the flat gate valve is small, and the flow resistance of the flat gate valve without shrinkage is similar to that of the short straight pipe. The flat gate valve with diversion holes can be installed on the pipeline and can be directly cleaned with a pig. At the same time, since the gate plate closely slides between the sealing surfaces of the two valve seats when opening and closing, it can be suitable for media with suspended particles. In addition, the flat gate valve will not overload the sealing surface due to thermal elongation of the valve stem. However, flat gate valves have the following disadvantages:
a. When the medium pressure is low, the sealing force of the metal sealing surface is not enough to achieve satisfactory sealing performance;
b. When the medium pressure is high, frequent opening and closing may cause excessive wear on the sealing surface;
c. The gate will vibrate violently when cutting off high-speed and high-density media;
d. The circular gate that moves laterally on the circular flow channel is more sensitive to flow control only when it is at 50% of the valve closing position.
