When the gate valve is closed, the sealing surface can be sealed solely by the medium pressure, that is, it relies solely on the medium pressure to push the sealing surface of the gate plate towards the opposite valve seat to ensure the sealing of the sealing surface, which is known as self-sealing. Most gate valves use forced sealing, meaning that when the valve is closed, external force must be applied to forcibly push the gate plate towards the valve seat to ensure the sealing integrity of the sealing surface.

Operation Mode: The gate of the gate valve moves linearly along with the valve rod, also known as a top-mounted stem gate valve. Typically, there is a trapezoidal thread on the lifting rod, which converts rotational motion into linear motion through the nut at the top of the valve and the guide slots on the valve body, thereby changing the operating torque into thrust. When opening the valve, the gate is raised to a height equal to 1:1 of the valve passage diameter, ensuring a fully open fluid passage. However, this position is not observable during operation. In actual use, the top point of the valve rod is used as a reference, indicating the fully open position where it cannot be moved further. To account for locking due to temperature changes, it is usually opened to the top point and then reversed 1/2 to 1 turn, which serves as the fully open position. Therefore, the fully open position of the valve is determined by the position of the gate (i.e., the stroke). In some gate valves, the nut on the valve rod is located on the gate plate. The handwheel rotates to move the valve rod, lifting the gate, which is known as a rotating stem gate valve or a submersible stem gate valve.