When the gate valve is closed, the sealing surface can be sealed solely by the pressure of the medium, that is, by merely relying on the pressure of the medium to press the sealing surface of the gate plate against the opposite side of the valve seat to ensure the seal. This is what is known as self-sealing. Most gate valves employ forced sealing, which means that when the valve is closed, external force must be applied to forcefully press the gate plate against the valve seat to ensure the integrity of the sealing surface.

Operation Method: Gate valves with a gate that moves linearly along with the valve rod are also known as handwheel gate valves. 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, effectively changing the operating torque into a pushing force. When opening the valve, when the lifting height of the gate is equal to one-to-one with the valve bore diameter, the fluid passage is completely open. However, this position is unmonitorable during operation. In practical use, the top point of the valve rod is used as a marker, indicating the fully open position. To address potential locking issues due to temperature changes, it is usually necessary to reverse the valve by 1/2 to 1 turn after reaching the top point to achieve the fully open position. Therefore, the fully open position of the valve is determined by the position of the gate (i.e., stroke). Some gate valves have the nut on the gate, and the handwheel rotation drives the valve rod, lifting the gate, which are called swivel stem gate valves or blind stem gate valves.