When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, only rely on the media Pressure will seal the gate to the other side of the valve seat to ensure the sealing surface of the seal, which is self-sealing.
Most of the gate valve is the use of forced seal, that is, when the valve is closed, to rely on force to force the gate pressure valve seat, in order to ensure the sealing surface sealing. Movement mode: Gate valve with the valve stem together for linear motion, also known as the bar gate valve. Usually there is a trapezoidal thread on the lift rod, through the nut on the top of the valve and the guide groove on the valve body, the rotary motion becomes a linear motion, that is, the operating torque into the operating thrust. When opening the valve, when the gate lifting height is equal to 1 of the valve diameter: 1 time times, the fluid channel is completely unblocked, but at the time of operation, this position is not monitored. The actual use of the valve stem is the vertex as a sign, that is, the position is not moving, as its full open position. In order to consider the deadlock phenomenon of temperature change, usually at the vertex position, and then back to the 1/2-1 ring, as the position of the open valve. Therefore, the open position of the valve, according to the position of the gate (i.e. the trip) to determine. Some gate valve stem nut is located on the gate, handwheel rotation drive valve stem rotation, and make the gate lift, this valve is called rotary bar gate valve or Dark rod gate valve.