Gate valve with the stem together for straight line movement, called lift stem gate valve (also called rising stem gate valve).Usually there are trapezoidal threads in the lift rod, through the nut at the top of the valve and the guide groove in the valve body, to change the rotary motion into linear motion, that is, to change the operating torque into operating thrust.Sealing surface can only rely on the medium pressure to seal, that is, rely on the medium pressure to press the sealing surface of the disc to the other side of the seat to ensure the sealing surface, this is self-sealing.Most gate valves are forced sealing, that is, when the valve is closed, to rely on external force to force the gate plate to the seat, to ensure the sealing surface of the sealing.