According to the sealing surface configuration, it can be divided into wedge gate valve and traveling gate valve, and wedge gate valve can be divided into single gate type, double gate type and elastic gate type. Parallel gate valves can be divided into single and double gate valves. According to the position of the screw thread of the stem, it can be divided into two types: open stem gate valve and dark stem gate valve. When the gate valve is closed, the sealing surface can be sealed only by the medium pressure. That is, the sealing surface of the gate plate can be pressed to the seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are hermetically sealed, that is, when the valve is closed, it must rely on external force to force the gate to the seat to ensure the sealing of the sealing surface. The gate plate of a gate valve moves in a straight line along with the stem. Generally, there are trapezoid thread on the lifting rod. Through the nuts on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. When the valve is opened, the flow channel is completely unblocked when the height of the gate lift is equal to 1:1 of the valve size, but this position cannot be monitored during operation. In practical use, the top of the stem as the mark, that is, the position of the immovable valve, as its full open position. In order to take account of the temperature change, the lock occurs, usually at the opening to the peak position, and then back 1/2 to 1 lap, as the position of the full open valve. Therefore, the full open position of the valve shall be determined by the position of the gate (i.e. > stroke). Stainless steel gate valves, forged steel gate valves, flanged gate valves, flanged ball valves, two-chip ball valves some gate valves, stem nuts set on the gate, handwheel rotation drive stem rotation, and raise the disc, this valve is called rotary stem gate valves or dark stem gate valves. According to the sealing surface configuration, it can be divided into wedge gate valve and traveling gate valve, and wedge gate valve can be divided into single gate type, double gate type and elastic gate type. Parallel gate valves can be divided into single and double gate valves. According to the position of the screw thread of the stem, it can be divided into two types: open stem gate valve and dark stem gate valve. When the gate valve is closed, the sealing surface can be sealed only by the medium pressure. That is, the sealing surface of the gate plate can be pressed to the seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are hermetically sealed, that is, when the valve is closed, it must rely on external force to force the gate to the seat to ensure the sealing of the sealing surface. The gate plate of a gate valve moves in a straight line along with the stem. Generally, there are trapezoid thread on the lifting rod. Through the nuts on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. When the valve is opened, the flow channel is completely unblocked when the height of the gate lift is equal to 1:1 of the valve size, but this position cannot be monitored during operation. In practical use, the top of the stem as the mark, that is, the position of the immovable valve, as its full open position. In order to take account of the temperature change, the lock occurs, usually at the opening to the peak position, and then back 1/2 to 1 lap, as the position of the full open valve. Therefore, the full open position of the valve shall be determined by the position of the gate (i.e. > stroke). Stainless steel gate valves, forged steel gate valves, flanged gate valves, flanged ball valves, two-chip ball valves some gate valves, stem nuts set on the gate, handwheel rotation drive stem rotation, and raise the disc, this valve is called rotary stem gate valves or dark stem gate valves.