The gate valve is a gate of the opening and closing piece. The movement direction of the gate is perpendicular to the fluid direction. The gate valve can only be fully opened and fully closed, and cannot be adjusted and throttled. The gate valve is sealed by the contact between the valve seat and the gate. Usually, the sealing surface will be welded with metal materials to increase wear resistance, such as 1Cr13, STL6, stainless steel and so on. The gate has a rigid gate and an elastic gate. According to different gates, the gate valve is divided into a rigid gate valve and an elastic gate valve.
The opening and closing part of the gate valve is a gate. The movement direction of the gate is perpendicular to the fluid direction. The gate valve can only be fully opened and fully closed, and cannot be adjusted and throttled. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used gate valves form a wedge shape. The wedge angle varies with the valve parameters, usually 5 °, and 2 ° 52 'when the medium temperature is not high. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its processability and make up for the deviation of the sealing surface angle during processing. The plate is called a spring gate. When the gate valve is closed, the sealing surface can be sealed only by the pressure of the medium, that is, the sealing surface of the gate is pressed against the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are forcedly sealed, that is, when the valve is closed, the gate is forced to be pressed against the valve seat by external force to ensure the tightness of the sealing surface. The gate of the gate valve moves linearly with the valve stem, which is called a lift lever gate valve, also known as an open lever gate valve. Usually, there is a trapezoidal thread on the lifting rod, and the rotary motion is changed to linear motion through the nut on the top of the valve and the guide groove on the valve body, that is, the operating torque is changed to the operating thrust. When the valve is opened, when the lift height of the gate is equal to 1: 1 of the valve diameter, the fluid channel is completely clear, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a mark, that is, the position where it cannot be opened, as its fully open position. In order to consider the lock-up phenomenon caused by temperature changes, it is usually opened to the top position, and then back to 1 / 2-1 circle as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the shutter, that is, the stroke. For some gate valves, the stem nut is set on the gate plate. The hand wheel rotates to drive the valve stem to rotate, and the gate plate is lifted. This kind of valve is called a rotary lever gate valve, or a dark lever gate valve.