Basic introduction to the national standard gate valve.
Gate valves can only be fully opened and closed, and cannot be adjusted or throttled. Gate valve is a widely used valve. Usually a cutting device with a diameter of DN ≥ 50mm is used. Small diameter shut-off devices are also available for gate valves. The gate has two sealing surfaces. The two most commonly used gate valves form a wedge for each sealing face, and the angle of the wedge depends on the valve parameters. If the medium temperature is not high, it is usually 50,2°52'. The gate of the wedge gate valve can be called the whole gate of the rigid gate. Can also be used as a gate, can cause slight deformation, improve manufacturability, and compensate for deviations in sealing surface angle during machining. This board is called a flexible door. Gate valves are the primary control device for the flow and transportation of powders, grains, granules and small items. In industries such as metallurgy, mining, building materials, food and chemical, gate valves can control or quickly prevent flow changes.
The national standard gate valve refers to the type of cast steel gate valve. According to the configuration of the sealing surface, it can be divided into wedge gate valve and parallel gate valve. Wedge gate valve is divided into single gate, double gate and elastic gate. Gate and Parallel Gate Gate valve is divided into single gate and double gate. According to the screw position of the stem, it can be divided into two types: open stem gate valve and dark stem gate valve.
If the national standard gate valve is closed, the sealing surface can only be sealed according to the medium pressure. In other words, due to the medium pressure, the sealing surface of the gate is pressed against the valve seat on the opposite side to ensure the sealing of the sealing surface. This is self-sealing. Most gate valves are forced to seal. In other words, when the valve is closed, the gate must be pressed against the valve seat by external force to ensure the sealing performance of the sealing surface.
The gate of the national standard gate valve moves linearly with the valve stem called the lifting rod gate valve. Typically, the lift rod has a trapezoidal thread, and the rotary motion is turned into a linear motion through a nut and guide groove at the top of the valve body. In other words, the operating torque is the operating thrust.
When the valve is open and the lift height of the gate is equal to 1:1 of the diameter of the valve (gate valve manufacturer), the fluid passage will not be completely blocked, but this position cannot be monitored during operation. In actual use, mark the top of the valve stem, that is, the position that cannot be opened, as the fully open position. Taking into account the locking phenomenon caused by temperature changes, usually open to a higher position, and rewind 1/2-1 turn at the fully open valve position. Therefore, the fully open position of the valve depends on the position of the gate.
For some gate valves, the stem nut is installed on the gate valve, and the rotation of the handwheel drives the rotation of the valve stem to lift the gate valve. This valve is called a rotary valve or dark valve gate valve.