Application Conditions and Operation of Gate Valves

A gate valve refers to the valve whose closing parts move along the vertical direction of the path center line. The gate valve can only be used to fully open and close the pipeline, but it can't be used for regulation and throttling. A gate valve is a kind of valve with a wide range of use. Generally, it is selected for the cut-off device with DN ≥ 50 mm, and sometimes it is also used for the cut-off device with small diameters.

The gate plate has two sealing surfaces. The wedge angle of the two sealing surfaces of the most commonly used gate valve varies with the valve parameters. Wedge gate valves can be made into a whole, which is called a rigid gate. It can also be made into a small amount of deformation of the gate in order to improve its process and to make up for the deviation of sealing surface angle in the process of processing. This kind of gate plate is called the elastic gate plate.

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 is pressed to the valve seat on the other side to ensure the sealing of the sealing surface, which is self sealing. Most gate valves are forced to seal. That is to rely on external force to force the gate to the valve seat in order to ensure the sealing of the sealing surface.

Gate plates of gate valves are moved with the valve stem for linear movement, which is known as rising stem gate valves (also known as rising stem gate valves). Generally, there are trapezoidal threads on the lifting stem. Through the nut 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 the operating thrust.

1. Gate valves are usually used in open close applications and cannot be used in throttling applications.
2. The gate valve is usually installed on the horizontal pipe with the stem vertical upward. It can also be installed in vertical piping or horizontal piping where the stem is not vertically upward, but special construction may be required depending on the valve size, application environment and material. If the purchased valve is to be installed in a special way, the orientation of the valve should be specified when placing an order.
3. Flexible or split wedges are recommended for applications where the temperature exceeds 260℃ to avoid wedges being stuck due to thermal expansion. This may occur when the valve is cold closed and then hot opened.
4. When gate valves are used in high-speed fluid (turbulent) or thermal cycling applications, threaded seat rings should be lockwelded to the valve body to avoid loosening. 
5. After closing the gate valve, the stem should be slightly rotated (1/8 to 1/4 turn) to release the stem load. This allows the stem to expand slightly without jamming or damaging the valve or affecting the closing effect.
6. If the seat ring mounting lug is removed, the high integrity shut-off gate valve can be used in the hot water outlet or soft iron piping system. 
7. If the pump station uses the valve which is not limited by the site, there are a lot of debris in the water and they are easy to block the important positions. The manual and electric gate valve can be used. On the contrary, butterfly valves can be used, especially in the pump room reconstruction project, so as to effectively utilize the space of the original pump room and improve the water supply under the premise of the original pump room area being unchanged.