Installation and use of gate valves

1. Gate valves are shut-off valves with inferior sealing performance compared to globe valves. The primary function of gate valves is to ‘stop flow’ and to ‘maintain flow’ with minimal resistance. They are not suitable for regulating the flow and pressure of the medium. If used for long-term regulation, the sealing surfaces may be eroded and worn by the medium, affecting sealing performance. Attention should be paid to the medium temperature and pressure when using gate valves to ensure reliability. At high temperatures and pressures, temperature changes may cause the gate plate to become stuck, and due to uneven medium temperatures in different areas, leakage may occur. This phenomenon is particularly pronounced in wedge-type gate valves.

2. Gate valves can be installed on horizontal or vertical pipelines. Single or double gate plate gate valves should be installed on horizontal pipelines, with the handwheel located above the valve; installation with the handwheel facing downward is not permitted. The flow direction of the medium through the gate valve is unrestricted. Gate valves typically use flanged connections, though welded connections may be used in special cases.

3. For large-diameter and high-pressure gate valves, the torque required for opening and closing is significant. To reduce the torque, a bypass valve can be installed. The bypass valve is installed externally on the main gate valve, with its inlet and outlet connected to both sides of the main gate valve in parallel. Before opening the main gate valve, the bypass valve should be opened first to reduce the pressure difference before and after the gate plate of the main gate valve, thereby reducing the opening torque of the main gate valve. The selection of the bypass valve diameter should be based on the main valve diameter and usage requirements.