News/Blog
News/Blog
01, 1970
A gate valve is the most common valve for water supply systems. It represents a linear-motion isolation valve and has a function to stop or allow the flow. Gate valves got their name from the closure element sliding into the flow stream to provide shutoff and, therefore, acting like a gate. Gate valves are used to isolate specific areas of the water supply network during maintenance, repair works, new installations, as well as to reroute water flow throughout the pipeline.
Gate valves are renowned for their straightforward design, making them suitable for various applications, especially where low pressure-drop is essential. These valves are often employed in full-port configurations, meaning the valve's port diameter matches the inner diameter of the connecting pipe. This design ensures an unobstructed fluid flow, minimizes pressure loss, and allows for pipeline cleaning with a pig.
A typical resilient seated gate valve with a non-rising spindle includes the following components:
- Wedge: The moving part that opens or closes the valve by moving into or out of the flow path.
- Ductile Iron Valve Body: The robust outer casing that houses the internal components.
- Seating Area: The surface against which the wedge seals to stop the flow.
- Stem (Spindle): The rod that moves the wedge up and down.
- Spindle Bearing: Supports the stem and allows smooth rotation.
- Bonnet: The cover attached to the body, providing access to the internal parts for maintenance.
- Packing: The sealing material around the stem to prevent leaks.
The valve body is the most significant part of the gate valve, providing structural integrity and housing all other components. In a non-rising spindle design, the spindle rotates within the valve body, facilitating a more compact and economical bonnet construction. The bonnet, bolted to the body, can be easily removed for cleaning and maintenance. During operation, as the valve closes, the wedge moves downward until it seals against the valve seat, achieving a complete shutoff. Conversely, when the valve opens, the wedge slides upward, away from the seating area, allowing fluid to flow freely.
Based on construction, gate valves for water supply systems can generally be divided into the following types:
- By Wedge: Includes parallel gate valves and wedge gate valves.
- By Seat: Can have either metal seats or resilient seats.
- By Stem: Available with either rising stems or non-rising stems.
Gate valves are typically operated by a handwheel, a valve T-key (wrench), or an actuator. The handwheel is connected to a valve stem and converts rotational energy into linear motion. When opening the gate valve, turning the handwheel threads the gate stem into the gate, raising it, and vice versa for closing, lowering the gate. In underground installations, an extension spindle is used for operation without direct valve access.
Gate valves are usually installed in pipeline areas where they remain open or closed for extended periods, as switching between these positions takes time. For frequent or remote operation, motorized gate valves equipped with electric actuators are preferred.
Gate valves are designed as isolation valves and should be used only in the "fully open" or "fully closed" position. They are not suitable for regulating water flow. Throttling a gate valve can create turbulent flow, causing vibration and cavitation. This turbulence can damage the valve's wedge and seat, leading to leaks and reduced sealing effectiveness.
