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Swing Check Valve Structure And Working Principle

Views: 32     Author: Site Editor     Publish Time: 2024-10-30      Origin: Site

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Swing Check Valve Structure And Working Principle

Swing check valve is a check valve in which the valve disc rotates around the rocker axis in the valve body.

In a pipeline system, when the valve is in normal working condition, fluid in the connected pipeline may experience reverse flow or backflow. However, the check valve operates automatically based on system conditions. When fluid flows in the designated direction, the check valve remains open. Once the fluid stops or begins to flow in the opposite direction, the check valve closes immediately, preventing backflow.

Swing check valves are widely used due to their simple design and effectiveness in many applications. Their bodies are similar to those of globe valves, but most check valves lack a valve stem handle or handwheel. The main components of a swing check valve include a replaceable valve seat, valve disc, pivot arm, and bonnet. The bonnet is the top part of the valve body and can be removed for easy maintenance of the valve disc.

Swing-Check-Valve-Parts-Drawing

Swing Check Valve Symbol

swing check valve symbol


Structure and Principle of the Swing Check Valve

In a swing check valve, the valve disc is hinged to the top of the valve body by an arm and pivot pin. When fluid flows into the valve, the valve disc is pushed open, allowing fluid to pass through the valve. The flow of fluid within the valve remains relatively straight, so as long as the flow rate is steady, the pressure drop across the valve is minimal. While the flow continues, the valve disc stays lifted. However, if the flow stops, changes in fluid pressure and gravity pull the valve disc back onto the valve seat, thereby closing the valve.

Swing-Check-Valve-Flow-Diagram


Behavior During Reverse Flow

If the flow reverses, backflow pushes the valve disc toward the seat, closing the valve. In cases of intermittent flow, turbulence may cause the valve disc to rise and fall repeatedly or to slam against the seat, with the disc continuously striking the seat. This phenomenon can damage the valve disc and seat, leading to leaks around the disc. Therefore, swing check valves are generally not suitable for applications with intermittent flow.

Installation Requirements for Swing Check Valves

Swing check valves can only be installed horizontally or vertically with upward flow to ensure the valve disc opens and closes properly under gravity and fluid pressure. Each valve has an arrow indicating the direction of fluid flow, which should be followed during installation. The valve should not be installed upside-down or sideways, as this would interfere with proper function and sealing effectiveness.

Installation direction of swing check valve


Vertical Swing Check Installation

It is important to note that vertical installation of swing check valves is only suitable for applications where the fluid flows from bottom to top. They should not be used in places where the fluid flows from top to bottom, as without upward flow, the valve disc may remain open.

Wrong installation direction of swing check valve


Limitations of Swing Check Valves

Swing check valves have a relatively slow closing speed, which may delay closure when backflow occurs. When the valve closes, the disc can shut rapidly, creating a pressure surge or shock wave if high-speed or high-pressure flow suddenly stops—a phenomenon known as water hammer. Water hammer can cause pressure spikes, pipeline vibration, and equipment damage. To address this issue, a damping device can be installed on the valve disc, and a metal seat can be used to reduce seat wear.

Difference Between Swing Check Valve and Lift Check Valve


Swing Check Valve

Lift Check Valve

Structural Differences valve disc is disk-shaped and rotates around the rotating axis of the valve seat channel. valve disc moves up and down along the centerline of the valve seat.
Fluid resistance Smaller flow resistance than lift check valve Large fluid resistance
Installation direction Horizontal direction and vertical direction of fluid flow from bottom to top Horizontal direction only

Applicable scene

Large diameter, low flow velocity and situations where the flow does not change frequently, but it is not suitable for pulsating flow.

For smaller diameter applications, it must be installed on horizontal pipes.

Sealing performance Sealing performance is inferior to lift check valve

Good sealing performance

That’s it for information about swing check valves. TFW is a professional butterfly valve manufacturer in China that provides custom designs to meet customers’ precise specifications. For more information, please contact us.


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