There are significant differences between piston check valves and swing check valves in structure, working principle and application scenarios. The main differences are as follows:
1. Core structure and movement mode
Piston check valve
A cylindrical piston is used as the opening and closing part. The switch is realized by axial sliding. The piston moves up and down in a straight line in the valve cavity.
It is usually equipped with a spring-assisted closing mechanism. The piston is pushed open by the medium during forward flow, and the spring pushes the piston to quickly reset the seal during backflow or pressure balance.
Swing check valve
The opening and closing part is a disc-shaped valve disc, which rotates around the axis through a rocker arm and a pin structure (similar to the swing of a door panel).
Closing depends on the deadweight of the valve disc and the thrust of the backflow medium, and there is no spring structure; large-diameter models may add a heavy hammer to enhance the closing force.
2. Performance characteristics comparison
Closing speed and sealing performance
Piston type: The spring drive makes it close very quickly (millisecond level), which can effectively prevent water hammer; the piston vertically presses the valve seat, and the seal is tighter, which is especially suitable for high-pressure and high-requirement systems.
Swing type: The closing speed is slow (especially for large diameters), and the valve disc is prone to impact when it is tilted and seated; the sealing surface is in line contact, and there may be slight leakage under low-pressure conditions.
Flow resistance and applicable working conditions
Swing type: The channel inside the valve is streamlined, and the flow resistance is smaller, which is suitable for low-flow and large-diameter pipelines.
Piston type: The fluid needs to pass through the annular gap between the piston and the valve cavity, and the flow resistance is large, but it can be improved by optimizing the design.
Installation requirements
Piston type: It usually needs to be installed horizontally, and special designs (such as damping devices) are required for vertical installation.
Swing type: There is no installation direction restriction (horizontal/vertical), and it is more adaptable.
3. Typical application scenarios
Piston type applicable scenarios
Pump outlet protection (preventing backflow from causing pump reversal)
Steam system, high-pressure pipeline (relying on its tight sealing and rapid response)
Occasions where water hammer needs to be strictly prevented (such as chemical and power station pipelines)
Swing type applicable scenarios
Water supply and drainage, water conservancy projects, and other large-diameter, low-pressure pipelines (giving full play to its low flow resistance advantage)
Media containing particles or viscous fluids (simple structure and not easy to get stuck)
When the installation space is limited (a wafer-type swing valve can be selected)
4. Maintenance and cost
Piston type: precise structure, maintenance requires professional disassembly; high manufacturing cost.
Swing type: simple structure, convenient maintenance; high cost performance, large-diameter valves have obvious cost advantages.