Cast Steel Swing Check Valve H44H

Working Principle

Check valves are designed to permit fluid flow in one single direction and automatically prevent backflow. Normally functioning automatically: when fluid flows forward, internal pressure lifts the valve disc open. When fluid reverses direction, the combined force of back pressure and the disc’s own weight presses the disc firmly against the seat, shutting off the flow completely.

There are two primary categories: swing check valves and lift check valves.

1. Swing Check Valve: Built with a hinge mechanism. The disc swings freely like a door against the inclined seat surface. The hinged design ensures the disc can fully swing open and achieve complete, tight sealing against the seat every time it closes. Disc bodies can be manufactured entirely from metal, or fitted with rubber/soft facing overlay depending on working condition requirements. When fully opened, fluid resistance is nearly negligible, resulting in very low pressure loss across the valve.

2. Lift Check Valve: The disc rests on the valve body seat surface. Upstream fluid pressure lifts the disc to allow passage; once flow reverses, the disc drops back onto the seat to block reverse flow. Also available in all-metal construction or with resilient sealing surfaces. Compared with swing check valves, lift check valves feature a narrower flow path, higher pressure drop, and their flow capacity is greatly restricted.

 Installation & Type Classification

1. Swing Check Valve: Disc is disc-shaped, rotating around a pin shaft outside the valve seat. Internal flow channel is streamlined, with far lower flow resistance than lift type valves. Ideal for large diameter pipelines with low-velocity and stable service conditions; not suitable for pulsating flow or applications requiring ultra-tight sealing. Available in single-disc, double-disc and multi-disc configurations, primarily used to stop medium backflow and protect pipelines from water hammer damage.

2. Lift Check Valve: Disc slides vertically along the pipeline centerline. Threaded end versions are only for horizontal installation; wafer type can be mounted on both horizontal and vertical runs. Higher flow resistance. Structure is similar to a globe valve. When medium flows, pressure pushes the disc upward; on reverse flow, the disc reseats tightly to block backflow. Outlet flow direction is perpendicular to the pipeline axis for lift check valves, while parallel to pipeline for swing type.

3. Butterfly Check Valve: Rotates around a central spindle. Simple structure, can only be installed on horizontal pipelines with reliable sealing performance.

4. Wafer Lift Check Valve: Disc moves along the valve central axis. As a newer generation product, it features compact size, light weight, optimized manufacturing craftsmanship, and is one of the fastest developing check valve designs. Its flow resistance is slightly higher than swing check valves.

5. Pressure Seal Check Valve: Specially engineered for boiler feedwater and steam exhaust service. Combines the dual advantages of swing check valves and globe/angle stop valves.

In addition, there are special-purpose check valves for unique installation scenarios, including foot valves, spring check valves, Y-type check valves, etc.