304 Stainless Steel Swing Check Valve H44W

Check valves allow fluid to flow in only one direction and block backflow. Normally, this type of valve works automatically. Under the pressure of forward-flowing medium, the disc opens; when the medium flows backward, the combined force of fluid pressure and the self-weight of the disc presses the disc against the valve seat to cut off the flow. Internal threaded check valves and wafer check valves fall into this category, including swing check valves and lift check valves.

A swing check valve is equipped with a hinge mechanism, and a door-like disc rests freely on the inclined valve seat surface. To ensure the disc can reach the proper seating position every single time, the disc is designed with a hinge structure, providing sufficient rotation stroke for full and complete contact between the disc and the valve seat. The disc can be made of all-metal structure, or be fitted with rubber, composite or cladding on the metal sealing surface, depending on application requirements. When a swing check valve is fully opened, the fluid resistance is extremely low, resulting in a relatively small pressure loss across the valve.

For lift check valves, the disc is seated on the valve seat at the lower part of the valve body. In addition to the free up-and-down movement of the disc, the rest of the structure is similar to a globe valve. Fluid pressure lifts the disc upward to open the valve during forward flow; when backflow occurs, the disc falls back onto the seat to shut off the pipeline. Depending on working conditions, the disc can be all-metal, or installed with rubber or gasket sealing on the disc holder. Just like globe valves, the internal passage of lift check valves is relatively narrow, so their pressure drop is much larger than that of swing check valves, while swing check valves have very limited flow capacity.

 Installation Types

1. Swing Check Valve

The disc is disc-shaped and rotates around a fixed shaft above the valve passage. The inner channel adopts a streamlined design, with smaller flow resistance than lift check valves. It is applicable to working conditions with low flow velocity and stable large flow rate, but not suitable for pulsating flow. Its sealing performance is inferior to that of lift check valves. Wafer swing check valves are available in single-disc, double-disc and multi-disc designs, which are mainly installed at pipeline outlets to reduce water hammer when medium stops flowing or reverses direction.

2. Lift Check Valve

The disc moves vertically along the central line of the valve body. Female threaded lift check valves can only be installed on horizontal pipelines. For high-pressure small-diameter check valves, a ball disc structure can also be used. The shape of a ball check valve is similar to a globe valve (can be used in shut-off scenarios), so its fluid resistance is relatively high. Its structure is similar to a globe valve, with matching guide sleeves machined on the upper valve body and lower valve cover. The disc can move freely up and down between the guide sleeves. When medium flows forward, the disc is pushed open by fluid pressure; when medium stops flowing, the disc falls back onto the seat to block reverse flow. For straight-through lift check valves, the inlet and outlet directions are consistent with the channel direction; for angle lift check valves, the inlet and outlet channel directions are perpendicular to each other.

3. Wafer Swing Check Valve

A check valve that rotates around a pin inside the valve body. The structure of wafer check valves is simple, they can only be installed on horizontal pipelines and feature excellent sealing performance.

4. Vertical Lift Check Valve

A check valve that slides along the vertical center line of the valve body. Pipeline vertical check valve is an emerging type. It features compact size, light weight, excellent manufacturability, and is installed to prevent medium reverse flow. However, its fluid resistance coefficient is slightly larger than that of swing check valves.

5. Piston Check Valve

This type of check valve is used for boiler water supply and steam cut-off pipelines. It is a combined integrated structure of lift check valve and globe/angle stop valve.

In addition, there are special check valves that cannot be installed at pump outlets, such as foot valves, spring check valves, Y-type check valves, etc.