1. Lift Check Valve

A lift check valve features a disc that slides along the vertical centerline of the valve body.

Installation: Primarily for horizontal pipelines. For high-pressure, small-diameter valves, the disc may be a spherical shape.

Design: The valve body is shaped like a globe valve (interchangeable with globe valves), so it has a relatively high flow resistance coefficient.

● The valve disc and body are structurally similar to a globe valve.

● The upper part of the disc and lower part of the bonnet have a guide sleeve, allowing the disc to freely move up and down within the valve body.

Operation:

● When fluid flows forward, the disc is pushed open by the fluid.

● When flow stops, the disc falls under its own weight onto the seat, preventing reverse flow.

Flow Orientation:

● Straight-through lift check valve: Inlet/outlet passage is perpendicular to the seat passage.

● Vertical lift check valve: Inlet/outlet passage is aligned with the seat passage, resulting in lower flow resistance than the straight-through type.

2. Swing Check Valve

A swing check valve has a disc-shaped valve disc that rotates around a hinge axis at the seat passage.

Flow Characteristics:

● The internal flow path is streamlined, giving lower flow resistance compared to lift check valves.

● Suitable for low-flow and relatively stable large-diameter pipelines, but not recommended for pulsating flow.

● Sealing performance is inferior to lift check valves.

Types:

● Single-disc, double-disc, and multi-disc designs.

● These types are chosen mainly based on valve diameter, aiming to reduce hydraulic shock when flow stops or reverses.

3. Wafer/Dual-Plate Check Valve

The wafer or dual-plate check valve is structurally similar to a butterfly valve but differs in operation:

Automatic Operation: Unlike butterfly valves, which require external actuation, wafer check valves operate automatically.

Closing Mechanism: When flow stops or reverses, the disc(s) rotate onto the seat under their own weight and the reverse flow pressure.

Installation: Can be used in horizontal or vertical pipelines, typically wafer-style between flanges.

Operation Detail:

Two discs rotate around a pin shaft, overcoming spring force under fluid pressure.

The open position forms a “>” shape.

Straight pipe sections upstream and downstream are recommended to allow the discs sufficient rotation space.