Lift Check Valves
These feature a disc mounted on a spring that will lift vertically from the seat of the valve in response to fluid pressure. Its cracking pressure must be sufficient to overcome gravity. Backflow will reverse this movement. The valve may need to make a 90-degree turn when moving in each direction.
A stop check valve is a variation of the lift type, incorporating a stem that can be closed to prevent the disk from moving away from the valve seat, to create a tight seal.
Clapper valves are used in firefighting systems. They feature a hinged gate that opens in the direction of the incoming liquid and closes when there is no forward pressure.
Reverse Check Valves
Reverse flow valves are used in gas lifts and similar equipment to prevent backflow and fluid mixing and to allow the circulation of pressure.
Inlet Check Valves
Inlet types are used in vehicles to prevent fuel from spitting or spilling back out - called wellback - when refuelling.
Non-Slam Check Valves
A non-slam valve is a variation of the swing type in which the disk cannot slam shut in response to backflow. Instead, a pressure-sensitive spring moves the disc in a smooth motion.
Low-Pressure Non-Return Valves
These are designed to be sensitive to low-pressure fluid or gas flow in which standard models might not function properly.
Two-Way Check Valves
These are specialist types of valve used in air braking systems. Two input circuits apply pressure to a moving component called a shuttle. The highest pressure is then directed to the output and from there to the brakes themselves.