It is known to use check valves to allow fluid flow in one direction therethrough, and to prevent flow in the opposite direction. Check valves are widely used in a wide variety of applications, for example in air conditioning systems, for example in aircraft air conditioning systems.
One form of check valve includes a pair of hinged flappers that pivot open in the direction of fluid flow when the fluid pressure differential exceeds a predetermined valve “cracking pressure”. If a negative pressure differential exists across the valve, the flapper elements close, preventing flow reversal.
Such check valves typically include a pair of flapper elements and frequently employ stops or bumpers which restrict the opening movement of the flapper element past a predetermined maximum opening angle. Such a check valve is disclosed in, for example, GB 2514953.
When the cracking pressure is exceeded the flapper elements may open at high speed. When they subsequently cooperate with the stops/bumpers high stresses may be generated. This may lead to reduced part life and increased maintenance costs.