Check Valves
Check valves are a one-way, non-return valve that only allows flow in one direction. They normally use a ball or poppet that is spring loaded to block the flow of fluid in one direction. An essential idea in check valves is the cracking pressure which is the minimum upstream pressure required unseat the poppet to allow flow of the fluid. Typically the check valve is designed for and can therefore be specified for a specific cracking pressure.
Kepner
Legris
