Reverse -flow check valves require flow to close. As the differential pressure across the check dart of the valve increases, the dart contacts the soft seat and then the hard seat to form a seal and close the check valve.
Made of corrosion resistant material.
Dual seats, one metal to metal and one metal to buna-n.
Inconel spring loaded drop providing a normally closed check.
Heat treated stainless steel drop with a large flow bypass.