The
ANSI swing check valves provided by Weldon are
cast steel check valves in which the disc swings on a hinge or trunnion to block the flow, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-setcion may be perpendicular to the centerline between the two ports or at an angle. Although
swing check valves can come in various sizes, large check valves are often swing check valves.
ANSI Check valves mainly follow American Standards, including
API 6D,
ASME B16.34,
ASME B 16.5,
ASME B16.10, etc.