API 594 Check Valve Guide
API 594 is used across several check-valve constructions, including dual-plate and other configurations where the closing element, body style and piping interface influence system behavior.
Check-valve selection should consider pressure loss, reverse-flow velocity, closing speed, orientation, water-hammer risk, spring or hinge arrangement and the available straight-pipe conditions.
The purchaser should provide flow direction, line size, class, fluid, normal and upset flow conditions, installation orientation and any non-slam performance requirement before final selection.