Duo-Chek valves have long been the standard for low-pressure drop flow reversal protection. These valves are made from Cast Iron, Cast Steel, Stainless Steel, and a broad variety of exotic materials.
Retainerless designs to API 594 end to end dimensions in steel bodied wafer and lug style, can be specified with a wide varitey of trim materials including both metal and resilient seats to fit for almost any purpose. Sizes to 48" and pressure ratings to Class 4500.