Back Pressure Regulators Excess pressure regulator / back pressure sustaining valve - PREDEX | ARI Ari-Armaturen Excess pressure regulator / back pressure sustaining valve - PREDEX | ARI The ARI-PREDEX® is a self-operated excess pressure regulator, designed to automatically control upstream pressure in piping systems. It ensures precise and reliable pressure regulation for steam, gases, vapors, and liquids while preventing excessive pressure buildup. View