Self-operating and direct-acting, the proportional regulator regulates a high upstream pressure to a smaller downstream pressure. The downstream pressure is regulated, which means the valve closes when the downstream pressure rises. Pillarless construction and diameter-independent spring ranges are features of Ari-Predu. Additional features include screwed and marginal seats; three exchangeable spring sizes; balancing and sealing bellows; and easy change of spring and actuator. It can be used with mediums such as steam, neutral gases, vapors and liquids.