Sizing & selecting pressure reducing regulators

摘要

The second of a two-part series. Ramy Soliman discusses the selection of control valves versus regulators in different applications, details the selection and sizing procedure for regulators, and offers guidelines for installation The outlet pressure from a regulator always registers underneath the diaphragm, which is connected to a spring on its topside and a plug underneath. The plug throttles flow through the orifice. Although this is a simplified view, it outlines the relative locations of each of those components, When the pressure underneath the diaphragm (outlet pressure) decreases due to increased downstream demand, the spring will respond by extending until the spring force on top balances the force from the gas underneath., Springs with varying stiffness values will respond differently to a fluctuation in downstream pressure registering underneath the diaphragm. The spring with the least stiffness and that provides the desired outlet control pressure should be selected, as it will respond faster and the effect will be more noticeable, Hence, for the same size of regulator and orifice, the spring with the lowest stiffness will demonstrate the tightest control The lowest stiffness is usually indicated by the smallest spring range that includes the desired setting.