Pressure regulators are often misunderstood and misapplied. Somebody might call it a "pressure sustaining valve," still another might know it as a "pressure reducer valve." To make matters worse, backpressure regulators are commonly mistaken for pressure regulators. The backpressure regulator is a normally closed valve installed at the END of a piping system to provide an obstruction to flow and thereby regulate upstream (back) pressure. The backpressure regulator is called upon to provide pressure in order to draw fluid off the system. The pressure regulator is a normally open valve and is installed at the START of a system or before pressure sensitive equipment to regulate or reduce undesirable higher upstream pressure.
Uses of each
Where an obstruction will benefit everything prior to the valve, for example, at the end of a return line and just prior to the tank, a backpressure regulator should be used to provide an obstruction so that all equipment prior to the tank will have sufficient pressure. When pressure is too high, the backpressure regulator opens and dumps into the tank. Too often, a pressure regulator is installed at this point instead. In this case, the pressure regulator will simply stay wide open and just send liquid straight into the tank without maintaining upstream pressure...just a very expensive fitting.
Where an obstruction will benefit everything after the valve, a pressure regulator should be used so that all the equipment after it will not have excessive pressure. Used where it should be — at the beginning of a process — the pressure regulator will ensure safe downstream pressure.