The CL38 is a constant pressure loaded regulator for use where
closer PSIG-to-PSIG regulation is desired than can be obtained from
conventional spring-loaded regulators. Since this regulator requires an
inlet pressure supply of only 1/2 PSIG above outlet pressure, this unit
can be used where demand type loading will not meet the low pressure
differential.
ROOTS-CL38-REGULATOR [PDF]