Two-stage regulators are two regulators built into a single regulator body. The first regulator (first stage) is preset at a non-adjustable pressure to reduce the incoming pressure to a lower pressure referred to as the intermediate pressure. The second regulator (second stage) is adjustable within the desired delivery range.
The second stage then performs in a manner similar to that of a single-stage regulator, except that the inlet pressure to the second stage is relatively constant. The two-step pressure reduction produces a final delivery pressure showing little effect from changes in cylinder pressure (i.e. no adjustment is required as the cylinder empties).
When should you use a two-stage regulator?
applications where the delivery pressure rise from the cylinder pressure decay cannot be tolerated
situations where proper pressure is critical and the cylinders in use are in a remote or difficult to monitor location
typically are not required when using gases from low pressure (<3,445kPa (500psi)) sources