Why

Cylinder valves with identical outlet connections are commonly equipped with PRDs whose rating depends upon the service pressure corresponding to the cylinder test pressure. The different rated PRDs (e.g., 3000 psig, 3360 psig) are not easy to distinguish visually, leading to a mix up of cylinders.

How

Each pressure rating is assigned a unique colour code for easy identification of cylinders with different test pressures.

What

A colour-coded cap corresponding to the pressure rating is fitted to the retainer nut of the PRD.