The ball valves are used to drain condensed water from the incoming and pressure-regulated air lines. The additional length of pipe above the valves serves as a reservoir for condensation. The 2-inch pipe on the right also provides a reservoir to allow the regulator to adjust smoothly to small changes in air pressure and volume.

How do we use the gauges?

Set the regulator to a convenient pressure (probably 100 PSI for most shops). The regulator manufacturer recommends that you always increase pressure from a lower setting to your final setting-for consistent results. Then, check your portable stick or dial gauge by applying it to the Schrader-type valve. If the two gauges don't match, the portable one is probably defective and should be discarded. The master gauge shown here has a rated accuracy of ±2 percent in the middle of its range. That is, if it reads 100 PSI, the actual pressure will be between 98 and 102 PSI.

How often should we check gauges?

Some shops check theirs once a week, but the most important
thing is to do it on a regular schedule. And, to replace defective gauges immediately.

Editor's Note: Our thanks to Ryder System, Inc. for sharing
their master gauge design and specifications with us.