Although through the years many have used the phrase "Reserve-In-Use", it is not actually the correct terminology when speaking of normal changeover procedure for high pressure gas manifolds.

Bulk supply systems consist of a main supply vessel and a secondary cryogenic liquid vessel or a cylinder header.

During normal operation, the main vessel operates as the supply to the facility. When the main supply vessel is reduced to a level at or below the reserve activation pressure, the reserve supply will automatically begin to supply the facility. In this case the alarm signaled would be the "Reserve-In-Use".

When speaking in terms of a high pressure gas manifold with two equal headers, changeover from one bank (primary) to another (secondary) signals the "Secondary-Supply-In-Use" alarm.

If the manifold is a liquid by liquid system it must have a reserve header assembly. During normal operation, changeover from one bank (primary) to another (secondary) signals the "Secondary-Supply-In-Use" alarm just the same as the high pressure gas system does. If for some reason the secondary supply is depleted before the primary supply is replenished, the reserve supply will activate which will initiate the "Reserve-In-Use" alarm.

Jay D'Agostino

6020 Medical Gas System Inspector
6030 Medical Gas System Verifier
Vice President of Operations