A New Air System Improved Economics, but Jeopardized Safety

Here is another case history of a compressed air system that was modified to near disaster. Details of this incident are unavailable, but some years ago a chemical plant or refinery with multiple reciprocating air compressors and pneumatic instruments systems decided to modernize. The modernization project replaced the air supply system. Economics favored one large centrifugal air compressor, and no backup air supply was installed. 

Disaster was adverted when a safety technician entered the control room as part of an unrelated confined space entry permit. The technicians portable oxygen measuring instrument was activated and in the operating mode. The low-level oxygen alarm sounded, warning the people in the control room of the very serious condition. 

A well-meaning engineer modified the original system when he chose to use the plant nitrogen supply as a backup for this single air compressor. Several years after the new 

Anoll Incid t With Nitrogen Backup for a Compressed Air Supply 

During a several-day outage of the refrigeration unit, the ethylene tank absorbed ambient heat and the internal pressure increased. The backup plan to cool by autorefrigeration as vapor escaped via the open relief valve was underway. As planned, a flow of steam was routed to the stack in hopes of safely dispersing the cold gases. 

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