Job Safety Analysis (JSA) and improper compressor purging procedures were brought to the forefront on 8 December with the US Bureau of Safety and Environmental Enforcement’s (BSEE) issuance of Safety Alert No. 327.
The alert described two incidents that occurred in the Gulf of Mexico in June and July and the findings of BSEE’s investigations.
In the first incident in June, a gas compressor ran for approximately 20 minutes before shutting down due to a platform air compressor problem during normal startup operations. After the air compressor was back on line, there were two failed attempts to restart the gas compressor. The mechanic then made adjustments to the magnetic pickup and the flywheel. Two attempts later, the gas compressor appeared to be starting, but after 2–3 seconds, the engine backfired.
The subsequent explosion sent the scavenger box and debris airborne and ignited the paper filters in the filter housing. The fire was immediately extinguished; however, the mechanic standing next to the air box was injured by flying debris that contacted his chin and upper body.
The initial investigation indicates that failure to properly purge the gas compressor is the probable cause of the backfire because the compressor panel logic allows the purging process to occur with the starters engaged. After engagement, the panel logic allowed ignition causing the backfire and subsequent explosion.
In July’s incident, a reciprocating compressor ran for approximately 5 minutes without being loaded during normal startup operations. The engine then shut down due to low fuel supply. Once corrected, the compressor was restarted without being purged or loaded. The engine ran in idle for about 10 minutes with the blowdown valve in the open position.
During that time, an explosion occurred causing damage to the third-stage cooler and associated piping.
BSEE’s initial investigation showed that a lack of understanding of the proper purging technique and an insufficient JSA with respect to listing and job steps are probable causes of the failure to purge the compressor.
BSEE recommended the following:
Review JSAs involving compressors to confirm that they include the steps associated with properly purging equipment before startup.
Review operating procedures to ensure purging operations are stated in compressor startup procedures.
Review training program and work instructions to ensure personnel are aware of, and trained, in proper purging procedures.
Review compressor panel logic permissives to ensure the proper sequence of events in compressor startup.
Follow manufacturer’s recommendations for compressor maintenance.