Fatal compressor explosion caused by poor maintenance

An explosion in an air compressor aboard a containership bound for Montreal in January 1999 that killed an engineer was the result of poor maintenance practices and unfamiliarity with the equipment on the part of the crew, according to a recently released report published by the Transportation Safety Board of Canada (TSB).

The 793-foot Canmar Spirit was preparing for docking maneuvers at the port of Montreal’s section 78 on Jan. 27, 1999, when the second-stage air-cooler cover on the No. 3 compressor violently exploded, sending steel shrapnel in all directions. The vessel’s duty greaser, who had activated the compressor seconds earlier, was standing in the immediate vicinity. The crewmember received first-aid treatment by the other engineers on duty and was evacuated from the ship by the tug Ocean Intrepide, which was offering docking assistance at the time. He suffered multiple laceration wounds and later died at the hospital.

The TSB investigation determined that the crewmember had likely neglected to open the compressor’s system delivery valve. Failure to do so allowed pressure to build up within the system that overwhelmed the machine’s integrity and caused it to explode. However, the investigation also determined that the compressor’s non-return valves, or check valves, which prevent the reverse flow of air into the compressor from the air receiver, failed to operate. The compressor’s pressure-relief valves, which in this case were of the plunger-and-spring variety and designed to relieve pressure after pressure exceeded 10 percent of standard working pressure, also failed to operate. Automatic back-up devices on this unit, which were not required for this vessel, could have prevented the system from malfunctioning if they had been configured on the unit prior to the incident. The vessel’s two other compressors were found to be lacking similar safeguards, the investigation concluded.

The report indicated that the failure of the crewmember to open the system delivery valve was explainable for a number of reasons. For example, in describing the process of operating the compressors, the report explained that it would have been impossible for the duty greaser to have noticed, while standing at the controls during start-up of the machine, whether the valve was open, since it was out of his line of sight and did not have an identifiable open or closed position.

Blame for the casualty was also placed on maintenance procedures. The second-stage cooler tubes in the compressor, for example, had been retrofitted with different material, of a lighter grade, than what is recommended by the compressor’s manufacturer. “When tubing that met manufacturer’s specifications was tested to destruction, the burst pressure was found to be 7,000 lbs. per square inch (psi). Similar testing of the second-stage cooler tubes [aboard Canmar Spirit] resulted in a burst pressure of 4,000 psi,” the report said.

Investigators also found that the vessel’s pressure-relief valves were clogged with an “oily, sooty residue.” While the manufacturer recommends manually inspecting the integrity of pressure-relief valves every three months or 250 hours of use, the ship’s statutory requirement calls for inspection every five years. The report indicated, however, that there was no recommendation by the manufacturer for performing “on-site” evaluation of this equipment available to the crew. The non-return valves were equally fouled, the report determined.

The investigation allowed that, while containerships are not required to be compliant with Section 10 of the ISM Code, which legislates maintenance procedures, until July 2002, the vessel was already in compliance with these standards. Shortly after the incident the vessel’s operating company mandated inspection and testing of the system’s valves, which were to be removed if necessary.

Canmar Spirit was registered in Hong Kong and classed by Lloyd’s Register. All certificates were current at the time, according to the report.

By Professional Mariner Staff