202411 : Over-pressurised keel bladder sends warning shot across the bow

A cruise vessel in Antarctic waters offered sightseeing excursions to passengers using small inflatable open boats.

As edited from USCG (USA) Marine Safety Alert 04/23

On one occasion, the keel bladder of the boat suddenly ruptured in an explosion-like occurrence. One passenger was severely injured and another was thrown overboard. The investigation determined that the rupture was caused by excessive pressure in the keel bladder tube. The recommended manufacturer’s operating pressure is 240 millibars. A survey of inflatables on board the cruise ship noted pressures up to and exceeding 620 mb in other keel bladders. 

For this model of inflatable, and possibly others, the keel bladder is not protected by a pressure safety relief valve. The manufacturer recommends that they be inflated with a foot pump to reduce the chance of over-pressurisation. In this instance, it was found that crewmembers were routinely using an air compressor to fill the buoyancy chambers (including the keel bladder tube). Pressure levels were not being checked using a manometer as recommended by the manufacturer.

Lessons learned

• Follow all manufacturer recommendations for inflatable boat inflation and maintenance.
• Use manufacturer recommended inflation devices (eg foot pump) and appropriate pressure measurement tools to avoid overpressurisation.
• Verify that company policy addresses manufacturer recommendations and that crews are properly trained before operating and performing maintenance on inflatable boats.