An investigation zeroed in on a Zodiac keel bladder rupture due to excessive pressure in the tube.
During a sightseeing excursion in calm weather, the keel bladder suddenly ruptured, sending the passenger several feet into the air before landing on the deck and sustaining serious injuries including a fractured femur. Another passenger was thrown overboard into the freezing water, risking hypothermia.
Marine Safety Alert 04-23
The Coast Guard Office of Investigations and Analysis released Marine Safety Alert 04-23 to highlight the importance of proper maintenance and adherence to manufacturer’s recommendations for filling/inflating buoyancy chambers on some models of inflatable boats.
This incident involved a Zodiac MILPRO model FC 580/MK5. USCG did not name the cruise ship. However, a USCG spokesperson confirmed the safety alert springs from its investigation of the Viking Polaris Zodiac, which sustained a keel-bladder failure near Damoy Point.
Multiple inflatables exceeded recommended psi
USCG found the keel bladder ruptured due to excessive pressure in the tube. The manufacturer's recommended operating pressure is 3.4 pounds per square inch (psi) or 240 millibar pressure (mb). An on-scene survey of multiple inflatables onboard the cruise ship noted pressures up to and exceeding 9 psi (620 mb) in other keel bladders.
USCG noted the keel bladder is not protected by a safety relief valve, and the manufacturer recommends that they be inflated with a foot pump to reduce the chance of over- pressurization. However, crew members were routinely using an air compressor to fill the buoyancy chambers (including the keel tube) prior to the incident. In addition, pressure levels were not being checked using a manometer as recommended by the manufacturer.
Follow manufacturer recommendations
In its alert, USCG strongly recommends that operators of cruise ships and other companies employing inflatable boats review all manufacturer recommendations for inflatable boat filling and maintenance to verify those procedures are being followed. Operators should use manufacturer recommended inflation devices — for example, foot pump — and appropriate pressure measurement tools to avoid over-pressurization.
They should verify that company policy addresses manufacturer recommendations and that crews are properly trained before operating and performing maintenance on inflatable boats. Operators are also advised to contact the manufacturer of their inflatable boats for any additional recommendations and/or training options they may offer.