The Nautical Institute warns of the dangers of structural weakness in a new Mars Report. The report describes the fast sinking of a very large ore carrier (VLOC) due to hull failure.
The Nautical Institute gathers reports of maritime accidents and near-misses. It then publishes these so-called Mars (Mariners’ Alerting and Reporting Scheme) Reports (anonymously) to prevent other accidents from happening. This is one of these reports.
A very large ore carrier (VLOC) loaded with iron ore fines was underway with a combined wave (wind and swell) of about 3.7 metres on the starboard side. The vessel was built as a VLCC, but was modified and converted into a very large ore carrier after sixteen years of tanker operations.
After the conversion, the vessel’s length, beam, and depth remained the same (311.89 metres L, 58.00 metres B, 29.50 metres D respectively). However, the gross tonnage and the deadweight tonnage had increased due to structural changes to the cargo hold hatches and an increase in the load line. Following the conversion, the ship had been operating as a VLOC for eight years.
At about 13:20 local time, the vessel’s superintendent ashore received a social media message from the ship that said, ‘Emergency. The ship’s No. 2 Port is leaking. The ship is rapidly inclining to port.’ The superintendent asked the ship to call via satellite phone, but heard no response from the ship.
About one minute after the message was received, a distress signal from the vessel was received via INMARSAT-C Digital Selective Calling. The next day, two crew members were rescued from a liferaft. None of the remaining 22 crew members were ever found.
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Loud crash and vibrations
One of the survivors later said that he heard a loud crash and felt the hull vibrate. He went to his cabin to put on a lifejacket, got his immersion suit, then went to the muster station on the port side outside the accommodation area. However, no one was there when he arrived.
Then he heard the master’s announcement, saying ‘All crew go to bridge’. He went onto the bridge using the outside ladders of the accommodation area. Once on the bridge, he saw the master and some other crew, but the vessel was already listing heavily to port. The ship heeled further to port, and when water was about to flood on the bridge, he jumped into the sea from the port bridge wing. The vessel went down some five minutes after the initial loud bang had alerted crew to the situation.
Investigation findings
The investigation found, among other things, that the loading conditions of the vessel satisfied the damage stability criteria required by the conventions at the time of the accident. Even if ballast tanks 2 and 3 (P) were both damaged, it seems hard to establish that this would have caused the ship to sink in such a rapid fashion.
The investigation also found that although the vessel had loaded a liquefiable cargo of iron ore fines, the moisture content of the cargo was below the transportable moisture limit (TML) when loaded. There was no rain during loading, and no significant amount of bilge water was in the cargo holds while the ship was underway. Therefore, it was deemed unlikely that the cargo had liquefied during the voyage.
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Advice from The Nautical Institute
- Although liquefaction of cargo and the resulting loss of stability has been a contributing factor to some high-profile bulk carrier losses in the past, this accident seems to have been caused by another source.
- Over more than 24 years of operation, asymmetric loads (hence pressures) would have placed excessive stress on the lower shell plate, gradually causing a loss of hull strength, both structural and fatigue related. This resulted in catastrophic hull failure, causing the large vessel to sink within 5 minutes.
- Vessel loss due to ‘structural weakness’ seem unimaginable given the rigorous inspection regimes imposed on operators. Yet, this outcome can still occur, as this sinking demonstrates – twenty-three years after the sinking of the vessel Erika off the coast of France, where the investigation determined, among other things, that the vessel had sunk due to loss of structural strength. According to the Erika report, the visible elements of the hull had aged rather better than the structural elements, which were far more difficult to inspect on a continuous basis.
Also read: Dynamic separation of soil cargo contributes to sinking
Mars Reports
This accident was covered in the Mars Reports, originally published as Mars 202504, that are part of Report Number 387. A selection of the Mars Reports are also published in the SWZ|Maritime magazine. The Nautical Institute compiles these reports to help prevent maritime accidents. That is why they are also published (in full) on SWZ|Maritime’s website.
More reports are needed to keep the scheme interesting and informative. All reports are read only by the Mars coordinator and are treated in the strictest confidence. To submit a report, please use the Mars report form.
Picture: Casualty vessel before sinking (by The Nautical Institute).
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