Maritime Disasters Related to Vessel Instability
Recently, with vessels listing, capsizing or sinking, maritime incidents have been grabbing headlines. That’s why my February 2015 presentation at the ACI Admiralty & Maritime Conference in Houston focused on some types and causes of stability problems.
Stability issues can arise due to human error or problems with the vessel or its cargo. Inadequate crew training can lead to accidents resulting in poor navigation, improper ballasting operations, failing to close watertight hatches and the incorrect use of anti-roll tanks. Risks can increase when the crew is put on a newly purchased vessel or whenever a new crew comes on board.
Earlier this year the car carrier HOEGH OSAKA was intentionally grounded on her way out of Southampton, England. Only one-third full, the vessel began to list severely, prompting the captain to ground her and avoid blocking the Solent. Improper ballasting was given as a possible cause here; a survey conducted after the loss showed most cargo was well-secured on decks even after a list of more than 45 degrees.
Cargo-related stability problems are another cause of vessel capsizing. Improper loading, shifting cargo, overloading or the liquefaction of bulk cargoes can quickly overturn a ship, frequently with loss of life.
The bulk carrier BULK JUPITER, was en route from Kuantan, Malaysia to China, loaded with 46,400 megatonnes of bauxite in bulk. On Jan. 1, 2015 she issued a distress signal, then quickly capsized about 150 nautical miles off the Vietnamese coast. Only one crew member survived. A possible cause of her sinking could have been the liquefaction of the bauxite, but the cause is still under investigation. Interestingly, bauxite is often listed in the International Maritime Solid Bulk Cargoes Code (IMSBC) as low risk “Group C” cargo, even though high water content in bauxite aluminum ore or small particle size can lead to liquefaction. This makes it similar to high-risk “Group A” cargoes.
Problems inherent in the vessel itself can cause instability, including a fault in the original design or failure to properly test the vessel’s stability. Modifications and retrofitting to increase or alter load capacity can also lead to unforeseen accidents.
The worst containership loss in history (given the number of containers on board that were lost as well as the entire value of the ship) happened on June 17, 2013 when the MOL COMFORT, an 8,000 TEU [twenty-foot equivalent unit] containership built in 2008, fractured her hull and split in two about 200 miles off the coast of Yemen. The aft section sank on June 27 and the bow section was destroyed and sank on July 11 after catching fire.
Investigations showed a hull fracture began at the bottom shell plates. The official report concluded that the Post-Panamax* containership’s bottom shell plates experienced “plastic deformation” causing the hull girder to crack. It’s not clear whether the design or construction of the vessel was faulty, but another ship of same design also buckled.
One of the most tragic losses in recent history occurred on April 16, 2014, when the South Korean ferry, SEWOL, carrying 476 people (mostly students) capsized off the coast of South Korea, with the loss of 304 passengers and crew. The sudden capsizing and consequent high death toll were attributed to a catalogue of human errors, misdeeds and technical issues.
The vessel was 18 years old and underwent extensive, illegal modifications that added 239 tons to her weight. The Korean Register of Shipping (KRS) had approved the modifications, but later learned documents had been falsified. Regular complaints about stability by the captain were ignored. She was carrying cars, trucks and cargo totaling 3,608 tons - three times the legal limit.
The disaster was precipitated when an inexperienced third mate and helmsman were allowed to navigate through a dangerous channel. A sudden turn to starboard, combined with overloading and inadequate ballast water (removed to accommodate more cargo), as well as unsecured cargo and renovations made to the vessel, increased its instability with tragic results.
It makes painful reading, but understanding the reasons for losses like the SEWOL is critical if the maritime industry is to improve its safety record.
*Post-Panamax refers to ships that do not fall within the size limits for ships traveling through the Panama Canal.