Hull structure failure behind Stellar Daisy loss

Stellar Daisy Majuro Credit: International Registries, Inc.

A “catastrophic structural failure of the hull” has been identified as the likely cause of the loss of Stellar Daisy two years ago.

International Registries, Inc. (IRI), which operates the Marshall Islands flag under which the Stellar Daisy was entered, released its investigation report on 19 April 2019. The vessel in question, a 266,141 dwt ore carrier that was converted under the supervision of Korean Register (KR) in 2009 from a 1993-built single-hull oil tanker, sank during a routine voyage from Brazil to China on 31 March 2017, while carrying iron ore from Brazilian miner Vale SA.

The tragedy left 22 of 24 crew members dead or missing, with the 2 survivors claiming that the ship, owned by South Korean shipping company Polaris Shipping, broke in half and sank after listing rapidly.

The seafarers’ families appealed to South Korean President Moon Jae-in to carry out another search for the crew. Subsequently, the South Korean government appointed US seabed exploration company Ocean Infinity to do so.

In February 2019, Ocean Infinity located the wreckage and voyage data recorder of the Stellar Daisy where the ship went down in the southern Atlantic Ocean. Some human remains were also found and are pending identification.

The IRI’s investigation concluded that the rapid listing of the Stellar Daisy was due to a catastrophic structural failure of the hull, that resulted in a loss of buoyancy and uncontrolled flooding. The structural damage was likely due to a combination of factors, including material fatigue, corrosion, multi-port loading, and weather conditions prior to the disaster.

The first surviving seafarer reported hearing a noise that sounded like an explosion while the oiler, and only other survivor, stated he felt an earthquake-like rumble just before the ship began listing. The IRI report stated that these testimonies were “consistent with a major structural failure.”

The report also suggested that KR came up short in detecting material fatigue, conducting failure analysis and reporting the damage to the flag state. According to IRI, KR’s approval of the conversion of Stellar Daisy from a single-hull tanker was based on the assumption that all of the scantlings, had remained in their original condition, and did not consider material fatigue. IRI states that the KR had based its assumption on the analysis of the ship structure, which took into account stress and corrosion resulting from the local notch effects.

An independent review confirmed that KR’s structural analysis was conducted properly. The IRI also stated that KR did not conduct a failure analysis two years after vessel conversion was completed and several cracks were identified and repaired during a drydocking in 2011. As a result, potential design weaknesses were not identified.

KR responded that in line with International Association of Classification Societies (IACS) members’ practices, a failure analysis is carried out at the discretion of the attending surveyor when, in their assessment, a defect or damage is “out of the ordinary” and further scrutiny is required. KR confirmed that the attending surveyor determined that the cracks [and] defects were not ‘out of the ordinary’, for a vessel of its age and as long as proper repairs were performed, a failure analysis was not needed. It should be noted at the time, the vessel was already 18 years old.

Finally, the investigation report stated that KR did not comply with its agreement with the IRI to report structural breakdowns or failures relating to the Stellar Daisy. For example, during a voyage in February 2016, the vessel suffered a damaged transverse bulkhead. KR responded that it had examined the surrounding bulkheads of the ship as well as bulkheads on 29 other converted ore carriers to determine if there were any similar defects. The classification society said, “the result of this extensive investigation was that there were no areas of concern. However, mindful of the recommendations in the report, KR plans to review its reporting procedures to avoid any future misunderstandings.”