A bulk carrier loaded with logs nearly ran aground after losing its rudder shortly after departing the Port of Tauranga in New Zealand on July 24, 2023. Investigators from the Transport Accident Investigation Commission (TAIC) found that poor maintenance work during a previous drydock caused the incident.

The vessel, named Achilles Bulker, was fully loaded and outbound under pilot control when its heading started drifting to the port side just after leaving the harbor. While the crew and pilot attempted to steer it back to the center of the channel, the ship began shaking, followed by a loud sound. A second, louder bang was then heard as the ship continued moving uncontrollably into shallower waters.

The pilot ordered both anchors to be dropped after he realised that the vessel could not be brought back into the channel. The ship was brought to a halt around 30 minutes later, narrowly avoiding grounding. It stopped just outside the channel with less than one meter of water under its keel.

Divers were sent to inspect the vessel and were surprised to discover that the entire rudder was missing. It was recovered from the seabed two days later.

Following an investigation, TAIC reported that the rudder pintle, the pin that supports the bottom of the rudder, had dropped out before the rudder fell off. Without the pintle in place, the lower end of the rudder was unsupported, which allowed too much movement in the rudder system. This led to the rudder palm, the part that connects the rudder to the rudder stock, fracturing on both sides, eventually causing the rudder to detach completely.

Records showed that in 2021, Achilles Bulker had gone through routine drydock maintenance, during which the rudder pintle assembly was removed and reinstalled. Investigators concluded that the reinstallation was not done properly. The parts meant to hold the pintle in place failed over time, which allowed the pintle to fall out unnoticed.

The TAIC said that the welds used during the reassembly were porous and weak. Over time, normal vibrations while the ship was in service caused these welds to fail. As a result, the nut holding the pintle became loose and unwound itself.

Once the pintle was lost, the rudder started experiencing abnormal movements, side-to-side and forward-backward, which placed too much force on the top section that connects it to the steering system. This led to cracks in the coupling plate, and the rudder eventually broke off and sank.

The Achilles Bulker is a 32,729 deadweight-ton vessel built in 2003 and measures 177 meters in length. It was managed from Taiwan and was en route to China with a cargo of logs at the time of the incident.

The vessel was later repaired and returned to service. However, TAIC raised concerns over the quality assurance during the earlier maintenance and the lack of proper oversight by those responsible for the repairs. The Commission added that rudder pintles are critical parts and must be treated with high importance during maintenance work.

TAIC issued safety recommendations to prevent similar incidents. It has also shared its findings with the Maritime Safety Administration of China and plans to work with the International Maritime Organisation (IMO) to promote stricter global standards for rudder system repairs and installation.

Reference: TAIC

Source: www.marineinsight.com