The rudder of a bulk carrier fell off and the vessel nearly ran aground, a shocking incident that occurred in Australia in July 2023. The final report by TAIC reveals serious welding and maintenance errors, with divers locating the rudder on the seabed two days later.
Inspectors investigating the incident involving the bulk carrier Achilles Bulker, which nearly ran aground in Australia in July 2023, found themselves faced with an unprecedented case.
Investigators from New Zealand’s Transport Accident Investigation Commission (TAIC) published their final report on an incident that occurred in July 2023 concerning the bulk carrier Achilles Bulker, stating that poor welding during maintenance led to a series of failures that ultimately caused the vessel to lose its rudder and nearly run aground.
Following the investigation, divers identified the unusual cause behind the ship’s rudder loss, with investigators now having reported and warned shipyards, shipowners, management companies, insurers, and surveyors.
The Achilles Bulker, with a carrying capacity of 32,729 dwt and a length of 177 meters, had departed fully loaded from the port of Tauranga, New Zealand, with a pilot onboard on July 24, 2023. The vessel, built in 2003, was managed by a company from Taiwan. It was loaded with a cargo of logs destined for China.
Shortly after departing from the port of Tauranga, the bridge team reported that the ship was bouncing strangely and veering off course. As they attempted to bring it back on course, the vessel shuddered, and a loud noise was heard.
The pilot took control of navigation, trying to steer the vessel back on course when a second, louder crash was heard. Unable to return the ship to the channel, the pilot attempted to slow the vessel and ordered the crew to immediately drop both anchors.
Thirty minutes later, they reported that the ship had stopped outside the channel. It had narrowly avoided grounding, with reports indicating less than a meter of clearance beneath the keel. Divers inspecting the vessel were shocked to find that its rudder had disappeared. They managed to recover it two days later from the seabed.
Inspectors identified that the rudder pintle was missing and concluded that it left the lower part of the rudder unsupported, allowing excessive movement in the steering system.
They said the rudder broke when the rudder stock broke on both sides of the pintle.
Examining the ship’s records, they found that two years earlier, in 2021, during routine maintenance, the rudder pintle had been removed and later reinstalled.
“It is almost certain that the manner in which the rudder pintle assembly was reinstalled did not ensure the pintle would remain in place during the ship’s normal operations,” writes TAIC in its report.
“The way the rudder pintle was reinstalled meant the securing components used to hold the pintle in place failed, allowing the pintle to move out from the bottom of the rudder.”
TAIC concluded that the securing components that had been installed had weak, porous welds. After the ship returned to service, the welds fractured due to vibration. The locking nut that held the pintle as part of the securing assembly came loose, and at some undetermined point, the pintle fell unnoticed and was lost.
At this point, TAIC concludes that the rudder began to exhibit unintended movement, increasing stresses. Moving side to side and back and forth, the forces exceeded the designed strength of the coupling plate (stock) at the top that connected the rudder to the solid shaft (stock) linked to the internal steering mechanism. Fatigue cracks grew until the rudder finally failed.
The ship was repaired and returned to service. TAIC is now issuing a warning and calling for strict quality assurance procedures at the shipyard for the installation of the rudder pintle.
It also informed the China Maritime Safety Administration and stated it would collaborate with the International Maritime Organization to promote improved global standards for ensuring the quality of rudder systems during installation, maintenance, and repairs.
