Hyundai Heavy declares VLCC rudder woes solved

South Korea’s Hyundai Heavy Industries (HHI) says it has solved technical issues that had affected the rudders on some of its recently delivered and under construction VLCC newbuildings.

In a statement to TradeWinds, following an article published by this paper in December, HHI said: “We have carried out a full scale investigation to find out the root cause with regard to the rudder issue affecting some VLCCs at our yard.”

The facility, which also supplied supporting statements from classification societies ABS and Lloyd’s Register, identified two root causes and said a comprehensive action plan has been implemented to address these.

The first related to a new higher-efficiency rudder design supplied by a subcontractor. HHI said this design had a resonance at a particular frequency, which caused vortex shedding at the trailing edge of the rudder.

“HHI has fully investigated this and developed a modified design that avoids any significant resonances and, thus, improves the performance of the rudder,” it said.

The second cause was identified by the yard as “the poor-quality welding of one of our subcontractors in charge of some rudder production”.

“We have immediately implemented a series of corrective actions to remedy this, and enhanced subcontractor quality control,” the company said.

HHI confirmed that problems were discovered on four trading vessels, all of which have since been repaired.

DHT Holdings, which has a policy of inspecting the underwater parts of its vessels while they are still under shipyard warranty, confirmed it had found metre-long cracks on the port side of the rudder on two of six VLCCs delivered by HHI.

The owner returned to the shipyard in January, contracting two new VLCCs at $79m apiece, plus a number of optional slots.

In addition, TradeWinds understands that the rudders on two Euronav VLCCs were also affected.

Other delivered vessels with the same rudder design were inspected and defects were not found, the yard says.

“We also advised the owners to take the preclusive action of adding an additional trailing edge on their rudders,” HHI said.

Rudder issues found on newbuildings still at the shipyard were corrected in advance of their deliveries to owners, the shipbuilder adds.