Breaking waves a problem for expedition ships

2023-12-14T22:08:38+00:00 December 14th, 2023|Safety|

On 28th November, 2022, there was an incident involving one of expedition ship ‘Viking Polaris’ Zodiacs in Antarctica.

This resulted in a passenger being injured and another ending up in the water.

Following the incident, the ship interrupted her cruise to perform a medical evacuation. A day later, as the ship was crossing the Drake Passage from Antarctica to Ushuaia, she was hit by a breaking wave just southeast of Cape Horn.

The accident caused seven stateroom windows to break and caused major damage inside the staterooms. One passenger died and eight were injured.

In a report into the incident, the Norwegian Safety Investigation Authority’s (NSIA) said that the breaking wave in combination with the ship’s course and speed, caused the windows to shatter.

At the time of the accident, the crew did not have the sufficient knowledge to predict the risk associated with a breaking wave reaching so high up on the ships’ side with such great force.

Further, the investigation showed that the pressure from the breaking wave exceeded what the windows were designed to withstand.

Sea conditions at the time were within the sea states defined in the wave scatter diagram the ship was designed for. No faults of significance regarding the incident’s outcome were identified on the design.

However, it was revealed that the minimum requirements in the International Association of Classification Societies (IACS) class rules, including the ship’s class society DNV, doesn’t provide a dimensioning minimum pressure sufficient to withstand a breaking wave.

NSIA said that the windows were insufficiently dimensioned to withstand the pressure loads from this breaking wave, and that the applicable IACS rules, international requirements and standards give too low values to withstand pressure loads from breaking waves in the rules and regulations.

As a result, NSIA recommended that DNV highlighted the problem to IACS to ensure that all class rules, independent of class society, are developed to include requirements that account for breaking waves against the shipside. This also has to be reflected in DNV’s own rules.

NSIA also said that wind speeds that could cause waves to break are common for much of the year in Drake Passage and the area where the accident happened.

Under such conditions, it is therefore a possibility that ‘Viking Polaris’ and her sister ship ‘Viking Octantis’ will be exposed to breaking waves hitting the side of the ship.

NSIA considered that a robust design that takes account of breaking waves will constitute a stronger barrier than operational measures alone.

The current dimensioning of the windows means that they will not be able to withstand the pressure from all breaking waves, which may arise within the extent of validity of the rules and regulations.

In addition, NSIA recommended that the Norwegian Maritime Authority (NMA), which has the overall responsibility for safety for vessels flying the Norwegian flag, ensure that Viking Expedition Ship II Ltd included reinforcements to ensure that breaking waves do not cause damage to windows on the two existing expedition vessels.

NSIA also recommended that Viking Expedition Ship II Ltd, in co-operation with Wilhelmsen Ship Management (Norway), implement the reinforcements.