Joint project launched to expand ART application to large container ships

Japanese shipbuilder Nihon Shipyard, a joint venture between Imabari Shipbuilding and Japan Marine United Corporation, has signed a joint Research and Development (R&D) agreement with compatriot classification society ClassNK and IMC Co. (IMC) to ensure the safety and performance evaluation of anti-roll tanks (ART) installed on large container ships.

An anti-roll tank is a device designed to suppress the ship’s roll by moving liquid, such as water, within the tank.

As shown in the illustration (left) in yellow, the ART is planned to be positioned in the middle of the vessel, maximizing its effectiveness in stabilizing the ship’s motion. By positioning the tanks closer to the ship’s center of gravity, they can exert a more significant influence on reducing rolling motion.

Consideration for ART installation on large container ships is growing as this solution is expected to improve container loading efficiency by reducing roll motion and preventing parametric roll, which is regarded as one of the causes of container collapse accidents.

Parametric roll is a resonance phenomenon in which the roll of a ship is rapidly amplified when the roll period of the ship and the encounter period of waves are in a certain relationship. When a ship encounters parametric rolling it is almost impossible to take any action.

Containerships operate at higher speeds than tankers and bulk carriers, so their bows and sterns are skinnier. Therefore, the surface where the hull sinks into the water is more variable than that of tankers and bulk carriers. This also makes the ship’s resilience unstable, as explained by Japan Transport Safety Board.

Precautions and effective measures against parametric rolling include early avoidance of danger zones and immediate course changes, the installation of devices such as fin stabilizers or anti-roll tanks, as well as parametric rolling monitoring and alert systems.

Anti rolling tanks are expected to take some space on a vessel, potentially impacting the container loading capacity to a certain extent. However, it is a solution that does not appear to limit container loadings across the vessel, which had earlier been suggested as a likely consequence of measures to address parametric rolling.

Under the agreement, Nihon Shipyard, which specializes in the development of large containerships, will design an optimal installation plan for ARTs on large container ships.

IMC, which has extensive experience in the design and sales of ART, will carry out a demonstration of ART’s reduction effect on a ship’s roll, while ClassNK will work on the establishment of appropriate evaluation methods for ART.

ClassNK has already developed the requirements in its “Guidelines on Preventive Measures against Parametric Rolling (Edition 1.0)” to grant a notation to the ship equipped with ART. Additionally, through a tank test of ART-related R&D conducted in 2023, ClassNK confirmed their anti-rolling effect against parametric and synchronous roll, and collected data.

The latest project is expected to enable the classification society to further update the guidelines and regulations with more practical concrete requirements.

“Utilizing the obtained data and knowledge, each party will collaborate to ensure the safer application of ART on an actual ship and performance evaluation,” ClassNK said.

Parametric rolling has been an issue in the container shipping industry for a long time, as it has been identified as the likely cause of loss of containers overboard. Vessels that have lost containers due to the phenomenon over the past few years include Maersk Essen in 2021, APL England in 2020, and Yang Ming Efficiency in 2018. Parametric rolling is also believed to be the likely cause of the loss of containers by ONE Apus, back in 2020.

Based on the incident investigation report, ONE Apus, with the master and 23 other crew members aboard, was sailing off the northwest coast of Niihau Island, Hawaiian Islands, U.S.A., on November 30, 2020, when rollover caused the cargo to collapse, causing 1,841 containers to fall overboard. The vessel experienced swells of approximately 5 to 6m and suffered a hole in the container hatch cover, and 983 of the remaining containers were damaged, but there were no casualties.