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Parametric Rolling IG Circular - Roll Risk Estimator

SSM Roundel

Published: August 05, 2022

The International Group is a member of the Maritime Research Institute of the Netherlands (MARIN) Top Tier project. The project has been established to examine and assess the causes of container losses arising from at-sea incidents onboard various sizes of container ships with a particular focus on ultra large ships. The project has been approved by a cross section of industry, academic and government interests and MARIN will produce a report of its findings including recommendations in due course. It is envisaged that the recommendations will eventually lead to operational and technical improvements that should mitigate the risk and underlying causes of container losses at sea.

The International Group has received the annexed roll risk estimator. It indicates combinations of speed, heading and wave period that result in unfavourable tuning of roll motions that should be avoided. It does not give indication of the maximum roll motion and the wave height at which the vessel is vulnerable to adverse rolling must be judged by the master’s experience. In addition, it does not address other dangerous ship behaviour like e.g. large vertical accelerations, shipping green water and slamming.

All clubs in the International Group have issued a similarly worded circular.

The Club encourages Members to share this Circular with their fleet and wish to stress that the Roll Risk Estimator is a tool intended to assist masters, being an aid to indicate the possibility of encountering parametric rolling and the possible changes of speed and course that may avoid/ reduce this. Its use is not mandatory and dependent on the individual circumstances, the recommendations may not always apply or be appropriate. 

The Roll Risk Estimator is no substitute for the exercise of good seamanship and due diligence by the vessel’s master.

Please note: MARIN's video “Parametric roll in the Following Seas”, which talks about and demonstrates parametric rolling, is available on their website, YouTube and Vimeo channels .  

Related Resources


Risk Alert on “Containerised Cargo Stowage and Securing”

Top Tier - Parametric Roll

January 2022

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