Developing a Technical Methodology for the Evaluation of Safe Operating Speeds in Various Ice Conditions

The International Maritime Organization (IMO) has adopted Guidelines for Ships Operating in Polar Waters (2010), formally recognizing the need to mitigate the additional risks resulting from increased development of natural resources and marine traffic in the Arctic and Antarctic regions. An effort is underway to develop a mandatory and comprehensive Polar Code. It has been agreed among IMO delegations to require an onboard Polar Water Operational Manual (PWOM) which is to include guidance for safe navigating speeds in ice. Ultimately, this may have significant implications for operators, ship owners and ship builders intending to mobilize assets in Polar regions. The Russian authorities have long required all Russian Arctic-bound ships to maintain on board an Ice Passport (or Ice Certificate) which contains safe speed guidance as a function of the ship’s structural configuration and anticipated ice conditions. This is the only known existing regime which explicitly regulates the speed of ships in ice. Other technical approaches to the concept of safe speed exist. Some are based on probabilistic methodologies while others rely on purely deterministic analysis. This paper presents an overview of some existing technical approaches for safe speed guidance based on available literature. A proposed framework of a synthesized procedure for the evaluation of safe navigating speeds in various ice conditions is offered and a simple case study is provided for an Ice Class PC5 offshore supply vessel. Directions for future research are outlined with regard to the selection of ship-ice interaction scenarios, the influence of speed on flexural ice failure, and matching safe speed to suitable structural limit states.