ABSTRACT

Winterization design for ship systems has become more and more interesting topic due to increasing interest for shipping activities in Polar Regions. Shipping has been conducted in arctic waters for decades and traditionally winterization requirement of various systems has been based on the practical experiences of operators and ship designers. During last years all classification societies have created own notations for defining winterization levels for various systems and additionally the recent implementation of the Polar Code has brought some new requirements for vessels operating in the area. Many new ship owners and operators aiming for the region do not have sufficient experience in operating vessels in arctic conditions and thus are mainly relying on these regulations, when making decisions on winterization scope for new buildings. However, the requirements of various classification societies vary and usually do not give ready solutions, additionally these notations do not consider the type of the vessel. This scenario, depending on selected class, might lead to costly and inefficient solutions. This paper introduces an alternative design approach, which is based on risk analysis including the effects of ambient conditions at the intended operating areas and evaluation of required operational capabilities. The effects of using the method are indicated with example cases based on different vessel types.

INTRODUCTION

Ship designers and ship owners have implemented winterization to various ship systems for many decades for vessels operating in cold climate conditions. In the past, the selection of appropriate methods and systems has been mainly based on practical experiences. The first winterization notations by DNV (Det Norske Veritas) and LR (Lloyd's Register) for example, were issued in 2006. Thus, the classification societies' interest in the topic is considerably new. The main problem with the various winterization notations and also to some extent with the Polar Code is, that mostly they provide a list of systems to be winterized but very seldom offer a clear method on how to secure the operational capability in desired ambient conditions. Further issues are caused by the definition of design ambient temperatures and corresponding certification temperatures for the systems, since application of design temperatures below -30 °C has major impact on the availability and cost of various ship systems. This is especially the case when design temperature is set below -40 °C.

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