DNV DNV CLASSIFICATION NOTES 51.1 PDF

This Classification Note contains procedures and methods necessary for verification of the load carrying capacity (ultimate and fatigue strength) for the following components in the propulsion plant subject to loads due to ice impacts:

— propeller blades, hub and pitch mechanism

— shafts

— reduction gears

— pod/thruster underwater housing.

The assessment of other components together with the general applicability, required safety factors, material requirements and design ice loads for the different ice classes are given in the respective sections of the Rules for Classification of Ships, Pt.5 Ch.1 Sec.3 (Northern Baltic ice classes: ICE-1A* - ICE-1C) and Pt.5 Ch.1 Sec.8 (Polar ice classes: PC-1 – PC-7). Consequently, this document should be read together with the rules referred to above, in order to describe all aspects of the strength assessment.

The ice loads described in the Rules for Classification of Ships Pt.5 Ch.1 Sec.3 and Sec.8 are meant to be total loads, i.e. in general they include the open water hydrodynamic loads (unless otherwise stated). In cases where the calculations described herein result in smaller scantlings than derived from other class requirements, the latter requirements prevail.

The calculation methods specified herein are to some extent prepared based on empirical considerations and studies of conventional design known at the time of writing. This means that they are applicable for “standard” materials and geometrical shapes within a limited range of geometry and size.

Hence, the presented formulae should not uncritically be used for novel designs or be transferred to other applications.

 In principle, other relevant calculation methods may be applied for this purpose