The article presents a methodology for determining ice loads on the elements of azimuth thrusters for ice-going ships of Arc4-Arc9 classes according to the Russian Maritime Register of Shipping (RS) Rules. The results of the calculation of ice loads on the azimuth thrusters for ice ships of Arc5-Arc7 classes are presented. A comparative analysis of the loads was carried out according to the developed methodology, Det Norske Veritas - Germanischer Lloyd (DNV-GL).
Ensuring the design and operational strength of azimuth thrusters in ice conditions is one of the main tasks of modern shipbuilding and navigation in the Arctic. Determination of ice loads on the elements of azimuth thrusters is a component part of this task. These tasks are actualized by the intensive development of marine transport systems for the export of crude oil and natural gas from the Arctic regions by large tankers. The use of azimuth thrusters on ice ships and icebreakers significantly determines their operational efficiency and design solutions for the structure of the transport system (type and number of ships and icebreakers) and organization of its work. As an example, Yamal-1 project for the transportation of LNG from Ob Bay: icebreaker support along the seaways of the Northern Sea Route (NSR) was minimized due to large double-acting LNGCs with three AZIPOD-type azimuth thrusters. This project along with the ongoing projects of marine transport systems (project Arctic LNG-2) call for the development of design methods and regulatory requirements to the ice loads on azimuth thrusters of the arctic-class ships together with strength assurance. This article presents the main results of the researches fulfilled by Central Marine Research and Design Institute (CNIIMF) and the RS in this direction.
Determination (assignment) of ice loads on azimuth thrusters of modern ships of the Arctic classes Arc4-Arc9 includes the solution of the following interrelated tasks (stages). First of all, it is necessary to assign design regimes of ships' movement in ice conditions, morphological and strength characteristics of ice formations depending on the class of the ship. The second task is to develop scenarios for the interaction of azimuth thrusters with ice formations. The final stage includes the development of models of ice breakage by the elements of azimuth thrusters; design schemes for determining contact ice pressures and global ice loads as well as their verification.