Safe Arctic Operations (SafeArc)

The main goal of the SafeArc project was to increase the knowledge on ice loads acting on azimuth thrusters operating in cold climate areas. The project is a collaboration between Rolls-Royce Marine AS (RR) and Det Norske Veritas (DNVGL). An azimuth thruster is used for propulsion of ships, and provides both thrust and heading control. There is limited research available on ice loads acting on thrusters while operating in ice. More knowledge will provide equipment manufactures a better foundation for design of propulsion equipment, and class societies a better foundation for development of rules and regulations. The majority of the project work was focused on conducting full scale measurements and analyzing data from thrusters operating in sea ice, in order to gain a better understanding of the loads acting on equipment subjected to ice impacts on propellers or on the thruster itself. In addition to measuring ice loads, the project has researched operational and environmental aspects. Within the environmental studies, the focus was on noise, oil leakages from equipment and the properties of environmentally friendly lubricants. A five day measurement campaign was undertaken onboard the Swedish coast guard ship KBV002 Triton in March 2013. Nine people from RR and DNVGL conducted measurements in very good weather conditions, in various ice conditions and while performing various maneuvers. The KBV002 Triton is a multi-purpose vessel designed for towing, coast guard operations and oil pollution response. The vessel features the highest baltic ice class 1A*. The vessel has a traditional bulbous bow for optimum open water performance, and has diesel electric propulsion with two azimuthing thrusters. Both thrusters were instrumented on input shaft and steering gear using strain gauges. The goal was to measure over-load conditions on shafting and structure due to ice impacts on propeller and thruster body. The highest measured load on the thruster body was 367 kN, recorded while transiting from open water into thick ice. The predicted maximum load is extrapolated to an estimated 1400 kN. Compared to ice class rules, the predicted max load is significantly lower than the rule maximum load which is 2800 kN. The drive line is usually subject to dynamic excitations. This is relatively easy to model in open water, but harder for operation in ice, due to irregular impact loads from ice. The loads will depend on ice conditions and how the vessel is operated. For the KBV002 Triton, more than 40 hours of ice operation was analyzed to find drive line torque response and a model was created based on the new Polar rules. The results obtained correlates well with the loads suggested in the Polar rules. During May 2014, another campaign was carried out onboard the M/V Pajuttaat, a vessel owned by Royal Arctic Lines, serving the west coast of Greenland. This vessel has a conventional shaftline propulsion arrangement and traditional rudder. The shaftline was instrumented using strain gauges. The vessel is operated with extreme caution and all measured ice loads were within the design limits, despite the fact that the vessel is operating in the Arctic while only carrying an Baltic ice class of 1A. 86 hours of data was collected, and during one 3 hour sequence, only two cases of overload is seen, both at 1.5 times nominal load. These are the highest recorded loads. A quay-side test of the new RR permanent magnet thruster was also conducted. Ice was fed into the running thruster while filming and measuring response. Only small loads were observed, but the video provides valuable insight into how the ice is cut by the propeller. Energy consumption was measured in 50-60 cm thick ice. The bulbous bow of KBV002 Triton results in about 50% more fuel consumption compared to an ice-breaker bow without bulb. In addition, measurements show that the fuel consumption is almost doubled when going from light ice conditions into moderately large coherent floes. An optimum operation requires knowledge of the ship performance, ice conditions and a well understood risk philosophy. After 3 years of project work, it seems clear that a major challenge is to link ship designers and operators closer together. There is a need for a forum where knowledge can be passed both ways. A seminar was arranged to disseminate the results of the project. More than 100 persons representing ship owners, ship designers, ship yards and equipment manufactures gathered in Fosnavåg on 2015.01.13 for a full day seminar. The current rules, the new Polar Code and the results of the measurement campaigns were presented.

Demands for vessels and surface platforms operating in arctic areas are expected to increase in the years to come. This opens new possibilities also for the Norwegian maritime cluster. Current knowledge on operational loads and constraints in arctic wate rs is, however, restricted. Beyond that, increased environmental awareness adds to the knowledge gap that currently exists. In the project covered by this proposal, the project parties have joined forces in a R&D program that investigate operational load s through modelling and full scale validations, enabling the generation of best practice design and operational guidelines for arctic service, in particular associated with offshore gas and oil exploration. In particular azimuthing thrusters for icebrea king and ice milling operations with power up to some 8 MW, reduction gears with transmission capacity up to some 15 MW and maneuvering thrusters up to some 2.5 MW are propulsion systems that will be focused in the program planned. The project work is di vided in three main activities: 1. Loads from Ice - podded propulsion systems 2. Ice management - operational control 3. Environmental aspects - operation in ice Together these activities will form the necessary basis to meet the objectives as outlined fo r the project. Use of validations in ice laboratories are not a part of the project, hence, related uncertainties are avoided. This project constitutes a unique possibility for jointly utilization of the cooperating parties different strengths, for the development of knowledge and technology for safe arctic operations of the future to a level that is not reachable by the parties individually.