Reaching for the remote

As the leading electric propulsion systems supplier for icebreaking vessels, ABB Marine says there is still work to be done in developing the technology capable of dealing with the harshest of requirements.

According to a 2008 U.S. Geological Survey estimate, the Arctic Circle promises 90 billion barrels of undiscovered, technically recoverable oil, 1,670 trillion cubic feet of technically recoverable natural gas, and 44 billion barrels of technically recoverable natural gas liquids in 25 geologically defined areas.

These resources account for about 22% of the undiscovered, technically recoverable resources in the world. About 84% of them are expected to be recovered by offshore operations.

While the wider shipbuilding market may languish as a result of over-ordering and global recession, underlying demand for vessels capable of operating in this harshest of environments cannot be questioned. Russian gas giant Gazprom, for example, has gone on record as saying that field development offshore Russia to 2020 will drive orders for over 10 production platforms, over 50 tankers and other specialised ships, and at least 23 liquefied natural gas carriers.

Last year, the International Association of Classification Societies (IACS) issued a set of harmonised rules on the construction of all ships meant to operate in ice-covered waters, including areas where multi-year ice may be present. However, while progressive, these rules are by no means definitive for all aspects of ship design raised by the need to operate in the harshest of environments.

One of the main answers to the need of developing the reliability required for operations in frozen, remotes areas has been the application of electric propulsion. Vessels operating in ice need high torque at the propeller shaft, and an electric motor is distinguished by the fact that it can produce full torque from zero RPM up to full power. If ice blocks hit the propeller blades, an electric motor simply keeps the propeller rotating more effectively than is the case for a diesel engine of equal power. Continuous propeller rotation means a better ability to navigate in ice.

Meanwhile, as good manoeuvrability in ice has become ever more imperative, Azipod propulsion, with its 360 degree rotation offering full torque and thrust in any direction, and its ability to withstand quick thrust changes and high impact loads during ice-milling has proved itself indispensible.

Both of these solutions are mainstay products for ABB Marine, whose expertise in delivering electric propulsion for icebreaking vessels dates back to the 1930s, with over 80 icebreaking vessels featuring the company’s technology. At the same time, ABB has Azipod unit references for 26 vessels with Ice Class 1A Super and above, and more than 870,000 operating hours on the clock. Its experience extends to vessels built for the Great Lakes, the Caspian Sea, the Kara Sea, the Pechora Sea, the Okhotsk Sea, the White Sea, the Donau Rover, the Baltic Sea and the Barents Sea.

In general, ABB is the only supplier to manufacture a total electric power and propulsion solution including power generation and distribution systems, propulsion drives and thrusters.

The development of the Azipod concept has created new opportunities for ship designers. For example, ABB Azipod units were selected for the breakthrough Kvaerner-Masa Yards-designed (now STX Europe), Sumitomo Heavy Industries-built double acting tankers Mastera and Tempera for Fortum Shipping. Equipped with one 16MW Azipod unit apiece, these vessels were the first in the world to use the Double Acting Tanker design to travel bow-first in open water and stern-first in ice, for optimised performance in each environment.

Recent references for ABB have included three crude oil tankers from Samsung Heavy Industries for Sovcomflot, the first of which, Vasily Dinkov, was delivered in January 2008.

In a project indicating that ABB is also a key player in the potentially significant Russian shipbuilding market, the supplier’s latest reference involves providing systems for two 70,000dwt shuttle tankers under construction at Admiralty Shipyards, St Petersburg, also due delivery to Sovcomflot. Like Vasily Dinkov, these ships (Mikhail Ulyanov and Kiril Lavrov) are set for operations in the Pechora Sea.

Where Tempera and Mastera operate in relatively mild ice conditions, these ships will need to shuttle between the Prirazlomnoye platform and Murmansk at speeds of up to 16 knots, with occasional voyages to Atlantic destinations. These 259m long ships are being built to the Russian Maritime Register of Shipping’s Ice Class LU 6 criteria, for operations in thick first year ice conditions. They are also to benefit from dynamic positioning class notation, which sets high requirements for propulsion system redundancy and vessel manoeuvrability. Driven by four Wärtsilä 9 L 38 main engines, each ship will include twin 8.5MW pulling Azipod units, featuring propeller diameters of 5.6m and ABB’s latest ACS6000 drive technology.

Based on its long experience, the technology developer recently brought together all of the major classification societies to present findings of a four year research project it conducted on the Azipod units affixed to the cargo ship Norilskiy Nickel and the support vessel Fesco Sakhalin.

Measurements of the forces and vibrations acting on the Azipod units attached to Fesco Sakhalin were taken between 2005 and 2008 in Okhotsk Sea, close to Sakhalin Island and the Orlan oil platform. The 169.5m long, 14,500dwt, double acting Norilskiy Nickel, which features a single 13MW Azipod unit, saw measurements taken between 2006 and 2009 on its regular route between Murmansk and Dudinka in Russian Kara Sea.

ABB Marine manager, Azipod sales support, Samuli Hänninen said that one of the key objectives of the event was to explore the contribution that could be made to ice rule development by full scale, real life measurements of ice loads and vibrations acting on Azipod units.

“For ice going Azipod units of the required power range, the major design parameters are propulsion power, classification society ice class and design ice conditions, the propulsion motor over-torque requirement, and the ship type, vessel main characteristics and operational purpose,” said Mr Hänninen. “These parameters and their combinations are the major factors influencing Azipod component design and equipment size. It normally requires a close co-operation between ABB, the ship designer and the classification society at the early project stage to tailor the propulsion system according to each project’s needs.

“Differences in classification society requirements for different ice classes and different technical requirements for each project often result in the need for a tailor-made Azipod.”

Therefore, he said that such measurement projects were critical, as ships are increasingly expected to operate in thicker multi-year ice, with propellers facing the highest loads when confronted with ice ridges where, in extreme cases, milling of ice occurs.
“While classification societies, of course, have more stringent requirements for vessels designed for multi-year ice operations, the higher the ice forces encountered acting on a vessel’s hull and propulsion system, the greater are the challenges and design requirements for the hull itself, the overall propulsive power, propeller blades and the mechanical properties of podded propulsors.

“The ship’s actual operational practice and ice measurement systems onboard may also have an effect on the vessel design criteria and requirements.”

The growing need for ships capable of operating in the most remote and unforgiving conditions is witnessed by plans from the oil majors and North American owners for a totally new fleet of icebreakers and tankers to operate in the Beaufort Sea. The number of vessels to be built for this project has yet to be ascertained, as analysis of the entire transport chain envisaged is not complete. However, Mr Hänninen said that ABB was well advanced in the design work for podded propulsors to meet the coming requirements. Azipod unit bearings and shells are being made more robust as a direct consequence of the expected demands of the Beaufort Sea project, he said.

Again, where the market for new LNG carriers has stalled in general, as noted, Russia’s appetite for ice-going LNG carriers remains unbowed. “We are following up on the development in Arctic LNG projects,” said Mr Hänninen.

“There are project prospects for low ice class vessels (eg. Shtokman) and high Arctic ice class vessels (eg. Yamal). The requirements and optimum ship and propulsion solutions for different projects might vary a great deal.”


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# 4(30), 2009
Ocean and shelf exploration