Azipod® C units from ABB are finding favour across an increasing range of specialised vessel types delivered from leading Asian yards.
ABB is beginning to reap the rewards of its strategic investment in Shanghai as the new centre for production of its compact Azipod (‘C’) unit. The versatile propulsor has been making an impact in the ship market for over half a decade, but design refinements and the new plant at the heart of Asian shipbuilding has brought further advances in established and new markets.
The new plant focuses on CO and CZ Azipod unit production, respectively ranging between 1.3-4.5MW and 3.3-4.7MW output. It was opened to consolidate the company’s position in the growing ship propulsion market in China and Asia, with emphasis on the high volume production of medium power propulsors. By September 2012, more than 20 Azipod C units had been delivered from Shanghai.
In China itself, the relationship between ABB and Chinese owner Sinorail Bohai Train Ferry has been developing since 2006, when the customer took delivery of its first Finnish-built 4.1MW Azipod C unit for the ferry Zhong Tie Bo Hai 1 Hau. Three 22,700gt ro-pax rail-ferries now operate across the Bohai Strait between Yantai and Dalian, all featuring ABB Azipod C units.
Early this year, the customer took delivery of the first Azipod C unit in operation to be fully assembled in Shanghai, as a ‘spare’ for the Bohai Strait service. The unit was requested to ensure service rotation in case of an accident or mechanical failure. Given that the owner intends to expand the fleet further, the prospect for further Azipod C deliveries out of Shanghai is strong, while a larger fleet would likely also extend the need for spare units.
ABB China Limited Vice President Matti Holmsten explained that standard recommendation for thrusters servicing is in line with a ship’s five year mandatory drydocking, but that the availability of spare units can prevent unexpected service interruption. During drydocking, ABB recommends particular attention is given to bearing and sealing wear. “The replacement of bearings and seals is not necessarily a time issue when it comes to overall maintenance,” said Mr Holmsten. “Should it become one, though, the availability of the spare Azipod unit means that owners can replace the entire propulsor and service the original unit in the workshop.”
New research ships
September 2012 saw the delivery of a new 4,000T research vessel to the Institute Oceanology, Chinese Academy of Science (IOCAS), which has also been fitted with Azipod C units (in this case two 1.9MW propulsors). These units were actually the first to feature a contribution from the Shanghai production plant. The order, placed in 2009, called for delivery to the CSSC Wuchang Shipyard in July 2011, a schedule that led ABB to supply steering units out of Finland and thrusters out of China.
At time of writing, ship designer MARIC was preparing a report for IOCAS based on sea trials highlighting how design aspirations have been converted into ship performance benefits. The installation of Azipod C units has proved to be a key factor. The report reveals that the vessel can achieve its design service speed (12 knots) by using only one of its 3+1 main engines, and sea trials showed a maximum speed of 15.88 knots was possible, against a design maximum speed of 15 knots. Again, noise levels inside Master’s cabin were recorded as just 40dB.
The IOCAS delivery confirms ABB’s strong position in supplying Azipod units for research vessels, the company having already delivered four 1.9MW units for installation onboard two State Oceanic Administration vessels.
Units from Shanghai have also been delivered to major South Korean yards. Here, the Azipod unit has proved a key attribute in the success achieved by Samsung Heavy Industries and STX in securing niche orders for specialised ships such as wind turbine installation vessels (WITVs).
Swire Pacific Offshore took delivery of Pacific Orca on July 27th, 2012, the world's largest wind farm installation vessel (WIV), from Samsung Heavy Industries (SHI). The vessel, distinguished by her ability to stand 17m above the surface of the ocean using six jack-up legs, will be deployed to provide service for the Danish utility company DONG Energy. Pacific Orca is the first of two WTIVs from Samsung for Swire, with Pacific Osprey scheduled for delivery at the end of this year and planned to be deployed for the Dan Tysk project.
Featuring four 3.4MW Azipod C main thrusters (CO1250 units plus one spare), these 161m long vessels (49m beam) have a capacity to carry and install up to 12 turbines of a 3.6 MW design. This is clearly a significant reference for the Azipod C propulsion solution in particular, given that demand for offshore wind farm installation vessels of this type is expected to increase in line with rapid growth of the marine wind power market. On delivery of the vessel, Swire itself cited industry expectations that the sector will grow as a source of energy from 3.55 GW in 2012 to 239 GW by 2030, prompted by the global push for renewable energy generation.
In the normal course of events, it might be expected that ABB as a supplier would choose to draw attention to the fact that all of the above vessels feature its full package of electrical power systems, but Mr Holmsten preferred to emphasise the Azipod C unit’s compatibility with a range of systems. “To date all Azipod units have been delivered with ABB total electric propulsion systems, but there is no special requirement tying the Azipod to our packaged offer,” he said. General vessel arrangements could be very much the same whether it is an ABB system or a competing system that is installed.
“In fact, I would say that the contrary is the case; the simplicity of the Azipod design opens up possibilities of simplified and improved vessel design, because the Azipod needs considerably less space inside the vessel than competing mechanical Z-drive systems and therefore yields greater flexibility to optimise their designs. Optimised installation of thrusters, working with a pulling propeller, increases the hydrodynamic efficiency of the propulsor (and vessel) and reduces noise and vibrations.”
Mr Holmsten said that simplicity also brought reliability. “Most mechanical thruster system shut downs are caused by problems with auxiliary systems,” he said. “With the podded solution the propeller is directly connected to the propulsion motor, so auxiliary equipment between the propulsion motor and the propeller is simply eliminated. This means less down time and overcomes limitations during operation.”
He went on to emphasise that the Azipod C design conferred benefits to owners that included high electrical efficiency due to the use of permanent magnet propulsion motor, high mechanical efficiency since the units featured no gears and only two bearings, and high hydrodynamic efficiency due to pulling propeller. Higher overall efficiency meant lower fuel consumption and emissions, he said.
“Again, because the propulsion motor is directly cooled to sea, Azipod units experience a lower level of losses related to auxiliary systems. There are also environmental benefits for owners because the Azipod C features a water lubricated outer seal and grease lubricated lip seals -there is no oil used on any seals that could result in leakage to the sea.”
For yards, the Azipod C conferred faster and easier installation, he said, as well as involving less auxiliary equipment and piping, not requiring alignment of a propulsion shaft and freeing up space inside the vessel, among other benefits.
These attractions continued to yield interest from a broadening range of potential customers, Mr Holmsten said. “Clearly, the offshore drilling and support vessel market are the biggest segments where conventional thrusters are widely used. ABB is currently developing new features to improve the suitability of Azipod C for the market – this is one of our key focus areas.”
Work is also being done with leading owners of drillships and semi-submersible rigs to incorporate retractable Azipod units, which could be adjusted to a ‘withdrawn’ position to reduce resistance during ship transit and enable maintenance to be undertaken without drydocking.
“The capability to retract also makes it easier to operate in shallow waters and drydock the vessel. Retractable systems are widely used, especially in the offshore support vessel segment. However, in that case power levels are typically below 2.5MW, and larger retractable systems (3-5MW) are not so common. We have worked with shipyards and designers to develop a retractable design
“Our next objective is to amplify the benefits of the system to some of the bigger shipyards that are familiar with retractable systems of this scale but have so far taken their lead from available ship designs in the market. We have already verified that the retractable Azipod C unit is acceptable to a number of leading ship designers and have also been part of joint studies with owners.”