Breakthrough for CRP Azipod
ABB has been awarded a contract by Japan's Mitsubishi Heavy Industries to supply CRP Azipod propulsion systems for two 17,000 grt RoPax ferries. The vessels are under construction at the Nagasaki Shipyard. They will commence operation by Shin-Nihonkai Ferry next year. They will be the largest and fastest in Japan.
Instead of a conventional rudder, the two 224.5 m, single-skeg vessels will each be equipped with a steerable 17.6 MW Azipod unit installed in a contrarotating mode aft of the mechanically driven main propeller to give the vessel a maximum speed of 31.5 knots..
The main shaftline will be powered by two Wärtsilä 12V46 engines via a reduction gear.
The efficiency gain of the contrarotating principle (the ability for a downstream propeller to absorb energy from the main propeller) has been known for decades. But it has rarely been exploited in commercial vessels. In high power applications, requiring co-axial shafts rotating in opposite directions, the mechanical complexities of gears and bearings have been an obstacle to commercial success.
Azipod propulsion offers an attractive solution by allowing an efficient single skeg design combined with the CRP effect.
In addition to the promised efficiency gain of 10-15% with its resulting fuel economy, the innovative "power rudder" concept offers enhanced maneuverability in adverse weather and sea conditions as well as reduced exhaust emissions. Total installed power can be considerably reduced compared with a conventional twin-skeg configuration.
The ABB contract with MHI for each vessel covers the Azipod unit with propulsion control, combining control of the Azipod unit and the main shaftline for optimum CRP efficiency in all powering situations. It also includes the 27 MW main electrical power plant with three main alternators and a 6.6 kV main switchboard.
In recent years, the CRP Azipod concept has been investigated and tested by several shipyards,engine builders and model basins. With this contract, MHI and ABB are bringing it into full-scale reality. Apart from RoPax vessels, the system has considerable attractions for vessels such as large container vessels, Ro/Ro ships and LNG carriers.
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