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Closeup of one of USCGC Mackinaw's 3.3 MW Azipod units

Azipod is an electric podded azimuth thruster produced by ABB Group. Developed in Finland jointly by the shipbuilding company Masa-Yards and ABB, Azipod is a marine propulsion unit consisting of a fixed pitch propeller mounted on a steerable gondola ("pod") which also contains the electric motor driving the propeller.

Although "Azipod" is a registered brand name, it is sometimes used as a generic trademark for podded propulsion units manufactured by other companies, such as Queen Mary 2's Rolls-Royce Mermaid pods.[1][2][3]

Contents

ConceptEdit

In the traditional azimuth thrusters such as Z-drive and L-drive thrusters, the propeller is driven by an electric motor or a diesel engine inside the ship's hull. The propeller is coupled to the prime mover with shafts and bevel gears that allow rotating the propeller about a vertical axis. This type of propulsion system has a long tradition throughout the 1990s and today such propulsion units are produced by a number of companies around the world.[4]

In the Azipod unit, the electric motor is mounted inside the propulsion unit and the propeller is connected directly to the motor shaft.[5] Electric power for the propulsion motor is conducted through slip rings that let the Azipod unit rotate 360 degrees about the vertical axis.[6] Because Azipod units utilize fixed-pitch propellers,[7] power is always fed through a variable-frequency drive or cycloconverter that allows speed and direction control of the propulsion motors.[8]

The pod's propeller usually faces forward because in this pulling (or tractor) configuration the propeller is more efficient due to operation in undisturbed flow. Because it can rotate around its mount axis, the pod can apply its thrust in any direction. Azimuth thrusters allow ships to be more maneuverable and enable them to travel backward nearly as efficiently as they can travel forward. In order to get the most out of it, shiphandling training on simulators and manned models is required.[9]

The podded design typically achieved a 9% better fuel efficiency than the conventional propulsion system when it was first installed in the 1990s. Improvements to the conventional design have shrunk the gap to 6%-8%, but on the other hand the hydrodynamic flow around the Azipod has been improved by fin retrofits and a dynamic computer optimization of the respective operating angles of the pods in multipod installations, yielding overall efficiency improvements now in the range of 18%.[10]

HistoryEdit

DevelopmentEdit

 
The first Azipod unit, installed on the Finnish fairway support vessel Seili in 1990, is now displayed at the Forum Marinum maritime museum in Turku, Finland

In 1987, the Finnish National Board of Navigation made a co-operation proposal to the multinational electrical equipment corporation ABB Group and the Finnish shipbuilder Masa-Yards for the development of a new type of electric propulsion unit.[11] Prior to this, the companies had been working together for decades in the field of diesel-electric propulsion systems and in the 1980s produced the first icebreakers with alternating current propulsion motors and cycloconverters.[12]

The development of the prototype started in 1989 and the first unit was ready for installation in the following year.[13] The 1.5 MW unit, dubbed "Azipod" (short for azimuthing electric podded drive[14]) was installed on the 1979-built Finnish fairway support vessel Seili at Hietalahti shipyard in Helsinki, Finland. After the refit, the vessel's icebreaking performance was considerably increased and she was also found out to be capable of breaking ice astern (backwards). This discovery of a new operating mode eventually led to the development of the double acting ship concept in the early 1990s.[15][16] When Seili was refitted with new propulsion system in the 2000s, the prototype unit was donated to Forum Marinum and put on display in Turku, Finland.

Following the encouraging experiences from the prototype installation, the development of the Azipod concept continued and the next units were retrofitted on two Finnish oil tankers, Uikku and Lunni, in 1993 and 1994, respectively. Nearly eight times as powerful as the prototype, the 11.4 MW Azipod units considerably increased the icegoing ability of the vessels that were already built with independent icebreaking capability in mind.[15] Since the 1990s, the vast majority of ships capable of operating in ice without icebreaker escort have been fitted with Azipod propulsion system.[17]

The first three Azipod units were of so-called "pushing" type in which the propeller is mounted behind the gondola. In the subsequent installations, ABB adopted the more efficient "pulling" configuration similar to propeller-driven airplanes.

The world's first cruise ship fitted with Azipod propulsion units, Elation, was delivered by Kværner Masa-Yards Helsinki shipyard in the spring of 1998.[18] Even though the Azipod was initially developed for icebreaking vessels, cruise ships have become the largest group of ships by type to be fitted with Azipod propulsion system since the 1990s and the success of the electric podded propulsion units has paved the way for competitors such as the Rolls-Royce Mermaid. Among the vessels fitted with Azipod units are Royal Caribbean International's Voyager-, Freedom- and Oasis-class cruise ships, each of which held the title of the largest cruise ship in the world at the time of delivery.[17]

Another further development of the original electric podded propulsion concept is the Compact Azipod, a smaller Azipod unit introduced in the early 2000s. It is intended for smaller ships such as research vessels and yachts as well as dynamically positioned drilling rigs that may utilize up to eight such propulsors.[17][19] The smaller Azipod Compact differs from the full-size unit by its permanent magnet synchronous motor which is directly cooled by sea water. For drilling vessels, it is also available in "pushing" configuration and can be fitted with a nozzle to increase bollard pull thrust in stationkeeping applications.[20] Unlike the full-sized Azipod units which are assembled in Finland, the Compact Azipod units are manufactured in China.[21]

Bearing-related problemsEdit

During the initial years in service, some widely publicised cruise ship service disruptions with the bigger Azipod V design have occurred, see e.g.[22]

The latest design, the Azipod X, incorporates these improvements, with a view to a service interval of five years, and features bearings that can be taken apart and repaired from inside the pod while the ship is harbored normally.[23][24]

NotesEdit

  1. ^ Inside view: What makes QM2 go. Beyond Ships. Retrieved 2014-04-26.
  2. ^ Marine Propulsion & Auxiliary Machinery: The Journal of Ships' Engineering Systems. Riviera Maritime Media. 2005. 
  3. ^ Brian J. Cudahy (2001). The Cruise Ship Phenomenon in North America. Cornell Maritime Press. pp. 53–. ISBN 978-0-87033-529-7. 
  4. ^ Tammiaho, Erkki. "Ruoripotkurilaitteiden liiketoiminta Suomessa, TEKES, 258/2009" (in Finnish). Archived from the original (PDF) on 2010-12-08. Retrieved 2013-12-05. 
  5. ^ Pakaste, Risto; et al. (February 1999). "Experience with Azipod propulsion systems on board marine vessels" (PDF). Retrieved 2012-12-25. 
  6. ^ Society of Naval Architects and Marine Engineers (U.S.) (1994). Transactions - The Society of Naval Architects and Marine Engineers. Society of Naval Architects and Marine Engineers. 
  7. ^ Lakeside Publishing Co. (May 2002). Cruise Travel. Lakeside Publishing Co. pp. 42–. ISSN 0199-5111. 
  8. ^ Mukund R. Patel (17 February 2012). Shipboard Propulsion, Power Electronics, and Ocean Energy. CRC Press. pp. 188–. ISBN 978-1-4398-8850-6. 
  9. ^ Port Revel Pod Shiphandling course
  10. ^ "Azipod propulsion drives take the next step". Skipsrevyen. March 2011. Archived from the original on 2013-10-02. Retrieved 2013-09-24. 
  11. ^ Hepo-oja, Anssi; Mäki-Kuutti, Viktor (2012). Mekaanisen ja sähköisen propulsiojärjestelmän esittely (PDF). Satakunta University of Applied Sciences. 
  12. ^ Cycloconverters for the new icebreaker from Kymmene-Strömberg. Navigator 1985.
  13. ^ 1. Dynamosta Azipodiin - vuosikymmenien kokemukset jäänmurtajista. ABB Group. Retrieved 2013-10-05.
  14. ^ ABB-teknologiat: Azipod®-propulsiojärjestelmät. ABB. Retrieved 2016-02-12.
  15. ^ a b Juurmaa, K et al.: The development of the new double acting ships for ice operation. Kvaerner Masa-Yards Arctic Technology, 2001 Archived 2012-03-03 at the Wayback Machine. and 2002 Archived 2012-09-04 at the Wayback Machine..
  16. ^ Juurmaa, K et al.: New ice breaking tanker concept for the arctic (DAT) Archived 2012-03-03 at the Wayback Machine.. Kvaerner Masa-Yards Arctic Technology, 1995.
  17. ^ a b c References - Propulsion Products. ABB. Retrieved 2014-04-26.
  18. ^ 6.11. Azipod ® propulsion. ABB. Retrieved 2014-04-26.
  19. ^ Compact Azipod. ABB. Retrieved 2014-04-26.
  20. ^ Azipod C Archived February 24, 2014, at the Wayback Machine.. ABB. Retrieved 2014-04-26.
  21. ^ ABB Propulsion Products for Main Propulsion and Thrusters Archived February 25, 2014, at the Wayback Machine.. ABB, June 2012. Retrieved 2014-04-26.
  22. ^ Fredrickson, Tom (2000-07-22). "Carnival's Paradise Coming To Yard For Repairs". Newport News, Virginia: Daily Press. Retrieved 2013-09-24. 
  23. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2013-12-30. Retrieved 2012-12-27. 
  24. ^ "Propulsion Systems by ABB Marine". Wplgroup.com. 2012-02-13. Archived from the original on 2013-12-30. Retrieved 2013-09-24.