Royal Caribbean’s Allure of the Seas — the largest cruise ship in the world, is being taken out of service in February due a failure in one of its Azipod propulsion pods. Here we go again.
Royal Caribbean announces Allure of the Seas will undergo repairs in February 2014
Propulsion pods may be the greatest thing that ever happened to cruise ships. Or maybe the worst, when they don’t work, which is far too often. A propulsion pod is an electric motor which drives a propeller mounted on a rotating “pod” which extends out from the bottom of the ship. Because they can be made to rotate 360 degrees, the pod replaces the traditional rudder and stern thrusters and does away with the need for long propeller shaft runs. They are more fuel efficient than conventionally mounted propellers, by around 6-9%, which given today’s fuel costs is significant. Two manufacturers dominate pod propulsion — Rolls Royce who manufactures the “Mermaid pod” and ABB which manufactures the “Azipod.”
The problem is that all of the thrust of the propeller is transmitted to the ship’s hull by the circular bearing that connects the pod to the ship — the bearing that also has to rotate through 360 degrees. These bearing have been failing far more frequently than they should. This is apparently what has happened on at least one of the three Azipods on the Allure of the Seas. Because RCCL detected excessive bearing wear, they initially slowed the ship to reduce the load on the bearing and then decided to take the ship out of service.
This is by no means the first time that propulsion pods have knocked cruise ships out of service. In 2000 the Carnival Paradise was pulled from service due to failed Azipods. Carnival and Royal Caribbean have had greater problems with the Rolls Royce MerMaid pods. In 2010, Royal Caribbean settled a lawsuit with Rolls Rolls over pod failures on the Celebrity Cruises’ Millennium-class ships. Celebrity is a subsidiary of Royal Caribbean. Rolls Royce reportedly paid Royal Caribbean $65 million for the failures. In 2011, Carnival Cruise Lines was awarded $24 million in a lawsuit with Rolls Royce over Mermaid pod breakdowns.
The lawsuits did not mean an end to the failures, unfortunately. This August, the Celebrity Millennium was knocked out of service for the rest of the Alaskan season by pod failures.
While the ABB Azipods have had fewer casualties than the Rolls Royce Mermaid pods, they have had their share of problems. Last March, the Carnival Legend limped into port with Azipod problems. And now, Azipods are sending Royal Caribbean’s Allure of the Seas into drydock. Propellers on shafts in front of rudders are looking better and better.
“They are more fuel efficient than conventionally mounted propellers, by around 6-9%, which given today’s fuel costs is significant.”
Of course my first thought on reading that line was; why aren’t there more sailing cruise ships? You could save a lot of money by sailing when the winds are favorable and could pick routes with dependable winds. I know there are a few, but they seem to be specialty lines that cater to a small, elite clientele. I’d think there’s a place for some mid-range sail-powered carriers. But I’m definitely no businessman!