13
Nov 2008

Captain’s Log: Eurodam’s Azipods

Submitted by: Captain Mercer

Our Azipod-drive vessels are the Vista-class ships, including “Amsterdam”, “Eurodam” and the soon to be added to the fleet, “Nieuw Amsterdam”.

The “Amsterdam” is slightly different in concept, in that the Captain has to chose beforehand which pod he is going to use as his ‘maneuverable’ one, the other stays fixed in the fore-and-aft line.

Below is a picture of the ‘E’s” starboard pod. It always amazes me that something so small in diameter can drive so large a ship through the water.

Azipod is the registered brand name of the ABB Group for their azimuth thruster. Originally developed in Finland by Wärtsilä dockyards, these are marine propulsion units consisting of electrically driven propellers mounted on a steerable pod. The first cruise ship fitted with this system was “Carnival Paradise”, way back in 1998. Since then the system, after some initial teething challenges, has become the norm for our Carnival group of companies.

The pod’s propeller faces forward, (the propeller is more efficient oriented that way). In addition, because it can rotate around its mount axis, the pod can apply its thrust force in any direction. Azimuth thrusters allow ships to be more maneuverable and enable them to travel astern nearly as easily as they can travel forward. In fact, almost 70 percent of my dockings involve going astern down waterways or into dock slips.

In the traditional azimuth propulsion system the electric motor is located inside the ship’s hull and rotation is transferred to the propeller through a gearbox. In our Azipod system the electric motor is installed inside the pod. The propeller is connected directly to the motor shaft. No gearbox is required, thus providing greater efficiency.

Electric power for the Azipod motor is conducted through slip rings that allow the Azipod to turn through 360 degrees. Because fixed-pitch propellers are used in Azipods, power for the pod is always fed through a variable-frequency drive that allows speed control of the propulsion motor.

When the ‘E’ is at full speed, the Azipods act just like a ‘powered’ rudder and have conventional characteristics, with a maximum rudder angle of 35 degrees, however, because it is ‘powered’ (and therefore very responsive), when at full speed, only 2 or 3 degrees of rudder are required.

The Azipods have an output of 24,000 horse power (or 17.6 mega-watts) each when at full speed, or ‘open sea’ mode. When maneuvering and rotational, they are stepped down to 10 MW or 13, 500 hp each.

We have three bow thrusters, each of 2,500 hp or 1.9 MW each

With the combination of these thrusters forward and the Azipods aft, the ‘E’ becomes an extremely maneuverable ship. In fact, the combination has drastically changed established ship-handling maneuvers and captains can think ‘outside the box’ when finding themselves in awkward or unconventional situations.

They are not infallible, of course, and the ‘E’, like our Vista class, has far more power available from her Azipods than forward in the thrusters. As a consequence, in higher wind situations, control of the bow will be lost long before control of the stern. The ‘E’ is unique, (for the time being), in that we have additional superstructure and as a result, more ‘windage’ (the area which acts as a sail), and I am always wary of wind direction and speed. Having sailed on other Vista-class ships, I know they will push bodily upwind at wind speeds of 25 knots on the beam. The ‘E’, with its additional ‘sail area’, will manage 20 knots, and those 5 knots of wind can be make or break when docking, or conversely, getting off a pier.

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