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Thrust to trust
Submerged propulsion technology
In any propulsion system with spinning parts, bearings play an integral role. With a submerged Azipod unit, however, there is the difficulty of a harsh, salty and sometimes icy environment.
An Azipod typically has three bearing positions: a slewing bearing, making it possible to turn the whole pod; a cylindrical roller bearing or a CARB® toroidal roller bearing, acting as a non-locating bearing; and an axial thrust bearing unit. The last function includes two spherical roller thrust bearings, holding the propeller shaft, or rotor, in place.
SKF has worked with ABB Azipod since 2000. Already, SKF supplies a tailor-made solution to the Azipod compact units that includes two axial thrust bearings, complete with housing and insulation on the thrust end. SKF also supplies the cylindrical roller bearing on the propeller end of the shaft.
On the bigger Azipod units, from 5MW up to 38MW, SKF’s CARB bearings have become the industry standard. The reason for this is that the heat from the electrical motor inside the Azipod can create an elongation of the propeller shaft of 5 to 10 mm.
A CARB bearing permits axial movement of the shaft internally in the bearing as well as angular misalignment caused by shaft deflections or coaxiality between the two rotor bearing positions. ABB is currently installing such bearings on large Azipod units.