The Nautilus bearing from SKF USA Inc., Landsdale, Pa., is a double-row tapered bearing set that is compact and used in wind turbines to carry all rotor loads, forces, and moments. Up to now, most large turbines used two bearing sets to handle axial and radial loads separately. Using only one bearing means only rotor torque gets transmitted to the drivetrain and that weight and cost are reduced. The two rows of tapered bearings are arranged back to back and lock the unit axially, so it delivers high levels of stiffness.
The bearing is also more compact than the two bearings traditionally used. This makes for a smaller, lighter, and less-costly nacelle. And the large number of rolling elements makes for extreme precision between raceways, so the unit can carry high loads. The Nautilus bearing is, in fact, designed for multimegawatt turbines — and those turbines can be directly driven or have gearboxes, have outer or inner-ring rotation, and be mounted on shafts or bolted onto the surrounding structure.
The bearing uses an Ecopur polyurethane seal that is held in place by built-in carriers. The seal can be replaced on top of the turbine, simplifying maintenance. Seals and grease help prevent corrosion, a constant threat for offshore turbines.
The bearing comes standard with a bolted outer ring. A bolted inner ring is optional, which lets the bearing be attached to the rotor hub and the mainframe. This eliminates any effects of excessive tolerances between the bearing and the surrounding structure, including the shaft, housing, and lock ring. It also reduces variations in preload during operation.
