Abstract: A rotor system for a rotating machine, including a rotating shaft, an auxiliary bearing, and a primary bearing configured to provide a bearing and seal combination. The auxiliary bearing may include a support structure extending around a circumference of the rotating shaft, such that an annular gap is defined between the support structure and the rotating shaft when the primary bearing supports the rotating shaft. The auxiliary bearing may also include a first pedestal extending radially-inward from the support structure, and first and second beams extending from opposite sides of the first pedestal in a plane perpendicular to an axis of the shaft. The auxiliary bearing may further include a first roller operatively coupled to the first beam, and a second roller operatively coupled to the second beam, such that the first and second rollers are configured to engage the shaft.

Abstract: Balance piston assembly, apparatus, and methods are provided. The assembly includes a balance piston coupled to a rotatable shaft and configured to rotate therewith, the balance piston including a first shelf and a second shelf, the first and second shelves being axially-overlapping and radially-offset. The assembly also includes a seal including a first sealing surface configured to seal with the first shelf and a second sealing surface configured to seal with the second shelf.