Definition(s)
Ring Gear
External or internal gear with which the swing pinion on the revolving upper-structure meshes to provide swing motion.
Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global Standards
Ring Gear
See swing gear (also known as bull gear).
Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Sixth Edition, May 2007. Global Standards