Casper, Phillips & Associates Inc.(CPA) recently completed remediation of three 40 metric ton capacity rail-mounted gantry cranes(RMGs) at a major North American port, after conducting a root-cause analysis following gearbox failure.
CPA—the company offers a wide variety of services, including procurement, specification, design, manufacturing review, modification, and accident investigation—was contracted by the port, as the RMGs’ main hoist gearbox bearings and gear teeth were experiencing early failure and excessive vibrations. CPA was retained to investigate the causes and to provide retrofit solutions. Gearboxes fail for several reasons, such as soft foundations, misalignment, overload, poor contact, and sometimes poor design practices.
Mike Zhang and Richard Phillips, both mechanical engineers at CPA, completed the initial site investigation on an RMG that was used for intermodal(moving freight by two or more modes of transportation) container handling. It
was apparent that under load the drum would bend the gearbox output shaft. The bending of the shaft caused the gear teeth to misalign. In other words, only parts of the gear teeth were in contact, which led to rapid wear.