Faults prevention for the gear coupling of the azimuth thruster L-drive through a study of shaft alignment measurements

Abstract

The propulsion system is one of the most important systems in a vessel. It is considered critical, since if it fails, directly compromises the operation and safety. A common fault on the azimuth propulsion L-drive system is the gear coupling failure, where on the last stage of damage the shaft can broke causing propulsion loss. The two main reasons of this problem are the shaft misalignment and lack of gear coupling teeth lubrication. Through a specific alignment measurement procedure, performed on three different vessels and 17 azimuth thruster L-drive, this study will prove that the shaft alignment between motor and thruster is affected by the steering rotation of the azimuth system. The alignment changes due to steering position sometimes can be greater than alignment tolerance values, generating gear coupling damages. Then a specific procedure is proposed to measure, evaluate, and correct the alignment to prevent gear coupling failures and improve the system reliability.