Rotor Magnetization in Turboexpander and its Effect on Vibration Readings

Abstract

A magnetized rotating machine behaves like an electrical generator. It often produces localized stray current that usually discharges across small clearance paths imposing damage to machine internals and vibration probes. In several cases, this has also resulted in erroneous vibrations reading that can cause misguided decisions leading to unplanned downtime, waste of resources and significant production loss. Turboexpanders are high speed radial expansion turbines and are very sensitive to any residual magnetism in the rotor. A case studies has been discussed in this presentation involving rotor magnetization and it focuses on source of magnetism, failure modes, problem identification and successful resolution of the issue. Lesson learnt from the incident is also being shared. If the problems is diagnosed early, costly outage can be averted by adopting proper maintenance practices.