48th Turbomachinery & Pump Symposia Proceedings

Lecture Presented During the 48th Turbomachinery & 35th Pump Symposia, Sept. 2019

Addressing High Sub-Synchronous Vibrations in a Turboexpander Equipped with Active Magnetic Bearings

This paper presents the authors’ experience with a turboexpander (TEX) equipped with active magnetic bearings (AMBs) in a natural gas processing facility. The TEX was unable to achieve design performance due to high sub-synchronous vibration since its commissioning. Rotor dynamic simulations revealed that the most likely root-cause of the high vibration was the excitation of an unstable rigid body mode of the rotor-bearing system due to high cross-coupled stiffness effects. The paper also contains a summary of the redesign features incorporated in the TEX that resolved the sub-synchronous vibration.