Modal Structure Imbalance Fault Detection For Rotating Machines

• Author / Creator

  Smith, Brendan S

• Fault detection methods have become an important tool in the prevention of safety and reliability issues for industrial rotating machines. Faults in these machines often develop progressively and are not easily observed under operating conditions until severe damage has occurred and further damage during the shut-down process is unavoidable. This type of fault is common in centrifugal separators, where nozzle plug imbalance faults occurring at supercritical operating speeds can lead to catastrophic failure during coast-down after the fault has progressed to the point that an alarm is triggered.
  This thesis presents a vibration-based subspace fault detection method intended for de- tecting rotor imbalance faults. This output-only method detects rotor imbalance faults using an asymptotic local approach that is sensitive to small changes in modal structure. The method was originally developed for stationary structures but is adapted here for constant- speed rotating systems. The faults of interest are static and dynamic rotor imbalances representative of the nozzle plug faults experienced by centrifugal separators.
  Two physical models of an idealized centrifugal separator are also presented and used to demonstrate the subspace fault detection method. The first is a mechanical simulation based on rigid body and flexible rotor dynamics derived from finite element analysis of a physical rotor. A physical laboratory bench model based on the simulated machine is also presented that allows the detection method to be demonstrated on a realistically complex system with limited instrumentation.
  Subspace fault detection results are presented for both machines using a range of static and dynamic imbalances of increasing severity. For comparison, results are also presented for two alternative detection methods for vibration faults that have received recent attention: sinusoidal synthesis and the Hilbert-Huang Transform. These results demonstrate that the subspace method produces superior results for imbalance faults, particularly in the case of dynamic imbalance.

• Subjects / Keywords

  • Rotating machines
  • Simulations
  • Subspace methods
  • Fault detection
  • Modelling

• Graduation date

  Spring 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3SF2MM0R

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.