1. Bearing Defect Detection At Very Low Frequencies Bill Kilbey

2. 2 Case History 2 BOF Vessels at an integrated Steel Mill 6 weeks purchasing lead time on vessel bearings 32 hours labor time to replace outboard vessel bearing, 16 hours estimated labor time to replace inboard vessel bearing Previous failure with no warning led to need for condition monitoring

3. 3

4. 4 Vessel Operation Normal vessel operation does not include full rotation –rotate 60 degrees to load vessel with scrap –rotate back 60 degrees to place charge –steel processing in place (no rotation) –rotate 90 degrees to unload vessel Potential for significant wear in bearing load zone, no wear elsewhere

5. 5 Vessel Testing To test for bearing degradation, off-line testing is necessary –Removal of material from vessel –Complete rotation of vessel to circulate all rolling elements –Speed = 115seconds/revolution

6. INITIAL FAULT DETECTION Vessel Speed = 0.52 rpm BPFI = 0.1332 Hz (T = 7.51s) BPFO = 0.1104 Hz (T = 9.06s)

7. 7 Full Transient PeakVue Waveform - Vessel #2 One Cluster of Impacts Between 35-80 seconds

8. 8 Full Transient PeakVue Waveform - Vessel #1 Lower Amplitude Levels Than Vessel #2 No Repeatable Impacting Pattern Seen

9. 9 PeakVue Waveform Impacts Equally Spaced T = 7.51s

10. 10 FINDINGS Initial Fault Detection Impacting as a result of initial bearing defect definitely present on Vessel #2, not present on Vessel #1 Multiple impacts indicate multiple inner race defects Amplitude levels very low, repeating impacting pattern every rotation NOT confirmed

11. SECOND DATA POINT Vessel #2 Vessel Speed = 0.52 rpm BPFI = 0.1332 Hz (T = 7.51s) BPFO = 0.1104 Hz (T = 9.06s) (t = 2 months after initial detection)

12. 12 Full Transient PeakVue Waveform Two Clusters of Impacts Spaced at Rotational Speed

13. 13 Full Transient Waveform With Normal Signal Processing

14. 14 PeakVue Waveform Impacts Equally Spaced T = 7.95s

15. 15 PeakVue Spectrum Generated From Previous Waveform Bearing Defect Frequency (0.1277 Hz) + 4 Harmonics

16. 16 FINDINGS Second Data Point A repeating impacting pattern every rotation is now confirmed Amplitude levels have increased significantly Multiple impacts still present, indicating multiple inner race defects A significant “noise floor” is now present in the areas where impacting occurs

17. THIRD DATA POINT Vessel #2 Vessel Speed = 0.52 rpm BPFI = 0.1332 Hz (T = 7.51s) BPFO = 0.1104 Hz (T = 9.06s) (t = 4 months after initial detection)

18. 18 Full Transient PeakVue Waveform Two Clusters of Impacts Spaced at Rotational Speed

19. 19 PeakVue Waveform Impacts Spaced T = 7.62s

20. 20 FINDINGS Third Data Point Amplitude levels have decreased Pattern no longer repeatable every revolution “Noise floor” in waveform is still at the same amplitude levels in the same areas of the waveform as in the Second Data Point

21. 21

22. 22 CONCLUSIONS/THEORIES #1 Between the initial defect detection and the second data point, individual defects became more severe and the impact energy greater, causing the large increase in amplitude.

23. 23 CONCLUSIONS/THEORIES #2 Between the second and third data points, raceway defects became deeper and possibly two or more defects may have become one larger defect. This would explain the reduction in impacting energy and the reduction in amplitude and number of severe impacts in the time waveform

24. 24 CONCLUSIONS/THEORIES #3 The amplitude and width of the “noise floor” in the time waveform dictates in large part the severity of a bearing defect on a very slow speed machine. Smaller amplitude, nearly continuous impacting will indicate a raceway with a deep, nearly continuous defect

25. 25 FINAL NOTE: Cost Avoidance Reactive To Planned Maintenance –32 hour labor estimate for replacement of outboard bearing @ $4300/hour - $135,000 Catastrophic Failure Without Warning –6 weeks bearing lead time at (conservatively) 75% capacity = $4300/hour x 6 hours lost/day x 42 days = $1,080,000