Lasse Hansen Vitek Consultoria Ltda. Fontes: Deane Horn, Tomek Lech and Attila Kiss

1. Evaluation of Turbomachinery by means of Transient Analysis Lasse Hansen Vitek Consultoria Ltda. Fontes: Deane Horn, Tomek Lech and Attila Kiss Emerson Process Management

2. Natural Why Machinery Health… • Machinery failures are the single largest pain issue for process plants • Operators lack feedback to know they are abusing machinery Causes of Large Losses Maintenance Spending • “68% of reported equipment failures result from improper installation and start-up.” • source: Factory Mutual Causes of Plant Incidents Source: Marsh & McLennan Protection Consultants

3. Multiplex system is perfect for… Gear Mesh Fault Sidebands increase with gear wear Many distinct peaks

4. Rolling Element Bearing Fault Multiplex system is perfect for… Bearing wear shows up at specific peaks related to the geometry of the bearing

5. Supported by sleeve bearings, over critical

6. High Stakes of Turbomachinery • Large, heavy, high speed, expensive assets • US$50M - US$100M cost for turbomachinery • Machines close to 65 meters long with 100’s of thousands of Kg of rotating mass • Spinning 50 times per second, 24 x 7 x 365 • Blades nearing supersonic speeds with wafer thin clearances

7. High Stakes of Turbomachinery • The consequences of faults and failure are often dramatic • Human safety at risk if machines fly apart spreading debris over 100’s of meters • Missed production schedules and customer commitments • US$100,000 per hour in downtime typical • Weeks or months to make repairs

8. Difficulties of Spectrum Analysis If we have nonlinear system elements… Misalignment Looseness Response = Force x System

9. TurboMachinery – nonlinearities The spectrum is less important, than the transient behaviour…

10. Performance • Key Performance Indicators • Total Equipment Performance • Individual Section Performance • Impact of Components upon Performance • All Compared to Design & Expected

11. Extending Process Control • What would the process control system show? • Nothing until high bearing temperature Bearing Case • What would you do? • After high bearing temperature… • Eventually schedule maintenance to investigate if it didn’t suddenly fail and schedule maintenance for you

12. Extending Process Control • What’s really going on inside… Bearing Case Rotor

13. X Extending Process Control 1Y 1Y Shaft Centerline Orbit • What would vibration monitoring and process control show together? • Early on, rotor movement or position changes • What would you do? • Correlate movement and position at other bearings • But with this information, you might know that this was an oil instability • Change oil temperature, and might correct the problem 1X 1X 270 270 180 180 Y Machine

14. First stage of rotor is 480C (900F) HP outlet inlet Turbines Have Unique Challenges case “hogs” • Start-up • Changes vs. RPM • Thermal transitions of rotor and stator • Rubs, rotor bow • Generator • Critical speed characteristics • Production • Changes vs. time • Changes vs. load • Coastdown • True mechanical assessment • Stopped, turning gear Temperature effects on rotor during start-upovercome forces of gravity HP

15. Every time you start-up a turbine… Result: Rub seals, seal leak Rub, damage bearings Bow shaft Crack, or broken blades …or healthy, optimized start-up Rotor expands more rapidly than stator Rotor could contact stator

16. Transient Monitoring, Introduction • Transient analysis is usually synonymous with start-up and coast down vibration monitoring of extremely critical turbo machinery • In this presentation • Explain transient analysis • The five operating modes of a turbine • Explain the plot types and examples of how they are used to evaluate machine health • Practical tips throughout the presentation you can use

17. Transient Monitoring • Instrumentation • Plot Types • Turbine Mode, Start-up

18. Instrumentation 1 Y 2 X 2 4 X 3 1 3 Y 4

19. Y 2 X 3 1 Y Y Y 4 2 2 2 X X X 1 1 1 3 3 3 4 4 4 What is Transient Monitoring • Multi-channel simultaneous data acquisition • All bearings simultaneously • View changes • vs. rpm • vs. time • vs. process parameters • Monitoring for all turbine operating modes

20. What is transient monitoring? • Instrumentation Tach IP HP LP GEN EXC

21. Transient Analysis • Long time waveform • Orbits • RPM vs. time • Shaft centerline • Bode plots • Polar or Nyquist plots • Cascade plots • Monitoring critical speeds • Monitoring critical resonances • Start-up, coast down and bump in the night • Transducer output vs. speed and/or time • Live and post processed data (extraction)

22. Trend

23. Waveform and spectrum

24. Waveform and spectrum – runout compensated

25. Waterfall spectrum

26. Waterfall spectrum – runout compensated

27. Cascade spectrum

28. Cascade spectrum – runout compensated

29. Plot Types: Orbit • AC, dynamic motion or the path of the shaft centerline as seen by the transducers • Shape can help determine rubs, oil instabilities, imbalance Y 2 X 3 1 4

30. Unfiltered Orbit

31. Unfiltered Orbit – runout compensated

32. Filtered Orbit

33. Filtered Orbit – runout compensated

34. Plot Types: Shaft Centerline • Average, DC position of the shaft centerline • Should rest at the center and bottom of the bearing at zero RPM • Rotor should rise in the fluid film and load will influence final position • SCL can help determine misalignment, bow Y 2 X 3 1 4

35. Plot Type: Shaft Centerline • Shaft centerline forced near bearing clearance • Misalignment forces shaft in opposing quadrants of shaft centerline plot in adjacent bearings Bearing 1 Bearing 2

36. Shaft CenterlineExample

37. Shaft Centerline

38. Bode and Polar plots

39. Bode and Polar plots – runout compensated

40. Live and Replay Mode

41. Live Turbine Dashboard for Rapid Decisions Overlay baseline data on live plot Multiple shaft centerline plots for bearing-to-bearing comparison

42. Turbine Mode, Start-up • Start-up • Shaft position and motion • Case position and motion • System dampening • Changes in resonance speed • Compare with baseline • Changes vs. speed First stage of rotor is 480C (900F) HP 540C (1000F) outlet inlet

43. Turbine Mode - Start-up, Rotor Bow • A rotor that is bent, or bowed, will produce 1X vibration at slow roll speed • It can be mathematically shown that rotor bow “repairs itself” if you get through the first critical resonance • Remember, imbalance will not produce 1X at slow roll `

44. + Turbine Mode - Start-up, Rub • Worn bearing, rotor moves away from bearing then re-contacts the bearing • Loose support structure • Unlubricated contact (must often) • Creates hot spots, local melting, welding, bowing • Lubricated contact • May occur once per several revolutions • Full annular rub • Forward precession is light • Reverse precession, forces are large, can rapidly destroy a machine, acts like a planetary gear

45. Symptoms of rub • Changes in 1X vibration • Abnormal orbit shape • Look for flattened orbit • Look for 1/2X component in spectrum • Subsynchronous or subharmonic vibration • Reverse precession components • Harmonics in spectrum • Thermal bow • Changes in average shaft centerline position • Wear, damage, lose of efficiency

46. Turbine Mode - Start-up, Bode, Polar Plot • What is a Bode and Polar Plot? • Used to analyze systems to determine critical resonance frequency • 1X vibration will peak • 1X phase will shift 180˚ • Polar plot is 1X peak and phase on same plot

47. Turbine Mode - Start-up, Bode/Polar Plot • Look for changes in critical resonance frequency • Shifts in resonance means that dynamic stiffness has changed (dampening or spring stiffness) in the system

48. Turbine Mode - Start-up, Bode/Polar Plot • Look for changes in synchronous amplification factor • Changes in SAF means changes in the dampening or spring stiffness properties of the bearing.

49. Turbine Mode - Start-up, Bode/Polar Plot • Look for 1X vibration below and above critical • Certain anomalies will have vibration at 1X below critical, others will only have 1X above, others will have 1X at both.

50. Turbine Mode - Start-up, Bode/Polar Plot • Look for shaft centerline movement with rpm compared to baseline.