1. Prepared by: Marimuthu Gurusamy Combined vibration analysis (velocity and acceleration envelope) for Prediction of rotating equipment (with rolling element bearings) and its component’s deterioration to determine the duration for maintenance

2. Velocity vibration analysis How do we make decision whether we stop the machine or continue to run to meet the production requirement? ISO 10816

3. Stop the machine based on Velocity readings Is it Correct? If not, Why?

4. Vibration Basic Back to vibration school

5. Vibration Basics Vibration Parameters Displacement pk-pkmicrons/mils Velocitypeak/RMSmm/sec or inch/sec Accelerationpeakm/sec 2 or g Vibration Amplitude Peaka Peak-Peak2a RMS0.707a RMS a 2a

7. frequency Amplitude 1 khz 5 khz 10 khz 15 khz 20 khz frequency Amplitude 1 khz 5 khz 10 khz 15 khz 20 khz frequency Amplitude 1 khz 5 khz 10 khz 15 khz 20 khz Displacement Velocity Acceleration

8. Rolling Element Bearing Structure Radial Load Rolling Element Bearing Under Simultaneous Radial and Axial Loading Rolling Element Bearing Under Simultaneous Radial and Axial Loading  Element Contact Angle,  Cage Elements Inner Race Axial Load Pitch Diameter, D Outer Race

9. Spectral Enveloping Process With each impact, the machine structure “rings” at its natural resonance frequency. These impact events are embedded in a complex vibration signal, and are typically not detectable until they are extracted by the enveloping process. 1. Periodic impact events 2. Unfiltered Vibration Signal Amplitude 3. High Frequency Filtering Amplitude 4. Low Frequency Filtering Amplitude 5. Signal Rectification Amplitude 6. Enveloping Step

10. Traditional Vibration Analysis Overall Vibration (Amplitude in peak/RMS/pk-pk) Level1 :Define Severity (as per ISO 2372,7910 & 10816) Frequency(Hz, CPM & Orders) Level 2:Define Source of Problem Phase (Degree) Level 3:Confirm Problem Can – Unbalance, Misalignment & Looseness Can not – Bearing, Gear, Impeller damage Envelope Level 2&3Useful to analyse Problems in Rolling Element bearings.

11. Decisions making based on Velocity readings Is it Correct? If not, Why?

12. Case studies Challenges in monitoring velocity reading alone and how to interpretive combine analysis of Velocity and envelope spectrum.

13. Case-1 Low velocity high envelope-Level 1

14. velocity Envelope Bearing replaced

15. Case2- Low velocity high envelope readings-Level 2

16. Envelope Envelope in danger limit Velocity Within acceptable limit Velocity

17. Case Study 2- Spectrum before bearing replacement Envelope Spectrum Velocity Spectrum

18. Case Study 2- Spectrum - After bearing replacement Envelope Spectrum Velocity Spectrum

19. Case-3- high velocity Low envelope Casing distortion-Level 2

20. velocity Envelope

21. Case-4- Envelope relationship with unbalance-Level 2

22. Envelope Velocity Case-4- Envelope relationship with unbalance- Level 2 Bearing replaced Fan cleaned

23. Conclusion We seen 4 scenarios – Case 1- Low velocity and high envelope reading Level 1 analysis – Case 2- Low velocity and high envelope reading Level 2 analysis. – Case 3 – High velocity and Low envelope reading Level-2 analysis. – Case 4- Envelope relationship with unbalance.

24. Key guide line in Envelope reading Analysis Understand the envelope processing technically. Must use acceleration sensor for envelope readings. Collect horizontal reading for envelope acceleration for radial bearing and axial direction for thrust bearings. Do not use top-vertical direction. Always follow combine analysis with velocity spectrum and overall readings. Use appropriate filters on collection of acceleration envelope readings. Use frequency filtering range as follows – 1. 1500 / 3000 rpm 500Hz- 5 to 10Khz – 2. General 1. High Pass – 10x rpm / HFFx3 2. Low Pass – 5 to 10KHz (depending on sensor mounting type)

25. Key guidelines in Envelope Spectrum Analysis Do not correlate between normal spectrum analysis technique to envelope spectrum. Example like – 1x amplitude is unbalance – 2x amplitude as misalignment – Harmonics as looseness Domination of 1x amplitude alone as like unbalance symptom in normal spectrum, indicates severe bearing damage in one of the location in the raceways. Domination of Bearing forcing frequencies like BPFI,BPFO,BSF and FTF will indicates directly related to the problem. Harmonics of 1x indicates that the high envelope readings are due to impact of mechanical problem like unbalance and misalignment. Use waveform data analysis before make conclusion on super critical machines. Use waveform interaction analysis where the gear problems are involved in the machine.

26. Key points to be considered in Envelope analysis Always correlate envelope readings with velocity readings. Increasing of envelope readings to 5g considered for important attention on lubrication. If no reduction in envelope reading after lubrication, plan the spare, increase the monitoring frequency and watch till it reaches 10g. If no spare arrives and no plan for maintenance after reaching 10g. Expedite the spare procurement process. Do not allow the machine to run >25g at any cost. From 10g to 25g is the duration for replacement of bearings, if velocity readings are normal. When velocity also abnormal plan the bearing replacement at 10g itself.

27. Measuring Techniques used by different Manufacturers for Rolling Element Bearings 1. SPM - Shock Pulse Method (32Khz) & Envelope 2. IRD - Spike Energy (30Khz) & Envelope 3. SKF - SEE & Envelope 4. Csi - Peak View & Envelope 5. DLi - Cepstrum & Envelop 6. Bently- REBAM & Envelope 7. Others - (Commtest, Pruftechnik, ACOEM etc) Note: All above manufacturer instrument and software are capable of data collection and analysis of envelope reading analysis for bearing failures.

28. Thanks you