2S2: Case Study: Demystifying the Resonance Issue of Pump Motor in Commissioning



In 2015 a 02-pole,13.2Kv & 5000 HP Boiler Feed Water Pump Motor for the mixed feed cracker shown amplified bearing casing vibration levels at twice line frequency in its first solo run itself during commissioning stage. Considering the criticality & expected availability of 99.99% to maintain Asset Utilization targets for the site, detailed vibration analysis performed with various tests to address the root-cause of the problem and met with the numerous stakeholders for investigations.
The relentless pursuit of data analysis and research helped everyone to understand the typical characteristics of high vibration issue is due to Resonance at twice line frequency with 2 times motor speed causing beating phenomenon with pulsating vibration amplitudes & coinciding of natural frequencies of motor end plates at both DE & NDE dispel the common beliefs that this was a normally acceptable trait.
OEM agreed to re-design the motor end plates at both DE & NDE bearings for providing sufficient Resonance margin by shifting the natural frequencies.
After design modification, the motor vibration levels effectively reduced to acceptable limits and Motor successfully handed over to Operations.

*Importance of vibration analysis in addressing not only the operational/mechanical faults of the rotating assets but also the design level flaws.
*Importance of Asset FAT & SAT tests in Commissioning & Start-up phase.
*What should be included in the Purchase Legal Agreement(PLA) document if it is required to raise warranty claim to OEM.


Munna has more than 17 years of extensive experience in condition monitoring and asset reliability management with a demonstrated history of working in the top world class companies in Oil & Gas, Petrochemicals including SADARA & SABIC and other manufacturing industries. Skilled in: Various Condition Monitoring Technologies & Techniques, Root Cause Analysis, Continuous Improvement, Commissioning & Startup, Project execution, Manufacturing & Engineering, Reliability Engineering, Asset Management & Asset Optimization. He has solved various chronic and design related challenging problems with unique problem solving approach. His mindset is “Thinking out of the box” in critical problems solving, and he has the ability to see “abnormal in normal ” & “explore the unexplored.“