Case Study of Resonance Issue in 02-pole,13.2kv,5000 HP BFW Pump Motor in Commissioning

Munna Naik Dhanavath, Reliability & Condition Monitoring SME, Independent Consultant


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 & motor successfully handed over to operations.

Bio - Munna Naik Dhanavath


Mechanical Engineer with over 15 Years of rich hands-on Industry experience in Condition Monitoring and Reliability Services division. Having sound knowledge in the vibration analysis of all industrial rotating equipment’s using various technologies with unique problem-solving approach. Playing critical role in ongoing AI/ML based IIOT advanced analytics platform along with Tri-axial wireless vibration sensors & integration services for operational excellence in one of the reputable Oil & Gas Refinery in India. Experienced in condition monitoring and asset reliability management with a demonstrated history of working in the chemicals and other manufacturing industries. Skilled in Root Cause Analysis, Continuous Improvement, Commissioning, Manufacturing with strong professionalism. Having sound knowledge and experience in top Oil & Gas & Petrochemical industries from project, Commissioning and start up to shutdown phase in top companies like Sabic-Saudikayan, Sadara chemical company (i.e., one of the biggest petrochemical complexes in the world located in Saudiarabia). Skilled in below condition monitoring technologies: Vibration analysis Ultrasound Thermography Motor current signature analysis Balancing Alignment Root cause failure analysis of various chronic design flaws.