S. KUMAR, Vibration Institute, Indorama, West Africa
Critical motors are the backbone of industrial processes, driving essential machinery and ensuring seamless operations. These motors are deployed in high-demand applications where performance, reliability and efficiency are paramount. Any malfunction can result in substantial downtime, significant production setbacks and critical safety hazards. To uphold the operational integrity of critical motors, meticulous selection, precise installation and stringent maintenance protocols are indispensable. Key factors such as adherence to exact motor specifications, optimal lubrication, precise alignment and rigorous temperature monitoring are crucial in mitigating premature degradation.
Among these key factors, boiler scanner fan motors are particularly vital, functioning as essential components in regulating cooling, ventilation and thermal equilibrium. Unchecked heat accumulation can severely impair sensitive equipment, leading to functional deterioration and catastrophic failures. Additionally, energy efficiency plays a pivotal role, as well-maintained scanner fan motors minimize power consumption while enhancing overall system performance. Given their crucial role in operational stability, scanner fan motors are classified as high-priority assets, demanding proactive maintenance strategies to extend their service life and prevent unforeseen disruptions.
Case study. The initial installation of scanner fan motors experienced frequent premature bearing failures due to the use of shielded bearings, leading to increased production downtime and necessitating frequent condition monitoring. To address this issue, two re-greasable 5.5-kW motors were procured as replacements to reduce downtime. However, during a solo test that was run post-installation, high temperatures were observed at the drive end, with vibration spectrum analysis indicating bearing looseness (FIG. 1). During the initial solo run test, the drive-end (DE) temperatures for both motors spiked to 90°C (194°F) within 15 min despite normal vibration readings. The heat was also observed to transmit to the shaft, raising concerns about long-term reliability.
To further investigate, load condition testing was performed. Thermal imaging captured during testing showed high temperatures of ~97.5°C (~207.5°F) (FIG. 2), an unacceptable level for newly commissioned motors under both solo and load conditions. When tested under load, both motors exhibited increased vibration and temperature levels exceeding International Organization for Standardization (ISO) standards and those of the previous shielded bearing motors. Spectrum analysis indicated looseness but did not reveal any bearing fault frequencies. When the shielded bearing motors were reinstalled, they operated without temperature or vibration issues.
Since the motor was under warranty, the issue was escalated to the original equipment manufacturer (OEM), which recommended verifying alignment, base and other process parameters. However, as the shielded bearing motors had been functioning without issues under identical conditions, the in-house electrical team, in collaboration with the reliability maintenance center, took the initiative to resolve the problem due to inadequate support from the OEM.
Actions taken. To identify and rectify the root cause of the problem, a solo test run was conducted with the DE seal removed and later installed without the spring, both showing acceptable vibration and temperature levels. Inspection revealed excessive motor end cover clearance—0.03 mm at the motor non-drive end (MNDE) and 0.04 mm at the DE—along with poor seal quality. Corrective actions included sleeving the bearing housing and installing a high-quality DE seal without the spring. Post-repair tests showed significant improvements (TABLE 1).
Takeaways. To preclude the recurrence of such anomalies and uphold optimal motor functionality, the following imperatives must be rigorously enforced. Ascertain that all motors conform meticulously to prescribed technical specifications and performance benchmarks prior to procurement. This necessitates the explicit verification of grease composition, bearing classification and bearing housing dimensional integrity. Further, ensure that motors are accompanied by a robust warranty and exhaustive post-sales support to rectify potential defects or operational deviations. Execute comprehensive factory acceptance testing to meticulously assess vibration and thermal parameters during an isolated operational trial, ensuring they remain within permissible thresholds. Moreover, scrutinize the temperature differential (∆T) between motor bearing temperature and ambient conditions to guarantee operational reliability.
By strictly enforcing these measures, the likelihood of premature failure in new motors can be substantially reduced, thereby improving their longevity and reinforcing their operational durability in industrial environments. HP
Sanjay Kumar is a condition monitoring specialist with more than 14 yr of experience in refineries, combined-cycle power plants and thermal power plants, and liquefied natural gas (LNG) process plants, focusing on the condition monitoring and asset reliability of rotating equipment. Currently, Kumar works at a fertilizer and petrochemical plant in Indorama, West Africa. His expertise includes vibration analysis, ultrasound and root cause analysis of rotating equipment, aiming to optimize performance and reduce downtime. Passionate about industrial innovation, Kumar actively shares insights on best practices in maintenance and reliability engineering.