Real-World Examples of Condition Monitoring Success
Discovery: Vibration analysis showed an increase in gear mesh and gearbox bearing frequency, indicating bearing wear.
Recommendations: Inspect and replace bearings. Inspect gear.
Corrective Actions: Bearings and idler gear were replaced. The stub shaft for the gear was broken. An issue with the bearing on the dryer caused it to drop; the weight of the dryer was then carried by the gear.
Discovery: The pump was found to have a sub-synchronous frequency and was also found to be leaking out of the packing severely. It also had a rattle indicating the bearings/bushings were worn.
Corrective Actions: Replace the pump.
Equipment Importance: The pump sends water to the pit to make a slurry of the mined materials. Without, the capacity of the plant is reduced by one-third.
Discovery: Spectral analysis showed dominance of the operating frequency, which is related to the presence of mass imbalance, in the fan blades of the carbon black collector.
Recommendations: Perform a G 6.3 balancing on the dust collector to reduce the vibration amplitudes.
Corrective Actions: Execution of major maintenance, balancing of blades, changing of bearings, replacement of bands, and cleaning of pulleys were all performed.
Discovery: The spectral analysis presented a peak at 2X the operating frequency of the equipment in a vertical direction. The base of the peak presents a mound of energy that is affected during data collection, having increases and decreases in amplitude. A bump test was carried out with a rubber hammer on the base structure of the system to search for natural frequencies of the system. The test showed the presence of two of them at 19.55 Hz and 23.01 Hz, which confirmed the existence of resonance in the system.
Recommendations: Increase the rigidity of the system to move the natural frequencies. Add a beam in the middle of the base of the system.
Corrective Actions: The base structure of the equipment was reinforced with a steel beam as recommended. After the installation of supports to improve the rigidity of the system, the equipment presented decreases in amplitudes.
Discovery: During the plant shutdown scheduled for March 2024, the gearbox corresponding to mill number 6, which provides rubber to the 4Z calender, was replaced. Thermography acceptance test showed an average temperature of 85.2°C (185.36°F) in the body of the gearbox. This temperature is not acceptable according to the parameters established for this type of asset. An inspection of the cooling system was carried out, where it was observed that the outlet line to the heat exchanger was cold.
Recommendations: Clean the outlet lubrication lines, strainer, and heat exchanger, looking for obstruction points that are preventing the cooling of the lubricating oil.
Corrective Actions: The maintenance technician completed the recommended actions, finding the strainer completely clogged and causing zero circulation and cooling of the lubricant. A new inspection showed the average gearbox temperature was 56.8°C (134.24°F).
