Vibration analysis & In-situ balancing of motor drive unit coupled through fluid coupling
Many mechanical industries involved in metal extraction use blast furnaces as an integral part of their process. At Bhilai Steel Plant, raw materials for steelmaking are transported to the blast furnace using a belt conveyor system driven by Main Belt (MB) drive units comprising a motor, fluid coupling, and gearbox. NV Dynamics was contracted to perform vibration analysis and in-situ balancing on Blast Furnace 8’s MB drive units.
For vibration analysis tri-axial accelerometers were mounted on the drive motor’s DE and NDE bearing housings, while uni-axial sensors were placed on the gearbox input/output ends. Data was acquired using a multi-channel system with phase and speed tracking. Tests were conducted without load, at the operating speed of 1260 RPM. Unbalance and high vibration levels was observed at these operational speeds and in-situ balancing was performed to reduce the overall vibration amplitudes within acceptable limits of ISO 20816.
In-situ balancing involved three steps. First, resonance tracking was performed from 1200 to 1500 RPM to identify peak vibration magnitudes. Then, motor-end balancing was done by decoupling the fluid coupler and adding trial weights on the motor drive end. Once an acceptable level of vibration was achieved on the motor, the fluid coupler was recoupled and balancing on the full assembly was performed. Correction masses were applied as needed and residual vibrations were measured. Post-balancing, the system was run again across the speed range and vibration data was recorded for final analysis and comparison against the ISO 20816 standard.
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