Ball Mill Pinion Drive Vibration Monitor

Per ISO 10816, up to 3.5 mm/s RMS is new-machine condition (zone A) and up to 7.1 mm/s is acceptable for unrestricted long-term operation (zone B). Between 7.1 and 11 mm/s the machine should be scheduled for corrective maintenance (zone C), and above 11 mm/s vibration is severe enough to cause damage (zone D).

A once-per-girth-gear-revolution modulation — usually eccentric girth-gear mounting or a high spot, sometimes a cracked gear segment joint. Time how long the beat takes; if it matches the mill shell revolution period, inspect girth-gear runout and the joint bolts at the next stop. Don't confuse it with charge slosh, which is irregular.

On the pinion bearing housings, horizontal, plus the reducer and motor bearings — as close to the bearing as possible, on stiff metal (never on covers or guards). Take horizontal, vertical and axial readings if you can; use the highest for the ISO grade and always re-measure at the same spot, load and speed.

The usual suspects are girth-gear/pinion misalignment and wear, pinion bearing defects, foundation loosening, and charge-induced impacts transmitted through the shell. A frequency spectrum tells them apart: imbalance shows at 1× running speed, misalignment at 2×, bearing defects at non-synchronous frequencies, and looseness as a raised noise floor with harmonics.

Velocity in mm/s RMS, 10–1,000 Hz. ISO 10816 zone tables are defined on broadband RMS velocity because it weights low- and high-frequency faults evenly for general machines. Acceleration (g) suits high-frequency bearing analysis and displacement (µm) suits low-speed machines, but neither maps onto these zone boundaries.