Diesel Generator Set Vibration Monitor

Per ISO 10816, up to 2.3 mm/s RMS is new-machine condition (zone A) and up to 4.5 mm/s is acceptable for unrestricted long-term operation (zone B). Between 4.5 and 7.1 mm/s the machine should be scheduled for corrective maintenance (zone C), and above 7.1 mm/s vibration is severe enough to cause damage (zone D).

A lot. The mounts share a tuned load; one collapsed mount shifts the set's natural frequency and can put the whole frame into resonance at running speed, doubling vibration everywhere and hammering the radiator and exhaust bellows. Inspect mount heights with a ruler — a sagged mount sits visibly lower — and replace them in full sets.

On the alternator drive-end bearing and the engine block at the mounts (compare both) — 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 engine misfire or injector imbalance, failed anti-vibration mounts, coupling/flex-plate wear, alternator bearing wear and crankshaft torsional issues. 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.