Centrifugal Pump Vibration Monitor (ISO 10816)

Per ISO 10816, up to 1.4 mm/s RMS is new-machine condition (zone A) and up to 2.8 mm/s is acceptable for unrestricted long-term operation (zone B). Between 2.8 and 4.5 mm/s the machine should be scheduled for corrective maintenance (zone C), and above 4.5 mm/s vibration is severe enough to cause damage (zone D).

Cavitation sounds like gravel and shows as raised broadband noise that changes when you throttle the discharge or raise suction pressure; bearing faults produce distinct repetitive frequencies that don't respond to process changes. If the reading drops when you raise suction head, it's cavitation — fix NPSH, not bearings.

On the pump bearing housing (drive end), horizontal direction — 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 impeller imbalance from erosion or fouling, coupling misalignment, cavitation, bearing wear and operating far from the best-efficiency point. 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.