Hydraulic Power Unit Vibration Checker

Per ISO 10816, up to 1.12 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 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).

Probably not. Wrong viscosity raises pulsation and can cavitate the pump at cold start; under-filled reservoirs or disturbed suction plumbing pull air. Verify oil grade against the pump spec, check suction strainer and clamp tightness, bleed the system, and let it reach operating temperature before re-measuring.

On the pump casing and the motor DE bearing on the HPU — 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 pump cavitation/aeration, worn pump internals (pistons, vanes), coupling misalignment inside the bellhousing, and pressure-pulsation resonance in piping. 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.