ISO 10816-3, now published as ISO 20816-3, is the international standard for deciding whether an industrial machine's vibration is acceptable. You measure broadband vibration on the bearing housings and compare the reading to defined severity zones. It answers the question every reliability team asks: how much vibration is too much?
Instead of analysing individual frequencies, ISO 10816-3 uses a single broadband number: the root-mean-square (RMS) vibration velocity in millimetres per second, measured over roughly 10 to 1000 Hz on the non-rotating parts of the machine. In practice that means a sensor on each bearing housing, read in the horizontal, vertical and axial directions. Velocity is used because, across normal industrial running speeds, it tracks the fatigue-causing energy in a machine better than displacement or acceleration alone.
Every reading lands in one of four zones:
The three figures that separate the zones are the A/B, B/C and C/D boundaries.
The limits depend on machine size and mounting:
The standard covers machines running between 120 and 15,000 rpm.
| Machine class | A/B | B/C | C/D |
|---|---|---|---|
| Group 2, rigid support | 1.4 | 2.8 | 4.5 |
| Group 2, flexible support | 2.3 | 4.5 | 7.1 |
| Group 1, rigid support | 2.3 | 4.5 | 7.1 |
| Group 1, flexible support | 3.5 | 7.1 | 11.0 |
So a 150 kW motor on a rigid base reading 3.0 mm/s RMS sits in Zone C: keep it running, but schedule the fix. The same reading on a large machine with a flexible support would still be in Zone B.
ISO 20816 is the current, consolidated series. It merges the older ISO 10816 (vibration on non-rotating parts) and ISO 7919 (shaft vibration) into one family, with clearer machine-group definitions and updated guidance on where to measure. The zone concept and the familiar velocity limits carry over, so a reading judged against ISO 10816-3 gives the same verdict under ISO 20816-3.
A severity zone tells you a machine is in trouble, not why. A rising broadband velocity is the trigger to look deeper with a spectrum: unbalance shows up at running speed, misalignment at twice running speed, and bearing faults at their own defect frequencies. For the two most common causes, see dynamic balancing, and how vibration compares with other techniques in thermography vs vibration analysis.
A severity chart only prevents failures if a Zone C or D reading turns into action. That is where continuous monitoring beats a quarterly route: a system that watches the trend and raises a work order the moment a machine crosses a boundary closes the gap between detecting a problem and fixing it. Fabrico reads machine condition and OEE from the line and turns a threshold breach into an automatically routed work order, so a vibration alarm becomes a completed repair rather than a note in a spreadsheet. Book a Fabrico demo to see the closed loop on your equipment, and read breakdown vs preventive maintenance for the wider picture.
It has been superseded by ISO 20816-3, but the two share the same zones and velocity limits, and ISO 10816-3 is still widely referenced in the field. A reading evaluated against either gives the same result.
On the bearing housings, as close to the bearing as practical, measuring in the horizontal, vertical and axial directions. The standard evaluates vibration on the non-rotating parts of the machine, not on the shaft.
It depends on machine size and mounting. For a medium machine on a rigid foundation, up to 2.8 mm/s RMS is acceptable for long-term operation (Zone B), 2.8 to 4.5 mm/s is Zone C, and above 4.5 mm/s is the damage zone.
Across the typical 10 to 1000 Hz industrial range, RMS velocity correlates best with the energy that fatigues a machine, which is why the standard uses it for the overall severity number. Acceleration is more useful for high-frequency bearing and gear defects, and displacement for slow-speed machines.
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