ISO 10816 · Vibration · ThresholdsD — Technical & analytics

ISO 10816 Vibration Analysis — Thresholds Explained

ISO 10816 defines vibration severity by mm/s RMS across four equipment classes; exceeding Zone C means damage is already accumulating in the rotating component.

ISO 10816 (and its modern successor ISO 20816) is the canonical reference for evaluating mechanical vibration on non-reciprocating rotating machinery. Every credible vibration report in the world cites it; almost none explain it in language an asset owner can act on.

This page is the plain-English version. The threshold table is the part most people want; the consequences and action windows are below it.

Equipment class: Class I — small machines (< 15 kW)
≤ 0.71
0.71 – 1.8
1.8 – 4.5
> 4.5
Equipment class: Class II — medium (15 – 75 kW)
≤ 1.12
1.12 – 2.8
2.8 – 7.1
> 7.1
Equipment class: Class III — large rigid mount (> 75 kW)
≤ 1.8
1.8 – 4.5
4.5 – 11.2
> 11.2
Equipment class: Class IV — large flexible mount (> 75 kW)
≤ 2.8
2.8 – 7.1
7.1 – 18.0
> 18.0
01

What the four zones actually mean

  • Zone A — newly commissioned machine. Acceptable for unrestricted long-term operation.
  • Zone B — acceptable for long-term operation, but trending should be watched.
  • Zone C — unsuitable for long-term operation; the machine should be repaired at the next planned opportunity.
  • Zone D — sufficient to cause damage; immediate action required.
02

How to use the thresholds in practice

Vibration is a trend, not a snapshot. A single reading in Zone B means little; a reading that has crossed from Zone A to Zone B over six weeks means a bearing is degrading. The action is to flag it, schedule the intervention, and avoid the unplanned stop.

Novek's analytics layer does this automatically — the alert fires on the trend transition, not the absolute value.

03

ISO 10816 vs ISO 20816

ISO 20816 is the modern successor and the more accurate citation in 2026 documents. The threshold philosophy is unchanged; the structure is reorganised by machine type rather than power. Most field practice still uses 10816 by habit.

04

What gets missed without continuous vibration measurement

Walk-around vibration surveys catch faults at Zone C or D, which is too late. Continuous sensors catch them at the A → B transition. That difference is typically a planned overhaul in October vs. an emergency call-out in August.

Related insights
Frequently askedFAQ

Questions buyers actually ask.

Should I cite ISO 10816 or ISO 20816?
ISO 20816 if the document is new; ISO 10816 if you're cross-referencing existing reports. The thresholds are equivalent.
What class is a typical Dubai chilled-water pump?
Most secondary chilled-water pumps are Class II (15–75 kW). Primary pumps and chiller-shaft motors are usually Class III.
How often should vibration be measured?
Continuous monitoring at 5-minute cadence is the modern standard. Walk-around surveys at quarterly intervals miss most degradation cycles.
What causes vibration to rise?
Bearing wear, misalignment, imbalance, looseness, cavitation, electrical faults in the motor. Each has a distinct frequency signature visible in spectrum analysis.
Is mm/s RMS the only metric?
It is the canonical severity metric. Peak acceleration (g) and spectrum-band energy are used for diagnosis once severity has flagged a machine for review.

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