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Vibration severity (ISO 20816)

Choose the machine class, enter the reading and history and see the severity zone, suggested alarm and trip limits, and how many days the current trend takes to reach the alarm.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

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Machine
Measurement

Converting between displacement, velocity and acceleration holds for a single frequency; broadband spectra require measuring velocity directly.

Trend history
See what was read
—Severity zone
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Measurement against the standard’s zones

Zones A, B, C and D for the selected class; the line marks the measured value converted to RMS velocity.

Tap the chart to see the values.

Trend and projection

History readings, a line fitted to the last six and a projection to alarm and zone D.

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Method, assumptions and references

Equations used

Single frequency f: v_RMS = a_RMS ÷ (2πf); d_pp = 2√2 · v_RMS ÷ (2πf)
Zone: A if v ≤ A/B; B if v ≤ B/C; C if v ≤ C/D; D above
Alarm = min(baseline + 0.25 × B/C boundary; 1.25 × B/C boundary); trip = 1.25 × C/D boundary
Trend: least-squares line through the last six readings; days to alarm = (alarm − last reading) ÷ slope

Assumptions and limits

  • Zone limits from ISO 20816-3:2022 (industrial machines 15 kW to 40 MW, 120 to 30,000 rpm) and ISO 10816-1:1995 Annex B; measurements on bearing housings.
  • Centrifugal pumps have their own limits in ISO 10816-7; turbines, reciprocating compressors and gearboxes have specific parts in the series.
  • The projection is linear; bearing defects tend to accelerate near the end of life, so treat the time as an upper bound.

Standards and technical documents

  • ISO 20816-1:2016: Mechanical vibration — Measurement and evaluation of machine vibration — Part 1: General guidelines
  • ISO 20816-3:2022: Industrial machines with power rating above 15 kW and operating speeds between 120 r/min and 30 000 r/min
  • ISO 10816-1:1995: Evaluation of machine vibration by measurements on non-rotating parts — General guidelines
  • ISO 10816-7:2009: Rotodynamic pumps for industrial applications
  • ISO 13373-1:2002: Condition monitoring and diagnostics of machines — Vibration condition monitoring

U.S. regulations

  • There is no legal vibration limit for machines; ISO 20816 is the technical reference used in contracts and predictive programs
  • OSHA 29 CFR 1910.147: lockout/tagout before corrective work
  • Occupational vibration on people is covered by ANSI S2.70 and ISO 2631, not by this machine evaluation

Frequently asked questions

What is the vibration limit for an electric motor?

For 15 to 300 kW motors on rigid supports (ISO 20816-3, group 2), up to 0.055 in/s (1.4 mm/s) RMS is zone A, up to 0.11 in/s (2.8 mm/s) is acceptable for long-term operation, 0.11 to 0.18 in/s (4.5 mm/s) calls for planned correction and above that is severe.

What is the difference between ISO 10816 and ISO 20816?

ISO 20816 is gradually replacing the ISO 10816 and ISO 7919 series, merging housing and shaft measurements. The part 3 limits for industrial machines stayed practically the same.

How should the vibration alarm be set?

ISO 20816 suggests starting from the baseline of the machine in good condition and adding 25% of the B/C boundary, without exceeding 1.25 times that boundary. The trip is usually up to 1.25 times the C/D boundary.