What are the ISO 10816 machine classes?

ISO 10816-3 defines four machine groups: Class I (small machines up to 15 kW), Class II (medium machines 15-75 kW or up to 300 kW on special foundations), Class III (large machines on rigid foundations >300 kW), Class IV (large machines on flexible foundations, e.g. turbogenerators).

What do zones A, B, C, D mean?

Zone A: New or reconditioned machines. Zone B: Acceptable for long-term operation. Zone C: Not suitable for long-term continuous operation — take corrective action. Zone D: Dangerous — damage could occur, shut down immediately.

Free Engineering Tool

Vibration Severity Chart

Interactive ISO 10816 / 20816 vibration severity chart. Enter measured velocity and machine class to evaluate zone A/B/C/D instantly.

ISO 10816-3 ISO 20816-1 Zones A–D

Evaluation

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Velocity (mm/s RMS)	Class I ≤15 kW	Class II 15–75 kW	Class III >300 kW rigid	Class IV >300 kW flex

ISO 10816 / 20816 Overview

ISO 10816 (now superseded by ISO 20816) classifies vibration severity based on broadband velocity in mm/s RMS, measured on the bearing housing of rotating machines. The standard defines four evaluation zones:

Zone A — Vibration of newly commissioned or reconditioned machines
Zone B — Acceptable for unrestricted long-term operation
Zone C — Not suitable for long-term continuous operation; remedial action required
Zone D — Dangerous vibration levels; damage could occur; immediate action needed

Machine Classes

Class	Description	Examples
I	Small machines ≤15 kW	Small pumps, fans, electric motors
II	Medium machines 15–75 kW (or ≤300 kW on special foundations)	Medium motors, pumps, generators
III	Large machines >300 kW on rigid/heavy foundations	Large motors, centrifugal compressors
IV	Large machines >300 kW on flexible/lightweight foundations	Turbogenerators, gas turbines, large fans

Zone Boundary Values (mm/s RMS)

Boundary	Class I	Class II	Class III	Class IV
A/B	0.71	1.12	1.80	2.80
B/C	1.80	2.80	4.50	7.10
C/D	4.50	7.10	11.2	18.0

ℹ️ Note: These values are from ISO 10816-3 for general industrial machinery. Specific machine types (e.g., reciprocating machines, hydraulic machines) have their own sub-parts with different limits. ISO 20816-1 provides the general framework.

⚠️ Important: Velocity is measured as broadband RMS in the 10–1000 Hz range. Peak velocity or narrowband readings should not be directly compared with these limits.

Vibration Severity Chart | ISO 10816 / 20816 Quick Reference

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Evaluation

ISO 10816 / 20816 Overview

Machine Classes

Zone Boundary Values (mm/s RMS)