Overview
ISO 20816-3:2022 provides guidance for evaluating vibration severity on industrial machines with rated power above 15 kW and operating speeds between 120 rpm and 30,000 rpm. This standard replaces ISO 10816-3:2009.
ISO 20816-3 maintains the same zone boundaries but introduces clearer machine group definitions, updated measurement location guidance, and better alignment with ISO 20816-1 general principles.
The Four Severity Zones
Vibration severity is classified into four zones based on measured velocity (mm/s RMS):
Zone A
New machines
Zone B
Acceptable for operation
Zone C
Limited operation
Zone D
Damage may occur
Machine Groups
Machines are classified into groups based on power, foundation type, and operational characteristics:
| Group | Description | Examples |
|---|---|---|
| Group 1 | Large machines, rigid foundation (>300 kW or flexible rotor) | Large pumps, compressors, generators |
| Group 2 | Medium machines, rigid foundation (15-300 kW) | Medium motors, pumps, fans |
| Group 3 | Large machines, flexible foundation | Machines on isolators, offshore equipment |
| Group 4 | Medium machines, flexible foundation | Packaged units, skid-mounted equipment |
Zone Boundaries (mm/s RMS)
Velocity zone boundaries for broadband vibration measurement:
| Zone Boundary | Group 1 | Group 2 | Group 3 | Group 4 |
|---|---|---|---|---|
| A/B | 2.3 | 1.4 | 3.5 | 2.3 |
| B/C | 4.5 | 2.8 | 7.1 | 4.5 |
| C/D | 7.1 | 4.5 | 11.2 | 7.1 |
Zone Interpretation
| Zone | Condition | Recommended Action |
|---|---|---|
| Zone A | Excellent - New or recently overhauled machines | Continue monitoring at normal intervals |
| Zone B | Acceptable - Normal for unrestricted long-term operation | Monitor and trend; investigate significant changes |
| Zone C | Alert - Acceptable only for limited periods | Plan corrective action; increase monitoring frequency |
| Zone D | Not Acceptable - Damage may occur | Take immediate corrective action |
Measurement Requirements
Measurement Locations
- Horizontal (H): In plane of axis, toward coupling
- Vertical (V): Top of bearing housing
- Axial (A): Parallel to shaft axis
Measurement Parameters
- Velocity: mm/s RMS (primary parameter)
- Frequency range: 10 Hz to 1,000 Hz (standard)
- Averaging: RMS over measurement period
ISO 20816-3 zone boundaries apply to broadband (overall) vibration. Spectral analysis with narrowband data provides additional diagnostic value but uses different evaluation criteria.
Quick Reference Summary
| If velocity is... | Group 2 Status | Group 1 Status |
|---|---|---|
| < 1.4 mm/s | Zone A - Excellent | Zone A - Excellent |
| 1.4 - 2.8 mm/s | Zone B - Acceptable | Zone A - Excellent |
| 2.8 - 4.5 mm/s | Zone C - Alert | Zone B - Acceptable |
| 4.5 - 7.1 mm/s | Zone D - Danger | Zone C - Alert |
| > 7.1 mm/s | Zone D - Danger | Zone D - Danger |