What machines does ISO 20816-3 cover?

ISO 20816-3 covers industrial machines with power ratings from 15 kW to 50 MW, including electric motors, generators, pumps, compressors, fans, and blowers. It replaces the former ISO 10816-3 standard.

How do I determine the machine group?

Group 1: Large machines >300 kW on rigid foundations. Group 2: Medium machines 15–300 kW on rigid foundations. Group 3: Pumps (multistage, vertical, submersible). Group 4: Large machines >300 kW on flexible (soft) foundations. The foundation type is as important as the power rating.

What is the difference between rigid and flexible support?

Rigid support means the machine foundation natural frequency is well above the operating speed (typically concrete block or heavy steel baseplate). Flexible support means the foundation natural frequency is below or near the operating speed (such as steel frame structures, offshore platforms, or elevated floors). Flexible supports generally result in higher vibration levels, so the zone limits are more relaxed.

What velocity measurement is used?

Vibration velocity in mm/s RMS (root mean square), measured on the bearing housing in the frequency range 10–1000 Hz. Broadband RMS velocity is the standard parameter for evaluating industrial machine condition per ISO 20816-3.

How does ISO 20816-3 differ from ISO 10816-3?

ISO 20816-3 replaces ISO 10816-3 with essentially the same zone boundaries and machine group definitions. The main changes are editorial updates, alignment with the ISO 20816 series structure, and additional guidance on evaluation methodology. Zone limits remain unchanged.

Free Engineering Tool #021

Vibration Limits — Industrial Machines 15 kW–50 MW

Evaluate vibration severity for industrial rotating machines per ISO 20816-3. Select machine group, support type, enter measured velocity, and get the zone classification.

ISO 20816-3 Zones A/B/C/D 15 kW – 50 MW

Machine Group

Support Type

Measured Velocity (mm/s RMS)

Quick presets

Results

Vibration Zone

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Measured Velocity

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Recommendation

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Zone	Boundary (mm/s RMS)	Description

ISO 20816-3 Scope

ISO 20816-3 provides vibration evaluation criteria for industrial machines with power ratings from 15 kW to 50 MW, operating at speeds between 120 and 15,000 RPM. This is the most widely used standard for evaluating industrial rotating equipment including:

Electric motors and generators
Centrifugal and axial pumps
Compressors (centrifugal, axial, screw)
Fans and blowers
Gearboxes (input/output shafts)

Zone Boundaries by Machine Group

Zone boundaries depend on the machine group, which combines power rating and foundation type:

Zone Boundary	Group 1 Large rigid	Group 2 Medium rigid	Group 3 Pumps	Group 4 Large flexible
A/B	2.3 mm/s	1.4 mm/s	2.3 mm/s	3.5 mm/s
B/C	4.5 mm/s	2.8 mm/s	4.5 mm/s	7.1 mm/s
C/D	7.1 mm/s	4.5 mm/s	7.1 mm/s	11.0 mm/s

Measurement Requirements

Vibration velocity is measured in mm/s RMS on the bearing housing in two radial directions (horizontal and vertical) and optionally in the axial direction. The highest reading governs the zone evaluation.

Example — Centrifugal Pump 55 kW

Given: Group 3 (pump), measured velocity = 3.2 mm/s RMS

Zone boundaries for Group 3: A/B = 2.3, B/C = 4.5, C/D = 7.1 mm/s

3.2 mm/s is between 2.3 and 4.5 → Zone B — acceptable for long-term operation

⚠️ Important: Always consider vibration trending in addition to absolute levels. A significant increase (e.g., doubling) from baseline may warrant investigation even if the absolute level is within Zone A or B.

ISO 20816-3 Vibration Limits — Machines 15kW–50MW | Vibromera

Published by Nikolai Shelkovenko on February 15, 2026 March 5, 2026

Results

ISO 20816-3 Scope

Zone Boundaries by Machine Group

Measurement Requirements