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.
Results
| 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 |
If the machine is on a flexible (soft) support, the next-higher published boundary set applies: Group 1 or 3 flexible → 3.5 / 7.1 / 11.0 mm/s, Group 2 flexible → 2.3 / 4.5 / 7.1 mm/s (values from the former ISO 10816-3 support-class tables). The calculator applies these when the flexible foundation option is selected.
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.
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.
Professional field balancing instruments and vibration analyzers for industrial machines. Evaluate condition per ISO 20816-3 on-site. Used in 50+ countries.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
