Free Engineering Tool #020
Vibration Limits — Steam Turbines & Generators >40 MW
Evaluate vibration severity for steam turbines and generators per ISO 20816-2. Supports bearing housing velocity and shaft relative displacement measurements.
Results
| Zone | Boundary | Description |
|---|
ISO 20816-2 Scope
ISO 20816-2 specifies vibration evaluation criteria for steam turbines and generators exceeding 40 MW output, operating at speeds between 1500 and 3600 RPM (50/60 Hz power generation). It covers both bearing housing vibration and shaft relative vibration.
Bearing Housing Vibration
Broadband vibration velocity is measured on the bearing housing (pedestal) in mm/s RMS, typically in the frequency range 10–1000 Hz. The boundary values below correspond to the published table column for shaft speeds of 1500 r/min and 1800 r/min; for 3000–3600 r/min machines the published boundaries are higher (A/B 3.8, B/C 7.5, C/D 11.8 mm/s RMS), so this simplified single table is conservative for 2-pole machines.
| Zone Boundary | Velocity (mm/s RMS) |
|---|---|
| A/B | 2.8 |
| B/C | 5.3 |
| C/D | 8.5 |
Shaft Relative Displacement
Shaft vibration is measured with proximity probes, expressed as peak-to-peak displacement in μm. These values are simplified for general application.
| Zone Boundary | Displacement (μm p-p) |
|---|---|
| A/B | 50 |
| B/C | 100 |
| C/D | 165 |
ℹ️ Note: Shaft displacement limits may vary with operating speed. The values above are simplified for general use. For exact speed-dependent limits, consult the full ISO 20816-2 standard.
⚠️ Important: Both bearing housing and shaft vibration should be monitored. A machine may show low bearing housing vibration but high shaft vibration, or vice versa. The worse of the two assessments governs the overall evaluation.
Professional vibration analyzers and field balancing systems for turbomachinery. ISO 20816 compliant evaluation on-site. Used in 50+ countries.
