Free Engineering Tool #022
Vibration Limits — Gas Turbines
Evaluate vibration severity for gas turbines per ISO 20816-4. Supports bearing housing velocity and shaft relative displacement for industrial, aero-derivative, and small gas turbines.
Results
| Zone | Boundary | Description |
|---|
ISO 20816-4 Scope
ISO 20816-4 specifies vibration evaluation criteria for gas turbines used in power generation and mechanical drive applications. It covers industrial heavy-duty gas turbines, aero-derivative gas turbines, and small gas turbines below 3 MW.
Bearing Housing Vibration (Industrial Heavy-Duty)
Broadband vibration velocity measured on the bearing housing in mm/s RMS, frequency range 10–1000 Hz.
| Zone Boundary | Velocity (mm/s RMS) |
|---|---|
| A/B | 4.5 |
| B/C | 9.3 |
| C/D | 14.7 |
Shaft Relative Displacement (Industrial)
Shaft vibration measured with proximity probes, expressed as peak-to-peak displacement in μm. The fixed values below are simplified conservative guidance; the standard’s shaft-displacement zone boundaries are speed-dependent (decreasing with increasing shaft speed).
| Zone Boundary | Displacement (μm p-p) |
|---|---|
| A/B | 65 |
| B/C | 130 |
| C/D | 200 |
Gas Turbine Types
| Type | Power Range | Typical Speed | Characteristics |
|---|---|---|---|
| Industrial heavy-duty | >40 MW | 3000–3600 RPM | Single-shaft, journal bearings, heavy rotor |
| Aero-derivative | 20–60 MW | 3600–15000+ RPM | Multi-spool, lighter rotors, may use rolling element bearings |
| Small (<3 MW) | <3 MW | Variable | Package units, microturbines, industrial drives |
ℹ️ Note: For aero-derivative and small gas turbines, the zone boundaries shown are based on the industrial heavy-duty values as a general guideline. Manufacturer-specific limits may differ. Always consult the OEM vibration specifications for your specific machine.
⚠️ Important: Gas turbines typically have automatic vibration trip systems. Ensure that protection system setpoints are aligned with the ISO 20816-4 zone boundaries or OEM specifications. Never disable vibration protection systems.
ISO 20816-4 covers all types of gas turbines used in power generation and mechanical drive:
- Industrial heavy-duty — Large frame machines typically >40 MW (e.g., GE Frame 7/9, Siemens SGT-800/2000)
- Aero-derivative — Derived from aircraft engines, typically 20–60 MW (e.g., GE LM2500/LM6000, Rolls-Royce Trent)
- Small gas turbines — Units below 3 MW including microturbines and small industrial drives
Strictly, the ISO standard itself addresses gas-turbine sets with fluid-film bearings; applying its guideline values to aero-derivative or small units with rolling-element bearings is a simplified non-ISO extension.
Bearing housing vibration is measured with sensors (accelerometers or velocimeters) mounted on the bearing pedestal. It provides overall machine vibration in mm/s RMS and is the most common measurement for protection and monitoring.
Shaft relative displacement is measured with proximity (eddy current) probes installed inside the bearing clearance. It measures the actual shaft orbit in μm peak-to-peak and is essential for detecting rotor dynamic issues that may not be visible on the bearing housing.
Gas turbines generally have higher allowable vibration limits due to:
- Combustion-induced vibration — a source not present in steam turbines
- Higher power density and different rotor dynamics
- Operating environment factors (thermal gradients, fuel variations)
- Different bearing and support configurations
For example, bearing housing velocity Zone A/B boundary is 4.5 mm/s for gas turbines (ISO 20816-4) vs. 2.8 mm/s for steam turbines (ISO 20816-2).
Aero-derivative gas turbines have unique characteristics:
- Multi-spool design — gas generator and power turbine rotate at different speeds
- Higher speeds — gas generator may run at 8000–15000+ RPM
- Rolling element bearings — some aero-derivatives use ball/roller bearings instead of journal bearings
- Lighter rotors — more responsive to unbalance and thermal effects
The zone boundaries in this calculator apply as general guidelines; always check OEM specifications for your specific machine.
A sudden vibration increase on a gas turbine requires immediate investigation:
- Check combustion dynamics — combustor issues can cause sudden vibration spikes
- Foreign object damage (FOD) — blade loss causes immediate unbalance
- Bearing deterioration — sudden change may indicate bearing failure
- Coupling problems — misalignment or coupling component failure
- Thermal transients — rapid load changes can cause temporary rotor bowing
Most gas turbines have automatic vibration trip systems. Never override or bypass vibration protection.
The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.
Professional vibration analyzers and field balancing systems for turbomachinery. Evaluate gas turbine condition per ISO 20816-4 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.
