What types of gas turbines does ISO 20816-4 cover?

ISO 20816-4 covers all types of gas turbines used in power generation and mechanical drive applications, including industrial heavy-duty gas turbines (typically >40 MW), aero-derivative gas turbines (typically 20–60 MW), and small gas turbines (<3 MW). It applies to both single-shaft and multi-shaft configurations. 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.

What is the difference between bearing housing and shaft measurement?

Bearing housing vibration is measured with sensors on the bearing pedestal in mm/s RMS velocity. Shaft relative displacement is measured with proximity probes inside the bearing in μm peak-to-peak. Gas turbines typically require both measurements for comprehensive evaluation, especially those with fluid-film bearings.

Why do gas turbines have higher vibration limits than steam turbines?

Gas turbines generally operate at higher speeds (up to 15,000+ RPM for aero-derivatives) and have different rotor dynamics compared to steam turbines. The combustion process also introduces additional vibration sources. The zone boundaries in ISO 20816-4 reflect these operational characteristics.

How do aero-derivative limits differ from industrial gas turbines?

Aero-derivative gas turbines typically operate at higher speeds with lighter, stiffer rotors and rolling element bearings (rather than fluid-film). They generally have tighter vibration tolerances for shaft measurements but may show different spectral characteristics due to their multi-spool design.

What action should I take when vibration increases suddenly?

A sudden increase in gas turbine vibration requires immediate investigation regardless of the absolute zone. Check for combustion dynamics issues, foreign object damage, bearing deterioration, coupling problems, or thermal transient effects. Many gas turbines have automatic trip systems that activate at Zone D levels.

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.

ISO 20816-4 Zones A/B/C/D Gas Turbines

Results

Vibration Zone

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Measured Value

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Turbine Type

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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.