ISO 22266-1:2022 PDF

Overview

ISO 22266-1:2022 - "Mechanical vibration - Torsional vibration of rotating machinery - Part 1" - provides guidelines for assessing torsional natural frequencies and shaft/ component strength of coupled shaft trains in steam and gas turbine generator sets connected to electrical networks. The standard focuses on torsional responses at grid frequency and twice-grid frequency caused by electrical excitation of the network. It covers modelling, analytical assessment and test validation methods for shaft trains that include long elastic rotor blades, and it specifies how to treat modelling uncertainties and acceptance criteria.

Key technical topics and requirements

• Scope and limitations
  • Applies to turbine-generator sets connected to the electrical network (steam and gas).
  • Covers excitation at grid and twice-grid frequencies only; subharmonic and steam-induced excitations are not addressed.
• Shaft train modelling
  • Guidelines for modelling coupled shaft trains including elastic blade behaviour, generator rotor windings, grid/excitation representation, damping, gearboxes and flexible couplings.
  • Emphasis on quantifying modelling uncertainties and their impact on torsional natural frequencies.
• Natural frequency assessment
  • Procedures for identifying torsional modes, assessing frequency margins, and defining natural frequency acceptance criteria relative to electrical excitation.
  • Advice on when a mode is “insensitive” to electrical excitation and therefore of no practical concern.
• Stress and fatigue assessment
  • Requirements for evaluating shaft cross-sections, couplings and component strength; defines actions required if strength criteria or frequency margins are not met.
• Calculation and measurement
  • Describes available analytical assessment methods and factory/site test validation to verify calculated torsional natural frequencies.
  • Annexes provide measurement techniques (Annex A), frequency margin examples (Annex B), and common electrical faults (Annex C).
• Reports and responsibilities
  • Guidance on required calculation and measurement reports, supplier/customer responsibilities and acceptance criteria.

Practical applications and users

Who uses ISO 22266-1:

• Turbine and generator OEMs for design verification and factory testing
• Power plant engineers and commissioning teams for on-site torsional evaluations
• Condition monitoring and vibration specialists performing torsional measurements
• Consulting engineers assessing torsional risk and recommending mitigation
• Test laboratories performing torsional natural frequency validation

Typical uses:

• Design-stage verification of torsional natural frequencies and selection of safe frequency margins
• Pre-installation factory tests and on-site validation to prevent resonance with grid excitation
• Defining corrective actions when shaft strength or frequency margins are inadequate

Related standards

• ISO 20816-2 - radial/axial vibration assessment of turbine-generator sets
• ISO 2041, ISO 11086, IEC 60050-602 - terminology and vocabularies referenced in ISO 22266-1

Keywords: ISO 22266-1, torsional vibration, torsional natural frequencies, steam and gas turbine generator sets, electrical excitation, grid frequency, shaft train modelling, torsional measurement, frequency margins.