ISO 3046-5:2001

Overview

ISO 3046-5:2001 - "Reciprocating internal combustion engines - Performance - Part 5: Torsional vibrations" defines general requirements, terminology and procedures for assessing torsional vibrations in shaft systems of sets driven by reciprocating internal combustion (RIC) engines. The standard covers land, rail-traction and marine applications (explicitly excluding many mobile and automotive/aircraft uses) and forms part of the ISO 3046 series on engine performance.

Key topics and technical requirements

• Scope & definitions: Establishes terms such as shaft system, torsional vibration amplitude, natural frequency, natural mode, resonance speed, vibration order, synthesized torsional stress and barred speed range (forbidden continuous operation).
• Calculation of torsional vibration:
  • Free vibration analysis to obtain natural frequencies and mode shapes (eigenvalues/eigenvectors).
  • Forced vibration analysis using excitation torques (Fourier/harmonic components).
  • Required input data: polar moments of inertia, torsional stiffness, excitation torque, operating speed band, damping data where applicable.
  • Typical outputs: natural frequencies, resonance speeds, torsional stresses, vibratory torques in couplings, amplitude distribution and thermal power dissipated in damping devices.
• Measurement and validation:
  • Measurement devices: eddy probes (non-contact), strain gauges, optical encoders (or agreed alternatives).
  • Measured parameters: shaft rotational velocity, engine power, torsional amplitude/strain, ambient conditions, natural frequencies/critical speed ranges, possibly firing order.
  • Reporting: measurement method, sensor positions, calibration, deviations from contract conditions and any corrections.
• Responsibilities & contractual items:
  • The set supplier (engine maker, driven-machine maker or purchaser acting as integrator) is responsible for calculations and measurements even when subcontracted.
  • Guarantee of satisfactory torsional performance may be conditional on correct installation/maintenance.
  • Supplier must address critical speed zones and corrective design actions where required.
• Normative references: ISO 2041, ISO 2710‑1 and ISO 2710‑2 are referenced for vibration and engine vocabulary.

Applications and users

ISO 3046-5 is used for:

• Design and validation of engine-generator sets, propulsion shafts, and other rotating machinery driven by RIC engines in land, rail and marine sectors.
• Torsional vibration analysis by vibration engineers, mechanical designers, test laboratories and system integrators.
• Procurement and contract specifications where suppliers must deliver torsional vibration calculations and/or measurement reports.
• Classification societies and inspection authorities assessing shaft system safety and resonance avoidance.

Related standards

• Other parts of ISO 3046 (Parts 1–7) covering power declarations, test methods, speed governing, overspeed protection and power codes.
• ISO 2041 and ISO 2710 series for vocabulary and definitions.

Keywords: torsional vibrations standard, reciprocating internal combustion engines, shaft system torsional analysis, torsional vibration measurement, resonance speed, natural frequency, synthesized torsional stress.