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.