ISO 20283-4:2012

Overview

ISO 20283-4:2012 - Mechanical vibration - Measurement of vibration on ships - Part 4 provides practical guidance for instrumentation, measurement and evaluation of vibration of ship propulsion machinery. It focuses on repetitive (steady‑state or quasi‑stationary) mechanical vibration of main propulsion plants during sea trials, and is applicable to diesel, turbine and electrically driven propulsion systems. The part is intended to produce reliable vibration data compatible with classification society requirements and IACS unified requirements (e.g., UR M68) when evaluating torsional and other vibration effects.

Key topics and technical requirements

• Instrumentation and accuracy
  • Use transducers, signal conditioning and data storage suitable for the required frequency range; measurement accuracy of ±10% is recommended.
  • The full transfer function of the measuring chain must be known and validated.
  • Phase reference markers (e.g., engine TDC or propeller phase) are recommended for phase measurements.
• Frequency guidance
  • General linear vibration upper limit: 1 000 Hz (typical).
  • Strain‑gauge/torque on rotating parts: ~100 Hz for low‑speed two‑stroke engines and ~400 Hz for four‑stroke engines (upper frequency should cover max speed × number of cylinders).
• Test conditions
  • Ship loading close to contracted operating condition (ballasted sea‑trial condition with submerged propeller).
  • Water depth ≥ 5× ship draught (exceptions agreed and reported).
  • Rudder adjustment ±2° for free‑route tests; specified maximum sea states (small craft SS1, small ships <100 m SS2, large ships ≥100 m SS3).
• Test procedures
  • Steady‑state data by speed steps (guidance: ~5% intervals) or slow run‑up/run‑down.
  • Recommended run‑up rates: direct‑coupled two‑stroke: <2% nominal speed/min (~30 min); medium/high‑speed four‑stroke: <15% nominal speed/min (~10 min).
  • Simultaneous multi‑channel storage or phase recording for comparative evaluation of torsional, bending, axial vibrations.
• Data processing and measurement descriptors
  • Use r.m.s., peak and peak‑to‑peak metrics; FFT spectral techniques and windowing considerations are referenced.
• Scope limits
  • Emphasis on steady/quasi‑steady vibration; not intended for very fast transients or shock signals.

Applications

• Sea‑trial vibration acceptance and verification of propulsion systems
• Torsional vibration assessments to meet classification society rules (IACS UR M68)
• Performance monitoring, troubleshooting abnormal vibration, and post‑repair verification
• Measurements on shaft lines, gearboxes, clutches and propulsors (including special guidance for azimuth drives and Voith‑Schneider units in annexes)

Who should use this standard

• Shipyards and builders performing sea trials
• Marine engineers and vibration analysts
• Classification societies and surveyors
• OEMs of engines, gearboxes, propulsors and monitoring equipment

Related standards

• ISO 2041:2009 (vibration vocabulary)
• Other parts of ISO 20283 (structural vibration, pre‑installation measurement, and planned general guidelines)

Keywords: ISO 20283-4, mechanical vibration, ship propulsion machinery, vibration measurement, sea trials, torsional vibration, strain gauges, FFT, vibration severity, IACS UR M68.