Overview
ISO 23048:2018 - Ships and marine technology - Verification method for portable power measurement using a strain gauge - specifies a laboratory procedure to verify portable shaft power measurement equipment that uses strain gauges. The verified portable equipment can be used on merchant ships for shaft power and engine performance assessment. The standard describes the verification system composition (torque generator, RPM generator, torque sensor), installation guidelines, test procedure, and reporting requirements.
Key Topics and Technical Requirements
- Verification equipment composition: torque arm, weight surface plate, torque arm axis, shaft, torque sensor (or verified permanent torque sensor/strain gauges) and an RPM generator.
- Torque generation: Real torque is produced by calibrated weights on a torque arm of known length; shaft material properties must be stated in the test report (see ISO 15016 reference).
- RPM generation and control: an RPM generator (0–1 000 RPM capability implied) and a tacho sensor are used to supply and measure precise RPM. RPM error rates must be recorded and measured at least five times per test condition. Calibration by an ISO/IEC 17025 facility is recommended.
- Strain gauge measurement principle: strain gauges detect shaft distortion via resistance change (usually measured with a Wheatstone bridge). Shaft distortion combined with RPM yields shaft power (kW).
- Installation and performance requirements (Annex A): strain gauge attachment on the intermediate shaft (not on flange or bearing), surface preparation (cleaning, degreasing), temperature control during bonding, angular alignment within ±1.5°, and integrity checks (E output ≤ ±0.5 mV/V with engine stopped).
- Test procedure and reporting: install the portable shaft power meter, verify strain gauge attachment, apply calibrated weights to generate torque, compare outputs between the verification equipment and the portable meter, record torque and RPM error rates, and prepare the verification test report per Annex C.
Practical Applications and Users
- Use cases:
- Pre-sea trial verification of portable shaft power meters.
- Calibration checks for on-board portable instrumentation used during speed and power trials.
- Quality control for manufacturers of portable strain-gauge-based shaft power meters.
- Typical users:
- Marine surveyors, shipbuilders, and ship operators conducting speed/power trials.
- Testing and calibration laboratories (including ISO/IEC 17025 labs).
- Naval architects, marine engineers, and equipment manufacturers.
- Classification societies and purchasers specifying verification before use on merchant ships.
Related Standards
- ISO 15016:2015 - Guidelines for assessment of speed and power performance by analysis of speed trial data (referenced in ISO 23048:2018).
- ISO/IEC 17025 - Laboratory competence for calibration of RPM and other verification instruments (recommended for RPM generator calibration).
Keywords: ISO 23048:2018, strain gauge, portable power measurement, shaft power meter verification, torque generator, RPM generator, ships and marine technology.