Overview
ISO 20673:2022 - "Ships and marine technology - Electric rudder angle indicators" - defines construction, performance requirements, testing methods and required test results for electric rudder angle indicators used to meet Clause 2.5.4, Regulation 19, Chapter V of SOLAS 1974. This second edition (2022) updates the 2007 version and aligns the indicator requirements with relevant IMO resolutions and IEC guidance. Where ISO 20673 differs from IEC 60945, ISO 20673 takes precedence.
Key topics and technical requirements
- System scope: Covers the complete indicator system (transmitter and receiver/indicator), including earthing, robustness and maintenance access.
- Indicator types: Requires an analogue-type indicator; a digital display may be fitted in addition. Display presentation must comply with IEC 62288 where applicable.
- Mechanical/transmitter design: Transmitters must be driven from the rudder head (lever, belt or similar), adjustable and resistant to vibration at pivot points.
- Scale and graduation: Maximum indicated angle must be equal port/starboard and not less than 40°. Graduations generally ≥ 1°; wide-angle indicators (≥ 70°) may use 2° graduations with longer marks every 10°.
- Calibration accuracy: Difference between transmitter shaft angle and indicator reading must be within 1.5% of full scale; conversion resolution minimum 0.1°.
- Damping efficiency: Indicator pointer must reset to the correct position within 5 s when power is applied from an offset position.
- Power supply resilience: Must maintain performance under specified voltage/frequency fluctuations (settled and transient conditions) and repeated power makings/breakings.
- Alerts and interfaces: If alerting is provided, compliance with IMO/IEC alert standards (IEC 62923-1/2, MSC.302(87)) is required; digital interfaces must meet IEC 61162 series as applicable.
- Testing & environment: Environmental tests per IEC 60945; insulation/high-voltage testing may apply IEC 60092-504.
- Marking & documentation: Manufacturer ID, model/type, serial number and compass safe distance marking required; user documentation must support operation and maintenance.
Applications and users
ISO 20673:2022 is used by:
- Marine equipment manufacturers for product design, type testing and certification.
- Shipyards and system integrators during installation and bridge equipment integration.
- Ship operators, marine surveyors and classification societies for compliance checks with SOLAS and IMO resolutions.
- Test laboratories executing calibration, damping, environmental and power fluctuation tests.
Use cases include newbuild bridge outfitting, retrofit of rudder indicators, procurement specifications and conformity assessment.
Related standards
- IEC 60945 (general marine equipment testing) - note ISO 20673 precedence where different
- IEC 62288 (display presentation)
- IEC 61162-1 / -2 / -450 (digital interfaces)
- IEC 62923-1 / -2 (bridge alerts)
- IEC 60092-504 (insulation/high voltage guidance)
- IMO Resolution A.694(17), MSC.302(87), SOLAS Reg. 19 (Chapter V)
