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ROTEC MARINE ENGINEERING
Measurement for marine propulsion systems
Torsional vibration, shaft power and machinery vibration: ROTEC combines independent measurement with vessel-specific analysis for newbuilds, retrofits and the investigation of operating concerns.
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Three measurement tasks. One coordinated approach.
Torsional vibration measurement
Investigate rotational motion, angle and phase behaviour at agreed locations, such as the engine, vibration damper and shaftline. Speed and load conditions, including any required transitions, are defined in advance. Measured quantities and the assumptions used for calculations remain distinguishable.
Shaft power measurement
Measure transmitted torque using strain gauges and combine it with rotational speed to determine shaft power. The measurement location, shaft data, calibration and measurement uncertainty are part of the plan: strain measurement alone does not determine power.
Vibration and noise analysis
Investigate broadband vibration on engines, gearboxes and generators. Structure-borne and airborne noise can complement the campaign. The appropriate quantities and assessment criteria depend on the machinery, its installation and the question being investigated.
Where measurement supports decisions
Newbuild and commissioning
Agree the measurement scope and required evidence with the yard, operator and relevant specialists. Measurement data can support technical assessment; they are not equivalent to independent class approval.
Retrofit and repowering
Changes to engines, gearboxes, couplings or shaftline configurations change the combination under investigation. Existing calculations and the new operating conditions inform an appropriate measurement plan.
Existing fleet and fault investigation
Investigate concerns under defined operating conditions, such as speed-dependent vibration, a barred-speed-range question or behaviour following a damage event.
From the measurement question to a traceable report
The Marine Engineering flyer connects scope, instrumentation, measurement, assessment and reporting. Torsional vibration, shaft power, vibration analysis and alignment questions can be planned together. The actual scope is agreed before the campaign.
Define the task and constraints
Establish the propulsion layout, reason for the investigation and required decision. Review available calculations, manufacturer information and project-specific class requirements; agree measurement locations, access, safety arrangements and the time window.
Instrument and measure
Select sensors and the measurement chain for the agreed quantities. Record operating conditions and relevant constraints. Measurements follow the agreed test plan and remain within the approved operating limits.
Assess and report
Relate results to the operating conditions and agreed criteria. Define the report scope in advance: measurement set-up, analysis methods, relevant plots, assessment, limitations and next steps. Any required approval remains with the responsible authority.
Measurement, assessment and monitoring: key questions
Is torsional vibration the same as machinery vibration?
No. Torsional vibration concerns variations in rotational motion; casing or radial shaft vibration concerns other directions of movement. ISO 20816-1:2016 expressly excludes torsional vibration. The measurement method and assessment basis therefore need to be selected separately for each question.
What is the role of IACS UR M68?
IACS UR M68 Rev.3 (2021) addresses dimensions and permissible torsional vibration stresses for traditional forged propulsion shafts, such as intermediate and propeller shafts. It does not cover every drivetrain component. Rev.3 is intended for ships contracted for construction from 1 July 2022. Applicable class rules and project requirements govern the assessment; a ROTEC measurement does not replace class approval.
What matters when investigating a barred speed range?
A barred speed range (BSR) is not an ordinary steady-state test point. Existing calculations, approved limits and the transitions to be recorded are agreed with the responsible parties. Depending on the question, the speed trace and passage time may matter alongside vibration amplitudes. This does not replace the vessel’s operating instructions or approvals.
Is shaft power measurement a complete speed and power trial?
No. ISO 15016:2025 covers the preparation, execution and evaluation of speed trials for displacement ships with a length between perpendiculars of 50 to 500 metres. Additional trial and environmental data, and their evaluation, are required. A torque and speed measurement alone does not demonstrate conformity of the complete trial.
Is ISO 6954 still the current reference for habitability vibration?
ISO 6954:2000 has been replaced by ISO 20283-5:2016. This addresses vibration affecting habitability on passenger and merchant ships with intended voyages of at least 24 hours and was confirmed in 2026. Its subject is different from torsional vibration or shaft strength. The assessment basis agreed for your project is checked in advance.
How does engine health monitoring differ from a measurement campaign?
A campaign answers defined questions over an agreed period. The ROTEC monitoring flyer instead describes analysing high-resolution speed signals for changes in combustion regularity in marine diesel engines. Suitability for your engine depends on the sensor arrangement, operating conditions and validation. This is not a general prediction of every engine failure or a replacement for existing protection systems.
Does the time advantage in the monitoring flyer apply to every engine?
No. The approximately one-minute figure relates to a reported proof of concept: fuel cut-off at cylinder 1 at 20 per cent load. It does not establish a general alarm time for other engines, load points or fault types. Detection, alarm handling and integration need to be checked for the intended application.
What information helps us plan the work?
Please provide the vessel type and operating profile, propulsion layout, engine and gearbox details, shaft drawings, available torsional vibration calculations, speed and load ranges, and the specific concern. Include measurement locations and access, proposed modifications, classification, location and time window. Also identify the required outputs and any reporting requirements.
What question should your next campaign answer?
Newbuild, repowering, unusual vibration or a monitoring concept: share the key details. Together we can define the measurement scope, prerequisites and required documentation.
Discuss your measurement campaign