1. Current status: ISO 6954 is withdrawn
ISO lists ISO 6954:2000 as withdrawn and identifies ISO 20283-5:2016 as the new version. ISO 20283-5 remains published and is currently under systematic review. The 2016 edition cancelled and technically revised ISO 6954, but publication status does not automatically amend a signed building specification, class notation or acceptance agreement.
2. Understand what ISO 20283-5 covers—and what it does not
The ISO abstract describes habitability guidance for all persons onboard passenger and merchant ships, especially crew. It applies to normally occupied spaces on vessels with intended voyages of 24 hours or more and uses overall frequency-weighted r.m.s. vibration over 1 Hz to 80 Hz. The purchased standard and agreed project documents remain the controlling source for the detailed procedure and guideline values.
| Technical question | Strongest starting reference | Boundary |
|---|---|---|
| Are cabins, offices, mess rooms or passenger spaces acceptable for habitability? | ISO 20283-5:2016 and the agreed contract/class basis. | Habitability evaluation is not a machinery health diagnosis. |
| Is low-frequency motion contributing to motion sickness? | ISO 2631-1, as identified by ISO 20283-5. | Do not force very-low-frequency ship motion into the 1–80 Hz habitability result. |
| Is the global or local structure responding excessively? | Structural diagnostics and, where applicable, ISO 20283-2. | ISO 20283-2 primarily addresses propulsion-excited structural vibration; it is not a universal fatigue criterion. |
| Is an engine, generator, pump or fan faulty? | Machinery vibration analysis under equipment-appropriate methods and criteria. | A cabin peak can be a response to remote forcing, not proof of the machinery fault. |
3. Choose habitability, structural or combined measurement
| Observed problem | Primary canonical service | Evidence needed |
|---|---|---|
| Crew report that cabins are shaking, sleep is disturbed or occupied spaces feel uncomfortable. | Whole-body and habitability vibration survey. | Three-axis occupied-space measurements, frequency weighting, location/posture context and controlled operating states. |
| A deck, bulkhead, foundation, superstructure or hull area responds strongly at one RPM. | Structural and hull vibration survey. | Speed/order reference, simultaneous response mapping, direction, phase or operational-deflection evidence and structural context. |
| The human complaint and structural response occur together. | Combined attendance with separate conclusions. | Common operating log and reference channels, but distinct habitability and structural evaluation paths. |
| A particular machine is vibrating abnormally. | Marine machinery vibration analysis. | Bearing/casing points, speed, load, waveform, spectrum and equipment-specific evidence. |
4. Freeze the vessel operating-condition matrix
A result is only comparable when the vessel state is traceable. Before harbour trial, sea trial, commissioning, pre-delivery acceptance or in-service troubleshooting, agree the draught and loading condition, water depth, sea state, heading, vessel speed, shaft and engine RPM, propeller configuration, thruster state, generator and major auxiliary combinations, HVAC/cargo loads, location occupancy and measurement duration.
- Use steady operating plateaus long enough for the agreed method and stable observation.
- For a narrow RPM complaint, add controlled run-up/run-down or stepped-speed evidence without substituting it for required acceptance plateaus.
- Synchronise bridge and machinery logs with every vibration channel.
- Record deviations, transients, slamming, manoeuvres and unrelated impacts rather than averaging them invisibly.
5. Build a reproducible measurement chain
- Identify accelerometers, signal conditioner/data acquisition system, serial numbers, calibration status and field checks.
- Record sensor location, axis, mounting method, surface and orientation; a loose handheld placement is not equivalent to controlled mounting.
- Use the frequency range, weighting, r.m.s. processing and integration interval required by the agreed basis.
- Capture unweighted time histories and spectra where permitted so a high weighted result can be investigated rather than merely reported.
- Include reference locations or speed/order channels when structural or machinery forcing must be separated from the occupied-space response.
- Document uncertainty, noise floor, overloads, clipped data, inaccessible spaces and any condition that prevents a valid comparison.
6. Evaluate the right metric against the right space
Do not compare a single unweighted peak, a machinery velocity reading or a smartphone output directly with ISO habitability guideline values. The evaluation must use the defined frequency-weighted r.m.s. quantity, axis treatment, location category and operating condition from the controlling standard and project basis. Preserve the spectrum and time history because two spaces with similar overall values can have different dominant frequencies, sources and corrective options.
Guideline values, contractual limits and class-notation criteria are not automatically interchangeable. State whether the conclusion is informational, contractual acceptance, notation-related or diagnostic.
7. Diagnose why a cabin shakes at one RPM
A narrow response peak occurs when excitation from propeller orders, engine firing, shaftline, gears, fans, pumps or other rotating equipment approaches a structural natural frequency. That correlation supports a resonance hypothesis but does not prove the source. Compare speed/order tracking, directions, adjacent decks, foundations and candidate machines; change one operating variable at a time where safe and permitted.
| Pattern | Focused confirmation | Possible decision route |
|---|---|---|
| Sharp peak over a narrow speed band across several cabins | Speed sweep, tachometer/order reference and structural response map. | Identify forcing order and responsive structure before stiffness, mass, damping or operational restrictions are considered. |
| One panel or deckhead rattles while surrounding spaces remain moderate | Local mapping, attachment/boundary inspection and simultaneous reference. | Local repair may address a receiver without correcting the original forcing source. |
| Response changes with generator or pump selection at constant propulsion state | Controlled machine on/off or load comparison, bearing/foundation measurements. | Proceed to machinery/foundation diagnosis with supporting evidence. |
| High response occurs only in rough weather or slamming | Separate transient-event records from steady-state propulsion evidence. | ISO 20283-2 excludes transient ship vibration such as slamming; agree a separate investigation basis. |
8. Produce an acceptance- and diagnosis-ready report
- Vessel identity, project purpose, standard/edition, contract and recipient.
- Spaces, measurement points, axes, photographs and controlled drawings.
- Instrument chain, calibration evidence, mounting and processing settings.
- Draught, water, weather, speed, RPM and machinery operating matrix.
- Frequency-weighted results with the applicable space and criterion category.
- Spectra, time histories, orders and response maps used for diagnosis.
- Deviations, uncertainty, excluded events and limitations.
- Pass/fail or comparison statement only against the explicitly agreed basis.
- Confirmed findings, hypotheses, corrective priorities and exact retest conditions.
9. Class, flag and supplier context
ABS, BV, CCS, CRS, DNV, IRS, KR, LR, ClassNK, PRS, RINA and Türk Loydu may apply society rules, optional habitability notations or project-specific review requirements. Singapore, Panama, Liberia, Marshall Islands, Bahamas, Malta, Cyprus, Hong Kong and Isle of Man flag requirements must be checked where relevant. Acceptance depends on the contract, vessel type, notation, flag and attending surveyor. IACS does not approve service companies, and Vessel Doctor is not presented here as approved, recognised or appointed by any class or flag.
Authoritative references
- ISO 20283-5:2016 — ship vibration measurement, evaluation and reporting with regard to habitability.
- ISO 6954:2000 — withdrawn legacy edition, with ISO 20283-5 identified as the new version.
- ISO 20283-2:2008 — measurement and diagnostic evaluation of ship structural vibration.
- ISO 2631-1:1997 — general evaluation of human exposure to whole-body vibration; a replacement draft is under development, so confirm current status before use.
10. What to send before attendance
Send the vessel/IMO number, vessel type and voyage profile, class and flag where relevant, affected spaces, crew complaint, speed/RPM band, loading and operating condition, machinery/propeller details, recent retrofit or repair, drawings, previous data, contract/standard clause, witness requirements, port or shipyard, trial window and reporting deadline. Attendance can be assessed in Singapore, Malaysia, India, Sri Lanka, Indonesia, Thailand, the Philippines, the Middle East, Asia-Pacific and worldwide, subject to access and availability.