Marine generator commissioning is the structured project workflow that takes a genset from Factory Acceptance Test inside the OEM's facility through documentation handover, onboard installation verification, dock trials, and the sea or shipboard trial — confirming that the installed unit matches its approved configuration and performs as required by the project specification. Many readily available commissioning checklists cover generic land-based generator commissioning; this guide is written from a marine generator manufacturer's perspective as a class-informed commissioning framework applicable across the major IACS-member societies (ABS, DNV, Lloyd's Register, Bureau Veritas, CCS), with the understanding that the specific rule numbers, witness scope, and certificate names vary by class and project scheme.
Table of Contents
- What Commissioning Covers — 5 Stages
- Factory Acceptance Test (FAT) Checklist
- Pre-Shipment Documentation Checklist
- Onboard Installation Verification Checklist
- Dock Trial Checklist
- Sea or Shipboard Trial Acceptance Checklist
- Common Acceptance Failures — and How to Avoid Them
- Frequently Asked Questions
Quick Answer
Marine generator commissioning is a five-stage project workflow: Factory Acceptance Test (FAT) at the OEM, pre-shipment documentation package, onboard installation verification, dock trials at quayside, and the sea or shipboard trial. Class attendance at each stage depends on the applicable class rules, the certification scheme, the approved inspection and test plan, and the project specification — sea or shipboard trials are normally attended where required for vessel classification. The surveyor records satisfactory completion of the applicable machinery and electrical trials as part of the vessel's overall class certification process; for engines subject to MARPOL Annex VI Regulation 13, the EIAPP certificate is normally issued following engine pre-certification, while onboard verification confirms continued conformity with the approved NOx Technical File. Common issues observed in projects include incomplete documentation, sizing margin failures under transient load, and pre-existing combustion deposits from low-load FAT runs — all of which can be reduced with a structured checklist.
All checks in this guide are typical industry observations. Specific requirements vary by class society, flag state, vessel type, and current MARPOL Annex VI amendments. Always confirm against the latest class society guidance and the engine OEM's commissioning manual for your specific project.
What Commissioning Covers — 5 Stages
Marine generator commissioning is typically structured as a five-stage project workflow. Each stage has its own responsible party, indicative duration, and witness scope that varies by class rules and project specification. Skipping a stage — or running them out of order — is frequently observed to extend delivery timelines.
| Stage | Location | Responsible | Indicative Project Allowance |
|---|---|---|---|
| 1. Factory Acceptance Test (FAT) | OEM factory | OEM (class attendance per ITP) | 1-2 days |
| 2. Pre-Shipment Documentation | Paperwork | OEM quality team | 1-2 weeks |
| 3. Onboard Installation Verification | Shipyard | Shipyard + OEM service engineer | 2-5 days |
| 4. Dock Trials | Quayside | Shipyard + OEM + owner rep | 1-3 days |
| 5. Sea Trials | At sea | Class surveyor + owner + shipyard + OEM | 1-3 days |
Class attendance at FAT depends on the applicable class rules, the certification scheme, the approved inspection and test plan, and the project specification. Sea or shipboard trials are normally attended where required for vessel classification. Type approval, individual product survey, and FAT attendance are distinct concepts and should not be conflated.
Factory Acceptance Test (FAT) Checklist
The FAT is the first major commissioning milestone — the OEM demonstrates that the genset meets nameplate performance, applicable class society type approval requirements, and the project specification before the unit leaves the factory. A clean FAT shortens downstream dock trials and sea trials; a messy FAT typically extends the project timeline.
12-Point FAT Checklist
- Run-in test at rated load — duration and acceptance limits follow the approved FAT procedure, engine and alternator manufacturer limits, applicable class rules, and project specification.
- EGT verification per cylinder — cylinder-to-cylinder spread within the OEM-published limit at the test load points specified in the approved test procedure.
- Progressive load test at agreed load points — typically including 25, 50, 75, and 100% rated load (or the load steps defined in the approved FAT procedure).
- Sudden load application and rejection test — verify acceptance of step changes per the approved test procedure; voltage and frequency transient recovery measured against the contractually specified ISO 8528 performance class.
- Sustained load run for combustion stability — duration and load level per the approved FAT procedure; this run also helps clear any light combustion deposits accumulated during earlier no-load checks.
- Voltage regulation — steady-state regulation within manufacturer-specified limits and the applicable class rules.
- Frequency stability — droop and steady-state frequency per the agreed ISO 8528 performance class where contractually specified.
- Insulation resistance — alternator winding insulation tested cold and after heat run, per the manufacturer's procedure.
- Vibration measurement — at the engine and alternator locations specified by the respective manufacturers, within their published limits.
- Power-factor capability — confirm performance at the rated power factor and any additional operating conditions defined in the approved test specification.
- Paint, corrosion protection, and marinization features — marinized alternator with anti-condensation heaters (where specified), salt-air protection on connections, paint scheme per marine specification.
- Spare parts package, documentation, photos, and signed FAT report — including class surveyor signature where attendance applies, owner representative signature, and full test data log archived.
For projects requiring IMO Tier III emissions compliance, the engine NOx Technical File and EIAPP arrangements should be referenced during FAT planning — see our IMO Tier III compliance and certification framework for marine generators.
Pre-Shipment Documentation Checklist
The documentation package travels with the genset to the shipyard and forms the evidence base for class society sign-off later. Missing or incorrect paperwork at this stage is one of the top causes of dock-trial delays — easily preventable, rarely caught.
7 Core Documents
- Engine NOx Technical File — required for marine diesel engines subject to MARPOL Annex VI Regulation 13, generally installed engines above 130 kW, excluding engines used solely for emergency purposes.
- EIAPP certificate — Engine International Air Pollution Prevention certificate, normally issued following engine pre-certification by or on behalf of the flag Administration through a recognised organisation.
- Engine type approval certificate, where required — confirming that the engine type and relevant rating/configuration fall within the approved scope.
- Applicable product or works certificate — the class society's individual-product certificate confirming the as-built genset matches the approved design (the exact title varies by society).
- Recommended spare parts list — typically a 2-year operating spare parts inventory matched to vessel duty cycle.
- O&M manuals — operation and maintenance documentation, in the language(s) required by the flag state and vessel's working language.
- Commissioning report from FAT — including all test data logs, photos, surveyor signatures, and signed acceptance pages.
For background on which class society's documentation framework applies to a specific vessel, see our comparison of the big 5 marine classification societies.
The EIAPP (Engine International Air Pollution Prevention) certificate is the primary Tier III compliance document, issued by the class society after engine parent testing to NOx Technical Code 2008 protocols. For the full compliance framework — SCR vs EGR technology paths, applicability by NOx ECA and keel-laid date, and cost breakdown — see our detailed guide on EIAPP certificate and IMO Tier III compliance pathway.
Onboard Installation Verification Checklist
Once the genset arrives at the shipyard and is mounted in the engine room, the OEM service engineer walks the installation against the engineering drawings before any start-up. Catch issues now; fixing them after dock trials begin is structural-rework expensive.
12-Point Onboard Verification Checklist
- Foundation and alignment verification — confirm skid level, foundation contact, permissible skid distortion, and coupling alignment where field verification is required, within OEM-published tolerances.
- Anti-vibration mount installation — correct type, correct preload, no shim bridging that would short-circuit the isolation path.
- Exhaust system routing — pipe diameter, length, number of bends, and bellows installation within OEM backpressure spec; exhaust insulation per fire-safety class.
- Fuel system connections — supply and return lines correctly sized, day tank height and gravity head correct, no air entrainment risk at fuel injection pump inlet.
- Cooling system connections — coolant fill, vent points, expansion tank, and (for marine) raw-water cooling loop or remote radiator piping correctly hooked up.
- Electrical bus tie connections — alternator output, neutral grounding, surge protection, and protection relay coordination match the single-line diagram.
- Control panel and monitoring — engine control unit, paralleling controller, SCADA / vessel monitoring system interface verified.
- Battery and starting system — correct battery type, capacity, and parallel/series arrangement; isolator and charging path verified.
- Day tank and bunker tank routing — sounding, vent, overflow, and fuel transfer pump routing complete.
- Insulation and heat shielding — exhaust manifold and turbo housing properly lagged; SOLAS A-class divisions respected.
- Fire detection and suppression interface — verify shutdowns, alarms, ventilation stops, fuel isolation, and other cause-and-effect actions against the approved fire-control philosophy; automatic genset shutdown applies only where specified.
- SOLAS emergency switching — for emergency gensets, auto-start signal from main switchboard blackout detection verified.
For the underlying sizing assumptions that shape these installation specifications, see our marine generator sizing methodology guide.
Dock Trial Checklist
Dock trials are the first opportunity to actually run the genset in its installed environment. The vessel is moored at the quayside, shore power may still be connected for safety, and the testing protocol works progressively from cold start through full electrical load — proving the system before committing to sea.
11-Point Dock Trial Checklist
- Cold start sequence — verify start-up time from cold against the manufacturer specification and the applicable class rules.
- Warm-up to operating temperature — controlled ramp to normal jacket water temperature; no excessive smoke or vibration during warm-up.
- No-load operation (limited) — short no-load verification only; extended no-load runs are avoided to limit early combustion deposits on a brand-new engine.
- Progressive load test at agreed load points — load steps via shore load bank (typically 25 / 50 / 75 / 100%, or as defined in the approved test procedure), verifying voltage and frequency stay within the applicable class rules and the contractually specified ISO 8528 performance class.
- Sudden load application and rejection test — verify voltage and frequency transient recovery against the approved test procedure.
- Parallel synchronization — for multi-generator installations, verify automatic synchronization and load sharing across all units; confirm anti-islanding and reverse-power protection.
- Auto load sharing — under varying load conditions, verify the PMS (Power Management System) distributes load proportionally across paralleled gensets.
- Blackout recovery test — simulate main switchboard blackout; verify automatic detection, sequenced restart, and load restoration per the vessel's blackout recovery plan.
- Emergency power source verification — for SOLAS-compliant installations, verify automatic starting and connection of the emergency source so that the required emergency services are supplied within the SOLAS time limit (normally within 45 seconds where applicable).
- EGT trend logging — capture per-cylinder EGT data across all load steps as the baseline for future maintenance benchmarking.
- Fuel consumption baseline — measure fuel consumption at 25/50/75/100% load steps to establish the commissioning baseline used in later performance audits.
The load bank discipline applied here protects the genset from early-life wet stacking — see our marine generator wet stacking prevention framework for the mechanism and longer-term operating discipline.
Sea or Shipboard Trial Acceptance Checklist
The sea or shipboard trial is the project's witnessed acceptance event — the vessel is underway, auxiliary systems are live, real vessel loads (HVAC, thrusters, mission systems) are exercised, and the class surveyor records satisfactory completion of the applicable machinery and electrical trials as part of the vessel's overall class certification process.
12-Point Sea or Shipboard Trial Acceptance Checklist
- Load endurance test at rated load — duration and load level per the approved test procedure, applicable class rules, and project specification.
- Sudden load application and rejection test — simulate worst-case step changes (typically the largest motor start or thruster engagement) and verify voltage and frequency transient recovery against the agreed ISO 8528 performance class.
- Harmonic distortion measurement — assess voltage and current distortion against the approved power-quality specification, applicable class rules, and IEC 60533 or another contractually specified standard.
- Vibration measurement at manufacturer-specified locations — at the engine and alternator measurement points defined by the respective manufacturers, within their published limits.
- NOx conformity verification — where applicable, complete the approved onboard verification method, normally an Engine Parameter Check against the NOx Technical File. Simplified measurement or direct measurement is used only where specifically approved.
- Noise measurement — engine room sound pressure level and any specified accommodation-area limits, per the approved specification.
- Class surveyor witness signatures — on each required test data sheet; the surveyor records satisfactory completion of the applicable machinery and electrical trials as part of the vessel's overall class certification process.
- Commissioning sign-off document — formal acceptance signed by class surveyor (where attendance applies), shipyard, owner representative, and OEM service engineer.
- Owner acceptance signature — the owner representative signs off that the genset meets the project specification.
- Punch list resolution — any open items from dock trials or earlier stages must be closed (or formally deferred with sign-off) before sea trial acceptance.
- Warranty start date confirmation — capture the warranty start date in writing per the supply contract (the trigger event varies by contract — sea trial acceptance, delivery, commissioning sign-off, or another agreed milestone).
- Handover of test data and certificates — full commissioning binder transferred to the owner: test reports, surveyor records, EIAPP, applicable product or works certificate, recommended spare parts list, and O&M manuals.
The shipboard noise survey required by IMO Resolution MSC.337(91), together with habitability-vibration measurements under ISO 20283-5:2016, is part of the pre-delivery acceptance process on applicable new SOLAS ships from 1,600 GT. For a full walkthrough of the acceptance side — including dB limits by ship space, the airborne vs structureborne transmission paths, vibration isolation mount selection across 3 mount families, and the 8 most common installation observations from ASO field-service projects — see our shipboard noise and vibration acceptance guide with downloadable 3-page compliance checklist PDF.
For smaller vessels (yachts, small workboats) where sea trial scope is reduced, see our yacht generator selection and commissioning framework for the scaled-down acceptance protocol used on those projects.
Common Acceptance Issues — and How to Avoid Them
Common issues observed in projects from the manufacturer's perspective include the five patterns below. All five are avoidable with the right pre-shipment discipline; all five become expensive to resolve once the surveyor has flagged them.
1. Combustion deposits from low-load FAT runs
If the FAT is run at light load without a sustained-load cycle to clear residue, the engine can arrive at the shipyard already showing combustion deposits. The class surveyor at dock trials may observe oily exhaust and flag the unit. Prevention: include a sustained-load run during FAT per the approved test procedure. A sustained higher-load run may help clear light deposits; severe deposits typically require dedicated service intervention. See our wet stacking diagnostic and prevention framework.
2. Class society documentation gaps
Missing EIAPP arrangements, mismatched type approval scope, or wrong-language O&M manuals can delay dock trials by weeks. Prevention: lock the documentation checklist with the class society at the kick-off meeting, not at the dock. See our marine generator classification society comparison.
3. Sizing margin failure under transient load
The genset passes steady-state load but trips on the largest motor start. The sizing did not include adequate margin for the transient case. Prevention: verify transient margins at the sizing stage, not at sea trial. See our marine vessel generator sizing framework.
4. Tier III certification path not aligned to vessel route
The genset has Tier II certification only, but the vessel's commercial route enters a NOx ECA. This kind of mismatch should normally be caught at the design review and documentation review stage — not deferred to sea trial. Prevention: confirm the compliance path against the vessel's planned operating areas at the specification stage. See our IMO Tier III compliance buyer's guide.
5. Vibration limit exceeded
Foundation alignment, anti-vibration mount installation, or coupling tolerance issues can show up as out-of-spec vibration at the sea trial. Prevention: walk the installation against engineering drawings at the onboard verification stage, not at the witness event.
Frequently Asked Questions
What is marine generator commissioning?
Marine generator commissioning is the structured five-stage project workflow — Factory Acceptance Test, pre-shipment documentation, onboard installation verification, dock trials, and sea or shipboard trial — that confirms a marine generator set matches its approved configuration and performs as required by the project specification. The class surveyor records satisfactory completion of the applicable machinery and electrical trials as part of the vessel's overall class certification process. For engines subject to MARPOL Annex VI Regulation 13, the EIAPP certificate is normally issued following engine pre-certification.
How do you prepare for a factory acceptance test?
Pre-FAT preparation typically includes: confirming the engine type approval scope matches the project specification, agreeing the inspection and test plan with the class society (where attendance applies), assembling the test load bank capable of holding the load points specified in the approved FAT procedure, preparing the test data log forms, briefing the witness representatives on the expected duration and pass/fail criteria, and confirming the recommended spare parts kit is ready to ship with the genset.
What is a factory acceptance test?
A Factory Acceptance Test (FAT) is an evaluation conducted at the manufacturer's facility to verify the equipment meets classification society requirements, design parameters, and operational specifications before shipping. For marine generators, the FAT typically includes physical inspection, run-in test at agreed load points, per-cylinder EGT verification, voltage and frequency regulation checks, insulation resistance, vibration measurement, and a sustained-load run to confirm combustion stability — all per the approved FAT procedure.
What is the 80% rule for generators?
The "80% rule" is an informal industry reference to running a diesel generator at approximately 80% of rated load for a sustained period (during commissioning and during periodic maintenance) to maintain proper combustion temperatures. Sustained operation at very low load (typically below the 30-40% range, engine-dependent) can cause unburned fuel residue to accumulate in the exhaust system; periodic loading at higher levels may help clear light deposits. The specific duration, frequency, and acceptance limits vary by OEM, class society guidance, and project specification.
How long does a marine generator sea trial take?
Sea trial duration depends on vessel type, number of generators, class society scope, and the approved test procedure. The endurance portion typically runs for several hours; the full sea trial including transient response testing, harmonics measurement, vibration measurement, NOx conformity verification (where applicable), and surveyor witness sign-off typically takes 1-3 days. Larger commercial vessels with multiple gensets and full IMO Tier III compliance verification typically take longer.
Does the class society have to witness sea trials?
Sea or shipboard trials are normally attended by the class surveyor where required for vessel classification. The surveyor records satisfactory completion of the applicable machinery and electrical trials as part of the vessel's overall class certification process. For vessels without class certification (some small workboats), the requirement may not apply, but the underlying performance verification still does. Always confirm the witness scope with the certifying class society against the approved inspection and test plan.
Can commissioning be done dockside without a sea trial?
Partially, but not fully for most commercial vessels. Dock trials cover most of the operational verification (start-up, progressive load, parallel synchronization, blackout recovery), and for some smaller vessels or specific applications the class society may accept dockside acceptance with reduced sea trial scope. For most commercial vessels, however, the sea or shipboard trial is required. The applicable machinery and electrical functions must be demonstrated under the conditions specified in the approved trial programme; some tests may be completed alongside, while others require the vessel to be underway.
What is included in a marine generator commissioning checklist?
A complete marine generator commissioning checklist covers 34 checkpoints organized across 5 sequential stages. Stage 1 — Factory Acceptance Test (FAT): performance run at rated speed and voltage, no-load and full-load fuel consumption, governor stability, AVR response, protection trip tests, mechanical noise and vibration readings, and pre-shipment paint and preservation check. Stage 2 — Pre-Shipment Documentation: applicable product or works certificate from class society, EIAPP certificate for engines above 130 kW, Technical File for the engine, spare parts list, and packing list. Stage 3 — Onboard Verification: physical arrival inspection, foundation alignment check, isolator torque verification, exhaust and cooling connection sign-off, fuel system flush verification, and control cable termination check. Stage 4 — Dock Trials: safe start sequence, progressive load-up to 25/50/75/100%, engine parameter check (temperatures, pressures, exhaust smoke), governor and AVR steady-state stability, parallel synchronization with shore or other generators, and blackout recovery test. Stage 5 — Sea or Shipboard Trial: sustained full-load operation under way, sea state noise and vibration measurement, class society witness of applicable trials, and final acceptance protocol sign-off. Each stage produces documented evidence that feeds the vessel's overall commissioning file and the Certificate of Class handover.
How is marine generator commissioning different from industrial generator commissioning?
Marine generator commissioning differs from industrial (land-based) commissioning in five main areas. Motion and vibration: marine generators must be commissioned to accept continuous vessel motion (roll, pitch, heave) that never applies to a land installation — this affects lubrication tests, water pump priming checks, and vibration acceptance criteria. Corrosion and salt environment: pre-shipment preservation, coating condition on arrival, and initial isolator elastomer inspection are formal checkpoints for marine but not usually for industrial installations. Class society involvement: marine commissioning requires classification society (ABS, DNV, CCS, LR, BV, RINA) witness or documentary sign-off at multiple stages; industrial commissioning typically requires only the local electrical authority or owner's representative. Regulatory certificates: marine generators above 130 kW require an EIAPP certificate under MARPOL Annex VI and often an applicable product or works certificate under class rules; industrial generators typically only need local emissions certification (EPA Tier 4 Final in the US, EU Stage V in Europe). Sea trial requirement: marine commissioning ends with a sea or shipboard trial demonstrating the generator under actual voyage conditions — no direct industrial equivalent exists (industrial commissioning ends with load bank testing and site acceptance). For dual-role installations (offshore platform generators, port equipment), commissioning follows the marine track when the equipment is subject to class rules.
How often should load bank testing be performed on a marine generator?
Load bank testing on marine generators is performed at three points in the equipment lifecycle. Initial commissioning: a stepped load bank test at 25/50/75/100% of rated load is standard practice during dock trials before the sea trial, typically 60–90 minutes total at load. This proves the generator can deliver rated output steady-state and confirms governor, AVR, exhaust system, and cooling performance under real load. Periodic maintenance: annual or semi-annual load bank testing is recommended for generators that operate primarily at light load — this includes emergency generators (SOLAS-mandated on many commercial vessels), harbor-mode generators, and auxiliaries on vessels running frequently at low hotel load. Recommended test duration is typically 2 hours at 100% load or 4 hours at 80% load to burn off wet-stacking deposits and verify sustained performance. After major service: load bank testing is performed after top-overhaul, alternator rewind, or major control system replacement, to verify the repair before returning the generator to service. Class societies do not universally mandate a specific load bank schedule; the frequency is set by owner risk assessment, insurance requirements, and OEM recommendations. Some flag administrations require documented annual emergency generator load testing under SOLAS Chapter II-1 regulations — always verify against the current flag state requirements for your vessel type.
Free Download: Marine Generator Commissioning Checklist
A printable engineering checklist covering all five commissioning stages — Factory Acceptance Test, pre-shipment documentation, onboard installation verification, dock trials, and sea or shipboard trials — with class society sign-off rows applicable across ABS / DNV / Lloyd's Register / Bureau Veritas / CCS. Based on ASO Genset marine delivery commissionings.
Download PDF ChecklistPlanning a marine generator commissioning, or recovering from a failed acceptance event?
ASO Genset manufactures marine diesel generators across DNV, CCS, ABS, LR, and BV — including the Norwegian OSV and Mauritania fishing fleet projects referenced in our other marine guides. We support customers through every stage of commissioning, from FAT scheduling to sea trial sign-off, and we have the field experience to diagnose what caused a failed acceptance event when it happens. Send vessel particulars, project stage, and target class society to info@asogenset.com — we will respond with a commissioning support plan, typically within two business days.
Related Reading
- Marine Diesel Generator Sizing Guide — The sizing methodology and transient margins reviewed during FAT and verified at sea trial.
- ABS vs DNV vs CCS Marine Generator Classification — How the big 5 IACS societies certify marine generators and witness commissioning milestones.
- Marine Generator Wet Stacking Prevention Guide — Why sustained higher-load operation during FAT matters, and the longer-term operating discipline that protects the engine.
- Marine Generator IMO Tier III Compliance Guide — NOx Technical File, EIAPP certification, and onboard NOx conformity verification for vessels operating in NOx ECAs.
- Yacht Generator Selection Guide (6-30 kVA) — Yacht-specific sizing and commissioning where sea trial scope is reduced.
- Custom Offshore Generator Cabin Design Guide — Skid-mounted offshore generator commissioning for IECEx / ATEX hazardous-area applications.
