1. Topic and Background
This document belongs to the Lloyd’s Register (LR) Rules and Regulations requirements for main and auxiliary machinery, with particular focus on acceptance testing and trials for reciprocating internal combustion engines.
The core purpose is not merely to prove that the engine can run. It is to confirm engine performance, safety protection, shipboard system integration, and the safe handling of DF/GF engine fuel modes and fault scenarios.
FAT Factory acceptance test
Verifies the engine itself and design parameters, such as power, fire protection arrangements, maximum pressure limits, and functionality, while establishing baseline values for later operational reference.
Shipboard Trials Shipboard trials
Verifies how the installed engine integrates with propulsion, power generation, control, safety, and auxiliary systems onboard.
2. Document Structure
This section can be read in four main parts. The technical logic is: safety prerequisites -> works trials -> shipboard integration trials -> special fuel and electronic-control verification -> statutory and emission requirements.
| Clause | Topic | Main content |
|---|---|---|
| 11.1 Safety | Safety requirements | Pre-test safety equipment, overspeed protection setting, and low-pressure gas fuel pipe tightness |
| 11.2 General | General requirements | Test scope, LR Surveyor witnessing, QAM, test-bed conditions, measurement items, and no adjustment during acceptance tests |
| 11.3 Works trials / FAT | Factory acceptance test | FAT purpose, ambient-condition records, operating-parameter records, and test conditions |
| 11.4 Shipboard trials | Shipboard trials | Shipboard integration verification, test conditions, DF/GF engines, fuel changeover, and barred speed range |
3. Core Requirements Explained
This chapter summarises the key requirements of 11.1 Safety, 11.2 General, and 11.3 Works trials.
1. 11.1 Safety: pre-test safety conditions
Before any test starts, the manufacturer or shipyard must provide and ensure that all personnel-safety-related equipment is available and functioning correctly.
Crankcase explosive conditions protection
Protection against crankcase explosive conditions.
Overspeed protection
Overspeed protection.
Shutdown function
Shutdown protection function.
The setting of the overspeed protective device must not exceed the overspeed value proven acceptable for that engine type during type testing, and it must be verified by an LR Surveyor. This means the overspeed setting is not arbitrary; it must trace back to the approved type-test basis.
For engines using low-pressure gas fuel, the document requires confirmation of low-pressure gas fuel pipe tightness before starting. This is an important safety prerequisite for DF/GF engines because low-pressure methane can still form a flammable mixture after leakage.
2. 11.2 General: general test requirements
This section requires tests carried out on the manufacturer’s test bed to be witnessed by the Surveyor and performed within the scope of 11.3 Works trials. The test scope must be agreed between LR and the manufacturer before testing.
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Multiple engines of the same type may be accepted under quality assurance
Where multiple engines are of the same design and the manufacturer complies with QAM (Quality Assurance Scheme for Machinery), acceptance may be carried out under the quality assurance approach.
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Run-in must be completed before formal testing
The document requires the engine to complete run-in in accordance with the manufacturer’s instructions before formal testing.
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The test bed and test fluids must be suitable
The test bed must be capable of providing the loads required by Table 2.11.1. Fluids such as fuel oil, lubricating oil, and cooling water must be clean and, where necessary, preheated to the recommended operating temperature.
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No machinery adjustment during acceptance testing
Clause 11.2.7 states that no intervention or adjustment may be made to the machinery under test during acceptance testing. This is a key principle of FAT.
3. Surveyor inspection items
| Inspection item | Technical purpose |
|---|---|
| High-pressure fuel pipe jacketing and leak detection | Prevent high-pressure fuel spray from contacting hot surfaces and causing fire |
| Shielding of flammable-liquid pipe joints | Prevent leakage from joints from spraying onto hot surfaces |
| Hot-surface insulation and temperature spot checks | Verify whether fire-protection measures remain consistent with the type-test basis |
Temperature spot checks of hot surfaces should be compared with the corresponding type-test data. If insulation arrangements have been modified after type approval, LR may require enhanced temperature measurement. This means design changes after type approval cannot be ignored.
4. Factory Acceptance Test Scope
The factory acceptance test can be understood as baseline performance verification before engine delivery. The focus is not simply whether the engine can start, but whether it can operate stably at rated power, short-time overload, partial loads, starting, stopping, and protection-function conditions according to its intended service. Different applications, such as main propulsion, generator engines, PTO generation, or mechanical auxiliaries, have different test loads and durations.
Works trials verify design parameters, such as power, fire protection and fire-prevention arrangements, approved limiting values, and functionality, while establishing baseline values for later operational reference.
1. Ambient conditions to be recorded during FAT
Ambient air temperature
Ambient air temperature.
Ambient air pressure
Ambient air pressure.
Atmospheric humidity
Atmospheric humidity.
2. Operating parameters to be recorded during FAT
| Category | Parameter |
|---|---|
| Basic output | Power and speed |
| Fuel control | Fuel index, including gas and fuel oil, or equivalent readings |
| Gas fuel | Gas pressure and temperature |
| Ignition / pilot fuel | Pilot fuel temperature and pressure, or common-rail pressure |
| Combustion condition | Maximum combustion pressure |
| Exhaust condition | Exhaust temperature before turbine, individual-cylinder exhaust temperature, or manifold temperature |
| Scavenge / charge air | Scavenge / charge air temperature and pressure |
| Turbocharger | Category B and Category C turbocharger speed |
Measurements under all FAT conditions should be taken under steady operating conditions. For MCR / 100% power, readings must be taken at least twice, with an interval of not less than 30 minutes. This is an important acceptance requirement under 11.3.5 for the FAT report and Surveyor witnessing.
3. Main propulsion engines driving propellers or waterjets
| Test condition | Duration | Focus |
|---|---|---|
| 100% power at rated speed R | >= 60 min | Verify MCR capability |
| 110% power at 1.032R | 15 min or until steady condition is reached | Verify short-time overload capability |
| Approved intermittent overload | To be agreed with the manufacturer | Only where approved |
| 90%, 75%, 50%, and 25% power | No fixed duration specified | Engine speed according to the nominal propeller curve; test sequence selected by the manufacturer |
| Reversing operation | Where applicable | Applicable to reversible engines or relevant arrangements |
| Governor and independent overspeed protection | To be tested | Linked to control and monitoring requirements |
| Shutdown device | To be tested | Verify safe shutdown function |
1.032R is a useful engineering approximation for understanding the speed corresponding to 110% power. For a fixed-pitch propeller, power is approximately proportional to the cube of speed, so 110% power corresponds to the cube root of 1.1, or about 1.032 times rated speed. Actual acceptance remains subject to the conditions specified in LR Table 2.11.1 / 2.11.2.
4. Generator engines
| Test condition | Duration | Focus |
|---|---|---|
| 100% rated power at rated speed R | >= 60 min | Verify continuous rated output |
| 110% power | 15 min or until steady condition is reached | Verify transient governing and protection margin |
| 75%, 50%, 25%, and idle speed | No fixed duration | Verify load-step performance |
| Starting test | To be carried out | Verify starting capability |
| Governor and overspeed protection | To be carried out | Important for power quality and safety |
| Shutdown device | To be carried out | Verify protection logic |
The 110% capability for generator engines differs from that of main engines. Its purpose is to provide transient governing margin so that electrical protection can operate before the engine stalls.
5. Propulsion engines for PTO generators and engines for mechanical auxiliaries
PTO propulsion engine
Under a PTO arrangement, the engine carries both propulsion and generator branch loads. FAT therefore needs to confirm 100% engine power, 110% power, approved intermittent overload, and 90%, 75%, 50%, and 25% part loads.
Auxiliary mechanical auxiliary
Mechanical auxiliaries include pumps, compressors, or other mechanically driven equipment not used for generation. Their FAT requirement is relatively shorter: 100% rated power at rated speed R for >= 30 minutes.
5. Special FAT Requirements for DF/GF Engines
GF only engines and DF engines using low-pressure methane require integration testing to verify correct operation of mechanical, hydraulic, and electronic systems in all intended operating modes.
Fuel-oil mode and gas mode
DF engines using low-pressure methane should be tested, as applicable, in both fuel-oil mode and gas mode.
Methane Number
Where applicable, the document requires the gas methane number to be recorded and requires demonstration that the engine can achieve the declared power at that methane number.
Scope of integration testing
The scope covers GF only engines and DF engines using low-pressure methane; testing must cover all intended operating modes.
It is not sufficient to complete all FAT items in diesel mode and then claim dual-fuel performance is acceptable. Maximum available power in gas mode, combustion stability, methane-number effects, and control logic must all be verified.
Gas-fuel fault-scenario test items
- Ignition failure, such as spark ignition or pilot injection failure
- Failure of one cylinder unit
- Gas admission valve failure
- Combustion failure, such as misfiring, knocking, or exhaust-temperature deviation
- Abnormal gas pressure
- Abnormal gas temperature
These tests may be carried out by simulation or other alternative means, subject to special consideration and agreement by LR.
6. Requirements for Electronically Controlled Engines
For electronically controlled engines, the document requires FAT, integration testing, engine configuration verification, a software quality plan, and software configuration management procedures.
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Carry out FAT according to submission requirements
In accordance with LR Rules Pt 5, Ch 2, 1.4 Submission requirements 1.4.3, electronically controlled engines require submission of FAT-related test data and verification arrangements.
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Integration testing
Confirm that the mechanical, hydraulic, and electronic systems respond as intended in all operating modes.
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Verify engine configuration
Confirm that the actual engine configuration matches the approved documents.
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Confirm software quality and configuration management
Confirm that the approved software quality plan and software configuration management procedures have been implemented.
Acceptance of modern marine engines is no longer limited to mechanical performance testing. It also includes control engineering systems and software configuration management. If the software version, control parameters, or safety logic do not match the approved documents, it may become a class review issue even if the engine itself runs normally.
7. 11.4 Shipboard Trials Explained
The purpose of shipboard trials is to verify the integration of the engine with the power transmission system, driven machinery, safety systems, control systems, auxiliary systems, engine control systems, and shipboard control systems, as well as items not already covered during FAT.
Shipboard trials are not a repeat of FAT. They confirm that the engine, once installed onboard, works properly and safely under real system boundary conditions.
1. Main engines with fixed-pitch propellers or waterjets
| Shipboard test condition | Duration | Technical meaning |
|---|---|---|
| Rated engine speed R | At least 4 hours | Condition for main engines with fixed-pitch propellers or waterjets; this should not be simplified as 100% MCR power for 4 hours |
| Speed corresponding to 1.032R | 30 min | Verify overload / high-speed capability where permitted by engine adjustment |
| Approved intermittent overload | As agreed | Only where approved |
| Minimum engine speed | To be confirmed | Relevant to low-speed manoeuvring capability |
| Starting and reversing operation | To be demonstrated | Verify starting air and reversing capability |
| Opposite propeller rotation direction | 10 min | Verify astern or reverse-running capability |
| Control, monitoring, alarm, and safety systems | To be demonstrated | Verify shipboard installation and settings |
| Ability to pass through the barred speed range | Where applicable | Verify safe passage through the barred speed range |
2. Main engines with controllable-pitch propellers (CPP)
| Shipboard test condition | Duration | Focus |
|---|---|---|
| 100% power | >= 4 hours | Verify matching of the main engine and CPP at MCR condition |
| Approved intermittent overload | As agreed | Applicable where approved |
| Astern pitch manoeuvring | To be demonstrated | Verify manoeuvring capability |
| Control, monitoring, alarm, and safety systems | To be demonstrated | Verify integration |
CPP installations need to be tested at different pitches. The 100% power test should be carried out at rated speed R using the pitch corresponding to MCR; if 100% cannot be achieved, the test is carried out at the maximum achievable power.
3. Generator engines
| Shipboard test condition | Duration |
|---|---|
| 100% rated generator electrical power | >= 60 min |
| 110% rated generator electrical power | >= 10 min |
| Starting operation | To be demonstrated |
| Control, monitoring, alarm, and safety systems | To be demonstrated |
| Governor capability to withstand load steps | To be demonstrated |
For generator engines, shipboard trials are usually based on the rated electrical power of the generator. For electrical propulsion arrangements, the rated electrical power requirements of the electric propulsion motors must also be considered in accordance with the LR table notes; it is not sufficient to refer only to the generator rating.
4. Propulsion engines for PTO generators
| Shipboard test condition | Duration |
|---|---|
| 100% engine power MCR at corresponding speed R | >= 4 hours |
| 100% propeller branch power at speed R | 2 hours |
| 100% PTO branch power at speed R | >= 1 hour |
| Control, monitoring, alarm, and safety systems | To be demonstrated |
5. Engines for mechanical auxiliaries
| Shipboard test condition | Duration |
|---|---|
| 100% engine power MCR at corresponding speed R | >= 30 min |
| Approved intermittent overload | For the approved duration |
| Control, monitoring, alarm, and safety systems | To be demonstrated |
6. DF/GF engine shipboard trial focus
Gas pipe leakage and double-wall pipe ventilation verification
After the engine is installed onboard, the gas piping system must undergo leakage testing, and the efficiency of the ventilation arrangement for double-wall gas piping must be verified.
All applicable operating modes must be tested
DF engine test loads must be run in all applicable operating modes, including gas mode, diesel mode, and any other applicable modes.
Automatic changeover to fuel-oil mode
If the gas fuel system becomes abnormal, it should reliably change back to fuel-oil mode to avoid engine stall or interruption of propulsion / power generation.
Manual fuel changeover
Test manual changeover from diesel mode to gas mode and from gas mode back to diesel mode.
7. Barred Speed Range
The barred speed range is usually related to torsional vibration or shafting resonance. The vessel is not prohibited from passing through the range; it must not remain there for an extended time. Therefore, the control system must allow the main engine to pass through the range safely, quickly, and controllably.
- Both manual and automatic control systems must demonstrate acceleration and deceleration through the barred speed range
- The passing time must be equal to or less than the time in the approved documents
- The passing time must be recorded
- Also applicable when reversing direction, especially during stopping trials
- Vessel draught and speed must be recorded during demonstration
- If fitted with CPP, pitch must also be recorded
- The engine must run steadily at the upper and lower limits of the barred speed range
- Oscillation of the steady fuel index must be less than 5% of the effective stroke
8. Key Terms and Definitions
The following table summarises the professional terms, abbreviations, symbols, and meanings used in the document.
| Term | English | Explanation |
|---|---|---|
| FAT | Factory Acceptance Test | Factory acceptance test carried out on the manufacturer’s test bed to verify engine performance and safety functions |
| Shipboard trials | Shipboard trials | Shipboard trials verifying integration between the installed engine and ship systems |
| MCR | Maximum Continuous Rating | Maximum continuous rating; the approved maximum power at which the engine can run continuously |
| R | Rated engine speed | Rated speed |
| 1.032R | Speed corresponding to 110% power | Engineering approximation for understanding the speed corresponding to 110% power; actual acceptance is based on LR Table 2.11.1 / 2.11.2 |
| DF engine | Dual Fuel engine | Dual-fuel engine, normally capable of using fuel oil and gas fuel |
| GF engine | Gas Fuel engine | Gas-fuel engine |
| PTO | Power Take Off | Power take-off from the main engine for generation or other driven equipment |
| CPP | Controllable Pitch Propeller | Controllable-pitch propeller |
| FPP | Fixed Pitch Propeller | Fixed-pitch propeller |
| Fuel index | Fuel index | Fuel-oil / gas-fuel control indicator that can reflect load and fuel delivery |
| Methane Number | Methane Number | Methane number, indicating knock resistance of gas fuel |
| Pilot fuel | Pilot fuel | Pilot fuel used for ignition in gas mode on DF engines |
| Common rail | Common rail | Common-rail system for high-pressure fuel supply and electronically controlled injection |
| Barred speed range | Barred speed range | Barred speed range, usually related to torsional vibration or resonance risk |
| Overspeed protection | Overspeed protection | Overspeed protection preventing engine speed from exceeding safe limits |
| Shutdown device | Shutdown device | Shutdown device that stops the engine under dangerous conditions |
| Crankshaft deflection | Crankshaft deflection | Crankshaft deflection, used to assess crankshaft and main-bearing alignment |
| QAM | Quality Assurance Scheme for Machinery | LR Quality Assurance Scheme for Machinery |
| Surveyor | LR Surveyor | LR Surveyor responsible for witnessing, confirming, and accepting tests |
9. Technical and Regulatory Implications
The following points summarise how these requirements affect ship design, construction, survey, operation, safety, and compliance.
FAT establishes the baseline for class acceptance
The focus of FAT is to confirm that the engine itself achieves approved performance in a controlled environment and to establish baseline data for future operational comparison.
Shipboard trials verify system integration
Shipboard trials focus on how the engine works with the actual ship systems, including propulsion, power generation, control, alarms, safety, gas fuel piping, and ventilation.
DF/GF engines require higher risk-control attention
The main risks of gas-fuel engines are not only insufficient power, but also flammable gas leakage, abnormal combustion, and control failure.
Electronic control and software are now class review items
Electronically controlled engines must verify the software quality plan, software configuration management, and engine configuration.
Exhaust emission testing must be carried out in accordance with the applicable MARPOL (International Convention for the Prevention of Pollution from Ships) requirements. This means LR class tests and statutory emission requirements may apply at the same time.
10. Practical Use and Common Pitfalls
This chapter summarises how the requirements may be used by shipyards, class review teams, shipowners, operations managers, port State control, or examination preparation, and highlights common misunderstandings and limitations.
1. For engine manufacturers
- Test procedures agreed by LR
- Evidence of test-bed load capability
- Instrument calibration records
- Run-in records
- Ambient-condition record sheet
- Operating-parameter record sheet
- Safety-protection function test plan
- Fuel-mode test matrix for DF/GF engines
- Acceptance protocol / acceptance report
2. For shipyards
- Main engine, shafting, propeller, or waterjet installation completed
- Fuel oil, lubricating oil, cooling water, and starting air systems available
- Gas fuel piping leakage test completed
- Ventilation efficiency of double-wall gas pipes can be demonstrated
- Control, monitoring, alarm, and safety systems configured
- Shipboard trial conditions can achieve the required power and speed
- Vessel draught, speed, and CPP pitch can be recorded
- LR Surveyor has agreed the test scope
3. For class review and Surveyors
- Whether the test scope complies with Table 2.11.1 or Table 2.11.2
- Whether the overspeed protection setting does not exceed the type-test proven value
- Whether high-pressure fuel pipe protection is complete
- Whether hot-surface insulation is effective
- Whether steady condition is reached during testing
- Whether MCR / 100% power readings are taken at least twice with an interval of not less than 30 min
- Whether DF/GF engines complete all applicable mode tests
- Whether control, alarm, and safety functions operate correctly
- Whether the barred speed range can be passed through safely
4. Common misunderstandings and points to note
FAT and shipboard trials have different purposes
FAT verifies the engine itself. Shipboard trials verify the integration of the engine with ship systems. A successful FAT does not mean shipboard trials can be omitted, and shipboard trials cannot fully replace FAT unless LR agrees to an equivalent alternative scope.
100% power and 110% power should not be confused
100% power normally corresponds to MCR / rated power, whereas 110% power is a short-time overload or transient-margin verification. Their purpose, duration, and limits of application are different.
DF engines are not tested only in diesel mode
The document allows part of the 110% test to be demonstrated in diesel mode, but DF engines still need load testing in gas mode where required, and shipboard trials must be carried out in all applicable operating modes.
Methane number must be recorded
Gas-mode power cannot be separated from fuel quality. The document requires the methane number to be recorded and requires demonstration that the engine can achieve declared power at that methane number.
No adjustment during acceptance testing
The “no intervention or adjustment” requirement in 11.2.7 is critical. If fuel settings, control parameters, or mechanical conditions are changed during testing, the acceptance value of the test data is affected.
The barred speed range is not just a mark on a drawing
The vessel must demonstrate acceleration and deceleration through the barred speed range and record passing time, ship speed, draught, and CPP pitch where necessary. This is an important onboard verification of shafting vibration safety.
Electronically controlled engines require software version control
The software quality plan and configuration management of electronically controlled engines form part of class requirements. In practice, controller software versions, parameter settings, and safety logic should all be traceable.
This note summarizes the LR 2025 edition of Lloyd's Register rules for readers' reference. Class rules, IMO conventions, MARPOL, and authority requirements may change. For actual design, plan approval, trials, and delivery, always rely on the latest official LR Rules, class review comments, authority requirements, and contractual technical specifications.
11. Summary and Review Points
The following points are the most useful items from this section for exam review and quick engineering reference.
- This section governs FAT (factory acceptance test) and shipboard trials for marine reciprocating internal combustion engines.
- The core purpose of FAT is to verify engine performance, safety functions, design limiting values, and baseline data.
- The core purpose of shipboard trials is to verify integration between the engine and propulsion, generation, control, alarm, safety, fuel, and auxiliary systems.
- Before testing, safety equipment must be confirmed available, including crankcase explosion protection, overspeed protection, and shutdown functions.
- The overspeed protection setting must not exceed the overspeed value proven by type testing and must be verified by an LR Surveyor.
- FAT must record ambient conditions, power, speed, fuel index, gas pressure and temperature, pilot fuel pressure, maximum combustion pressure, exhaust temperature, charge-air parameters, and turbocharger speed where required. Measurements should be taken under steady operating conditions, and MCR / 100% power readings must be taken at least twice with an interval of not less than 30 min.
- Main propulsion engine FAT normally requires 100% power for >= 60 min. Shipboard trials for main engines must be interpreted by propulsion type: fixed-pitch propeller or waterjet arrangements use rated engine speed R for at least 4 hours, while CPP arrangements use 100% power for >= 4 hours.
- Generator engines must verify 100% and 110% rated electrical power and confirm governor capability to withstand load steps. For electrical propulsion arrangements, the rated electrical power requirements of the electric propulsion motors must also be considered.
- DF/GF engines require particular verification of gas mode, diesel mode, fuel changeover, methane number, gas pipe tightness, and double-wall pipe ventilation efficiency.
- Electronically controlled engines must verify correct integration of mechanical, hydraulic, electronic, and software configuration management aspects.
- The barred speed range must be safely demonstrated onboard, with passing time, ship speed, draught, and CPP pitch recorded where necessary.
- Exhaust emission testing must still follow applicable MARPOL requirements; class machinery performance testing alone is not sufficient.
Quick memory aid: FAT checks the engine itself; shipboard trials check system integration; DF/GF engines require fuel-mode and gas-safety verification; electronically controlled engines also require software and configuration management.