© Lloyd’s Register of Shipping Page 1 of 27 Emissions of Nitrogen Oxides from Marine Diesel Engines Questions and Answers July 2002

Emissions of Nitrogen Oxides from Marine Diesel Engines€¦ · Emissions of Nitrogen Oxides (NOx) from Marine Diesel Engines Jul 2002 Questions and Answers 1. General Aspects 1.1

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  • © Lloyd’s Register of Shipping Page 1 of 27

    Emissions of Nitrogen Oxidesfrom Marine Diesel Engines

    Questions and Answers

    July 2002

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers


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    © Lloyd's Register of Shipping, 2002

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers


    This document has been prepared as a usefulsource of information for surveyors dealing withthe implementation of MARPOL 73/78 Annex VIRegulation 13 and the NOx Technical Code.

    The information contained has been assimilatedfrom many sources and is by no means exhaustive.

    A simple ‘questions and answers’ format has beenadopted although some items have been includedin the form of notes with all common areas beinggrouped into sections.

    Each question is clearly differentiated from it’ssubsequent answer or note by the style of text.Questions are introduced in larger bold italicstext. Where sections of Annex VI or the NOxTechnical Code have been quoted a reference isgiven with the text appearing italicised.

    The questions and answers are for internal useonly. Their formulation is aimed at providingsurveyors with information which will allow themto deal with client enquiries.

    Lloyd’s Register of Shipping71 Fenchurch StreetLondon EC3M 4BSTelephone 020 7709 9166Telex 88379 LR LON GFax 020 7488 4796Web site www.lr.org



    Section Page

    1 General Aspects 3

    2 Control of NOx Emissions 4 - 8

    3 IAPP, EIAPP, flag states, 9 - 13MARPOL Annex VI and theNOx Technical Code

    4 On-Board Verification Procedures 14 - 15

    5 Engine Specifics 16 - 18

    6 Conformity of Production 19 - 20Procedures

    7 Pre-certification Testing 21 - 24

    8 Parent, Family & Group Engine 25 - 26Concepts

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    1. General Aspects

    1.1 What are oxides of nitrogen (NOx)?99% of engine intake air is comprised of nitrogen(N2) and oxygen (O2). The nitrogen remainslargely unreacted in the diesel engine combustionprocess, however a small percentage is oxidised toform exhaust gases containing various oxides ofnitrogen, predominantly nitric oxide (NO) withsmaller amounts of nitrogen dioxide (NO2) andminor concentrations of nitrous oxide (N2O). Theterm oxides of nitrogen, or nitrogen oxides (NOx)is used to group both the NO and NO2components.

    1.2 Are oxides of nitrogen (NOx) harmful?Nitric oxide (NO) is relatively inert and onlymoderately toxic but is readily oxidised to form themore harmful gas nitrogen dioxide (NO2). As anemission species oxides of nitrogen (NOx) are ofconcern for several reasons. They are responsiblefor acid deposition, respiratory illness in humansand in association with sunlight and organicmaterial, the formation of photochemical oxidants,namely ozone (O3) and smog.

    Ozone in itself has detrimental effects on humanhealth, vegetation and crop yields, and contributesin the degradation of certain materials. Ozone isalso a greenhouse gas, controlling the amount ofthe sun’s UVB radiation from reaching the earth’ssurface and so contributes to the problem of globalwarming.

    1.3 How are NOx formed?NOx are formed during the combustion processwithin the burning fuel sprays. At these elevatedflame or combustion temperatures nitrogen is nolonger inactive and reacts with oxygen to formnitric oxide (NO) and nitrogen dioxide (NO2). Theimmediate reaction is the formation of NO. Later inthe process, during expansion and in the exhaustsystem, part of the NO will convert to form NO2.NOx is controlled by local conditions in the spray,with temperature and oxygen concentrations beingthe dominant influences. The higher thetemperature and the longer the residence time athigh temperature, the more NOx will be created.

    1.4 When are NOx formed?The stoichiometric quantity of air is defined as thatquantity of air containing the minimum theoreticalamount of oxygen required to fully convert all thefuel into completely oxidised products, i.e. forcomplete combustion. The ratio of the actualfuel/air ratio to the stoichiometric fuel/air ratio isan informative parameter for defining thecomposition of a fuel mixture. This ratio is termedthe fuel/air equivalence ratio, φ, and is thusdefined:

    ( )( )φ =FA




    The critical equivalence ratio of the local mixture offuel and air for NOx formation is close to 1, i.e.maximum NOx creation occurs when the localair/fuel ratio is close to stoichiometric.

    The critical time period for NOx creation is whenburned gas temperatures are at a maximum i.e.between the start of combustion and shortly afterpeak pressure. It has been shown that almost allNO formation occurs within 20° of crank rotationfollowing start of combustion.

    After the time of peak pressure, burned gastemperatures decrease as the cylinder gasesexpand.

    The decreasing temperature due to expansion anddue to mixing of high temperature gases withcooler burned gas freezes the NO chemistry.

    NO forms both in the propagated flame front andin the post flame gases. In engines, however,combustion occurs at high pressure so the flamereaction zone is extremely thin ( in the order of0.1mm) and residence time within this zone isshort.

    Thus, NO formation in the post-flame gases almostalways dominates any flame-front produced NOwhich effectively de-couples the combustion andNO formation processes. However, the reactionswhich produce NOx take place in an environmentcreated by the combustion reactions, so the twoprocesses are still intimately linked.

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    2. Control of NOx Emissions

    2.1 What engine features control NOxformation rates?It has already been shown that NOx formationrates are primarily a function of combustiontemperature (and pressure) and residence time ofthe combustion gases at these high temperatures.Hence any features of an engine which mayinfluence these variables will also influence theemission rate. A list of the most influential of thesefeatures can be summarised as follows:

    • Injection and atomisation equipment• Injection timing equipment• Compression ratio• Combustion chamber geometry• Turbocharger type and build• Charge air cooler/pre-heater• Valve timing• Rated engine speed• Fuel composition

    Fuel injection equipment design, timing andpressure together with combustion space geometryand fuel properties all influence the fuelatomisation, spray patterns and penetration. Thesefactors are critical to the efficient mixing of the fueland air charge, significantly influencingcombustion efficiency. The quality of mixing of thefuel and air in turn influences the local mixtureequivalence ratio, having a critical value close to 1for high NOx emissions.

    Advancing fuel timing and increasing compressionratios tend to increase combustion pressures andtemperatures and so increase NOx formation rates.

    Ambient conditions, as modified by the charge airsystem, also influence NOx production. Increasedintake air humidity reduces peak combustiontemperatures and hence suppresses the formationof NO in the combustion process.

    Lower rated engine speeds increase the time overwhich combustion takes place, increasing residencetime of the combustion gases at high temperaturesand so tending to increase NOx formation rates.

    2.2 What effect does the presence oforganic nitrogen (N2) in heavy fuel oilhave on NOx emissions?Nitrogen present in residual fuel is also a factoraffecting nitric oxide (NO) formation via adifferent mechanism. Fuel derived NO proceedsvia a series of reactions, a key stage of which is theformation of a NH compound which may eitherprogress to form N2 or NO. The nature of thecompounds in which the nitrogen exists in the fuelis considered to be a factor in deciding the outcomeof the reaction but under certain conditions couldresult in a 100% NO yield (amount of fuel nitrogenconverted to NO).

    The NO yield is also sensitive to the fuel /airequivalence ratio. Relatively high NO yields areobtained for stoichiometric mixtures and are onlyweakly dependent on temperature, in contrast tothe strong temperature dependence of NO formedfrom atmospheric nitrogen.

    In summary, increased nitrogen content in residualfuels will increase NOx emissions.

    2.3 What are Primary NOx Emissionreduction methods? Why not designextremely low NOx emission engines?The modified engine design approach can bethought of as a primary method of controlling NOxformation rates. As discussed, lowering the peakcombustion temperature is a very effective meansof reducing the amount of NOx formed.Unfortunately, the amounts of other pollutants,namely Particulates and Hydrocarbons, willincrease instead and there is also a substantial fuelpenalty as efficiency drops due to poorcombustion. The control of NOx emissions bydesign is therefore an optimisation process,balancing satisfactory combustion efficiency withacceptable levels of all pollutants.

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    2.4 What Primary methods can beadopted to reduce NOx emissions?

    Manufacturers have explored many differentmethods of reducing NOx by primary controlmethods. Some of the more publicised are listed asfollows:

    • Delaying fuel injection. Retarded fuel injectiontiming retards the combustion process. Nitricoxide (NO) formation occurs later and withlower concentrations.

    • Reducing the amount of scavenge air, hencereducing the quantity of excess O2 available forconversion to NOx.

    • Common Rail control - Common Rail fuelinjection has proven to be a very effective wayin combating smoke problems as well as a NOxreduction technique. There are two mainingredients, one being the freedom to chooseinjection pressure and timing totallyindependently of engine load, the other addingan element of computerised control making itpossible to consider several engine parametersand then automatically optimise the injectionand therefore combustion in each load situation

    • Injecting water into the combustion chamber(Direct Water Injection, DWI) Greater heatcapacity is utilised to reduce high peaktemperatures as the water evaporatesimmediately upon injection. Rapid evaporationof the injected water also helps to create ahomogeneous fuel-air mixture.

    • Emulsified Fuel or Fuel-Water Emulsions(FEW) is favoured by some manufacturersclaiming clear reduction in NOx emissions atlow cost with no significant design changes andwith no adverse effect on the reliability of theengine. Other manufacturers claim that fuel-water emulsions in a conventional injectionsystem causes considerable problems.

    • Injection of very fine water mist after theturbocharger using special nozzles(Combustion Air Saturation System, CASS).The fine water droplets evaporate fast andfurther heat is introduced in the air cooler (now

    acting as an air heater) and humidifies thecombustion air.

    • Re-circulating part of the exhaust gas (EGR) -this is one method of adding dilutants to theintake air, reducing burned gas temperature forany given mass of fuel and oxygen. It has beensuccessfully employed in the automotiveindustry where good quality fuel is used butmarine diesel engine manufacturers claim thateven when the fuel has insignificant amounts ofsulphur, the practical application of EGR causesunacceptable operational problems.

    • Water Cooled Rest Gas (WaCoReG) -Developed for slow speed engines, this systemutilises the same mechanism as an EGR system,i.e. introducing some 'rest gas' into thecombustion space. In an engine withelectronically controlled exhaust valve timing itis quite easy to leave some of the exhaust gas inthe cylinder. This obviously has a negativeimpact on engine performance, however thiscan be dramatically reduced by cooling the restgas with a water spray, in which case the restgas accounts for some of the NOx reduction andthe water spray for the rest.

    • Humid Air Motor (HAM). Hot compressed airfrom the turbocharger is led to a humidificationtower and exposed to a large surface area andflushed with hot water. The water can beheated by a heat exchanger connected to thejacket cooling system or using an exhaust gasboiler. The principle is the same as thatdescribed under Combustion Air SaturationSystem, CASS previously. One manufacturerclaims considerable success in service inreducing NOx emissions with the added claimof increasing the indicated power of the engineat certain loads therefore reducing fuelconsumption hence proportionally reducingCO2 emissions

    The actual degree of NOx reduction varies from10% to over 60%, depending on the engine typeand which of the above reduction methods areadopted.

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    2.5 Can the various Primary methods ofNOx reduction be combined?Combinations of primary NOx reduction methodsare possible. Reduction of NOx in some mediumand high speed engines is achieved by exploiting acombination of high compression ratio withretarded fuel injection.

    This calls for the engine to inject fuel late in thecycle and over a short duration without destroyingperformance.

    2.6 What are Secondary NOx reductionmethods?Secondary methods reduce NOx in the exhaust gasby downstream treatment.

    Selective Catalytic Reduction (SCR) is such asystem and can cut emissions by well over 90%with figures of 98% NOx reduction being recorded.

    2.7 How does the Selective CatalyticReduction (SCR) system work?In an SCR system the exhaust gas, at a temperaturebetween 250 and 530°C, is mixed with ammonia(commonly in the form of a solution of urea inwater). This introduces single atom nitrogen (N)creating a reducing atmosphere before passingthrough a special catalyst. The NOx is reduced toharmless gaseous stable nitrogen (N2) and water.

    The catalyst core is often composed of a heatresistant ceramic honeycomb with a catalyticallyactive material, such as oxides of vanadium,dispersed on its surface. The surface in contactwith the exhaust gas needs to be extremely large inorder for all the molecules of NOx and N to touch acatalytically active site on the substrate. At thesame time the resistance to exhaust gas flowcreated by placing the catalyst in the exhaust gaspath must be minimised to reduce excessivepressure drops.

    2.8 If Selective Catalytic Reduction (SCR)has such an extremely high NOx reductionefficiency why is it so rare in marineapplications?There are many reasons contributing to the factthat SCR’s have not been widely taken up for usewith marine diesel engines, the major ones arelisted:

    • Large initial cost

    • Large spatial requirements.

    • Low efficiency

    • High pressure drop

    • Fouling tendency

    • Resistance to poisoning

    • Heat up time

    • Recycling of used catalysts

    • Safety aspects (handling ammonia)

    • Availability

    Probably the biggest disadvantage is the massivedimensions of most present commercially availableSCR reactors and as such are often impractical toretrofit to an existing marine installation.

    As technology progresses SCR systems for themarine environment are being further developedand installed on vessels operating in places such asSweden where there is a distinct financial gainfrom having extremely low NOx emission engines.

    2.9 How does adding water to the fuelreduce NOx emissions?Water addition to the fuel is effective in reducingNOx formation during combustion, mainlybecause the water evaporates immediately uponinjection. This improves the intimate mixing of thefuel and air and promotes a homogenous fuel - airmixture. Evaporation of the water also reduces themaximum combustion temperature.

    Water emulsified with the fuel prior to injectionrequires a significant increase in the fuel pumpcapacity. Special precautions are necessary to keepthe water-fuel emulsion stable and preventcorrosion of fuel system components.

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    Water can also be added to the combustion spacethrough separate nozzles or by the stratifiedsegregated injection of water and fuel from thesame nozzle (direct water injection).

    Some manufacturers consider direct waterinjection preferable to the introduction of water asan emulsified fuel. In order to reduce NOxemissions significantly it is claimed that theproportion of water in emulsified fuel mustapproach 50%.

    2.10 Are there any disadvantages inintroducing water into the combustionprocess using fuel emulsification?It is claimed that addition of water to thecombustion process has its drawbacks:

    • The emulsion is not always stable andvariations in the fuel type may producedifferent behaviour.

    • Severe corrosion could be a problem if theinjection system is not flushed with clean fuelbefore the engine stops.

    • The emulsion lowers the energy content pervolume of mix and so the injection equipmentmust be substantially enlarged to produce thesame power. This will increase the amount ofpower absorbed by the injection equipment.

    Another way of introducing water into thecombustion zone is by humidifying the scavengeair as detailed in 2.4. Warm water is injected andvaporised in the charge air increasing its absolutehumidity and reducing NOx emission formationrates. In turbo-charged engines the parameters ofcharge air humidity and temperature are obviouslyimportant downstream of the charge air cooler.

    2.11 How does Exhaust Gas Re-circulation (EGR) reduce NOx emissions?Exhaust Gas Re-circulation (EGR) is a method ofmodifying the inlet air to reduce NOx emissions,an approach widely used in automotiveapplications. Some of the exhaust gas is cooled andcleaned before re-circulation to the scavenge airside.

    Its effect on NOx formation is partly due to areduction of the oxygen concentration in thecombustion zone and partly due to the content of

    water and carbon dioxide in the exhaust gas.Introduction of these dilutants reduces flametemperatures by increasing the heat capacity of thecylinder charge per unit mass of fuel. AlthoughEGR is an efficient method of reducing NOxemissions (up to 60%) it is considered morepractical for engines burning ‘clean’ bunkers suchas low sulphur and low ash fuels, alcohol and gas.Engines operating on high sulphur fuels couldsuffer from corrosion of the turbochargers, inter-coolers and scavenging pipes.

    Increased fuel consumption is also associated withEGR due to the retarded heat release rate.

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    2.12 Can combinations of NOx reductionmethods be combined effectively?Research by one manufacturer has shown thatsubstantial reductions in NOx (80%+) have beenobtained with only minor increases in fuel oilconsumption by using the following combination:

    • modified fuel valve and fuel nozzle design with

    • 50% water addition to the fuel (FEW),

    • 20% Exhaust Gas Re-circulation (EGR)

    • Reduced firing pressure by retarding timing

    The effects of these modifications are shown :

    Claimed effects of combining NOx reduction techniques









    e N





    ���1. Reference - standard production engine���

    ���2. Nozzle design modifications���3. Nozzle design + 50% water + Reduced Pmax

    ���4. Nozzle design + 50% water + 20% EGR���5. Nozzle design + 50% water + 20% EGR + Reduced Pmax




    4 5

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    3. IAPP & EIAPP Certificates, Flag States, MARPOL Annex VI and theNOx Technical Code.

    3.1 What is MARPOL 73/78 Annex VIRegulation 13 and the IMO NOx TechnicalCode?In September 1997 the International MaritimeOrganisation (IMO) adopted, by means of aProtocol, a new Annex to the MARPOLConvention. The new Annex, Annex VI, is entitled‘Regulations for the Prevention of Air Pollutionfrom Ships.’ The IMO also adopted the ‘TechnicalCode on Control of Emission of Nitrogen Oxidesfrom Marine Diesel Engines’ (the NOx TechnicalCode).

    The Annex and the NOx Technical Code willbecome mandatory when the required number ofFlag States become signatories to the protocol.

    For compliance with Regulation 13 of the Annex alldiesel engines of 130 kW rated power and above(except those solely for emergency use) installed inships constructed on or after 1 January 2000 arerequired to meet certain Oxides of Nitrogen (NOx)emission limits.

    The NOx Technical Code establishes theprocedures for the testing, survey and certificationof diesel engines to ensure compliance with theNOx emission limits (Regulation 13).

    3.2 What is an IAPP certificate?The International Air Pollution Prevention (IAPP)certificate is issued to the vessel by the flagAdministration or an organisation authorised toact on its behalf, after the owner demonstrates thatthe vessel complies with all relevant requirementsunder MARPOL Annex VI.

    The IAPP is valid for five years, and is subject tosuccessful completion of the vessel’s initial andintermediate surveys.

    These certificates will not be issued until the Annexenters into force under Article 15 of the MARPOLConvention.

    3.3 What is an EIAPP certificate?The Engine International Air Pollution Prevention(EIAPP) certificate is issued by an authorised

    organisation for each applicable engine, enginefamily, or engine group after the enginemanufacturer demonstrates that the enginecomplies with the NOx limits set out in Regulation13 of Annex VI.

    The EIAPP certificate is good for the life of theengine subject to correct maintenance or until itundergoes a major conversion.

    These certificates will not be issued until the Annexenters into force under Article 15 of the MARPOLConvention.

    3.4 Can EIAPP certificates be issued eventhough MARPOL Annex VI has yet to beratified?At this time it is not possible to issue EngineInternational Air Pollution Prevention (EIAPP)Certificates. These can only be issued whenMARPOL Annex VI and the NOx Technical Codeare in force internationally. It is not possible to saywhen they might come into force as it is dependanton the required number of countries signing AnnexVI. Only a statement or certificate of compliancewith the NOx Technical Code can be issued atpresent .

    At MEPC 42 the International MaritimeOrganisation (IMO) adopted a circular which, ineffect, says that diesel engines installed on shipsconstructed on or after 1 January 2000 should havecertification for compliance with the NOxTechnical Code requirements.

    Our information is that statements or certificatesissued by Lloyds Register (and it is assumed byother IACS members) will be accepted by NationalAuthorities. These statements /certificates wouldthen be replaced by EIAPP Certificates issued onbehalf of the flag administration once Annex VIand the NOx Technical Code come into force.

    3.5 What is a Technical File?The Technical File is a record containing all detailsof parameters, including components and settings,that influence the NOx emissions of the engine.

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    According to the NOx Technical Code, theTechnical File must contain the followinginformation;

    • Identification of those components, settings andoperating values of the engine which influenceits NOx emissions,

    • Identification of the full range of allowableadjustments or alternatives for the NOxsensitive components of the engine in order tomaintain compliance within the IMO limits,

    • A full record of the relevant engine’sperformance, including the engine’s ratedspeed and rated power;

    • A system of on-board NOx verificationprocedures to verify compliance with the NOxemissions limits during on-board verificationsurveys in accordance with chapter 6 of thecode;

    • A copy of the emission test report used tocertify the engine

    • If applicable, the designation and restrictionsfor an engine which is a member of an enginegroup or an engine family;

    • Specifications of those spare parts/componentswhich, when used in the engine, according tothose specifications, will result in continuedcompliance of the engine with the NOxemission limits: and

    • The EIAPP certificate or Statement ofCompliance, as applicable.

    3.6 What is a ‘Record Book of EngineParameters’?The Record Book of Engine Parameters is adocument for recording all parameter changes,including components and engine settings, thatmay influence NOx emissions. This is anotheressential document for surveys and inspectionsbecause it contains a record of adjustments to theengine. At each survey the Record Book isexamined to ensure that no changes have beenmade to the engine that might affect NOxemissions.

    Vessel owners must make sure the Record Book isaccurately maintained up to date. If the settings onthe engine do not match those in the Record Book,an engine survey may include a more time-

    consuming investigation and, potentially, on boardmeasurement of NOx emissions.

    3.7 Can LR accept NOx Certificates ofCompliance issued by other IACSClassification Society's for engines thatare to be installed in LR classed whenrequested to do so by the enginebuilder/ship yard?It is not the intention to accept unconditionallycertification by another IACS member, with regardto NOx at this stage. This situation may changewhen methods and requirements of the FlagAdministrations become clearer after ratification.

    3.8 Can a body carry out NOx Emissiontesting of an engine with their ownequipment and then certify that engine?This would not be considered ethical. If the twofunctions were fully separate then this may beacceptable provided the chain of responsibility wastotally separate.

    In general, a third party should be employed towitness the testing and verify the accuracy of theequipment.

    This gives international credence to the testingespecially where the manufacturer may berequesting certification from different flagadministrations.

    3.9 When will MARPOL Annex VI andthe NOx Technical Code come into force?Annex VI of MARPOL 73/78, as adopted by theProtocol of 1997, contains regulations for theprevention of air pollution from ships and includesa resolution which introduces the NOx TechnicalCode.

    Under article 6 of the Protocol of 1997, Annex VIwill come into force 12 months after the date onwhich not less than fifteen States, the combinedmerchant fleets of which constitute not less than 50per cent of the world’s merchant shipping, haveratified it. Some countries have already ratifiedwhilst others are in the process of doing so.

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

    Questions and Answers

    Under paragraph 2 of Resolution 2 to Annex VI theNOx Technical Code will enter force, as mandatoryrequirements, for all Parties to the 1997 Protocol onthe same date as Annex VI comes into force.

    Therefore in spite of possible delays before AnnexVI comes into force, there will be retrospectiveapplication of the nitrogen oxide limits to marinediesel engines with a power output of more than130 kW which are installed in ships, vessels oroffshore installations constructed on or after 1stJanuary 2000. The same limits will also apply tomarine diesel engines with a power output of morethan 130 kW, which undergo a major conversionon or after 1st January 2000.

    3.10 What is meant by a “majorconversion” as detailed in Annex VI?“Major Conversion” means a modification of anengine where:

    • the engine is replaced by a new engine built onor after 1st January 2000, or

    • any substantial modification is made to theengine, or

    • the maximum continuous rating of the engine isincreased by more than 10%

    3.11 What is meant by “substantialmodification”?1.3.2 “Substantial modification of a marine dieselengine means:

    • For engines installed on ships constructed on or after1st January 2000, substantial modification meansany modification to an engine that could potentiallycause the engine to exceed the emissions standardsset out in regulation 13 of Annex VI. Routinereplacement of engine components by parts specifiedin the Technical File that do not alter emissioncharacteristics shall not be considered a “substantialmodification” regardless of whether one part ormany parts are replaced.

    • For engines installed on ships constructed before 1stJanuary 2000, substantial modification means anymodification made to an engine which increases itsexisting emission characteristics established by thesimplified measurement method in excess of theallowances set out in 6.3.11 of the NOx TechnicalCode. These changes include, but are not limited to,

    changes in its operations or in its technicalparameters (e.g., changing camshafts, fuel injectionsystems, air systems, combustion chamberconfiguration, or timing calibration of the engine).

    3.12 Will Annex VI Regulation 13 applyto second-hand engines to be fitted onexisting vessels ?Regulation 13(1)(a)(i) does not apply to second-hand engines, which may have been overhauledbut not modified or the continuous rating is notincreased by more than 10 per cent, if they arefitted to ships, vessels or offshore installationsconstructed before 1st January 2000, as this wouldnot constitute a major conversion under Regulation13(2)(a)(i). Regulation 13 does apply to any enginewith a power output of more than 130kW which isinstalled on a ship constructed on or after 1January 2000.

    Note: All ships will require to be issued with anIAPP certificate once Annex VI is ratified.However, only ships constructed after January 1st,2000 will require to demonstrate compliance withAnnex VI, Regulation 13, unless the engineundergoes a major conversion.

    3.13 What is the procedure for dealingwith enquiries on the certification ofdiesel engines for compliance withMARPOL Annex VI and the NOxTechnical Code?If requested by an owner, builder or enginemanufacturer Lloyd’s Register can carry out therequired technical file approval, testing andcertification for compliance with the NOxTechnical Code and regulation 13 of Annex VI.

    All enquiries regarding certification of dieselengines for compliance with the NOx TechnicalCode must be forwarded to MSG, EngineerServices (ES). ES will advise on the procedures fortechnical file approval and testing requirements.Unless other wise advised by ES, engine emissiontests are NOT to be undertaken without beingcontacted. NOx emission testing can only bewitnessed by authorised surveyors

  • Emissions of Nitrogen Oxides (NOx) from Marine DieselEngines Jul 2002

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    3.14 Which flag states have authorisedLloyd’s Register (LR) to issue NOxcertification?Lloyd's Register (LR) has contacted over 100administrations seeking authorisation to issue NOxcertification on their behalf.

    Many Administrations have intimated that a LRcertificate will be acceptable to them until suchtime as MARPOL 73/78 Annex VI and the NOxTechnical Code come into force. At that time theLR certificate will then be used to issue an EIAPPcertificate either by LR on behalf of theadministration or by the administrationthemselves.

    Where an administration has instructed LR to issuecertificates on behalf of the administration theGovernment Title will be referenced on the LRCertificate.

    The NOx authorisations have been included in theFlag Administration data on the LR web site;Marine/External Affairs/Library "Country Files".This is regularly up dated.

    In general it is our understanding that during theintervening period leading up to ratification themajority of Flag Administrations will accept testsand certification issued by LR for NOx compliantmarine diesel engines.

    3.15 Does MARPOL Annex VI apply tooffshore installations?MARPOL 73/78 Annex VI is applicable to all shipsof 400 tonnes gross and above and to offshoreinstallations which includes fixed and floatingdrilling rigs and other platforms .

    3.16 Where can the texts of Annex VI andthe NOx Technical Code be found?The IMO have published the texts of MARPOLAnnex VI and the NOx Technical Code in a singlepublication. The IMO sales number is IMO-664E,current price £14.00.

    3.17 What are LR’s fees for NOxcertification?LR’s services associated with NOx emissionscertification will be charged on the basis of a LR feefor the review of Technical File, assessment of thetest reports and issue of a certificate, together withthe fees for inspection and witnessing of NOxemission verification tests/survey.

    Fee quotations are based on the submitteddocumentation being complete, and beingsubmitted in the English language, or a languageacceptable to LR. Translation costs may beincurred for documentation submitted in otherlanguages. Where translation charges arenecessarily incurred for technical documentation,such additional charges will be invoiced at cost.

    For initial, periodical and renewal surveys, aquotation will be made upon acceptance of anapplication.

    Should a client withdraw his application forcertification, for whatever reason, LR reserves theright to charge fees for costs already incurred.

    3.18 What is the period of validity of thepre-certification certificate ?The pre-certification certificate remains valid for allengines validated as manufactured in accordancewith the Technical File for the Administrationunder whose authority it is issued.

    Certificates or Statements of Conformity willrequire to be replaced with an EIAPP Certificate onAnnex VI entering into force.

    EIAPP Certificates are to be issued by or on behalfof the respective Flag Administration.

    3.19 What are the allowable NOxemission limits as stated in Annex VIregulation 13?• 17.0 g/kWh where n is less than 130 rpm

    • 45.0*n(-0.2) g/kWh where n is 130 or more butless than 2000 rpm

    • 9.8 g/kWh where n is 2000 rpm or more

    where n is the rated engine speed (crankshaftrevolutions per minute).

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    The maximum values of 17.0 and 9.8 g/kWh andthe simple function of n can be better visualisedgraphically as shown:

    Max NOx Emission limits as a function of rated speed












    0 500 1000 1500 2000 2500

    Rated engine speed (crankshaft rpm)




    x lim

    it (g



    3.20 Which States have already ratifiedAnnex VI? Is there any mechanism toidentify the impediments to entry intoforce?As of early 2001 only three States have ratifiedAnnex VI, namely Norway, Sweden and Singaporerepresenting nearly 9% of the gross world tonnage.

    Conference resolution 1 "INVITES, if the conditionsfor entry into force of the 1997 Protocol have not beenmet by 31st December 2002, the Marine EnvironmentProtection Committee (MEPC), at its first meetingthereafter, to initiate, as a matter or urgency, a review toidentify the impediments to entry into force of theProtocol and any necessary measures to alleviate thoseimpediments".

    3.21 When a ship is classed by LR and theship owner requests NOx certification forengines installed on board, do certificateshave to be issued by LR or are certificatesissued by other classification societiesacceptable?There are two types of certificate that may beissued for compliance with MARPOL Annex VI:

    • Certification for diesel engines, above 130kWwhich are not used for emergency purposes,after satisfactory testing for compliance withthe NOx Technical Code. This is carried out on

    the test bed to demonstrate that the NOxemissions generated by the engine are withinthe limits set out in MARPOL Annex VI,Regulation 13. Marine diesel engines installedon board a new ship after 1st January 2000 mustbe certified in compliance with Regulation 13 ofMARPOL Annex VI and the NOx TechnicalCode. Until MARPOL Annex VI is ratified, thiswill be known as a Certificate or Statement ofCompliance. After ratification it will be termedan Engine International Air PreventionPollution (EIAPP) certificate.

    • Once MARPOL Annex VI is ratified, thenInternational Air Prevention Pollution (IAPP)certificates will become mandatory. Until thenthey are not required unless a specific flagadministration makes it mandatory for shipsregistered by them. The IAPP certificate coversthe following items as applicable to the type ofship being certified: Ozone DepletingSubstances, Nitrogen Oxides (NOx), Oxides ofSulphur (SOx), Volatile Organic Compounds(VOCs), Shipboard Incineration and Fuel OilQuality.

    Certificates are issued for and on behalf of the flagadministration with whom the vessel is registered,similar to current statutory certification.

    Whether an EIAPP certificate issued by oneclassification society is acceptable to another is amatter for the flag administration.

    This is a subject being discussed within theInternational Association of Classification Societies(IACS) Working Group on Exhaust EmissionControls forum but at this time there is no clearconsensus on the procedure to be adopted.

    The on-board surveys and issue of the IAPPcertificates would be carried out by theclassification society who has responsibility for theissue of the ship’s statutory certificates. Since theSociety has been appointed to act for theAdministration, they cannot delegate thatauthority to an other third party.

    In general, since LR is acting for and on behalf ofthe various Flag Administrations LR would preferto witness the testing to allow them to meet theircommitment to the authority. However, where theParent engine EIAPP certificate has been issued byanother body recognised by the FlagAdministration, LR could accept this to certifymember engines subject to certain conditions beingmet.

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    4. On-Board Verification Procedures

    4.1 What is an On-Board VerificationSurvey?Each diesel engine subject to the requirements ofMARPOL 73/78 Annex VI Regulation 13 shall besubject to an initial survey, an intermediate surveyand a periodical survey as part of the ships IAPPsurvey and certification regime. The On-boardVerification Survey is detailed in the approvedTechnical File. It describes the method forconfirming the engine remains in compliance withthe NOx emission limits and forms part of theship's IAPP survey.

    After a pre-certified engine is installed on-board aship, an initial installation verification survey iscarried out to confirm that the engine remains incompliance with the NOx emission limits. The on-board verification survey is not mandatory untilMARPOL Annex VI comes into force when eachship is required to be surveyed for the issue of andIAPP certificate.

    4.2 What methods are available for theOn Board Verification Survey ?Surveys will be conducted on board using one ofthe three methods of NOx Verification described insections 2.4.2 to 2.4.6 of the NOx Technical Code;

    2.4.4 On- board NOx verification procedures shall bedetermined by using one of the following methods:

    • Engine parameter check in accordance with section6.2 of the NOx Technical Code to verify that anengine’s component, setting and operating valueshave not deviated from the specifications in theengine’s Technical File;

    • Simplified measurement method in accordance withsection 6.3 of the NOx Technical Code , or

    • Direct measurement and monitoring method inaccordance with 2.3.4, 2.3.5, 2.3.7, 2.3.8, 2.3.11 and5.5 of the NOx Technical Code .

    4.3 Who decides which system of On-Board Verification is to be used?Making reference to Chapter 6 of the NOxTechnical Code :

    Onboard the vessel it is the owner who decides thesystem to be followed for the onboard verification.

    The engine manufacturer has the responsibility ofpreparing and documenting an engine surveysystem to allow the ship owner to use the systemhe so desires.

    The system is to be prepared by the enginemanufacturer and submitted to theAdministration, or the organisation acting on theirbehalf, for acceptance.

    4.4 What is involved in the EngineParameter Method?The engine parameter method of verificationdocumentation must form part of the TechnicalFile.

    The survey process detailed here is for guidance asto the typical information to be included in thedocumentation.

    This method is a check to verify that thecomponents, settings and operating values of theengine once installed on the vessel remain thesame as those recorded in the Technical File at thetime of the pre-certification.

    It may be carried out on engines which have a pre-certificate (EIAPP certificate), those which havebeen certified after installation (IAPP certificate)and after modifications or adjustments since theprevious survey.

    The surveyor with the assistance of a check sheetwill survey the following and confirm they remainwithin the allowable range specified in theTechnical File;

    • Review existing certificates and documentationon-board the ship.

    • Review the record book of engine parametersnoting all recorded changes and confirmingtheir acceptability or otherwise with theTechnical File.

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    • Inspect engine components affecting NOxemission limits and verify they are correct forthe engine type.

    • Inspect and test the adjustable settings of theengine, as applicable

    • Review and test, where applicable, the engineoperating values.

    • Check NOx emission treatment devices orsystems, where appropriate, and theirconsumption measurement devices,

    • Verify electronic engine management systemsagainst original settings, where relevant.

    • Complete the check list for the ship and submitwith the inspection report to appropriate LRoffice for review and issue of the appropriatecertification.

    4.5 Are deviations from test cyclesallowable when using the simplifiedmeasurement method of on-boardverification?Where maximum or minimum loads cannot beattained or where barred speed ranges precludeoperation the test procedure proposal has to basedon the engine manufacturer’s recommendationsbut be as close as possible to the test cycles definedin chapter 3 of the NOx Technical Code. Theproposal would still have to be approved by theadministration. Engine operation on board under a test cyclespecified in 3.2 may not always be possible, but the testprocedure shall, based on the recommendation of theengine manufacturer and approval by theAdministration, be as close as possible to the proceduredefined in 3.2. Therefore, values measured in this casemay not be directly comparable with test bed resultsbecause measured values are very much dependent onthe test cycles.

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    5. Engine Specifics

    5.1 If an engine is rated above 130 kW butwill NOT be fitted on an Annex VI shipdoes it need to comply?From an engine perspective Annex VI applies to alldiesel engines with a rated power of more than 130kW which are installed on ships constructed on orafter 1 January 2000 and every diesel engine with arated power of more than 130 kW whichundergoes a major conversion on or after 1 January2000.

    From a ship perspective Annex VI applies to allships, of 400 gross tonnnes and above whichoperates under a Flag Administration that hasratified the Annex.

    Note: Administrations who have ratified Annex VIare required to implement the requirements totheir own flag ships and to all other flag shipsoperating in their waters and ports subject to theexemption stated in the Annex.

    However, ships under 400 gross tonnes are onlysubject to the survey requirements at the discretionof the administration. The actual text reads:

    “In the case of ships of less than 400 gross tonnage, theAdministration may establish appropriate measures inorder to ensure that the applicable provisions of thisannex are complied with.”

    In summary, with specific reference to recreationalcraft, the requirements of Regulation 13 apply toall vessels, however only vessels over 400 grosstonnage would be subject to the surveyrequirements of Regulation 5. Vessels below 400gross tonnage would not be subject to the surveyrequirements of Regulation 5 unless the localAdministration establishes the necessary systems.

    Reference should also be made to Regulation13(1)(c) which allows the Administration to permita derogation to ships that are only engaged invoyages between ports within the territory of thatAdministration. This does not only mean that anand Administration could have a lower, or even nolimit values for exhaust emissions for its own intra-national ships, but could actually make stricterprovisions than those of Regulation 13 for its ownflag vessels.

    5.2 Does MARPOL Annex VI apply todiesel driven cargo pumps having a ratedpower greater than 130 kW?Yes. All marine diesel engines with a power ratinggreater than 130 kW, which are not usedspecifically for emergency purposes (i.e.emergency generator engines), are required to becertified in compliance with the NOx TechnicalCode as satisfying the NOx limits as stated inMARPOL Annex VI, Regulation 13. This applies toengines installed on new buildings or existingships from 1st January 2000.

    1.2.1 The NOx Technical Code applies to all dieselengines with a power output of more than 130 kWwhich are installed, or are designed and intended forinstallation, on board any ship subject to Annex VI,with the exception of those engines described inparagraph 1(b) of regulation 13.

    MARPOL Annex VI regulation 13 (1)(b)(i) states:

    This regulation does not apply to emergency dieselengines, engines installed in lifeboats and any device orequipment intended to be used solely in case of anemergency.

    Where engines are not solely for emergency use(i.e. a first start diesel generator which may also beused to supply part of ships electrical load undercertain condition), they are to be subject to therequirements of this Regulation.

    5.3 What is an ‘installed engine’?‘Installed’ relates only to permanently installedengines, that is those as given on the ship’s records.

    Packaged and other temporally installed enginesshould not be included.

    5.4 Can an engine having a higher ratingand more cylinders be certified based on aparent tested for a lower rating and/ornumber of cylinders?The Group and Family engine concepts areavailable to enable serially manufactured enginesto be certified against an approved Parent enginefor that Group/Family in order to reduce theamount of emissions testing to a minimum.

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    The allowable engine types/configurations/ratedpowers and rated speeds have to be approved bythe administration and clearly stated in the ParentEngine Technical File. The chosen Parent Enginefor the Group/Family must be shown to be thehighest NOx emission engine in thatGroup/Family. This means that any enginetype/configuration/rating of a Group/FamilyMember Engine must be shown either by priortesting or other means to be a lower NOx emissionengine than the Parent.

    Justification must be supplied as to why asubsequent engine with a higher rating orincreased number of cylinders is a lower NOxemission engine than the Parent Engine.

    The main criteria in this justification would be alower fuel delivery rate per cylinder.

    Other criteria that may be supplied to justify anengine as a Group/Family Member may include;

    • lower mean effective pressure

    • lower maximum cylinder peak pressure

    • lower compression pressure ratio

    • lower charge air pressure

    • lower charge air temperature

    5.5 Heavy Fuel Oil (HFO) is used inservice in most large marine diesel enginesyet the testing requirements detail the useof Marine Diesel Oil (MDO) to be usedduring the NOx emission test on the testbed. How can the emissions under testbed conditions therefore be related tothose under normal in service operation? The NOx Technical Code states:

    5.3.1 Fuel characteristics may influence the engineexhaust gas emission. Therefore, the characteristics ofthe fuel for the test shall be determined and recorded.Where reference fuels are used, the reference code orspecifications and the analysis of the fuel shall beprovided.

    5.3.2 The selection of the fuel for the test depends onthe purpose of the test. Unless otherwise agreed by theadministration and where a suitable reference fuel is notavailable, a DM-grade marine fuel specified in ISO

    8217, 1996, with properties suitable for the engine type,shall be used.

    If an engine is capable of residual fuel operation, itwill have been decided early in the planningprocess whether residual fuel oil or gas oil is to beused. As stated in the NOx Technical Code, in theabsence of a suitable reference fuel the requirementis simply that the fuels should conform to, and betested to ensure compliance with ISO 8217.

    Most commercial gas oils conforming to ISO 8217DMA or DMB grades are adequate reference fuelsin that the results from different tests can becomparable. There is therefore a requirement thatengines which will subsequently only burnresidual fuel oil should be initially tested using gasoil. The use of a residual fuel oil in such engineswould give results closer to those which would beencountered in service but the wide qualityvariations possible would create questionablerepeatability of the results. It should be noted thatignition quality and fuel bound nitrogen can havea significant effect on the overall in-serviceemissions.

    5.6 Due to technical reasons a Familyengine has to be modified before supply toa vessel. A different turbocharger has beenfitted. Can this engine still be certified asa Family member and if so what is theprocedure?The procedure would be as follows:

    • Submit details of the turbocharger withreasons why it is an acceptable alternative forthe approved NOx compliant diesel engine.Where verifying test results are available theseshould be submitted as part of the evidence.

    • The documentation will be reviewed andapproved if found acceptable. This approvalwill form an addendum to the originalTechnical File to which it is to be attachedcertifying it as an alternative turbocharger forthat series of engines.

    • A copy of the approval and turbochargerinformation should also be provided forattachment to the engine Technical Files toform part of the on board engine parametercheck method information.

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    5.7 A main propulsion engine is to be usedwith a controllable pitch propeller (CPP).This configuration has two differentoperating modes in normal service. Athigh speed the engine speed remainsconstant and the propeller pitch varies. Atlow speed the propeller pitch is fixed andthe engine speed is varied. Which testcycle is applicable?It must be understood that the test cycle appliedshould be in accordance with the normal servicecondition of the engine. In standard CPPconfigurations engine speed is constant and the E2test cycle would be applicable. This configurationwould invariably allow the capability to ‘fix’ theCPP pitch and operate the engine at variable speedas an emergency measure (in the case of a CPPfailure). This condition falls outside the definitionof normal service and therefore there is norequirement to test the engine in accordance withthe E3 cycle.

    In cases where both configurations are designed as‘normal service’ BOTH test cycles (E2 and E3)must be applied during pre-certification testing.The engine would then be provided with acertificate covering each cycle respectively.

    5.8 Two identical engine types are to beinstalled on a twin skeg ship. The onlydifference between them is the direction ofrotation (‘mirror engines’). Will theengine with different rotation from theParent Engine be required to undergofurther NOx testing?There is no requirement by LR to emission test anengine with opposing rotation to that of apreviously NOx certified Parent Engine. This is onthe condition that the engine is equipped withidentical NOx sensitive components to those fittedon the Parent Engine and all settings andadjustments are within the approved ranges asdefined in the Parent Engine Technical File.

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    6. Conformity of Production (COP)

    6.1 What is the purpose of theConformity of Production procedure?What are the roles of the enginemanufacturer, ship owner and surveyor?This relates to engines that are members of either a“family” or a “group” which are serially producedand are intended for compliance with the NOxTechnical Code. The manufacturer is required toimplement an approved control procedure whichwill ensure each subsequent engine is assembledusing identical parts to those installed in the Parentengine giving a presumption of conformity withMARPOL Annex VI, Regulation 13, NOx Emissionlimits. This allows the worst case i.e. highest NOxproducing engine, termed a “Parent engine”, to betested to reduce the number of engine testsrequired.

    The production control system must be in placebefore component manufacturing commences toensure each is to the same design and marked witha unique identifier.

    The attending surveyor monitors the production toconfirm the assembly of the final engine and thatthe control system is being implementedeffectively. After final assembly, the surveyorissues a Verification of Conformity report for theengine.

    For main and auxiliary engines, this monitoringcan be incorporated into the normal classificationinspection procedure. However, for the smallermassed produced engines the monitoring can bebased on a suitable quality scheme (LR QualityScheme for Machinery), in view of the volumeproduced. Reference should be made to the LRguidance document 'Conformity of Productionprocedure' for further information.

    The ship owner's role is to purchase a NOxcertified engine and to maintain it in compliancewith the NOx Emission limits. Thus, duringmanufacture he must not request modificationswhich would place the engine outside the limitsunless it is to be re-certified.

    6.2 What is a Conformity of ProductionVerification Report?This is a report prepared by the attending surveyorverifying that the subject ‘series produced’ engineshave been manufactured from compliantcomponents as identified in the Parent TechnicalFile in accordance with the manufacturersapproved Conformity of Production procedures.

    The form is prepared for each engine or series ofengines and forwarded to the approval office aspart of the approval procedure.

    The NOx Verification of Conformity Reportprovides the approval office with the necessaryconfirmation of the engine(s) presumption ofconformity with the Parent Engine NOx emissionlimits allowing the submitted Technical Files to beverified and approved.

    Typical form of a NOx Verification of Conformityreport:

    DateReport No.


    NOx VERIFICATION OF CONFORMITY REPORTSeries Produced Marine Diesel Engines

    Compliance withNOx Emission Limits

    This is to certify that the following Marine Diesel Engine(s) components and markingswere verified as complying with those detailed in the approved Parent EngineTechnical File during manufacture and assembly.

    Engine Type :Serial No(s) :Date of Manufacture :Parent Engine Type :Parent Engine TechnicalFile Approval No. :

    Surveyor yo Lloyd’s Register

    Ver_con.doc 8.99 Rev01

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    6.3 At what stage should the Conformityof Production procedure be put in place?The engine builder should be encouraged to have aConformity of Production procedure in placebefore testing the Parent engine. Normally thismeans incorporating the NOx controls into hisexisting engine production procedures.

    This ensures that he can easily demonstratethrough this system that the NOx sensitivecomponents in subsequent engines, after theparent, are the same as those components in theparent.

    Such a system is designed to reduces any necessityto test subsequent engines.

    6.4 Should the Conformity of Productionprocedure be included in the TechnicalFile?The Conformity of Production procedure is to besubmitted to the Administration for review andapproval as part of the certification process. Acopy of this document is retained by theAdministration together with the Technical Fileand any other ‘additional information’ submittedat the review stage. It is not required to form partof the Technical File as supplied with the engine.

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    7. Pre-Certification Testing

    7.1 What is Pre-certification testing?This is undertaken on the test bed at the enginemanufacturer’s works to ensure that the engine asdesigned and equipped complies with the NOxemission limits contained in regulation 13 ofAnnex VI. Under certain circumstances this maybe conducted on board the ship after installationand prior to entering service and issue of the IAPPcertificate.

    On completion of the approval process LR willissue either an LR Certificate or Statement ofCompliance or an Engine International AirPollution Prevention (EIAPP) Certificate whereauthorised by the Administration once Annex VI isratified.

    7.2 How much time should be allocatedto a Parent Engine test bed programme?Who should attend?

    Sufficient time needs to be allocated in the ParentEngine test bed programme to allow for theinspection of the engine to ensure that it conformswith the proposed Parent Engine design, fit andadjustment. The test bed equipment will need to beassessed for compliance with the NOx TechnicalCode requirements, this would include a review ofcalibration certification for the analysers and othermeasurement equipment.

    The actual parent engine test would be expected totake from 3-8 hours under the specified Coderequirements. From LR’s viewpoint this attendancewill be undertaken only by Surveyors with thenecessary experience, training and authorisation.

    7.3 On fuel testing.5.3.2 The selection of the fuel for the test depends on thepurpose of the test. Unless otherwise agreed by theAdministration and when a suitable reference fuel is notavailable, a DM-grade marine fuel specified in ISO8217, 1996, with properties suitable for the engine type,shall be used.

    Oil fuel used for the test is to be analysed for eachof the parameters in the ISO 8217 specification pluscarbon, hydrogen and nitrogen.

    They are not required to be tested for oxygencontent since this is taken as zero.

    When testing for ISO 8217 grades DMA and DMBthe ignition performance parameter is strictly to bedetermined as Cetane Number not Cetane Indexsince the latter cannot determine the effect of anycetane improvers.

    7.4 On exhaust gas analytical systems. An analytical system for the determination ofthe gaseous emissions (CO, CO2, HC, NOx, O2) in theraw exhaust gas shall be based on the use of thefollowing analysers:

    • Heated Flame Ionisation Detector (HFID) for themeasurement of hydrocarbons;

    • Non-Dispersive Infra-Red (NDIR) analyser for themeasurement of carbon monoxide and carbondioxide;

    • Heated ChemiLuminescent Detector (HCLD) orequivalent analyser for the measurement of nitrogenoxides; and

    • ParaMagnetic Detector (PMD), ElectroChemicalSensor (ECS) or ZiRconium DiOxide (ZRDO)sensor for the measurement of oxygen.

    The NOx Technical Code does not provide foralternative analyser principles to be used (unlikeISO 8178). In order to avoid, at least some of, thepossible problems with the future reproducibilityof test results only the analytical principles asgiven will be acceptable, i.e. onlychemiluminescence analyser is to be used for NOxmeasurements

    7.5 On non standard air inlet and exhaustsystems. The settings of inlet restriction and exhaust backpressure shall be adjusted to the upper limits as specifiedby the manufacturer in accordance with 5.2.4 and 5.2.5,respectively.

    In order to meet the requirements of 5.2.4 the inletair system should be adjusted, where a non-standard air inlet system is to be used, to give theminimum inlet depression i.e. maximum absolute

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    pressure post filter or at turbo-blower compressorinlet.

    In order to meet the requirements of 5.2.5 theexhaust system should be adjusted, where (aswould more normally be the case than for the inletair system) a non-standard exhaust system is to beused, to give the minimum pressure post turbo-blower turbine exhaust.

    7.6 On intermediate zero and span checks5.9.9 After the emission test, the calibration of theanalysers shall be re-checked using a zero gas and thesame span gas as that used prior to the measurements.The test shall be considered acceptable if the differencebetween the two calibration results is less than 2%.

    Analysers may be subject to intermediate zero andspan checks (i.e. between test load points), inwhich case the drift allowance is to be consideredbetween two consecutive checks. The span andzero may with some instruments be checkedwithout necessarily re-setting the analysers, inother cases such checks will automatically reset thevalues and hence could mask unacceptableperformance.

    7.7 On alternative test standards forEngine Family Certification. If the parent engine of an engine family is to becertified in accordance with an alternative standard or adifferent test cycle than allowed by the NOx TechnicalCode, the manufacturer must prove to theAdministration that the weighted average NOxemissions for the appropriate test cycles fall within therelevant limit values under regulation 13 of Annex VIand the Code before the Administration may issue anEIAPP certificate.

    The use of alternatives to those given in the Code,(i.e. CIMAC, national standards) would not beconsidered acceptable. Every effort should bemade to adhere closely to the requirements asstated in the NOx Technical Code and not tointroduce other test methods into the approvalsprocess.

    Even in terms of the test cycle, ISO 8178 is specificas to the order of the load points although it shouldbe understood that this is principally related to theeffect of load cycle order on hydrocarbon andparticulate emissions.

    If alternative methods etc. were to be adopted itwould remain necessary for the test conditionparameter to remain valid and that, as a minimum,the data required by the NOx Technical Code beobtained - under survey conditions.

    7.8 On the Test Condition Parameter andtest validity for engine family approval5.2.1 Parameter fa shall be determined according to thefollowing provisions:

    For naturally aspirated and mechanically superchargedengines:







    For turbocharged engines with or without cooling ofintake air:






    0 1 5.7 .

    Where Ps is dry atmospheric pressure (kPa) and Ta is theabsolute temperature of intake air (K).

    For a test to be recognised as valid, parameter fa shall besuch that:

    0 98 102. .≤ ≥fa

    It is stressed that this requirement applies only toFamily Parent Engine emission tests.

    The test condition parameter must be retainedwithin the required range across the whole of theengine test period

    Barometric pressure and ambient air temperaturereadings should be entered as whole numbers onlywith the result reported to the second decimalplace.

    At the Marine Environment Protection Committee(MEPC) 44th session it was agreed to approve aproposed amendment to paragraph 5.2.1 of theNOx Technical Code. The MEPC drafting group intheir report MEPC 44/WP.5 noted that it may notbe possible, due to engine size, to provide testfacilities where barometric pressure, temperatureand humidity of the intake air can be controlled to

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    maintain the ‘fa’ factor within the range 0.98 < fa >1.02. In consequence, the test for engine familyapproval may only be possible for a limited periodduring the year. The approved amendment statesthat the following statement is to be added to theend of paragraph 5.2.1:

    “If, for evident technical reasons, it is not possible tocomply with this requirement, fa shall be between 0.93and 1.07.”

    This amendment was approved but will not beadopted until Annex VI comes into force.

    To allow uniform application of the NOx TechnicalCode, and to assist Administrations in certifyingengines in accordance with it, this amendment isrecommended to be used prior to its date of entryinto force.

    7.9 Who decides which method of NOxcalculation is to be used?The responsibility to produce calculation resultslies with the engine manufacturer, or personsnominated by himself to act on his behalf, withregard to testing.

    It is the role of the Flag State Administration, orClassification Society acting on their behalf, towitness the testing and validate results andcalculations. LR’s validation, to date, has shownno significant divergences from the requirementsof the NOx Technical Code.

    7.10 Many auxiliary marine dieselengines are coupled to alternators andinstalled as generating sets. Can thisalternator be used on the test bed as theload dynamometer?The NOx Technical Code is written for testing witha dynamometer since in most instances it is notpossible to operate with the driven equipmentinstalled.

    Where it is possible to carry out testing in thecompleted condition, such as with the generatorinstalled, then it is acceptable to test in thiscondition provided the required test (e.g. D2) maybe followed.

    The alternator efficiency is normally evaluated atthe alternator trials. It is therefore not necessary toevaluate the efficiency during the NOx emission

    testing. Calculation using the manufacturer’s valueis acceptable.

    7.11 The NOx Technical Code statestesting is to be undertaken with a seawater temperature of 25°°°°C. What doesthis mean?This section of the NOx Technical Code describesthe procedures for NOx emission measurements ona test bed concerning only engines with charge aircooling: All engines when equipped as intended forinstallation on board ships must be capable of operatingwithin the allowable NOx emission levels of regulation13(3) of Annex VI at an ambient seawater temperatureof 25°C. 25°C seawater temperature is the referenceambient condition to comply with the NOx limits. Anadditional temperature increase due to heat exchangersinstalled on board, e.g., for the low temperature coolingwater system, shall be taken into consideration.

    The fresh water cooler outlet temperature, andhence the charge air cooling capability, must bebased on the inlet temperature of 25°C for the FWcooler coolant.

    For the test bed measurements this will require theprimary cooling circuit temperature to be suitablyadjusted

    7.12 It is sometimes difficult to simulatethe required 25°°°°C sea water temperaturedue to the limitations of the cooling watersupply at the factory. Can the test beperformed at a higher temperature?It must be understood that the seawatertemperature shall not be lower than 25°C for thepre-certification testing as reduced temperaturesresult in reduced NOx emission values.

    It is acceptable to allow a higher temperature at thetest bed as long as it maintains the engine atnormal operating temperatures as specified by themanufacturer and also that he is aware that themeasured NOx value will be higher.

    This temperature should also be recorded in thetest report.

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    7.13 What are the requirementsconcerning the design of the exhaust gassampling probe? In the LR Pre-certification checklist it states that the‘maximum sensor length in exhaust trunkshould be 0.75 times the exhaustdiameter’. Does this apply to multi-holedsensors?The NOx Technical Code does not specify the typeof sampling probe that should be fitted during theNOx emission pre-certification test. The testprocedure as stated in the NOx Technical Code isbased on the British Standard EN ISO 8178-1:1996(Reciprocating internal combustion engines -Exhaust emission measurement; Part 1 Test-bedmeasurement of gaseous and particulate exhaustemissions). This standard recommends a stainlesssteel, straight, closed-end, multi-hole probe:

    “The inside diameter shall not be greater than the insidediameter of the sampling line. The wall thickness of theprobe shall not be greater than 1mm. There shall be aminimum of 3 holes in 3 different radial planes sized tosample approximately the same flow. The probe mustextend across at least 80% of the diameter of the exhaustpipe.

    LR will accept an open-ended sampling probe onthe condition that it samples a representative gassample and therefore the open end should belocated sufficiently near the exhaust pipe axialcentre-line to negate the effects of samplingboundary layers of gas from the internal surface.The maximum figure of 75% penetration of theexhaust pipe diameter stated in the pre-certification checklist would facilitate thisrequirement and therefore would only apply toopen ended sampling probes.

    7.14 Why is the location of the samplingprobe relative to the engine and exhaustgas system exit so important? The sampling probes for the gaseous emissionsshall be fitted at least 0.5m or 3 times the diameter of theexhaust pipe – whichever is the larger – upstream of theexit of the exhaust gas system, as far as practicable, butsufficiently close to the engine so as to ensure anexhaust gas temperature of at least 70°C at the probe.

    The gaseous emission samples are required to betaken from a point at least 0.5m or 3 times the

    diameter of the exhaust pipe – whichever is thelarger – upstream of the exhaust gas exit to avoidpossible dilution of the exhaust gas sample by airstreams blowing across the atmospheric outlet.

    The specified minimum gas temperature of 70°C atthe sampling probe is stated to avoid anysignificant condensation of hydrocarbon (HC)material in the section of the exhaust system priorto the probe. At lower temperatures some of thecarbon material present (which would haveregistered as part of the HC emissions at highertemperatures) would be lost from the system.

    Typically the sample will be drawn from a pointcloser to the turbocharger outlet than exhaustsystem exit to atmosphere, resulting in gas sampletemperatures above 70°C to negate problems withHC condensation.

    To prevent the condensation of water vapour,nitrogen dioxide (NO2), and some of the HCspecies present, both the gas filter and the lineused to transfer the sample down to the analysersshould be heated, typically being maintained at190°C.

    7.15 How should the exhaust gas samplebe taken in ‘Vee’ engine configurations ? In multi-cylinder engines having distinct groupsof manifolds, such as in a “Vee” engine configuration, itis permissible to acquire a sample from each groupindividually and calculate an average exhaust emission.Other methods which have been shown to correlate withthe above method may be used. For exhaust emissioncalculation, the total exhaust mass flow must be used.

    When an engine is configured with distinct groupsof exhaust manifolds the practice of simplyconnecting the gas sample hoses together using 'y'connectors would not necessarily give arepresentative sample of the engine in that exactbalance between each manifold group is assumed.

    A sample must be acquired individually from eachmanifold group and the results mathematicallyaveraged.

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    8. Parent, Family and Group Engine Concepts

    8.1 What are the engine Family andengine Group concepts?Engines may be individually tested to demonstratethat they satisfy the MARPOL Annex VIRegulation 13 NOx limits.

    Alternatively, a manufacturer may nominate aParent Engine to be tested as representative of anengine family or engine group member to avoidtesting every engine which is intended to beserially produced in that range.

    The engine family concept may be applied toseries produced engines which have similar NOxemission characteristics where no modifications oradjustments which would affect the NOxemissions are required when installed on board aship. Where adjustable features are provided (e.g.for balancing cylinder peak pressures andindividual cylinder exhaust gas temperatures) theyare to be such that no setting, or combinations ofsettings, can adversely affect the engine’s NOxemissions. For engines within a particular familythe applicable characteristics detailed in 4.3.8 of theNOx Technical Code should be common to thoseengines.

    The engine group concept may be applied tosimilar type engines which require minoradjustment or modification during installation orin service on board a ship but whose NOx emissionwill still remain within the NOx emission limit forthe engine. These engines are normally seriesproduced in low numbers such as large poweredpropulsion engines.

    For engines within a particular group, theapplicable characteristics as detailed in chapter4.3.8 of the NOx Technical Code as well as thoseparameters and specifications indicated in chapter4.4.5.2 of the NOx Technical Code should becommon to those engines.

    With regard to the allowable adjustments withinan engine group the manufacturer is to providedocumentary evidence and/or historical data (e.g.previous test reports) to substantiate that the rangeof adjustments which are included in the TechnicalFile will permit the engine to operate within theemissions limits as set down in MARPOL AnnexVI Regulation 13(3)(a) and chapter 3 of the NOxTechnical Code.

    Some manufacturers have termed such testsParameter Sensitivity tests.

    It will be up to the attending surveyor, at the timeof the Parent Engine emission test to confirm thatthe allowable adjustments do not result in the totalweighted average NOx emission value of thatengine exceeding the permissible limits.

    In selecting the Parent Engine for a group the mostadverse features affecting the NOx emission levelshould be incorporated. In general the ParentEngine should have the highest NOx emissionlevel of any of the proposed configurations definedby the manufacturer as the engine Group.

    8.2 On Parent Engine selection for aFamily.4.3.3 The selection procedure for the parent engine issuch that the selected engine incorporates those featureswhich will most adversely affect the NOx emission level.This engine, in general, shall have the highest NOxemission level among all of the engines in the family.

    For the engine family concept the Parent Enginemust be selected based on criteria contained inchapter of the NOx Technical Code

    The parent engine must have the highest NOxemission value (as a weighted average in terms ofg/kWh).

    8.3 On the selection of a Parent Enginefor an Engine Group.4.4.7 The selection of the Parent engine shall be inaccordance with the criteria in 4.3.9 (Guidelines forSelecting the Parent Engine of an Engine Family), asapplicable. It is not always possible to select a parentengine from small volume production engines in thesame way as the mass produced engines (engine family).The first engine ordered may be registered as the parentengine. The method used to select the parent engine torepresent the engine group shall be agreed to andapproved by the Administration.

    For the engine group concept the Parent Enginemust be tested with the allowable adjustments setto those positions documented in the Technical Filewhich give the worst NOx emission limits.

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    The engine’s actual NOx emission value is thevalue obtained at the time of the test bed test of theParent Engine with the engine adjusted, within theallowable parameters as documented in theTechnical File, to give the worst case (highest) NOxemissions. This will ensure that the Parent Engineand all members of the group (or family) alwaysoperate at or below this worst case scenario andtherefore are always in compliance with the AnnexVI Regulation 13 limits.

    8.4 On the Parent Engine selection for afamily.4.4.5 The Administration shall review for certificationapproval the selection of the parent engine within thefamily and shall have the option of selecting a differentengine, either for approval or production conformitytesting, in order to have confidence that the completefamily of engines complies with the NOx emissionlimits.

    Where an Administration selects a different enginefrom that proposed by the engine builder then theengine builder could elect to test both but couldproceed on the basis of testing only the engine asselected by the Administration.

    8.5 On the Family concept andConformity of Production.4.3.7 Before granting an engine family approval, theAdministration shall take the necessary measures toverify that adequate arrangements have been made toensure effective control of the conformity of production.

    The extension of the engine family approval toother sites (whether or not part of the parentengine builder company) is dependant on wherecontrol lies which ensures conformity ofproduction. Where another site is responsible forits own conformity of production that buildercannot be covered by the original parent enginecertification.

    What is the definition of the word ‘adequate’ (hereand in subsequent references to the conformity ofproduction)? The existence of an ISO 9000 QualityAssurance scheme does not automatically satisfythe Conformity of Production (COP) controlprocedure requirements (section 6).

    8.6 Do tests which are used to producedata on which to base the Parent Engineselection have to be carried out undersurvey conditions?4.3.4 On the basis of tests and engineering judgement,the manufacturer shall propose which engines belong toan engine family, which engine(s) produce the highestNOx emissions, and which engine(s) should be selectedfor certification testing

    Tests which are used to produce data on which tobase the Parent Engine selection do not need to becarried out under survey conditions. Howeverthose tests do need to be carried out in accordancewith the NOx Technical Code procedures.

    Sufficient data must be submitted in order that theresults of such in-house testing can be verified aspart of the approval process.