4.4 Application of the engine group concept
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Statutory Documents - IMO Publications and Documents - International Codes - NOx Technical Code (2008) - Technical Code on Control of Emission of Nitrogen Oxides from Marine Diesel Engines - Chapter 4 - Approval for serially manufactured engines: engine family and engine group concepts - 4.4 Application of the engine group concept

4.4 Application of the engine group concept

  4.4.1 Engine group engines normally require adjustment or modification to suit the onboard operating conditions, but these adjustments or modifications shall not result in NOx emissions exceeding the applicable limits in regulation 13.

  4.4.2 The engine group concept also provides the possibility for a reduction in approval testing for modifications to engines in production or in service.

  4.4.3 In general, the engine group concept may be applied to any engine type having the same design features as specified in 4.4.6, but individual engine adjustment or modification after test-bed measurement is allowed. The range of engines in an engine group and choice of parent engine shall be agreed to and approved by the Administration.

  4.4.4 The application for the engine group concept, if requested by the engine manufacturer or another party, shall be considered for certification approval by the Administration. If the engine owner, with or without technical support from the engine manufacturer, decides to perform modifications on a number of similar engines in the owner’s fleet, the owner may apply for an engine group certification. The engine group may be based on a parent engine that is a test engine on the test bench. Typical applications are similar modifications of similar engines in similar operational conditions. If a party other than the engine manufacturer applies for engine certification, the applicant for the engine certification takes on the responsibilities of the engine manufacturer as elsewhere given within this Code.

  4.4.5 Before granting an initial engine group approval for serially produced engines, the Administration shall take the necessary measures to verify that adequate arrangements have been made to ensure effective control of the conformity of production. The requirements of 4.3.7 apply mutatis mutandis to this section. This requirement may not be necessary for engine groups established for the purpose of engine modification on board after an EIAPP Certificate has been issued.

4.4.6 Guidance for the selection of an engine group

4.4.6.1 The engine group may be defined by basic characteristics and specifications in addition to the parameters defined in 4.3.8 for an engine family.

4.4.6.2 The following parameters and specifications shall be common to engines within an engine group:

  • .1 bore and stroke dimensions;

  • .2 method and design features of pressure charging and exhaust gas system:

    • - constant pressure;

    • - pulsating system;

  • .3 method of charge air cooling system:

    • - with/without charge air cooler;

  • .4 design features of the combustion chamber that effect NOx emission;

  • .5 design features of the fuel injection system, plunger and injection cam or gas valve which may profile basic characteristics that effect NOx emission; and

  • .6 rated power at rated speed. The permitted ranges of engine power (kW/cylinder) and/or rated speed are to be declared by the manufacturer and approved by the Administration.

4.4.6.3 Generally, if the criteria required by 4.4.6.2 are not common to all engines within a prospective engine group, then those engines may not be considered as an engine group. However, an engine group may be accepted if only one of those criteria is not common for all of the engines within a prospective engine group.

4.4.7 Guidance for allowable adjustment or modification within an engine group

4.4.7.1 Minor adjustments and modifications in accordance with the engine group concept are allowed after pre-certification or final test-bed measurement within an engine group upon agreement of the parties concerned and approval of the Administration, if:

  • .1 an inspection of emission-relevant engine parameters and/or provisions of the onboard NOx verification procedures of the engine and/or data provided by the engine manufacturer confirm that the adjusted or modified engine complies with the applicable NOx emission limit. The engine test-bed results in respect of NOx emissions may be accepted as an option for verifying onboard adjustments or modifications to an engine within an engine group; or

  • .2 onboard measurement confirms that the adjusted or modified engine complies with the applicable NOx emission limit.

4.4.7.2 Examples of adjustments and modifications within an engine group that may be permitted, but are not limited to those described below:

  • .1 For onboard conditions, adjustment of:

    • - injection or ignition timing for compensation of fuel property differences,

    • - injection or ignition timing for maximum cylinder pressure,

    • - fuel delivery differences between cylinders.

  • .2 For performance, modification of:

    • - turbocharger,

    • - injection pump components,

    • - plunger specification,

    • - delivery valve specification,

    • - injection nozzles,

    • - cam profiles,

    • - intake and/or exhaust valve,

    • - injection cam,

    • - combustion chamber.

    • - gas valve specification.

4.4.7.3 The above examples of modifications after a test-bed trial concern essential improvements of components or engine performance during the life of an engine. This is one of the main reasons for the existence of the engine group concept. The Administration, upon application, may accept the results from a demonstration test carried out on one engine, possibly a test engine, indicating the effects of the modifications on NOx emissions that may be accepted for all engines within that engine group without requiring certification measurements on each member engine of the engine group.

4.4.8 Guidance for the selection of the parent engine of an engine group

4.4.8.1 The selection of the parent engine shall be in accordance with the criteria in 4.3.9, as applicable. It is not always possible to select a parent engine from small-volume production engines in the same way as the mass-produced engines (engine family). The first engine ordered may be registered as the parent engine. Furthermore at the pre-certification test where a parent engine is not adjusted to the engine-builder-defined reference or maximum tolerance operating conditions (which may include, but not limited to, maximum combustion pressure, compression pressure, exhaust back pressure, charge air temperature) for the engine group, the measured NOx emission values shall be corrected to the defined reference and maximum tolerance conditions on the basis of emission sensitivity tests on other representative engines. The resulting corrected average weighted NOx emission value under reference conditions is to be stated in 1.9.6 of the Supplement to the EIAPP Certificate. In no case is the effect of the reference condition tolerances to result in an emission value that would exceed the applicable NOx emission limit as required by regulation 13. The method used to select the parent engine to represent the engine group, the reference values and the applied tolerances shall be agreed to and approved by the Administration.

4.4.9 Certification of an engine group

4.4.9.1 The requirements of 4.3.10 apply mutatis mutandis to this section.

Parent topic: Chapter 4 - Approval for serially manufactured engines: engine family and engine group concepts
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