Answer
The concepts of Engine Family and Engine Group are established under the NOx Technical Code (adopted under Regulation 13 of MARPOL Annex VI) to facilitate the certification of marine diesel engines regarding their NO_x emission levels without needing to test every single engine on the test bed.
Key Conceptual Difference
Feature | Engine Family (Series Production) | Engine Group (operational / Modified) |
|---|---|---|
Primary Context | Newbuild / Series Production | Retrofits / In-Service Modifications / Minor variations |
Commonality | Engines are technologically identical regarding emissions. | Engines have similar emission characteristics but may be altered operationally. |
Application | Only the Parent Engine in a production series undergoes full certification testing. Other "member" engines get a statement of compliance based on the parent. | Used when a certificated Engine Family undergoes modifications (e.g., retrofit, tuning change) which are permitted within defined limits. Only the Parent Engine is verified. |
Modification Limits | Very strict, minimal deviation allowed from the Parent Engine specification. | Greater flexibility allowed for operational adjustments or alternative components, provided they are within approved technical limits. |
Detail on Engine Family
- Definition: A series production of engines where all engines possess identical characteristics regarding their design and are expected to possess identical emission characteristics.
- Parent Engine Concept: One engine is selected as the Parent Engine and undergoes the mandatory emission test to determine the fundamental emission levels for the entire family.
- Member Engines: All subsequent member engines built to the identical specification get certified based on the results of the Parent Engine. Minimal adjustments are allowed.
Detail on Engine Group
- Definition: An concept designed for in-service operational flexibility, permitting similar technological modifications to a range of technologically similar engines without individual testing.
- Application: Applies primarily to engines that are altered, adjusted, or modified after the initial certification. This includes:
- Re-rating of the engine.
- Alternative fuel operation (e.g., dual-fuel retrofit).
- Modification of turbochargers or fuel injection systems within specific approved limits.
- How it works: The Parent Engine of the group is verified. If its modification remains within the technical file limits, the entire Engine Group remains compliant.