The IMO’s Marine Environment Protection Committee (MEPC) has produced Guidance on the Application of Regulation 13 of MARPOL Annex VI Tier III Requirements to Dual Fuel and Gas-fuelled Engines, published as circular MEPC.1_Circ.854.

This provides the following clarification on outstanding issues concerning engine NOx certification for dual fuel and gas-fuelled marine engines:   

  1. For dual fuel engines that use gas fuel in a pre-mix combustion process with the liquid fuel as the pilot ignition source, the Tier III parent engine certification test should be carried out using the maximum liquid pilot fuel rate.
  2. One EIAPP certificate can include both Tier II (liquid fuel only) and Tier III (gas fuel with pilot fuel), and one single NOx Technical File can include both Tier II and Tier III operation modes.
  3. The NOx Technical File should include a written procedure showing how the Tier change-over is to be done.
  4. The auxiliary control devices (ACD) used on dual fuel or gas-fuelled engines can cover the following engine situations, such as starting and stopping, low load operation and manoeuvring and reversing operation. These ACDs should be disclosed at the time of engine Tier III certification and denoted in the engine’s NOx Technical File.

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