The Republic of the Marshall Islands issued marine guideline referring to the application of Regulation 13 of MARPOL Annex VI Tier III requirements to dual fuel and gas- fueled engines.
The NOx certification requirements of MARPOL Regulation VI/13 include dual fuel engines (those which can simultaneously use both liquid and gas fuels). MEPC 66 adopted amendments to the NOx Technical Code 2008 in order to specifically cover certain specific aspects related to the NOx certification of those engines.
MEPC 67 adopted amendments to MARPOL Annex VI which extend the scope of the definition of a marine diesel engine as given by Regulation 2.14 to include gas-fueled engines installed on ships constructed on or after 01 March 2016 and also such engines installed as additional or non-identical replacement engines on or after that date.
MEPC 68 subsequently approved amendments to the NOx Technical Code 2008 relating to the certification of gas-fueled engines. As such, these steps may be seen as complementary to the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code), adopted by MSC 95 in June 2015 (IMO Resolution MSC.391(95)).
Gas-fueled engines, where ignition is initiated by a spark plug or another external ignition device, are generally expected to readily meet the Tier III NOx emission limits and therefore it is possible that engine builders will seek only Tier III certification for such engines, irrespective of whether they are to be installed on ships which operate outside or inside Emission Control Areas (ECA) for NOx as described in regulation 13.6 of MARPOL Annex VI, currently the North American ECA and the United States Caribbean Sea ECA, both of which took effect as-of 01 January 2016.
In the case of dual fuel engines, those engines which use gas fuel in a pre-mix combustion process with the liquid fuel as the pilot ignition source (as opposed to gas-diesel engines which use high pressure gas injection directly into the combustion chamber) are expected to be certified to the Tier III NOx standards when operating in that arrangement.
Consequently, the Technical Files for such engines will include the restriction that, when operating in the Tier III condition, the liquid fuel rate will be limited to the certified maximum liquid pilot fuel rate and those engines will undergo their Tier III Parent Engine test on that basis.1 These engines are expected to be certified to the Tier II NOx standards when operating on liquid fuel oil only. In these cases, the EIAPP Certificate would be completed for both Tier II (liquid fuel only) and Tier III (gas fuel with pilot fuel), with a single Technical File giving two different modes of operation.
Circular MEPC.1/Circ.854 contains additional guidance regarding:
- recordkeeping (paragraph 6 therein);
- actions to follow in the event of operational problems (paragraph 7 therein);
- procedures to follow if gas fuel is not available (paragraph 8 therein); and
- the use of auxiliary control devices (ACDs) (paragraph 9 therein).
Operators should be familiar with these when operating dual fuel and gas-fueled engines.
Source: Marshall Islands
