MAN Diesel’s type 51/60DF four-stroke, medium speed dual-fuel gas engine has passed the final landmark on its way to its first commercial applications in the marine sector.
Having gained type approval in autumn 2007 on the seven cylinder prototype engine in the presence of eight major classification societies, the first production versions of the 51/60DF recently completed their factory acceptance tests (FAT) at MAN Diesel’s Augsburg works. The FATs were witnessed by representatives from shipyard STX of Korea, ship owner EN Elcano of Spain and classification society Bureau Veritas.
These first 51/60DF engines for marine application will power the world’s largest liquefied natural gas (LNG) carrier with electric propulsion based on dual-fuel engines. The new vessel will have an LNG capacity of 46 million gallons and its propulsion and onboard electrical power system follows MAN Diesel’s versatile diesel-electric concept, which stresses a high degree of fuel flexibility, redundancy and maintainability at any time during a voyage. This overall flexibility is based on five equally rated inline 51/60DF dual-fuel engines - in this case inline eight cylinder type 8L51/60DF engines each producing 8000 kW at 514 rpm. Compared to configurations consisting of vee and inline engines, the all inline concept maximizes load sharing potential and allows any engine to be serviced at any time without affecting the LNG carrier‘s sailing schedule or the engines’ level of fuel flexibility.
MAN Diesel states that testing of the five engines went smoothly. All planned operations were completed on time within a tight schedule to the full satisfaction of the yard, the ship owner and the Classification Society. The engines are now on their way from Germany to STX Shipbuilding in Korea. 51/60DF Dual-Fuel Technology Announced in 2006, MAN Diesel’s 51/60DF dual-fuel engine is based on the 48/60B heavy fuel engine and offers a 1000 kW/cylinder output in both gaseous and liquid fuel operating modes. For marine applications it is offered in inline versions with 6, 7, 8 and 9 cylinders and vee configuration versions with 12, 14, 16, and 18 cylinders.
The 51/60DF dual-fuel gas engine can be run on either gaseous fuel or liquid fuel and can switch between fuels at any engine load. In its gaseous fuel mode the engine burns natural boil-off gas (NBOG) evaporating from the LNG cargo, ignited by a distillate fuel micro-pilot. The distillate fuel micro-pilot amounts to less than 1% of the energy required by the 51/60 DF engine and is injected via a common rail system which allows flexible setting of injection timing, duration and pressure for each cylinder. In the back-up liquid fuel mode, the 51/60DF engine operates as a normal diesel engine injecting either marine diesel oil (MDO) or heavy fuel oil (HFO) through a separate, normally dimensioned injector in a camshaft actuated pump-line-nozzle system. At 1.5 g/kWh (IMO cycle E2), in gaseous fuel mode the 51/60DF already complies with IMO Tier III limits for emissions of oxides of nitrogen (NOx) by considerable margins.