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LNGCs primed 50DF engine sales surge


A dominant status in LNG carrier propulsion has been secured by Wärtsilä’s 500mm-bore medium speed dual-fuel engine, whose environmental merits are increasingly appreciated in other sectors


by Doug Woodyard A pioneer in applying dual-fuel


technology to marine engines, Wärtsilä continually extends its references in diverse arenas with a programme embracing 20DF, 34DF and 50DF medium speed designs. With respective bore sizes of 200mm, 340mm and 500mm, these engines cover an output range from 1,000kW to 17.5MW to target a wide range of shipping and offshore propulsion and genset market opportunities.


Over 1,000 Wärtsilä DF engines delivered by October last year had accumulated more than 7 million operating hours, 50DF models forming the electric power stations of LNG carriers accounting for a significant number of these installations.


Other references include the new P-63 FPSO vessel entering service offshore Brazil, whose 50DF machinery is the first to exploit gas-fuelled engines in producing more than 100MWe; the plant can run on treated well gas or treated crude as well as on marine diesel oil. Non-offshore shipping applications of 50DF machinery include Viking Grace, a 57,000gt/2,800- passenger Baltic cruiseferry delivered last year by STX Europe to Viking Line. The twin-screw propulsion plant of the world’s first LNG-fuelled passenger vessel is based on a quartet of eight- cylinder L50DF engines.


A recent contract calls for Wärtsilä to supply


eight 50DF engines for converting Totem Ocean’s two Orca-class roro cargo ships, Midnight Sun and North Star, to LNG-fuelled electric propulsion. The vessels transport around one-third of all the goods required by the inhabitants of Alaska, including food, vehicles and construction material, between Tacoma and Anchorage. Each vessel will be retrofitted with four V12- cylinder 50DF-driven gensets capable of running on either natural gas, marine diesel or heavy fuel oil. Wärtsilä will additionally supply two 1,100m3 LNG fuel storage tanks and associated


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automation and fuel gas handling systems. Wärtsilä’s DF technology was launched in


the early 1990s for land-based power plant applications, the first marine 50DF installation following a decade later. LNG carriers were a special target, such tonnage exploiting the capability of the engine to burn cargo boil-off gas as well as marine diesel and heavy fuel oils, switching between the fuel modes without disrupting power generation.


Electric power stations based on 50DF engines


became favoured for LNG carrier propulsion, breaking the steam turbine’s dominant grip when the first DF-electric tonnage was contracted in 2002. By the end of 2006 over 200 such engines were on order or in service with an aggregate rating of almost 2,000MW for 52 LNG carriers. The first three of these LNGCs – Provalys, Gaz


de France energY and Gaselys – were delivered to French owner Gaz de France by Chantiers de l’Atantique (now STX France) from end-2006 into 2007. Later in 2007 saw the handover of a fourth 50DF-driven LNGC, BP Shipping’s British Emerald, from Hyundai Heavy Industries. Different


quadruple-engine/single-screw


configurations were selected for these ships, depending on their size and operational requirements. Gaz de France energY, a 75,000m3 MedMax class carrier, is powered by a plant comprising four L6-cylinder 50DF-driven main gensets with a total output of 22.8MW. The 155,000m3 Provalys, Gaselys and British Emerald all tap an aggregate power rating of


Provalys pioneered Wärtsilä 50DF-electric power in LNG carriers


39.9MW; the two French-built vessels, however, each feature packages based on one L6-cylinder and three V12-cylinder 50DF genset engines, while British Emerald deploys two V12- and two L9-cylinder models.


Similar or variations of these machinery layouts were specified for subsequent LNGC projects using 50DF-electric solutions. By mid- February this year the LNGC reference list embraced 141 ships/567 engines.


Production of 50DF engines was initially assigned to Wärtsilä’s facility in Trieste, Italy, but demand stimulated investment in a dedicated new factory at Mokpo in South Korea, whose yards were building most of the new generation LNG carriers. The 50:50 joint venture Wärtsilä- Hyundai Engine Company (WHEC) came on stream in 2008 with the planned annual capacity to produce 100-120 x 50DF engines. WHEC remained the main source of 50DF engine production as LNGC building projects proliferated in Asia, with Trieste acting as a buffer supply. Developed from Wärtsilä’s


460mm-bore W46 medium speed diesel engine, the 50DF has a bore of 500mm and a stroke of 580mm. Running on either natural gas, marine diesel oil or heavy fuel oil – with seamless switching facilitated between them – the design delivers an output of 950/975 kW per cylinder at 500/514 rpm for 50Hz and 60Hz electricity generation respectively; offered in six, eight, and nine in-line and V12, 16 and 18-cylinder


successful


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