Elegant new expression of Finnish technology

‘Viking Grace’ is the first large passenger ship to be fuelled primarily by LNG ‘Viking Grace’ is the first large passenger ship to be fuelled primarily by LNG
Industry Database

David Tinsley looks at ‘Viking Grace’, the first large passenger ship to run primarily on LNG fuel, built by STX in Finland, and which is entering service this month in the Baltic.

Environmental consideration is ingrained in the Nordic culture, a factor which has a signal bearing on the manner and extent of the region’s commercial and industrial response to the challenges and opportunities presented by the drive for more ‘sustainable’ energy solutions and by the roll-out of tougher legislation and controls governing emissions from shipping activity.

A characteristic propensity for innovative design and engineering displayed over many years in the trans-Baltic ferry fleet, melded with a particularly bold and comprehensive approach to environmental compatibility and energy saving, has given rise to Viking Line’s mould-breaking, gas-fuelled Viking Grace. Due to be phased into service between Finland and Sweden in mid-January 2013, the 57,000gt ro-pax newbuild will be the world’s first large passenger-carrying vessel to use LNG as bunkers.

The ship’s dual-fuel electrical power and propulsion installation will confer a very high degree of flexibility, enabling prime mover usage to be closely matched and optimised to actual energy needs across the operating profile while providing the capability to switch between gaseous fuel and liquid fuels at any point with no interruption in power generation.

Constructed at STX Finland’s showcase Turku shipyard, the cruise-standard ferry will supersede the 1989-built, 35,154gt Isabella on the route linking the southwest Finnish port of Turku with Stockholm via the Aland Islands. Maintaining year-round service through the narrow, rock-bound leads and shallow waters of the ecologically-sensitive Finnish and Swedish archipelagos poses special demands and qualities with regard to vessel properties as well as continually testing the skills of the navigators.

Her anticipated, predominant reliance on natural gas will enable Viking Grace to meet and even exceed the most stringent, foreseeable IMO and EU emission edicts. A host of other engineering and design features have been adopted to minimise the ship’s carbon footprint and impact on nature and local populations. Issues addressed extend far beyond the provisions for the toughening air pollution regime, to encompass all spheres of operational impact.

While complying with the decrees of legislators and setting a new standard in the competitive Baltic ferry market, Viking Line’s environmental strategy and responsibility displayed in the Viking Grace project appears to have resonated with the Scandinavian travelling public, judging by the level and nature of feedback and volume of forward bookings. Achieving such acceptance, and across the generations, through such a focus is not to be underrated in terms of ‘future-proofing’ new fleet investments. It fosters demand growth. The technical approach used is also salient to the fact that freight generators and shippers in the Nordic region and elsewhere are increasingly applying environmental vetting to logistic choices and transport contractor selection.

Investing at a premium in comprehensive ‘green’ credentials can be expected to yield ongoing economic benefits from the array of energy-saving measures adopted. This has fundamentally important competitive and asset-value implications for the long-term.

Strengthened to Finnish/Swedish 1A Super ice class criteria so as to ensure scheduling dependability and self-reliance in Baltic winter conditions, Viking Grace provides stylish and comfortable accommodation for 2,800 passengers, with a total of 880 cabins arranged on Decks 5 to 9. The start to scheduled service on 15 January is to be preceded by a maiden cruise voyage, open to the public, on 13 January.

The design of the ship’s interiors was assigned to the Finnish studio dSign Vertti Kivi & Co, spanning all 12 public areas. Viking Line’s aim is to attract new categories of customer to ferry travel, and this has influenced the internal design, which is characterised by a broad spectrum of different styles, extensive and varied facilities, and a particular emphasis on maximising views of the archipelagos from within the public spaces. The round-voyage excursion or ‘cruise’ dimension to the business is considerable and well-established.

The maximum ro-ro freight payload equates to the 1,275 lane-metres of main deck loading capacity, complemented by some 550 lane-metres for cars and vans on the surmounting Deck 5, with the provision of a similar capacity on the intervening hoistable deck level. Vehicle handling to and from the main garage will be across the stern ramp and through the stern door, with dedicated ramp access to the uppermost deck from the main deck threshold.

The impending 0.1% sulphur cap, to be introduced in the Baltic Emission Control Area (ECA) on 1 January 2015, will be met by the Viking Grace by burning LNG, obviating the need for yet more highly refined, more expensive distillate or for the fitting of special after-treatment plant. Mariehamn-based Viking Line has a track record of in-house studies, trials and initiatives relating to emission minimisation, and is ahead of the game as concerns legislation. Although the current IMO sulphur limit in the Baltic is 1.0%, the company’s vessels have been using fuel with a sulphur content of only 0.5% since the 1990s.

Wärtsilä’s dual-fuel engine technology, essentially tri-fuel in its capability for heavy fuel oil, marine diesel oil or LNG, is central to the project. Four eight-cylinder models of the 50DF engine design drive ABB alternators, giving a nominal generator power of 8,191kVA for each of the four aggregates, delivering electrical energy to the main switchboards for the two 10,500kW ABB propulsion motors and other shipboard consumers.

Power is transmitted by the two shaftlines to stainless steel, Wärtsilä fixed pitch propellers, to enable the ferry to reach a speed of about 22 knots. Pressure impulses generated by the propellers are claimed to be the lowest possible, minimising vibration levels in the stern. Noise attenuation has also commanded special attention in the engine installation. With two drivelines, two electric propulsion motors, and a multi-engine genset plant distributed between two independent engine rooms, the system offers a high degree of redundancy.

In gas-burning mode, the engines operate on the lean-burn principle, whereby the mixture of air and gas in the cylinder has more air than is needed for complete combustion, reducing peak temperatures. The formation of NOx (nitrogen oxides) is accordingly considerably reduced, by a measure of at least 80%. Furthermore, Sox (sulphur oxides) emissions are virtually eliminated, while CO2 formation is lowered by at least 15% because the gas contains less carbon per unit of energy than liquid fuels. Since natural gas has no residuals, the production of PM (particulate matter) is cut by more than 90%.

Viking Grace will bunker LNG at Stadsgaarden, in the port of Stockholm, with the fuel supplied by AGA Gas from its new LNG terminal down the coast at Nynashamn. Onboard storage is in two vacuum-type, low-pressure tanks located on the ferry’s aftermost, open deck. The pipes as well as the tanks are double-mantled, providing added protection against leakage, while the gas detection arrangements will shut off the system in the event of escaping gas. As natural gas is lighter than air, any leakage in the outdoor areas will ventilate into the atmosphere.

The 200m³ stainless steel tanks and associated bunker fuel handling equipment, safety and automation systems constitute the integrated LNGPac solution developed by Wärtsilä. The company’s scope of supply also included a patented cold recovery system, utilising the latent heat of the LNG for the ferry’s air-conditioning system, and saving energy by reducing reliance on the cooling compressors.

The ship is classed with Lloyd’s Register, whose technical support for the owner during the project included a detailed risk analysis of the bunkering process. This sought to identify and minimise risks associated with the movement of the bunker barge and ferry within the confines of the port, and the risks associated with the simultaneous loading of passengers, cars, trucks and LNG. The study also helped ensure compatibility between bunker barge capacity and the ship’s systems.

Although the vessel’s regular service entails transits in relatively sheltered waters cradled by the archipelagos of Sweden and Finland, Viking Grace has been equipped with Blohm + Voss fin stabilisers to ensure smooth sailing in any conditions. Up to 90% roll reduction can be achieved. Each stabiliser fin is connected to a hydraulic actuator controlled by an automated system that constantly sets the fin angle according to the prevailing sea state.

When sailing through the archipelagos, attention has to be paid to wake formation at the ship’s different speeds, a complex phenomenon in itself. In arriving at a hydrodynamically optimised hull form, a mark of the critical requirement for maximum propulsive efficiency in all conditions, the designers had the added task of ensuring minimised wave formation when navigating the channels and leads of the islands and port approaches.

Another element in Viking Line’s environmental planning for the new ship has been its selection of Wärtsilä’s Compact Silencer System (CSS). The technology minimises noise emissions from the engines, being particularly effective in the abatement of disturbing low frequency impulses. Quiet operation has a direct bearing not only on passenger comfort and passenger perceptions, but also on noise impact when passing through the inhabited archipelagos. Furthermore, the Wärtsilä fixed pitch main propellers have been designed with the lowest possible pressure impulses.

ABB’s software tool EMMA ( energy management system for marine applications) will help the crew to monitor and administer energy-related processes, practices and decisions on the new ferry, better ensuring efficient fuel usage from the outset of operations

Viking Grace is a seminal ship and an impressive testament to Finnish marine industrial capabilities.

Principal particulars – Viking Grace

Length oa 214m + 4m ducktail
Breadth 31.8m
Draught 6.8m
Gross tonnage 57,000gt
Net tonnage 47,600gt
Passenger capacity 2,800
Passenger cabins 880
Trailer/truck capacity, Deck 3 1,250 lane-m
Car deck capacity, Deck 4 (hoistable) + Deck 5 1,000 lane-m
Main diesel-electric genset engines 4 x Wärtsilä 8L50DF
Main alternators 4 x ABB AMG1120, each 8,191kVA
Propulsion motors 2 x ABB AMZ1600, each 10,500kW
Service speed (85% MCR) 21.8 knots
Bow thrusters 2 x 2,300kW
Stern thruster 1,500kW
Flag state Finland
Class Lloyd’s Register, Ice class 1A Super

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