Heralding a new stage in the development of high-speed ferry transportation, Buenos Aires-based Buquebus has introduced an exceptionally fast vessel to the Argentina/Uruguay travel market. Putting the Buenos Aires/Montevideo ferry service on a stronger footing to compete with airline operators, the 99m catamaran Francisco can maintain schedules at 50 knots-plus with a full payload of over 1,000 passengers and 150 cars. The vessel has a lightship speed in excess of 58 knots.

As a response to a pressing commercial need to offer swift transits across the River Plate, the new wave piercer from the Incat cradle in Tasmania has been designed and engineered with long-term considerations relating to economic and environmental performance and asset value. Although aeroderivative gas turbine machinery is an established propulsion mode in the lightweight ferry sector, Francisco is the first vessel to have been built under the HSC (High-Speed Craft) Code with power by gas turbines using natural gas as the primary fuel and marine distillate for ancillary and standby purposes.

The aluminium-built ferry has thereby put down a new marker for the industry: not only in raw speed for a commercial vessel of her size and type, but also in her unique blend of systems and technologies. The innovative nature of the shipbuilding project lies in its combination and integration of technologies, including gas fuelling, gas turbine propulsion, and ro-ro equipped wave piercing catamaran design, all of which are proven in their own right.

Headed by Juan Carlos Lopez Mena, the Buquebus organisation ranks among the pioneers in the fast ferry domain. The evolution of its fleet has included the introduction in 1995 of an Incat 70m catamaran, the Juan Patricio, with a service speed of 47 knots, followed in 1997 by the Bazan-built, twin-hulled Luciano Federico L, powered by gas turbines. At the time, the latter was the world’s fastest car-carrying catamaran, capable of a fully-laden speed of 55 knots.

Buquebus’ familiarity with the Incat product and knowhow over a 20-year period is underscored by the fact that the Francisco is the eighth Incat vessel to be operated by the group. Four of these ferries, including Juan Patricio, have lightship speeds exceeding 50 knots.

On trials, the latest cat made just under 52 knots when ballasted to the 450t full load deadweight and attained a lightship speed of 58.1 knots at maximum power, although it is indicated that this could have been higher if less fuel had been aboard and delivery spares had been removed.

The unique nature of the new Buquebus ferry posed particular regulatory challenges for Incat and its associated company Revolution Design. At the forefront of classification rule development for LNG in marine applications, and having classed most of the vessels built by Incat, DNV was engaged for the Buquebus newbuild project.

However, as reported by Incat, “DNV rules had to be reconsidered to ensure compliance. This created some special issues. The society requires that with any unique or ‘novel’ design, an ‘equivalence’ of a requirement be provided to demonstrate that the design is at least ‘equivalent’ to a more ‘standard’ design or that it actually produces better safety outcomes than the regulations require.”

The detail of the construction of the Buquebus catamaran differed from that of other wave piercers from Incat in having only one driveline per hull instead of the typical two per side, and the jet rooms have a single large jet duct rather than the two comparatively smaller jets on a ‘standard’ 98m wave piercer catamaran. “The real challenges came in a number of areas, including each hull side cut out to enable the LNG tank with cold box to be fitted, which was about twice the size of a conventional engine room soft patch in the vessel side,” counselled Incat. Revolution Design structural engineers factored that into the ferry’s design.

The gas piping requirements, including the provision of ventilated ducts and the related welding and fixing, required many months of attention, while systems integration drawing the highly complex gas turbine plant and gas supply arrangements into the ship’s control and monitoring systems was a complicated and time consuming task.

The light weight, small footprint and high power density characteristics of gas turbines are well suited to criteria for the fastest, light displacement vessels. The Buquebus ferry was specified with two GE Energy LM2500 gas turbines modified to operate either on natural gas or MGO. The LM2500 is a single-rotor gas turbine with an aerodynamically coupled power turbine, and the version nominated for Francisco has a rated output of 22,233kW, compression ratio of 18:1, and speed range of 500-3,780rpm.

Natural gas will be the ferry’s primary fuel, whereby a secondary heat exchanger system will utilise waste heat energy from the turbine exhaust to vaporise LNG from the storage tanks, changing its state to gas for ingestion in the main machinery. The power plant uses marine distillate for start-up and during the ensuing minutes until the heat exchangers have produced enough gas from the LNG to allow changeover to LNG fuel. On arrival in port, the gas turbines revert to distillate for the vessel manoeuvring phase. The distillate will also serve as standby fuel.

Each prime mover and ancillary equipment is housed within a steel enclosure in each hull, and a 7:1 ratio ZF reduction gearbox is interposed on each driveline to a Wärtsilä LJX 1720SR axial waterjet. Configured for steering and reverse, the Wärtsilä design is notable for its comparatively small size, given the power input entailed. The proprietary Lipstronic 7000 system controls and indicates the steering angle, bucket position and impeller speed, and can be operated either by joystick or autopilot.

Two 200kW Caterpillar C9 gensets serve the gas turbine plant’s electrical power requirements, while four 340kW Cat C18-based aggregates cover the onboard electrical load, and are arranged for automatic start-up and paralleling. The electrical control system provides for one genset being maintained as a standby set.

Cryogenic equipment specialist Chart Ferox was contracted to design, manufacture and supply the LNG fuelling system, including the storage tanks, piping, controls and bunkering arrangements. Located in the northern part of the Czech Republic at Decin, Chart Ferox is a wholly-owned subsidiary of Chart Industries of the USA, and is a pioneer in the development of LNG fuel delivery systems used within the transportation sector at large.

Francisco has been fitted with two 43m³-capacity, super-insulated LNG storage tanks and associated cold boxes, with vaporisers, pumps, valves, bunker stations, control systems, safety detectors, a glycol circuit and a heat management system for the turbine exhaust gases. A cold box is effectively an airtight enclosure containing the wherewithal for fuel processing.

Each hull of the catamaran has one LNG tank. Positioned amidships in a compartment immediately above the double bottom marine distillate bunker tanks, the gas tanks are of double-walled, stainless steel construction. They embody proprietary, multilayer composite vacuum insulation to maximise fuel capacity and maintain the LNG in its liquid state at a temperature of -163°C. Changeovers between LNG and distillate will be automatically controlled and will be performed as a ‘seamless’ operation.

The tanks provide for up to four hours of high speed operation, affording the requisite capacity to cover the round trip of 250 nautical miles on the River Plate service, so that bunkering need only be undertaken at one of the terminal ports. This is carried out at Buenos Aires from trucks drawing cryogenic tank trailers. The ship’s system has been designed to facilitate LNG refuelling in less than one hour, with simultaneous intake from two LNG trailers.

Within the Chart system, a secondary heat exchanger utilises waste heat from the turbine exhaust gas streams to vaporise the LNG, changing its state from liquid to gas, which is then delivered to the propulsion turbines at a precise pressure and flow. When the machinery is started, or when the vessel is running at low speed or manoeuvring, the turbines are operated on marine gas oil.

The Buquebus fleet investment project also signifies an industry first through the company’s decision to purchase its own portable, shoreside plant for the production and supply of the LNG fuel bunkered by the Francisco. The chosen solution is in the form of seven Cryobox LNG ‘nano’ stations developed, patented and manufactured by the Argentinean firm Galileo.

In total, the seven units commissioned by Buquebus can produce 84t or 49,000 gallons per day of LNG, using a high-pressure thermodynamic cycle that converts natural gas into liquid by cooling to -163°C. The complete station has been designed for transportation on a trailer, and for direct connection to the gas distribution system. In this way, the requisite LNG will be trucked from the outskirts of Buenos Aires to the ferry terminal, where Francisco will be refuelled.

The integrated Cryobox solution thereby offers users a high degree of flexibility in meeting capacity and delivery requirements over time, and is an alternative to the cost and other issues associated with establishing a permanent bunkering or refuelling point.

The wave piercer’s two slender, aluminium hulls are connected by a bridging section with a centre bow structure at the forward end, and the resulting configuration makes for a beam of nearly 27m on a length overall of 99m. The single vehicle deck affords a clear height of 2.3m and maximum axle load of 2t, and the 150-car intake is based on spaces at 4.5m length by 2.3m wide. Ro-ro access and egress is via shore-based stern ramps across the transom.

The ferry’s interiors are elegant in style and open in layout, and were designed by Julio Cesar Ortega of Uruguay. The passenger spaces include tourist-, business- and first-class seating, and the expansive duty-free shop, extending over more than 1,100m², ranks among the largest shopping areas ever incorporated into a fast ferry, and had significant implications for the weight of the interior fit out. Gas turbine power provides additional comfort for passengers by reducing noise and vibration on board.

Operating performance and results with the Francisco can be expected to be closely followed by ferry operators worldwide, given the considerable challenges and uncertainties facing the industry due to high oil prices and ever-tougher environmental controls.

PRINCIPAL PARTICULARS -- FRANCISCO

Length, overall 99.0m Length, waterline 90.54m Beam, overall 26.94m Draught, design 2.98m Deadweight 450dwt Gross tonnage 7,100gt Passengers + crew 1,024 Car capacity 150 Main engines 2 x GE LM2500 gas turbine Main engine power 2x 22,000kW Speed, 450dwt @ 100% MCR 51.8 knots Speed, lightship @ 100% MCR 58 knots Gas turbine gensets 2 x 200kW Ship’s service gensets 2 x 340kW Class DNV Class notations +1A1, HSLC, R4, Car Ferry B, E0, Gas Fuelled Flag Uruguay