Marine Link
Monday, September 25, 2017

Investment in Design: New Solutions for LNG Tankers

March 8, 2005

With its bid for commercial marine power applications strengthened by the addition of the MT30 aeroderivative gas turbine to its range, Rolls-Royce is pushing the concept of gas turbo-electric powering in the buoyant LNG carrier market. Key benefits advocated for such plant are high power-to-weight ratios, and gains of up to 10-percent in cargo carrying capacity attributable to the compactness and layout flexibility offered by a gas turbine-based system.

A saving of around 40-percent in installation man-hours is claimed by Rolls-Royce for its powering solutions using either simple cycle or combined cycle arrangements, along with significant savings in weight relative to steam turbine, dual-fuel diesel-electric and low-speed diesel alternatives, all of which have now been embraced by the LNGC sector. Capable of dual-fuel operation, the MT30 will run primarily on cargo boil-off gas, meeting all power needs on that basis whenever sufficient gas is available, and obviating the wholesale need for comparatively expensive DMA distillate fuel. Rolls-Royce strongly advocates the combined gas turbine and steam electric system(COGES) system, employing a steam turbo-alternator using steam generated from the waste heat in the gas turbine exhaust stack. A typical combined cycle solution could comprise a 36-MW MT30 gas turbo-alternator set, a waste heat-powered, 10-MW steam turbo-alternator, and a 5.5-MW set driven by a smaller Rolls-Royce gas turbine.

It is understood that gas turbo-electric powering and propulsion plant is under consideration for at least one major, prospective program that would entail a series of large LNGC newbuilds. Although gas turbine plant is regarded by its advocates as suited to the most populous category of LNG tankers, that is to say in the 140,000-150,000 cubic meter range, Rolls-Royce's best chance of market entry may be among projects for the nascent generation of larger ships, where a new approach is having to be taken to technical aspects.

In the meantime, Wärtsilä Corporation is looking to consolidate its early successes with dual fuel(DF) engine-based plant for LNGCs by rolling out new design solutions anticipative of an industry move to higher operating speeds and lower unit transportation costs.

While steam turbines have been the dominant form of propulsion in LNGCs, and a service speed of 19.0-19.5 knots has become an industry standard, Wärtsilä 's latest study indicates that faster ship speeds attained with DF-electric machinery can result in reduced transportation costs.

The two vessel sizes covered by the research entailed a 150,000-cu. m. type, representing the present state-of-the-art in the business, and a 230,000-cu. m. design representing a future generation. Both single-and twin-skeg propulsion were investigated for both conceptual designs, and a hybrid propulsion configuration incorporating wing podded propulsors was additionally considered for the 230,000-cubic meter type. All options were optimized for five different service speeds, ranging from 17- to 25-knots.

In the case of a 21.5-knot LNG tanker of 150,000 cu. m., the DF-electric plant would consist of two Wärtsilä 16V50DF and two 9L50DF main gensets, giving a total installed power of 47.5-MW, with propulsive effect delivered through a single, fixed pitch propeller. The engines would use LNG boil-off as primary fuel and marine diesel oil as pilot and back-up fuel.

The largest DF-electric plant ordered to date have been the 39.9-MW installations in Gaz de France and BP Shipping newbuild projects, employing Wärtsilä prime movers in different configurations.

Identifying Research Needs

Tasked with drawing up a blueprint for the European maritime industries' future research needs, the recent launch of the Waterborne Transport Technology Platform signals a heightened political appreciation of the collective economic importance of the shipping, shipbuilding and allied sectors. Backed by funds from the European Union's Sixth Framework Program for research and technological development, the pan-industry Waterborne initiative has the ultimate goal of strengthening the knowledge base and stimulating innovation among EU companies and institutions. A statement from the European Commission described the maritime sector as "big business", in that 90-percent of the EU's external trade and 40-percent of its internal trade is transported by sea, and referred to the region's role as a world leader in the design, manufacture and production of specialist, complex vessels. Intensified competition from eastern Asia and, perhaps, EU enlargement, have sharpened Brussels' appreciation of the maritime field's contribution, potential and vulnerabilities. Italian classification and certification body Registro Italiano Navale(RINA), which is taking a leading role in the Waterborne project, estimated that total annual turnover within the maritime sector corresponds to around 2.5 percent of the EU's GDP.

While the direct forms of industrial aid of past years can no longer be countenanced, support for endeavors that can strengthen the technological base to sectoral or wide benefit seems to be an acceptable course for public financial backing. By January 2005, a total of Euro 153-million had been made available for maritime research under the Sixth Framework provisions. The anticipated level of sponsorship for Waterborne had not been revealed at the time of writing. However, the study will be a major exercise with a long-term remit, and will feed into and beyond the Seventh Framework program, currently the subject of discussion by the EU's budgetary authorities.

Pivotal to the latest project is an integrated approach. Better coordination of research across Europe is regarded as vital to future competitiveness, in terms not only of manufacturing and production but also in safe, environmentally-responsible operations. The Waterborne platform will therefore involve industry, national authorities, regulatory bodies, research centers and universities, and will aim to stimulate more effective public and private investment in R&D and improve the coherence of research activities.

"This is an unprecedented initiative in common R&D, confirming the EU understanding that, for certain priority sectors such as maritime transport, a national approach is not sufficient," stated RINA's chief executive officer Ugo Salerno, founding chairman of the Waterborne Support Group. The society's head of R&D, Mario Dogliani, will be the day-to-day technical manager for Waterborne. The role of classification societies as research project managers has found new expression through the nomination of Bureau Veritas to oversee a study implemented on February 1 this year to develop a new assessment tool. The objective of the CAS (condition assessment system) undertaking is to cut the time needed to process thickness evaluations of ship structures, by devising an electronic tool that can help reduce the time and costs of vessel repair and rehabilitation.

"It will cut out the manual handling and interpretation of thickness measurements, and simplify the handling of all thickness data, right from the measurement through to using the data in the most complex condition assessment tools, allowing definitive repair decisions to be made on the spot," explained BV's research and development director Pierre Besse. The initial focus will be on tankers and bulk carriers. It would help back up IMO's Condition Assessment Scheme for older single-hull tankers, which entails processing vast quantities of information.

BV's partners in the EU-sponsored, three-year CAS project are Germanischer Lloyd, Russian Shipping Register, Materiaal Metingen Europe, Intertanko, Total, Spanish engineering group Sener, the Portuguese institute IST, shiprepairer Lisnave, and French subsea robot maker Cybernetix.

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