McKillop said the final piece of the construction puzzle was to install the power plant and electrical switchyard. '(It) was completed by highly qualified turbine and electrical technicians specifically contracted by WMI for their dedication and "can do" attitude,' he said. 'PDMS was a vital tool in allowing accurate installation and fit-up in our balance of plant-to-turbine piping interfaces.' Providing needed electricityThe Margarita I and the Josefa Rufina I sport deck areas about the size of a football field and each weighs 6,700 short tons apiece. Their stack towers soar 100 feet above the decks. Boasting identical GE 7FA simple-cycle, dual-fuel turbine generators, the barges can each generate 171.4 MW of electricity for transfer to the Venezuelan grid. The turbines can run on natural gas or number 2 fuel oil. The barges will be moored in a shallow, man-made basin protected from the Caribbean Sea, near the Planta Termoeléctrica de Tacoa - an overtaxed 1940s-era power plant on the coast northwest of Caracas that cannot operate at anywhere near 100 percent capacity due to age. Venezuela's nearby hydroelectric plants have been unable to take up the slack with additional power due to a shortage of rainfall in the region, which has led to lower than normal reservoir levels needed to power the hydro turbines. As a result, Caracas and the surrounding areas have been experiencing frequent power 'brownouts.' Once online in mid 2011, the Margarita I and the Josefa Rufina I should alleviate at least some of the electricity shortages in the Venezuelan capital. Idea dates back to the '30sPower barges such as the Margarita I and the Josefa Rufina I are not a new concept. Indeed, as far back as 1931, Popular Mechanics magazine profiled the Jacona, a freighter that was being converted to a 'mobile seagoing power plant' that could go wherever electricity was needed. Development took off during World War II when barges delivered power to troops in the field and to bombed-out cities, such as Nagasaki, Japan. After World War II, construction slowed. However, over the past two decades, power barges have enjoyed a resurgence as an effective way to supply electricity to developing countries. Their short construction cycles, ease in deployment and competitive costs versus land-based plants have made them an attractive alternative. Today, more than 60 power barges are in use around the world, according to Power Magazine, including a few in the United States.'The client asked us if we could deliver it in six months and we did it. This has never been done before. No one thought we could do it. But we came through in the 180 days. I think we surprised the customer...'AVEVA World Magazine 2011|Issue 215 Photo courtesy of Waller Marine Inc.
The Margarita I and Josefa Rufina I onsite in a protected cove northwest of Caracas, Venezuela, ready for final installations and hookup to the power grid. Photo courtesy of Waller Marine Inc.What sets the Margarita I and the Josefa Rufina I apart from other such ventures is that these will not only be the largest of their kind in terms of size and capacity, according to WMI, but they were also successfully built in such a short turnaround time.Fast-track constructionWMI concentrated on design at its Houston offices and contracted with Signal International, Inc. for fabrication in its Orange, TX, shipyard. Faced with an extremely tight window, barge construction began even before design work had been completed. The first steel plates were put together in March 2010. Fabrication continued thereafter 24 hours a day, seven days a week. At times, work was so fast-paced that construction workers were being handed design documents that were sometimes only hours old.'The client asked us if we could deliver it in six months and we did it,' said Hugh O. Haggerty, WMI's Marine System Specialist. 'This has never been done before. No one thought we could do it. But we came through in the 180 days. I think we surprised the customer.'Marrying two engineering fields'The key thing to remember about this project is that it wasn't just a power plant,' Haggerty explained, 'It was a power plant on a barge.'While diesel engines have long been installed on ships for power generation, putting an industrial-sized dual-fuel turbine on a barge posed a few additional design challenges. GE Frame 7FA turbines, for instance, have strict limitations and tolerance for any longitudinal distortion along their shafts during operation. The design includes a reinforced concrete plinth that keeps the barge at zero deflection under all operating conditions. Special considerations were also needed for hull and foundation loading, stress and vibration. The main deck of each barge, for example, is built to support 5,000 psf. A plinth-barge interface, including a patented system of spring boxes and hydraulic supports, provides a way to control and dampen vibration from turbine operation.To accomplish this, WMI not only drew upon its naval architecture experience, but also on a knowledge of the power industry as well. 'The design of a floating power plant marries the engineering protocols of the Marine and Power Generating industries,' WMI explains in its promotional materials on floating power plants. 'However, with modern structural marine engineering and construction capabilities, coupled with an understanding of power generation concepts,' the company continues, 'the two industries can be fully integrated to perform their intended functions while afloat.' The firm has a more than 20-year history of success with power barges, dating back to the late 1980s when it inspected the 1940s-vintage Impedence, first used by the US Army in the Philippines and the barge that eventually led to the reintroduction of power barges in the late 1990s.PDMS' roleA team of two WMI engineers used AVEVA PDMS to design the intricate piping for each power barge and the software greatly aided the project, according to the company.'The piping went very well,' Haggerty said. 'The PDMS program was invaluable. Two guys were able to crank it out quite rapidly. We couldn't have done the project as fast as we did without PDMS.'16AVEVA World Magazine 2011|Issue 2