One-Two Power Punch For Venezuela Waller Engineering designed and installed a pair of 171 MW power generating barges for the city of Caracas, Venezuela
The city of Caracas, Venezuela, and surrounding areas now have the dependable electric power they have needed for decades thanks to a pair of 171 MW power generating barges designed and installed by Waller Engineering, Houston, Texas, U.S.A. Orange Shipbuilding, a Signal International company located in Orange, Texas, was the shipbuilder on the US$30 million contract.
The Margarita I and Josefa Rufina 1 are 91.4 m long, 30.5 m wide and 6.1 m deep. Deadweight is 6700 short tons (ST) with 2400 ST of barge and 4300 ST of equipment. Both vessels are classified with ABS and are of welded steel construction. These power barges, with combined power output of 342 MW, are Waller’s largest in operation today, besting another project of 200 MW in India.
The power plants feature the GE 7FA gas turbine. This is the first bargemounted marine application for this turbine. Each of the two barges will have an output of 171 MW and will be mounted side by side. They will operate in series with either one or both in operation, depending on the load. To successfully operate a gas turbine on a barge, a large vibration pad had to be constructed. This reinforced pad is 30.5 m long by 5.5 m wide and 2.7 m thick.
“Additionally, the turbine foundation is supported by barge structures that are designed to permit the flow of forces into the hull without overstressing components while still permitting flexure of the hull,” said David Waller, president of Waller Marine. “Tremendous forces are at play with the 650 ton turbine-generator rotating at high speed, developing 230 000 hp [171.5 MW]. Vibration during runup, operations and run-down, results in high structural loading, resonance and mass dampening, and other issues to be dealt with,” Waller added.
It takes electricity to make electricity, so there is a Caterpillar C-32 engine rated at 910 kW to provide power to lights, pumps and other essential services. Next, there is an excitation transformer that takes electricity in a backflow fashion from the grid to start turning the generator. Then the gas turbine is lit and begins turning the generator, supplying power to the grid in normal operation. GE supplied many of the pieces for this power plant. In addition to the gas turbine, it also supplied the generator, fuel filtering components, the power control center, essential circuit breakers and transformers.
Fuel and water will be supplied to the power plants by an offshore barge that will hold fuel oil and a 3028 L/min reverse osmosis plant for water. Waller engineered and constructed the 36 000- barrel-capacity floating fuel barge. Fuel travels from the offshore barge to a centrifuge on the power barges for particle separation and then to a 11 356 L day tank capable of providing 12 hours of operation. A GE fuel treatment module also treats the fuel before entering the turbine.
The power plants are designed as dual-fuel and can use either diesel oil or natural gas as primary fuel. However, at this time only diesel fuel is considered. The generated power travels to the main circuit breaker, then to the main transformer. From there it goes to the SF 6 breaker and then to a transmission takeoff tower from which it connects to the land grid. While producing electricity is the sole purpose of these barges, they do have several marine systems onboard, including including a ballast system, bilge system, oil water separators, fire pumps (both diesel and motor driven), marine sanitation device, potable water pressure sets, a domestic hot water system, belowdeck ventilation system, hot water system and barge mooring brackets.
The vessel has showers, a lunchroom and lockers, but no overnight accommodations are provided as work is done in shifts.The barge also contains a motor control center and switchgear, a central control room, offices, a warehouse, a water wash system, a CO2 storage and distribution system, a fire-fighting and fire protection system and a gas receiving station in case natural gas is used as the turbine fuel. The power barges traveled roughly 285 nautical miles on their own bottoms from the shipbuilder in Orange, Texas, to Corpus Christi, Texas, where the heavy lift ship Triumph transported them to Venezuela.
The building of these two power barges is the result of a large investment Signal International has made in the Orange, Texas, yard. “We invested more than US$40 million in this yard to achieve heavy fabrication using continuous flow manufacturing techniques and processes,” said Richard Marler, president and CEO of Signal. This event culminates a fast-track engineering, procurement and construction program undertaken by Waller Marine to design, construct and deliver the two power barges within a 180-day period.
The company is now in the early stages of engineering the second phase of the construction program, a 260 MW steam cycle barge that will be fitted with heat recovery steam generators and a 260 MW steam cycle turbine generator that will increase generating facility capacity
to 600 MW.
Source: Diesel and Gas Turbines Magazine