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| CSIRO | SOLVE | Issue 5 Nov 05 | |
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COVER STORY
POWER GENERATION: The Power of Teamwork
By Brad Collis
A collaboration between power station operators and researchers has become a case study of successful problem-solving. Power industry representatives and researchers who set out three years ago to brainstorm clever ideas have come up with their first development – a new technique for resurfacing worn power station turbine blades that is expected to cut millions of dollars from maintenance bills. Called ‘In Situ Laser Surfacing’, the development is the product of a collective effort by several research institutions and power station operators and has prompted a flurry of international interest. A spin-off company, Hardwear Pty Ltd, has been established to commercialise the process. As the name implies, In Situ Laser Surfacing allows flaws from wet steam erosion on the blades of low-pressure steam turbines to be repaired in place – without the need for the turbine to be dismantled and the blades removed. Some power station operators have reported that current blade repair, or replacement, costs $250,000 per turbine per day in downtime – or up to $2.5 million in total per turbine. The new method is said to reduce significantly this downtime duration and cost. A typical low-pressure steam turbine rotor has 180 last-row blades, each about a metre long, with a replacement cost of $10,000 each if they cannot be repaired to the level of their original aerodynamic precision. The development pulls together expertise in welding, laser and robotics technologies from the CRC for Welded Structures, CSIRO Manufacturing and Infrastructure Technology and the Industrial Research Institute Swinburne (IRIS) at Swinburne University of Technology. There was also input from the Australian Nuclear Science and Technology Organisation (ANSTO) and engineering firm Connell Wagner. The technology has been trialled at TRUenergy’s Torrens Island power station in Adelaide. TRUenergy is one of nine power stations sponsoring the CRC’s Power Generation research program. CSIRO’s Dr Nazmul Alam explains that the new method uses high-power laser energy to fuse a metal alloy powder to the turbine blade’s surface. “And the work can be done without the need to de-blade the rotor. It only has to be removed from its casing,” he says. “The laser is a portable unit that is taken to the power station, and the operation is performed by a robotic arm.”
Dr Alam says the process is technically not ‘welding’: “The laser supplies a high-energy stream into which a metal alloy powder is directed. The laser fuses the metal to the blade’s surface.” Dr Alam says conventional repair methods have used TIG (tungsten inert gas) welding, but the heat is difficult to regulate and blades can suffer thermal damage. Dr Alam says the project started in 2001 when the electricity industry nominated turbine blade repair as a significant cost. A team of researchers was assembled from within the CRC for Welded Structures, including CSIRO and Swinburne University of Technology, and the nine power station sponsors. The prime objective from the outset was to find a way to repair blades without having to remove them. It was known that laser energy would be an ideal heat source; the researchers had to develop a way to deliver it. Several ideas were tested, but the eventual success came from the development by IRIS of a nozzle for the laser delivery and a coaxial delivery of the metal powder, which together allow the unit to work front-on to the blade surface, rather than from above. “The challenge for working in situ was to find a way to direct the powder without it being affected by gravity,” says Swinburne’s Professor Milan Brandt. “The system we’ve developed focuses both the powder and the laser beam so that they come together at the target point on the blade’s surface.” Professor Brandt says the delivery system is considered a breakthrough internationally and part of the process has been patented. He says the new method not only saves downtime, but significantly increases the blades’ life. The head of the CRC for Welded Structures, Dr Colin Chipperfield, says the development stands as a case study of what can be achieved when industry and researchers come together to problem-solve. “We had nine sponsoring power stations on one side of the table and researchers on the other, creating a direct opportunity for industry to sponsor and guide the research it needed. For the scientists it means that whatever world-class technology emerges from this, they already have their industry partners to help drive it forward.” TRUenergy’s Asset Strategy Manager, Ralph Villarosa, says the initial field trial last year on six blades was successful and the company is now undertaking a second trial on a further 17 blades. He says the technique has significant commercial application. APPLICATION In Situ Laser Surfacing allows turbine blades to be repaired on the rotor – in a power station’s turbine hall and without the need for the turbine to be dismantled For further information contact: |
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