ERODED power station rotor blades usually scrapped at a cost of $10,000 each can be repaired in minutes with a new laser welding technique that also holds potential for the repair of pumps and valves.
The breakthrough comes as CSIRO scientists, in conjunction with Swinburne University and CRC Welded Structures have discovered a material and a process to repair blades while still on a turbine.
Called In Situ Laser Surfacing, a portable laser unit is taken to the power station and the operation performed by a robotic arm.
The robotic arm overcomes problems of complex access geometry while the laser fuses a cobalt based alloy powder to the mounted blade.
CSIRO scientist, Nazmul Alam told FEN while the cobalt based alloy is not a new material, its reactions to a laser were previously unknown.
“We knew the material had the same sort of intrusion properties as tollsteel, which is traditionally used in blade repair. This makes it resistant to loss of material under impact loading What we didn’t know was how it would react to a laser,” Alam said.
“We developed a technique that maintained position accuracy and found that our material was not significantly diluted by the laser.”
The technology has been tested at TRUenergy’s Torrens Island power station in Adelaide, where Alam said the successful use of robotics had proved to be a significant achievement.
Each turbine rotor has 180 last-row blades, each about a metre long.
Some power station operators have reported that to replace all the blades on a turbine can cost up to $2.5 million in total per turbine.
Dr Alam estimated that once In Situ Laser Surfacing has been patented it will cost around $500 000 to treat one turbine – potentially a two million dollar saving.
“In a lab test we did, an ordinary blade lasted five years, while a blade coated in our material lasted at least twenty years,” Alam said.