Laser Welding goes Nuclear
In the great scheme of things, a few nicks may be neither here nor there. However, when these nicks are found on a nuclear power plant turbine shaft, matters become serious.
The shaft in a nuclear plant has to be perfectly within spec to ensure that forces are distributed evenly across the shaft. Nicks can create inconsistences in the rotation, placing stress in the metal which may eventually cause it to crack. The smallest of cracks introduces more weakness into the metal, hence more inconsistences in rotation which creates more cracks until…
The go-to solution
Nicks in any metal can be removed by welding. With traditional TIG welding, a lot of damage can be done to the metal in the heat affected zone where the welding’s taken place. While the metal at the welds doesn’t appear to be damaged, it is in fact softer than the areas that weren’t repaired, making the shaft weaker at those points.
With laser welding, the heat affected zone is smaller and cools instantly so there’s no weakening of the welded areas. It’s also more precise. TIG welding creates a much larger build-up of material on the metal which has to be machined off to the 1000th of an inch.
Aware of the advantages of laser welding, the nuclear plant operator shipped the 20,000lb (9072 kg) turbine shaft to our product partners, Alpha Laser, for the necessary welding repairs.
Mobility and power
The shaft was 15ft (4.572m) long and ranged between 11in (27.94cm) and 6ft (1.828m) in diameter. Made of an extremely dense nickel alloy, mobility and power were the essential elements of carrying out a successful repair.
Alpha Laser rigged up a 500W Nd.YAG laser to an ALFlak mobile laser welding system which gave the powerful laser all the flexibility required to reach any spot on the shaft.
Done in days
All the nicks were repaired in just 5 days. The shaft was then transported to a machine shop for finishing with Alpha Laser still in attendance, so that any new inconsistencies could be quickly repaired and machined there and then.
The total turnaround time for the shaft repair including shipping, welding and machining was 20 days. If the operator had opted to order and pay for a new shaft instead of the laser welding repair, downtime at the plant may well have been 20 weeks!
For information and full details of Alpha Laser’s range of laser welding systems including the ALFlak mobile laser welding machines, please contact sales@tlm-laser.com