The proposed project objectives are as follows:
- Develop laser welding procedures at all positions (PH/PJ) and investigate the gap bridging capability without using filler materials. Various diameter (150-300mm) steel pipe will be used to develop the process parameters
- Source and integrate a process monitoring system with the laser welding head. This includes vision camera, illuminator, seam locator and joint geometry aligning device
- Develop closed-loop feedback control software interfacing the process monitoring system, robot manipulation and laser units
- Investigate joint design, to aid auto fit-up of pipe ends, for in-bore laser welding
- Develop in-bore autogenous laser butt welding procedures using the resultant joint design and process monitoring system
The project aims to address the limited external access problem faced during regular maintenance to replace deteriorated, often corroded, pipelines in the nuclear plant. The project will develop an in-bore laser welding process head and demonstrate laser welding at all positions, by adapting the processing parameters to overcome gravitational effects.
The challenges to the successful adoption of in-bore laser welding include:
- Reduce process cycle time, as compared with conventional arc welding, in order to minimise plant shut down time
- Removal of welding fumes and spatters
- Reduce weight and size of the resultant system to fit into small diameter pipe
- Real-time monitoring and closed-loop feedback control
When compared with arc welding, laser welding is anticipated to reduce cycle time by more than half. Laser welding is a faster welding process with reduced distortion and hence lower re-work requirements, although precision fit-up and manipulation are essential. Joint design, to aid auto fit-up, will be investigated in this project.
A vision camera will be employed to monitor the process, and integrated with a seam locating and joint geometry alignment system to confirm joint fit-up and aid beam alignment. Together with interfaced software, these will result in a compact process monitoring system that can be mounted onto the laser welding head and deployed far up a pipe.
To address these challenges the following needs identified, and have been will be addressed in this proposed project:
- Technology developments – the build, testing and proving of a compact in-bore laser welding head and in-bore manipulation strategy
- Process and inspection developments – preliminary laser welding procedures and associated pre-, in- and post-process monitoring
Relevant Industry Sectors
There is a strong interest in developing in-bore processing tools to remove old, and then install new pipelines, for reactors during regular maintenance. To prevent contamination to the reactor, no processing may be carried out external to the pipe. There is a need to develop technical capability in this area that can address in-bore welding issues such as distortion and low productivity.