The Nuclear AMRC has worked with heat exchanger specialist Thornhill Group to demonstrate a new welding method for small tube-to-tubesheet assemblies which could halve cycle time.
The welding head had to be customized for the job, with the large gas nozzle and shield removed in favor of a separate gas shielding nozzle, and laser power was reduced to just 2 kW from its maximum 16 kW. Ensuring a high-quality weld meant considering a host of factors, from the angle and position of the weld head to reducing the gas flow to avoid turbulence in the molten metal.
Initial trials showed that small tube-to-tubesheet welds could be successfully completed, with welding taking just over one second for each join. Allowing for movement time, a full tubesheet could be welded in a matter of minutes.
The project proved that a robotic laser welding cell can successfully join small tube-to-tubesheet assemblies, and the customers design can be manufactured to requirements.
Thornhill presented their full manufacturing proposal to their customer, secure in the knowledge that it had been practically tried and tested.