Numerical simulations to determine the most appropriate welding and ventilation conditions in small enclosed workspace.

In order to improve arc welding work in a small enclosed workspace, numerical simulations were conducted to find the most appropriate welding and ventilation conditions, such as welding currents, hood position and flow rates with no blowhole formation. In the simulations, distributions of airflow vectors and fume concentrations were calculated for two hood opening positions: one faced a welder's breathing zone, the other a contaminant source. As a result it was predicted that a hood opening facing a breathing zone remarkably lowered the fume concentration in the breathing zone compared with that facing a contaminant source. The reliability was confirmed in CO2 arc welding experiments in the enclosed workspace by using a welding robot. In addition, the number of blowholes in welds, examined with x-ray, decreased with the increase in the welding current and with the decrease in the exhaust flow rate. These results showed that the fume concentration near welder's breathing zone and the number of blowholes could be reduced effectively by appropriate selection of the welding current and hood position, and it was confirmed that the numerical simulations were sufficiently useful to predict these appropriate welding conditions.