Performance of a fume-exhaust gun system in CO2 arc welding.

Although the incidence of pneumoconiosis has been decreasing in Japan, welders’ health hazards due to welding fume inhalation are still serious, because effective engineering methods for controlling fumes are technically difficult to implement in many welding shops. In the 6th notification of general prevention of dust hazards issued by the Japanese Ministry of Health, Labor and Welfare (2003–2007), a fume-exhaust gun system was recommended as an effective ventilation device for welding fume control. An ordinary fume-exhaust gun system consists of a welding torch with a suction hood which exhausts the air around the welding arc, a fume collector, and a flexible duct which connects the hood to the collector (Fig. 1). The ventilation is supposed to be performed effectively by means of the suction hood distributed around the periphery of the torch. The air contaminated with welding fumes is carried from the hood through the flexible duct to the fume collector where it is cleaned and then recirculated to the welding shop. Since a fume-exhaust gun requires much lower air removal than other local ventilation systems or a general ventilation system, it should be beneficial to the running cost of the ventilation. In addition, a fume-exhaust gun is superior to the other local ventilation systems in applicability. Unlike the fixed hood of a usual local exhaust ventilation system, a fumeexhaust gun has a hood which does not limit the size of the work piece and welder’s mobility because its hood is always close to the arc point and does not require laborious repositioning or adjustment. However, the gun performance will be affected by the geometry of the weld joint and the shielding gas flow rate. When the hood suction is distorted due to some welding position or excess in shielding gas, the fume plume may tend to rise away from the hood of the gun. In this study the author investigated the effects of welding position, elevation angle of weld line and flow rate of shielding gas on fume-exhaust gun performance.