| 摘要 |
PURPOSE:To manufacture a circular duct with high accuracy by an on-site operation from forming to welding without using a large-scale installation by setting wires on a flat plate, pulling taut the wires to curve the flat plate to approximately a circular shape and mounting reinforcing rings into the curved plate to maintain a prescribed circular shape then welding the ends to each other. CONSTITUTION:A flat steel plate having the length provided with an allowance for welding to the outside circumference of a product, i.e., duct is used for a flat steel plate 10 which is a blank material. Wires 11 are set to the plate 10 and chain blocks 12 are connected to the respective wires 11. When the wires 11 are pulled taut by operating the blocks 12, the plate 10 curves to the state of having a slight spacing between the ends or the state having an allowance B for lapping at the end faces. Reinforcing rings 13 are mounted into the bore part of the plate 10 having the slight spacing and thereafter the wires 11 are further pulled taut to bring the plate 10 into tight contact with the reinforcing rings. On the other hand, reinforcing rings 14 are mounted on the outside diametral part of the plate 10 having the allowance B and thereafter the wires 11 are loosened, then the plate 10 is formed to the circular shape conforming to the bore part of the rings 10 by the recovering force thereof. The weld zone 15 of the plate 10 maintained at the prescribed circular shape is welded. |
