| 摘要 |
PURPOSE:To maintain stably the prescribed degree of vacuum and to prevent an increase in the size of a vacuum evacuating installation by stacking successively the circumferential joints of plural cylindrical structures by using a vacuum chamber and subjecting the joints to electron beam welding. CONSTITUTION:The 1st structure A1 is placed on a supporting table 9 and the 2nd structure A2 is stacked thereon in the case of subjecting plural cylindrical structures A1, A2... to circumferential welding. An annular supporting plate 32 is seal-welded to the inside circumferential surface in the lower part of the structure A2 and thereafter an intermediate partition 26 is welded to the circumferential part of the plate 32 to make the inside of the structure A2 airtight and to close airtightly the aperture at the top end. The outside circumferential surface in the lower part of the structure A2 and the top end of an outside wall 4 are further seal-welded and are airtightly closed. The inside of the chamber formed of the outside wall 4, an annular cover 27, the partition 26 and a floor plate 3 in the bottom is thereafter evacuated to a vacuum by a vacuum pump and while a welding device 10 is rotationally moved, the circumferential joint A12' is electron beam welded. |
