Abstract: To avoid the folding of a flat tubular bag 1, which has been set up supported on its bottom-side cross seam 4, a welding seam 7, 8 reinforcing the tubular bag 1 is provided along at least one edge 5, 6. A further tubular bag 101 is introduced, where on the side folds 110, 111 of which the edges 105, 106 have welding seams 107, 108. Because of the welding seams 107, 108, the stability of the tubular bag 101 is improved. The longitudinal seam 2, 102 in the two tubular bags 1, 101 extends in a reinforcing welding seam 7, 107. The tubular bagging machine 14 for the manufacture of the tubular bag 1, 101 has at least one expanding element on the fill pipe 20 for expanding the film tube 21. A longitudinal welding device 22 is provided following the expanding element 27 in film feeding direction (FIGS. 7, 8).