Abstract: Firstly, individual wall parts are welded together from a cooling rib element (1), a tub side wall (2) and a frame part (3), the cooling rib element (1) being reinforced by strips (8, 9) and bars (10, 11). The individual wall parts are mounted on an assembly plate (16) by means of positioning bolts (17) and are held together by stirrups (18). By means of spot welds on the sloping, upwardly bent edges (6, 7) of cooling rib elements (1), the wall parts form a dimensionally stable casing, on which the various vertical and horizontal welds can be made. Due to the fact that the dimensionally stable wall parts are used for producing the transformer tank, the proportion of manual labor in the production of this tank can be considerably reduced, because welding takes place at clearly defined, easily accessible points.