Large casings for low-pressure turbines are constructed from welded plates, and the joints of these casings are made steam-tight by precisely and smoothly matching the flange faces, eliminating the need for gaskets. Dowel pins ensure the exact alignment of the casing flange joints.

The outer casing is divided above the horizontal axial plane into an outflow part and an outflow hood and lateral steam feeds, which pass through the wall of the outflow part with seals.