Abstract: A double-layer pipe bend for a pipeline includes an inner pipe of cast steel, an outer pipe of weldable steel surrounding the inner pipe, and connecting flanges at the ends of the pipe bend. The connecting flanges are welded to the outer pipe. The inner pipe and the outer pipe are formed such that a pressure-compensating layer can be formed by the transported medium between the pipes. Another pressure-compensating layer can form between an inner wearing ring and an outer coupling ring of each connecting flange. The wearing ring and, thus, the inner pipe, is axially secured by a groove in the wearing ring and a radial collar in the coupling ring.

Abstract: A pipe for conveying solid matter, particularly for conveying concrete. The pipe has a cylindrical middle portion and a double-layer welding neck with annular coupling flange at each end of the middle portion. The inner layer is replaceably clamped in the outer layer in a positively locking and frictionally engaging manner. This is accomplished by a roof-like bevel of the inner layer which is engaged by a corresponding inner groove of the outer layer which is of limited elasticity. The inner diameter of the inner layer may be smaller than the inner diameter of the cylindrical middle portion.