Abstract: A Ljungstrom type heat exchanger in which the bottom sector plate is provided with welded sector plate ribs which are welded to ribs secured to the frame of the heat exchanger. The upper surface may be curved to be complementary to the thermally induced curvature of the rotor. The fairings associated with the support for the upper sector plate may be provided with ports for the passage of some hot gases to prevent distortion of the main beam. A cleaning device is disclosed in which a feed pipe is fully retractable having a nozzle at its radially outer end.