A cleaning apparatus for cleaning a cooling tube array (15) of a heat exchanger has a nozzle carriage (16) movably held on a truss beam, and a plurality of cleaning nozzles (40) mounted to the nozzle carriage. A truss beam has two parallel C-channel rails (20) having back sides that face each other, a tube (22) arranged separate and distant from the C-channel rails and at a different height than the C-channel rails in a cross-sectional plane of the truss beam, and truss supports (24) connecting the rails and the tube; the nozzle carriage has rollers (48) that are arranged for travelling in the C-channel rails. A water intake (82) is coupled to the nozzle manifold (42) and to a hydraulic drive (80) having a mechanical power take-off member (96) that is operably coupled to the nozzle carriage (16) for moving the nozzle carriage.