Abstract: A tank cleaning device, wherein a supply tube delivers cleaning fluid into a flushing head rotatable about the tube axis and then into the nozzle of a nozzle unit mounted in the flushing head for rotation about an axis perpendicular to the tube axis, comprises a hydraulic brake cylinder coupled to the nozzle unit for variably controlling the rotational speed thereof in dependence on the rotational position of the nozzle unit. A crank couples the brake cylinder (or piston) to the shaft on which the nozzle unit is rotated for oscillating the cylinder (or piston). A mechanism couples the piston (or cylinder) to the flushing head for rotating the flushing head about the supply tube axis upon oscillation of the cylinder (or piston).