Device (11) for driving a flexible lance (4) for cleaning a heat exchanger duct, provided with a frame (1) in which a drive (12) driving a flexible lance (4) is arranged for moving this flexible lance (4) in the direction of an outlet opening. The drive (12) is provided with a member (27) which can be clamped round the flexible lance (4) and which is movable in the frame (1) towards and away from this outlet opening.
