Abstract: The hammering is carried out by a device having a tubular outer housing (5) which is placed against a face of the tube plate around a flush end of the tube to be hammered. A tool comprising a nozzle for projecting particles is mounted for axial movement in the outer housing (5). The control device has at least one piezoelectric sensor (20) in contact with the wall of the outer housing (5) and apparatus for measuring (23, 24) the electrical signal generated in the sensor (20). The nozzle for projecting particles is introduced into the outer housing (5) at the height of the sensors (20) after each tube hammering operation. The electrical voltage of the signals produced by the sensors is measured.

Abstract: An ultrasonic beam is sent into liquid metal from a transmitting point (3) outside the enclosure (1) containing the liquid metal, the beam is detected outside the enclosure (1) after it has passed through the liquid metal, the amplitude of the ultrasonic waves detected is compared with the amplitude of the transmitted ultrasonic waves and the attenuation of the ultrasounds produced by the passage through the liquid metal which may contain gas bubbles (2) is determined. The device comprises a wave guide (4) metallurgically connected to the enclosure (1). A processing unit (10) connected to the ultrasonic transducers (3, 6) measures the attenuation.