Abstract: The scanning system of the invention includes a structure driven in rotation around a first axis, a structuremounted rotating on the structure around an axis parallel to the first axis, a structure for supporting an echographic probe mounted rotating on the structure around a third axis parallel to the axis, a coupling element between the structure and the structure and a coupling element between the support structure and the structure. This system being able to move the probe along a variable band arciform trajectory.

Abstract: The scanning system of the invention includes a structure driven in rotation around a first axis, a structuremounted rotating on the structure around an axis parallel to the first axis, a structure for supporting an echographic probe mounted rotating on the structure around a third axis parallel to the axis, a coupling element between the structure and the structure and a coupling element between the support structure and the structure. This system being able to move the probe along a variable band arciform trajectory.

Abstract: Acoustic waves are sensed in contact with or near the plant at at least two points (1, 2, 3, 4) whose position is accurately determined with respect to the monitored region. The order of arrival of the acoustic waves at the sensing points (1, 2, 3, 4) is determined and this order is compared with a predetermined order corresponding to a phenomenon occurring in the monitored region. An alarm is triggered if the order of arrival corresponds to the predetermined order. The apparatus includes an encoding logic (9), a comparator (10) and a monostable circuit (12) triggering the alarm. The invention is particularly applicable to monitoring nuclear reactors in operation.

Abstract: The present invention allows the position of a defect to be located when it emits acoustic waves into a closed structure. The waves travel around closed routes in a section of the structure.To this end, it comprises at least three acoustic sensors (22-24), uniformly distributed on the surface of the section of the structure monitored, connected to logic (26, 27) for encoding the order of arrival of the signals detected. Control means (16, 20, 35) for controlling display means and means (19) for controlling the writing means of the latter, which is preferably a conventional dual-trace oscilloscope are described. The image of the section monitored is traced by two beams rotating in opposite directions, only one of which is illuminated for a brief instant at the moment of detection of the acoustic emission, as it passes the image point identifying the defect.

Abstract: In an industial installation which is inaccessible during operation, acoustic-emission testing of each measurement line is performed by means of at least one transducer and a preamplifier which is connected to an acoustic signal processing unit by means of a signal transmission line and a supply line. A potentiometer circuit placed on the supply line produces a variation in the supply voltage and remotely operates a relay for switching the measurement line to testing means comprising a local pulse generator connected between the transducer and the preamplifier.

Abstract: An apparatus for measuring acoustic emission is activated only at critical periods which are determined by detection of the background noise from a reference level. An acoustic emission transducer continuously transmits a signal to a detection circuit which delivers the top modulation envelope of the background noise to a comparator at a reference level delivered by a control unit.When a mean level of the background noise does not exceed a threshold reference level the AE is sampled at a low rate, f. When the background noise exceeds the threshold reference level the data sampling unit is activated to sample AE at a much higher rate F. Therefore AE is sampled at a high rate only when the pump or other machine under test is running and at a low rate when the article under test is not operating. The AE testing device also includes a frequency spectrum correlator which allows background noise to activate the increased sampling rate only if the noise is in a given frequency range.

Abstract: Sound monitoring device for an industrial installation to detect possible impacts of stray bodies including at least one set of two sound detectors arranged in contact with the wall of the installation or in its vicinity, and a measuring and alarm circuit. The detectors are connected to this measuring circuit which includes a device for measuring the separation in time between the reception of the sound waves at one and the other detector, a comparator for this separation with at least one set of two predetermined values, and an alarm which is triggered if the separation in time falls between the two predetermined values. The invention is particularly useful for surveillance of the primary circuit of a pressurized water nuclear reactor.