Non destructive testing device and method for detecting possible anomalies of a wall thickness

A nondestructive testing device for detecting possible thickness anomalies of a wall, such device comprising at least one sensor assembly including a sensor for emitting and receiving ultrasonic waves along a direction selected from a set including at least a first direction, and a coupling element for transmitting, in operation, said ultrasonic waves to a surface of the wall to be tested, wherein said sensor assembly comprises a rigid enclosure sealingly defining a free internal volume, wherein the coupling element comprises a solid coupling body belonging to the enclosure, and a coupling liquid disposed in the free internal volume and in which the sensor soaks, wherein the sensor assembly comprises a stator and a rotor forming said enclosure, wherein the rotor is mounted rotatable, with respect to the stator, around an axis of rotation perpendicular to a plane including each direction of said set, wherein the rotor and the stator sealingly define therebetween said free internal volume, wherein the sensor is disposed within the internal volume and fixed to the stator, wherein the solid coupling body comprises a coupling ring, said coupling ring belonging to the rotor, being coaxial with the axis of rotation, and having said plane as a transverse plane, and the coupling liquid contributing with the sensor assembly to completely fill in the internal volume, the ultrasonic waves propagating along said first direction thus traversing a first active zone of the periphery of the ring which depends on the relative angular position of the rotor and the stator, but which is fixed with respect to the stator, wherein said device further comprises a plurality of spaced apart eccentrics for applying with a non null elastic force a peripheral contact zone of the ring onto the surface of the wall, to move, while applying it, the contact zone of the ring on the surface of the wall, and to cause each active zone of the ring permanently coincide with at least part of the contact zone, wherein said device, which is designed to detect possible thickness anomalies of the wall of a tube having a longitudinal axis, further comprises a carriage selectively movable in translation in the tube and on which the sensor is mounted, this carriage being provided with a plurality of spaced apart trains, with said plurality of eccentrics, and with a motor, wherein the trains are designed to cause a longitudinal axis of carriage to coincide with the longitudinal axis of the tube, and wherein the eccentrics are carried by the stator, carrying the sensor, rotationally movable with respect to the longitudinal axis of the carriage, and designed to rotationally drive said sensor around the longitudinal axis of the carriage by applying the contact zone of the ring on the internal surface of the wall of tube, and the motor being designed to rotationally drive the eccentrics with respect to the trains.