positioning an ultrasonic transducer on the inside surface of the cladding layer within the vessel for directing an ultrasonic pulse into the wall of the vessel at an angle substantially normal to the inside surface;
energizing the ultrasonic transducer with a broadband energy pulse to transmit an ultrasonic pulse into the wall of the vessel, a first ultrasonic pulse being reflected back to the transducer by the first interface, a second ultrasonic pulse being reflected back to the transducer by the second interface and a third ultrasonic pulse being reflected back to the transducer by the first interface again as a first multiple signal occurring later in time after the second ultrasonic pulse;
receiving the second and third reflected ultrasonic pulses with a broadband receiver to produce non-rectified signals representative thereof;
displaying the non-rectified signals representative of the second and third reflected ultrasonic pulses as waveforms on a high frequency, broad bandwidth oscilloscope for viewing by an operator; and
viewing the displayed waveforms and identifying a phase change of the displayed waveform representative of the second reflected ultrasonic pulse, in comparison with the displayed waveform representative of the third reflected ultrasonic pulse, as an indication of the presence and location of the first interface, measuring a time of flight of the ultrasonic pulse within the internal cladding layer, and calculating a thickness of the internal cladding layer using the measured time of flight and a predetermined calibration standard for the same type of known material as that of the internal cladding layer.
Abstract: An ultrasonic inspection method for measuring the thickness of non-welded (non-metallurgically bonded) cladding on the inside surface of a vessel from an outside diameter surface of the vessel relies upon the occurrence of a phase change at an interface between the base metal and cladding layers to precisely determine its presence and location. By measuring the length of time for the ultrasonic pulse to propagate through the cladding material, suitable predetermined calibration standards for the cladding material in question can be used to convert the time of flight of the ultrasonic pulses through the cladding into a thickness of the cladding. The cladding thickness can be measured from an outside surface of the vessel whether or not it is empty and/or without stopping the process and/or draining it, and the method can even be employed at elevated temperatures through the use of known delay lines. Alternatively, if safe access to the interior portion of the vessel is available, an internal direct inspection can be performed to determine the thickness of the non-welded cladding using a modification of the technique in which a first multiple or second reflection signal from the base metal/cladding layer interface is used.
U.S. Class: (73/622) (73/629) (364/507) (364/563)
IPC: (G01N 29/10)
US Patents Cited: 3056284 3942361 4189331 4334433 4435984 4446736 4493452 4507609 4603583 4634963 4669310 4673877 4679430 4719808 4918989 4936649 4978223 5108692 5132278 5156636 5225148 5294861 5329561 5349860
OG Section: Electrical
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