Tags: Ultrasonic

Ultrasonic Examination – Hydrogen Blisters

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Ultrasonic Examination – Hydrogen Blisters

The use of longitudinal wave UT for detecting, locating, and determining the size of hydrogen blisters is illustrated in Figure 700-17. The blisters are internal flaws that have a reflecting surface at a depth from the front surface that is less than the distance to the back surface (thickness) of the shell component. Therefore, the […]

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Ultrasonic Examination – Calibration

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Ultrasonic Examination – Calibration

Calibration of longitudinal wave UT consists of developing a “distance amplitude curve (DAC)” for the instrument and transducer, using test blocks manufactured from a material similar to the workpiece (i.e., with the same velocity of sound). Calibration for determining the remaining thickness of a corroded component can be accomplished by placing the transducer sequentially on […]

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Ultrasonic Examination – Longitudinal Wave UT

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Longitudinal wave UT is used primarily to determine the remaining thickness of corroded shell components, including the depth of pits. It can also be used to detect internal flaws that have developed during service and that have a reflecting surface essentially parallel to the surface of the workpiece (i.e., perpendicular to the longitudinal ultrasonic wave), […]

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Ultrasonic Examination – Couplants

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Attenuation of ultrasonic waves propagating through air is very high, and normal surface roughness (especially of the workpiece) will always create an air gap between an ultrasonic transducer and the workpiece. It is not practical to improve the surface of the workpiece to the extent necessary to effectively eliminate the air gap. Therefore, a “couplant” […]

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Ultrasonic Examination – Ultrasonic Transducers

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Ultrasonic Examination – Ultrasonic Transducers

Ultrasonic waves for UT are created in a metal workpiece with a piezoelectric transducer that is coupled to the workpiece. The piezoelectric transducer converts high frequency electrical impulses into correspondingly high frequency mechanical vibrations that induce ultrasonic waves in the workpiece. For detection of reflected waves, the piezoelectric transducer operates opposite to the manner in […]

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Ultrasonic Examination Instruments

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Ultrasonic Examination Instruments

Most UT systems used for the in-service inspection of a pressure vessel employ a “pulse-echo” method of operation, in which the same transducer (described below) that creates the ultrasonic wave (pulse) is also used to detect any ultrasonic waves (echos) reflected by flaws. A typical ultrasonic instrument for the pulse-echo UT is illustrated in Figure […]

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