Define the Ultrasonic Thickness Measurement?
Ultrasonic thickness meters measure the thickness of steel by passing an ultrasonic wave through the member. Thickness measurements are obtained because certain types of ultrasonic waves travel at a constant speed through a material, because they travel in straight line, and because a portion of the wave is reflected when it meets end interference. The variation in time among the detection of the front surface and back surface echoes is concurrent to the thickness of the material. Transducer is placed on one side only, and the thickness is displayed on LED readout. Completely submergible or surface display units are available.
Ultrasonic thickness meters available in the market can measure the thickness of the steel through coating up to 6 mm. For use in turbid water, thickness meters with topside repeaters can be used. Ultrasonic thickness measurements require thorough removal of marine growth. Measurement can be unreliable if the surface on which the instrument is placed is highly pitted. The applicability of use of ultrasonic thickness meters on cast iron has yet not been confirmed. Presence of random graphite spicks in cast iron reflects sound waves, which leads to erroneous data.