The use of Ultrasonic non-destructive testing (NDT) to check material properties such as thickness measurement is used in all facets of the industry. The ability to gauge the thickness measurement of material without access to both sides of the test piece offers this technology a multitude of possible applications
Ultrasonic thickness gauge can be set up for metals, plastics, composites, fiberglass, ceramics & glass. It is completely non-destructive with no cutting or sectioning required.
Ultrasonic thickness measurement is done by gages by precisely measuring how long it takes for a sound pulse that has been generated by a small probe called Ultrasonic Transducer to travel through a test piece & reflect back from the inside surface or for the wall.
Measurement is made from one side in “Pulse/echo” mode because sound waves reflect from boundaries between dissimilar metals. Ultrasonic thickness measurement is performed for the measurement of the thickness of Hot Metals, through coating and scale measurement of the inner surface of the pipe.
1) Measurement of Thickness through Hot Metals:
The thickness of the part can be measured in case of surface temperature reaches to 5000C. Particularly in metal, there may be instances when the thickness of the part needs to be measured during the going process where the test piece cannot be cooled down. Measurement of thickness is performed on one side of the part just as the measurement at normal temperature.
2) Measurement of Thickness through Coat/Paints:
The petrochemical industry used a network of pipes to transfer liquid and gases. These pipes are chemically coated or painted for their safety from any hazardous effects. Change in the thickness of the pipe affects its transmission capacity as well as overall performance. Hence it is necessary to measure the remaining thickness of a metal pipe or any other metal in the industry subject to corrosion through one or more coats of paints or similar non-metallic coatings. This presence of paint or similar coatings will cause measurement errors with conventional ultrasonic thickness gages.
The paint has a much slower sound velocity. Such measurement of the thickness of coated metal can be done in two ways; Echo-to-Echo measurement and THRU-COAT measurement.