Ultrasonic testing

The ultrasonic examination is an acoustic method for detection of material defects in which ultrasound is used. This approach is one of the nondestructive testing methods. As a result, objects, such as tanks, towers, heat exchangers and airfin coolers, can be tested at their built-in location.

To make ultrasound "visible", one needs so-called ultrasonic equipment. These are devices with which ultrasound is generated inside a medium, received and evaluated.

A ultrasonic probe sends a sound pulse in a frequency, which is appropriate for the testing. Then it listens for the echo to come back, which is reflected from the back wall or the defect.

The echo is displayed on a simple oscilloscope screen as an amplitude. Based on the echo height and the position on the display it is possible to localize defects and cracks in the material, and/or determine the thickness.

A common way to determine the defect size is the error comparison method, whereby the echo of a defect is compared with a known defect in a calibration block with the same material properties. It is also possible to calculate the depth and size of the defects inside the material.