Ultrasonic inspection uses sound waves of short wavelength and high frequency to detect flaws or measure material thickness. It is used as an alternative inspection method to radiography to locate sub-surface flaws in all industry sectors.
Usually, pulsed beams of high frequency ultrasound are used via a hand held transducer (probe) which is placed on the specimen. Any sound from the pulse that is reflected and returns to the transducer (like an echo) is shown on a screen, which gives the amplitude of the pulse and the time taken to return to the transducer. Flaws anywhere through the specimen thickness reflect the sound back to the transducer. Flaw size, distance and reflectivity can be interpreted.
Automated systems are used for testing in a production environment and for some special applications.
Ultrasonic inspection can also be used to measure the thickness of a wide range of metallic and non-metallic materials where access from one side only is available.
Applications of ultrasonic inspection are:
- Welded joints typically > 10mm thick
- Internal corrosion monitoring of pipelines and pressure vessels both on and offline
- Quality control during manufacture of plate steel
- Inspection of heat exchanger and boiler tubes using the IRIS method