Low frequency ultrasonic waves are used to detect defects and imperfections some distance away from the ultrasonic source in a range of components.
A typical application of LRUT is the detection of corrosion and metal loss in pipes and pipelines. A set of piezoelectric transducers sends the ultrasonic waves in both directions along the length of the pipe. The same transducers detect the return signal and identify how far along the pipe the imperfections lie.
This technology is particularly suitable for inspecting pipes that are covered in insulation, run under roads or are buried, as a significant length of pipe can be inspected by uncovering a small amount of the pipe at a single location. Although propagation distances vary according to pipe geometry, contents, coating/insulation and general condition, it is not unusual that a range of up to 30m (100') in either direction from the transducer can be inspected.
The technologies developed by the LRUT group are commercialised by Plant Integrity Ltd, which is a wholly owned subsidiary of TWI, offering long range ultrasonic testing systems and services in the form of Teletest®.