Ultrasonic Flaw Detector

The long-range ultrasonic system uses guided ultrasonic waves, so called because the pipe acts as a wave-guide along which the sound travels. These waves are similar to the Lamb waves, which may be generated in plates.  The frequencies used are much lower than those used for normal ultrasonic tests. Frequencies around 50kHz are used by the long-range ultrasonic system compared with around 5MHz for conventional thickness testing. The guided waves can travel many metres and therefore test large areas from a single point. Any changes in the thickness of the pipe, either on the inside or the outside, cause reflections that are detected by transducer wrapped around the pipe. Metal loss defects from corrosion/erosion inside the pipe or corrosion on the outside of the pipe can be detected. The system enables a trained operator to discriminate between metal loss and pipe features, welds in particular.

The main system components are:

• The low frequency flaw detector,
• The sensor tools for the pipe diameters to be tested,
• A ruggedised lap-top computer with specialised software for test, control and data analysis.

This is a 12 channel pulse-echo instrument, with all channels individually addressable. The long-range ultrasonic system 1 is designed for.

• Longitudinal operation
• Torsional operation

Basic Function

The long-range ultrasonic system detector is an intelligent remote unit operating under full control of the host computer. It operates on an umbilical cable, allowing the computer, peripherals and power supplies to be located in an appropriate environment. The umbilical is supplied up to 50m in length. All data transmission between the computer and the detector is digital.

The detector contains the transmitter circuitry to energise the ultrasonic transducers in the sensor tool and receivers to detect and amplify signals returned from the sensors. On-board signal processing allows pre-conditioning of signals prior to transmission to the host computer.

Dimensions