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Heat exchanger and boiler tube inspection using ultrasonic waves

Connect no.171

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TWI has been researching the use of ultrasonic guided waves for the rapid inspection of structures for more than two decades and now works closely with its sister company Plant Integrity Ltd. which provides commercial inspection equipment and services for the defect screening of pipelines with ultrasonic guided waves.

There is an industrial need to improve the inspection methods available for heat exchanger and boiler tubing.

The technology that has been developed for pipeline screening can be applied to pipes of small diameter. However, access is extremely limited and there are often thousands of low diameter pipes in each heat exchanger or boiler bundle, making the existing equipment unsuitable. TWI has developed a prototype probe that only requires to be inserted into the first 100mm of a small diameter pipe to be able to screen its entire length with ultrasonic guided waves.

By developing this system further, TWI would like to improve heat exchanger/boiler tube inspection and offer to the industry the following benefits:

  • Faster inspection and reduced downtime
  • No need for cleaning beyond that required for normal operation
  • More accurate and reliable inspection at tube bends and underneath baffle plates
  • More effective inspection for internal and external defects
  • One technique for ferrous and non-ferrous materials
  • A user-friendly system

TWI's prototype probe uses an inflatable shaft to couple the transducers onto the inside of the tube, which can then be used to transmit and receive ultrasonic pulses. This design allows for very quick probe deployment and single shot testing of entire tubes. A demonstration of the tool is given in the Figure, where a small defect was detected at 2.1m along a 2.9m copper pipe with a 20mm internal diameter.

For more information on this project, please contact us.

For more information please email:


contactus@twi.co.uk