Motivation: Many metal pipes or vessels have rubber or other linings on the inside diameter for transport or mixing of certain fluids. There is a common requirement to be able to inspect the bonding between the metal and liner.

Principle: By using a transducer that can penetrate the rubber through the bondline, the amplitude of the interface can be measured with a flaw gate. Good bonding will attenuate the signal. A disbond will return a higher amplitude echo since the sound cannot now penetrate the rubber.

Challenge: Initial tests with a 5MHz tranducer showed that we did not penetrate the rubber since a known disbond was not resolved. Therefore a lower frequency 2.25MHz was used with a composite construction to give better penetration and an improved signal to noise ratio. A dual-element was also required because of the curvature of the pipe; a single element was too sensitive to rocking of the transducer.

Solution:

· Raptor Imaging Flaw Detector
· RCA-10 or RCA-18 scanner
· Dual-element 2.25MHz composite transducer (1/4”) Part No. AE07E06

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Conclusion: Pipes and vessels with bonded internal liners can be inspected for disbonds automatically using the Raptor and RCA-10 or RCA-18 and a low frequency composite dual-element transducer.