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News from the Institute Branches – July 2018 

| Yorkshire Branch
Advances in eddy current testing

John Moody reports

Our recent Branch meeting started with a print-out of a proposal to PCN/BINDT asking for certification to cover the advanced eddy current systems now coming into mainstream use. Over 700 systems have been sold by one manufacturer alone and one trainer has trained over 140 people in the use of this equipment, hence the need for PCN certification. Fortuitously, there were two people present who are helping with this: Joe Heigold, the Chair of the General Technical Committee, and myself. Volunteers including Andy Waller of Lavender and Howard Garlic of IMechE ARL were also present. There is a working group (WG) that will be prioritised in the near future as the actions of other WGs are completed.

What is this advance in eddy current testing? Andy Waller was soon to explain with the help of James.  
Andy described how eddy current probes are now capable of being used in a phased array format. The coils are fired in such a way as to avoid mutual inductance or cross-talk. These coils are being manufactured in application-specific formats and are able to test the dovetail profiles of turbine blade roots with one scan instead of multiple scans and by using the coils in thin flexible pads over components of varying geometry. Another application is weld testing, where a jig has been developed that spring-loads the coils, allowing for flexibility over the varying weld profile.

Andy and James were present to give the Branch an overview of the potential gains in boiler tube testing using phased array eddy current probes. With a quick calibration via a tube with known flaws, the machine was ready to begin the inspection. The boiler mock-up was full of defective tubes with actual in-service defects, which could easily be swapped for other tubes. With one pass of the probe through the tube a complete set of data was obtained, showing both radial and transverse defects, both localised and general, and was able to show the support/baffle plates and the associated defects. In this kind of inspection, there is no need for long paper charts or complementary methods, such as internal rotary inspection systems (IRIS), and all of the data is stored in digital format and is easily traceable back to the individual tubes. The sizing accuracy has also increased and the time taken to obtain the results significantly reduced, with a figure of five to ten minutes reduced to five to ten seconds quoted.

As with all inspection methods and techniques, there is a need for good training to enable accurate and consistent results to be obtained. When Andy asked if there were any questions there were a significant number concerning the training and certification, particularly relating to equipment-specific training and how to cope with the ever-changing equipment and software that can differ significantly between manufacturers. It was recognised that the training courses can only cover a certain amount and, providing the main principles are covered, the employer has the responsibility to ensure that their staff are familiar with the specific equipment in use; this is a requirement of 
IS0 9712 and the employer has to authorise their employees to work.

The meeting concluded with the AGM.