Visual testing (VT) requirements for non-destructive testing (NDT) testers

Within the review of standards, there is a working group looking at the visual testing (VT) requirements for non-destructive testing (NDT) testers. The American and Canadian contingency wanted to add far distance to the requirements for those walkaround general visual inspections on plant and installations. Recently, a significantly large crack was reported in a steel support pillar holding up the Fury 325 ride at Carowinds amusement park in Charlotte, North Carolina, USA.

Jeremy Wagner, one of the visitors, observed the crack opening and closing each time the cars passed by. The ride is described as ‘the tallest, fastest, longest giga coaster in North America’. It is 1.25 m-long and reaches speeds of up to 95 mph with a peak of 325 ft and an 81° drop with a 190 ft-tall barrel turn. There are videos and images available on the internet and they do show the extent of the fracture; there is no requirement for any form of NDT other than visual testing. Looking at the extent of the fracture, it probably started at either a weld or some damage and propagated through the full circumference of the tubular section over time.

With a fracture of this size, a distance visual test would be able to recognise it at the later stages but probably not so in the beginning. Close visual inspection, alternating current field measurement (ACFM) and eddy current testing (ECT) would have all been useful tools in the first instance and the use of an aerial drone on a regular basis could have noticed the fracture earlier. It is more significant as the ride is in use and the carriages pass by.

It would appear that a far distance visual test and more frequent walkaround checks by trained personnel could add value and safety in some cases.

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