Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998, 1252
Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1252
23:41 Nov-30-2018 Re: Calibration using curved wedgesIn Reply to S.Williams at 13:44 Nov-30-2018 (Opening).
Shawn, as Ali noted, it is possible to obtain an IIW-Type block with a curved surface. As long as the apex of the curvature is accurately made so that the distance from the centre of radius at the apex to the 100mm radius is 100mm, your wedge delay and time-base calibration should be correct. There are good instructions in the ISO 2400 and ISO 19675 documents (for calibration block fabrication) to ensure that the calibration block velocities are held within a small range of tolerance. Therefore the velocity settings on your instrument should provide a good calibration. The calibration will require that your mid-point of the radiused wedge be centred on the curved contact. As long as the curvature of the block is smaller than the curvature of the wedge this will be possible. A reasonably small curvature on the cal block would be about 25mm radius.
In the attached image I made in Civa you can see how a wedge, radiused to 100mm fits on a 25mm radius surface. If the radius of the wedge is smaller than the radius of the block you will not be measuring the true wedge delay as there will be gap formed between the wedge and block. Assuming you can fill that gap with couplant it adds to the delay being detected by the instrument and the calculation for wedge delay will be incorrect in your calibration.
19:05 Jan-31-2019 Re: Calibration using curved wedgesIn Reply to Ed Ginzel at 23:41 Nov-30-2018 .
So how is everyone checking their exit points and beam angles? Is everyone using curved blocks. What range of diameters can you use a curved shoe on or does every diameter require it's own curved shoe?
Reminds of when ASME changed the cal block requirements so that you needed to have the same diameter and schedule then changed it back to the way it is now. I hope they change this back as well.
20:34 Jan-31-2019 Re: Calibration using curved wedgesIn Reply to S.Williams at 19:05 Jan-31-2019 .
Shawn, the issues relating to small diameter pipe girth-weld inspections are indeed frustrating. In the January 2019 issue of NDT.net, I have a rather lengthy paper where I tried to consider many of these parameters. https://www.ndt.net/article/ndtnet/papers/Modelling-Probe-Wedge-and-Pipe-Geometry-as-Critical-Parameters-in-Pipe-Girth-Weld-Ultrasonic-Inspections-Using-Civa-Simulation-Software.pdf
Getting away from notches is, I think, a good idea. Making specific provision for curved wedge requirements is also , I think, a good idea.
Perhaps discussing these issues will inspire the improved availability of reference blocks with curved surfaces such as Ali described back in November.
nick bublitz Other, Phased Array Analysist VeriPhase, USA, Joined May 2010, 123
nick bublitz Other, Phased Array Analysist VeriPhase, USA, Joined May 2010 123
23:18 Jan-31-2019 Re: Calibration using curved wedgesIn Reply to S.Williams at 21:05 Jan-31-2019 .
Most manufacturers will have standard curvatures available for the popular probe types, custom exact wedges can also be ordered but will usually cost more and have a longer lead time. Here are a few links to a few different manufacturers' charts.
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