04:13 Jul-25-2005 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1208
Re: Phased Array S-scans Promo
Salut François: The application of PAs to AWS projects was a separate matter that I also had interest in. The AWS D1.1 Code is very restrictive as written in the Section 6.20 where the requirements of UT are described. It has been awhile since I talked to Jonathan, I assumed that his Procedure was approved by the Engineer as per the provisions of the Appendix K. Is that so? This would seem to be the only option for anything new in AWS D1.1. Hopefully Codes such as AWS will, in the near future, be more receptive than they have in the past, to making the necessary changes to allow new technology.
----------- Start Original Message ----------- : Bonjour - I was the project leader for the solution at Hitachi. I chose Mr.Jonathan Buttram (Level III, Interwav) to write the AWS procedure. He made pretty clear in the procedure that data displayed from 0 to 35 deg. are not to be used for measurements. They should be used for detection only, for laminar defects only. Any rigorous technician with proper Level I or II background will know how to use this carefully. : Unfortunately, other manufacturers of phased aray sold it with a "does-it-all-black-magic" étiquette, which annoyed the market, and this reactivity and Whittle's article are a proof of it. : HARFANG sales pitch always starts with "This is not magic, this is normal ultrasonics." We are active promoters of ethical information disclosure on phased array. : François Mainguy : Founder and VP-Technology : HARFANG Microtechniques inc. (Québec) : : As one of those responsible for selecting this particular picture for the Insight front cover I suppose I had better respond to Ed's comment with some explanation. : : Firstly let me state that there is nothing much 'marketingy' about the image, its a photo taken by the customer of a real operator working on a real weld on a real tower, soon to be installed somewhere in North America. : : Of course Ed's points are valid, and no interpretation should be made of indications outside the range of around 35- 75 "onscreen" degrees. : : However: : : This is a manual test, If anything outside this shows up the probe can easily be moved so it is in the 'valid' region for investigation. : : A series of repeat backwall echoes can be seen down the left hand side of the screen. This provides a check for any unexpected thickness change delaminations, or loss of coupling. Of course the indicated position will not be correct as these are compression wave and the screen is calibrated for shear velocity. : : I would certainly not promote Phased array as 'you get a picture - thats whats in the metal' But these are experienced operators who know what they are looking at. They take the view 'why have a black area of screen when you can show something that might be useful' : : In general I would agree with Ed's view, and particularly his recommendation of Alison's paper (which I just reread) For the right applications Phased array equipment has huge potential advantages, both technically and financially. As equipment vendors we are well aware of the problems that can be caused by unreasonable expectations, and we certainly have no intention to raise them. : : For anyone wondering what this is all about I've posted a copy of the picture on : : http://www.joe.buckley.net/images/P5120037(Medium).JPG : : : : Joe Buckley : : : This is posted as an item for discussion. Having seen the hyperbole surrounding what I think is a valuable tool, (phased arrays) I am a bit concerned that Great Expectations are being stirred that are unfounded in science and practical application. : : : Phased array technology has been around since the 1950s but only lately has it been popularised in NDT. This popularity is probably due to the reduction in price and size of equipment. It has a variety of options, many of which duplicate multi-probe or multi-axis encoded systems. But the unique aspect of phased array systems seems to derive from the sectorial scan (also calledthe azimuthal or S-scan). : : : However, other than as a propmotional "gimmick" can anyone explain why some of the marketing images use a true-depth sectorial (S-scan) display that indicates capabilities far beyond reasonable expectations? : : : I just received my copy of the BINDT Insight where the front cover image is of a UT operator putatively working on a weld inspection with such an S-scan display. But the display shows an angular sweep from 0° to about 80°! Not only is it unlikely that any phased array probe (even on a wedge) has such capability for weld inspection, the fact that the sweep passes from 0° through 33° means the test is using nearly half of the sweep data from below the first critical angle. This would be virtually impossible for the UT operator to make sense of! : : : Flaw position is incorrectly plotted when the S-scan is so configured! e.g. A velocity is typically programmed into the system so as to correctly display flaw depth with respect to angle. Only one velocity can apply so, assuming Shear wave velocity was used, the focal producing the 30° shear wave will also produce a compression wave around 67° (in steel). But any flaw detected by the 67° compression wave will be ploted as if detected early along the 30° path. : : : AC Whittle wrote an article in the Nov. 2004 Insight questioning if phased arrays were a Pancea or a Gimmick. I suspect they are neither, but if unreasonable expectations are set by marketing gimmicks they may suffer in the long run. : : : Ed ------------ End Original Message ------------