Forum Technical Discussions      Re: Aggressive Radiographic Auditors Need to Take a Closer Look! Posted by: dermot p dwyer (PID_3227), E-mail: Address, on January 04, 2009 at 13:48 : In Reply to: Re: Aggressive Radiographic Auditors Need to Take a Closer Look! posted by : S.V.Swamy , E-mail: Address, on January 04, 2009 at 13:29 : ---Hi I have not had the experiances of the 'aggressive Auditors' but have used the technique of masking the 'lighter' areas of a radiograph and gradually moving the mask to and passed the lighter areas for many years now ( I did learn something on that Rad course in SANDT many, many years ago!!). The technique works very well and helps with those 'questionable' areas which tend to lead to a lot of head scratching. As for your Aggressive Auditors, we in the Aerospace industry generally do not have this problem. Our snag is auditors which are not up tp speed with how NDT operates in the workplace. good luck!! -------- Start Original Message ----------- : Ed, : Excellent post and many thanks from me for sharing it. I knew about optical illusions in a general way but this is really great. I might have asked for some needless repair though not too aggressively and I confess that my team was in any case, asking far beyond the code specifications, but that was worth it considering the critical nature of the equipment and the previous accidents. Our overstrict protocols have yielded excellent results in terms of longer equipment life and less repairs once put into service (in the particular case, repair of post-service welds was very difficult). : I will alert the team about your post so that they are better aware. : Thanks. : Swamy : Retired but not tired NDT Guru! : : I wonder if there have been others with experiences of radiographic auditors bullying their opinions of so-called lack of fusion or undercut on films where most radiographers see none? The origins of �perceived� lines of so-called undercut can be attributed to a well known optical illusion known by its illustrative image the �Herman Grid�. Here a series of black squares is separated by straight white lines and the observer perceives gray blobs in the intersections of the white crosses formed by the black squares. A similar perception is had when the black squares are made smaller and the viewer perceives faint diagonal lines in the �Springer� illusion (see http://www.sapdesignguild.org/resources/optical_illusions/contrast_phenomena.html) : : Apparent brightness of a stimulus depends not only on its own luminance but also on that of the surrounding stimulation. The effect of perceiving a contrast where none exists has been documented since 1828 (Eugene Chevreul) and is generally called simultaneous contrast. : : This effect has probably be responsible for more than its fair share of unnecessary repairs due to aggressive radiographic auditors calling the fine line that they �perceive� at the boundary between the pipe wall and the weld reinforcement (cap and root). : : The verification that it is an illusion is easily seen by covering the �whiter� region (with a piece of dark paper) to reduce the contrast at the boundary. The faint grey line disappears, thereby verifying it to be an illusion and not a real flaw. : : Yet failure to recognise this or to use this simple test, results in countless unfounded weld repairs around the world. Perhaps this issue could be (should be?) addressed in the radiographic codes and standards now used. : : Ed ------------ End Original Message ------------ Follow Ups: Post a Followup: Name: E-Mail: Subject: Comments: ----------- Start Original Message ----------- : ---Hi : I have not had the experiances of the 'aggressive Auditors' but have used the technique of masking the 'lighter' areas of a radiograph and gradually moving the mask to and passed the lighter areas for many years now ( I did learn something on that Rad course in SANDT many, many years ago!!). : The technique works very well and helps with those 'questionable' areas which tend to lead to a lot of head scratching. : As for your Aggressive Auditors, we in the Aerospace industry generally do not have this problem. Our snag is auditors which are not up tp speed with how NDT operates in the workplace. : good luck!! : -------- Start Original Message ----------- : : Ed, : : Excellent post and many thanks from me for sharing it. I knew about optical illusions in a general way but this is really great. I might have asked for some needless repair though not too aggressively and I confess that my team was in any case, asking far beyond the code specifications, but that was worth it considering the critical nature of the equipment and the previous accidents. Our overstrict protocols have yielded excellent results in terms of longer equipment life and less repairs once put into service (in the particular case, repair of post-service welds was very difficult). : : I will alert the team about your post so that they are better aware. : : Thanks. : : Swamy : : Retired but not tired NDT Guru! : : : I wonder if there have been others with experiences of radiographic auditors bullying their opinions of so-called lack of fusion or undercut on films where most radiographers see none? The origins of �perceived� lines of so-called undercut can be attributed to a well known optical illusion known by its illustrative image the �Herman Grid�. Here a series of black squares is separated by straight white lines and the observer perceives gray blobs in the intersections of the white crosses formed by the black squares. A similar perception is had when the black squares are made smaller and the viewer perceives faint diagonal lines in the �Springer� illusion (see http://www.sapdesignguild.org/resources/optical_illusions/contrast_phenomena.html) : : : Apparent brightness of a stimulus depends not only on its own luminance but also on that of the surrounding stimulation. The effect of perceiving a contrast where none exists has been documented since 1828 (Eugene Chevreul) and is generally called simultaneous contrast. : : : This effect has probably be responsible for more than its fair share of unnecessary repairs due to aggressive radiographic auditors calling the fine line that they �perceive� at the boundary between the pipe wall and the weld reinforcement (cap and root). : : : The verification that it is an illusion is easily seen by covering the �whiter� region (with a piece of dark paper) to reduce the contrast at the boundary. The faint grey line disappears, thereby verifying it to be an illusion and not a real flaw. : : : Yet failure to recognise this or to use this simple test, results in countless unfounded weld repairs around the world. Perhaps this issue could be (should be?) addressed in the radiographic codes and standards now used. : : : Ed ------------ End Original Message ------------ Optional Link URL: Example: "http://www....html". Alternative write "http://www.ndt.net/wshop/attach/filename.htm" if you transfered a filename.htm via FTP Page Title: is important! Optional Image URL: http://www....gif Attention! Please click the button only once. This may take a moment to process Forum Technical Discussions Help