XRay and leaks

By jarsanb (***)

Date 05-27-2010 12:27

Not uncommon. Incomplete fusion can lurk in rashes and is not easily detected by radiography depending on its profile. Even though it's pretty rare, it is more common with continuous wirefeed processes over SMAW due to coldlap on restarts.

By Shane Feder (****)

Date 05-27-2010 13:29

Pipeit,
For an example drill a 2mm hole right through the whole weld thickness at 6 o'clock on the pipe. The second of three radiographic shots is usually with the source at 0 (12 o'clock) so the 2 mm drill hole will be shown as very close to that size on the film.
If you have a maximum acceptance criteria of 3 mm for a rounded indication then your radiograph has passed but you have a rather large leak problem.
With radiography it is all about orientaion of the source relative to the defect, as jarsanb has stated RT can completely miss certain defects.
Regards,
Shane

By dbigkahunna (****)

Date 05-27-2010 17:21

And also size. I had a 2 inch standard wall butt weld pass xray and when it was put in service it leaked. Looked at the film and there was a real small GP at the edge of the weld. Missed it on the visual and was within allowable by film. Went all the way through the weld. Was on LPG line.
That is why you visual the weld and repair all gas pockets.
If I have just looked, hit the gp with the grinder and re-welded, there would not have been any issue. It was on fabrication and all I would have to done was just look.

By Metarinka (****)

Date 05-27-2010 16:56

I agree with the above posters, Xray will not catch certain defects depending on their orientation and position relative to the source.

Xray's measure the density of a material. A lamination or crack in certain plains won't change the density (same thickness but the material is unbonded) Hence you can have a weld leak like a seeve and still pass xray. however it is uncommon