Does anyone out there familiar with ASME and/or National Board Repair know if there is a minimum distance from the edge of a weld prep to a lamination that may be found by a UT scan in a pressure vessel that is being repaired?
We are looking at replacing heads on a few rather large pressure vessels and we would do UT on the cut line. If we find any problems in the area, we can move the cut line a bit, but too much.
I seem to remember seeing something somewhere, but I can't seem to find anything.
(Maybe I saw it in a structural steel code???)(Maybe I was in dreamland???)
Any help would be appreciated!
Thanks in advance!
~D~
100 mm from the bevel face and or as far back as the angle beam probe you are using needs to be in contact with the parent material in order to conduct your inpection. For example, if the angle beam probe needs to be 10" from the centerline then you need to lam check 10" back on both sides of the weld.
I was interperting the question as to determining the acceptablility of the laminar discontinuity specifically looking at its location in relationship to the new weld prep edge. Then possibly adjusting the cut line (new weld) as much as allowable and still stay the required distance away from the laminar discontinuity. But what is the required minimum distance?
AWS D1.1 and D1.5 has some limits of acceptability and repair of mill induced discontinuities. That section might give you some guidance. It allows for an internal defect to be 1" or more away from the face of a weld prep.
ASME Sect. VIII refers back to Sect. II (for the base metal) and offers some acceptable limits for edge and U.T. defects in the base material... that is if U.T. was specified when ordering the plate. But in your repair application you have to work with what you get.
I think in this case the Nat'l Board will only refer back to the orginial Code of construction.
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