A lamination is a material Imperfection that is evidenced by a second layer of metal overlaying another. It is usually created by a fin or overfill being folded over and being rolled into the primary mass of the material. Laminations can appear to resemble linear imperfections like seams, but they differ by having one edge a part of the material and folding over back again onto the product. A sem is just a linear void or crack with no evidence of folding or attachment. IF THERE IS NO evidence of foldover, overlap, and welding/ reattachment,I would NOT call it a Lamination. My experience is metallurgical lab and steel mill claims mansgement, not certified welder. Milo

Milo,

This would most definitely be a case of a preconceived finding, am I correct? (can't remember the specific philosophical law right now)!

One must inspect, evaluate, and abide by the Standard, which was not done here. Even when writing a Customer Specification or Procedure, the need to work within the guidelines of the appropriate standard is mandatory.

This would be a non relevant indication and not a lamination, but a practice related occurrence.

Too many times today I find indications and causes of such misidentified by Quality, Production, and Supervision.

Exactly right. Someone is using a term without regard to its relevance. The philosophy of preconception might be what you mean. Where one only sees what one excpects and thus everything they see validates their preconception. The ultimate in circular rwasoning. If I only have a hammer, everything looks like a nail is its practice. My guess is that the person calling it a lamination is a newbie and learned the term on their very first case; sadly for our op, their current job is the newbie's second! Milo

Reading and re-reading the OP as well as #1,2,3 replies ... I am perplexed.

Having seen (i.e., "detected") quite a few small laminations in pipelines, using either UT along a length or MPI on the cut ends (performing repairs), I have always understood that laminations arise from any number of *usually* non-metallic inclusions, to INCLUDE piping (that occurs in lengths/sizes as different as the snowflakes in a blizzard).

Never been involved in such "flattening" tests (well, except maybe THIS...). However, it would seem to me that a lamination existing near the point where the pipe-metal is being "pinched" just might possibly cause such a 'crack' to open-up to the surface.

[ An analogous effect (from laminations, "slipping", and causing 'ruptures' in the steel) has always been a concern exhibited by the operators of an underwater cold-forging process for repairing pipelines. ]

Granted, there may be other possibilities in the OP's scenario...but, shouldn't the possibility of lam's extending to the surface be given a high probability? (Just askin')

ndt-tom

Here is a link to my post on Laps.

I'll be following up on slivers, shearing, seams, and other such imperfections in the weeks ahead.

Milo

Nice page, "M" ... (looking forward to the follow-ups).

Still, back-to regarding the OP's comment: "...the inner wall undergoes compression and sometimes shows minor crack opening. This defect is considered as Lamination opening by some our Inspection agency..."

If these "minor crack openings" are, in fact, manifesting at the points where the pipewall metal is undergoing "compression/pinching", would a lamination that is close enough to the inner wall not possibly 'erupt', causing the events they are observing?