Grinding and Liquid Penetrant examination
Grinding and Liquid Penetrant examination
(OP)
Hi. I was told in my Liquid penetrant course that surfaces should not be grinded prior to testing, cause that would cause litlle round indications to hide. Now i am working in the pipeline industry, and a quality control engineer with far more experience tells my, after I finish the LP test, that the final weld should be grinded so that spaces between welding passes won´t hide real indications. You know, that would mean that the joint should be "blended" to be smoother, cause wipers don´t always reach that spaces, so penetrant remains, and it looks red. That would be bad for joints, specially if the final pass is ugly or if it is made with 6010 or 7010, because of the "waves they let". What is the best point of view? It is necessary to clean toroughly with the wiper again and again to avoid grinding? Thanks in advance





RE: Grinding and Liquid Penetrant examination
Most welds will need some touching up by grinding or sanding prior to a PT test due to the reasons you state. Remember to grind normal To weld bead direction, cross wise. Never turn a grinder on edge to dress the toe of the weld where you usually find cold lap. Never try to make a weld bead pretty.
RE: Grinding and Liquid Penetrant examination
RE: Grinding and Liquid Penetrant examination
RE: Grinding and Liquid Penetrant examination
I may get pounded one but there is no set way to PT test a particular component. It is up to the technician to be able to slightly modify a PT procedure to get the highest quality inspection. The only caveat is to appraise the owner and get permission as to what you are going to do..
RE: Grinding and Liquid Penetrant examination
ie the gap between two stringers may be on or close to the edge of the root, and what may well just be a gap, can look like a serious root defect....thats all.
Penetrant is probably too sensitive ( not sure thats the right word......) for carbon pipeline welds, the carbon can hold too much penetrant at times. Why not use MPI, much quicker and easier
RE: Grinding and Liquid Penetrant examination
Use of the proper media and technique are important. For example using a hand held SS welders wire brush is not likely to smear metal on a ferrous application, but, use of a stiff braided wire wheel on a large power tool will likely smear metal where ever it's used.
As in most things there's no one right way that covers all situations.