We normally use some method of cleaning to remove any loose scale, etc. If you don't pre clean properly it's difficult to get meaningful results. The really serious conditioning and inspection should be performed before PWHT because you don't want to be making weld repairs after PWHT.
Weld prep in the sense of blend grinding after welding is always beneficial for Inspectors to interpret WFMT results. Also, by eliminating undercut at weld toes and a "rope" weld bead texture will increase resistance to fatigue crack initiation in service.
Thanks for the responces thusfar (Weldtex & Metengr). Some additional information is the vessel have been PWHT and this will be the final inspetion. We are having a disagreement with the vessel fabricator as to what weld smoothing (grinding or buffing)of butt and/or fillet welds is necessary to perform the WFMT required inspection. They believe that fillet welds do not have to be smoothed off, just stress risers removed. Can anyone shed some light on fillet welds? Do they require the same preperation that the butt weld receives?
WDorey;
What you are describing is more of a contractual issue versus a technical issue. The Authorized Inspector (AI) has the right to require any blend grinding in evaluating visual imperfections or if there is an NDT interpretation issue related to surface condition.
Regarding blend grinding, in general, if you had specified it in your fabrication requirements for increased fatigue resistance it shall be done. If you did not specifically address blend grinding, the fabricator has the call in terms of final weld quality meeting Code requirements with input from the AI.
Whether or not surface prep is adequate depends somewhat on what your acceptance tolerance is for the WFMT. We have some jobs where No indications are allowed. In those cases a great deal of grinding and sanding may be required to remove ridges, ripples and minor undercut which would trap penetrant and give an indication.
There's not a one fit for every situation.
Yes, weld prep is required after PWHT. It should be no more than power brush.I don't know where all this grinding is coming from.Sounds like someone is not watching their welders.
