MT before or after shop blasting ~ what is allowed.

[fabengr]

I have a project that requires a great deal of MT testing of the fillet welds. We have an inspector that is telling me that you have to MT before you blast clean the material. The comment is that the blasting will affect the profile of the weld. It seem logical that if the weld is blast cleaned the MT test would be more accurate. Comments?

 

[JR97]

Fabengr,

MT can be performed before or after blasting. Perhaps what the inspector is remembering is that PT (liquid penetrant) must be performed prior to blasting because the blast operation has the potential to peen shut small defects. The magnetic field disruption caused by a defect in not materially affected by potential peening caused by the blast media, even if an AC inspection is performed.

JR 97