First thing- I work in the nuclear industry (Field Engineer). On one of my projects, we will be using a lifting beam (fabricated weldment). We are using this beam to lift 100+ tons. currently the beam is painted (manufacturers original enamel). Prior to use, our process requires that the welds in this beam be tested. In this case, our Level II will be using MT. Obviously, he has requested that the paint be removed. Now, finally, my question: How to remove the paint. The Inspector has told me not to use sandblasting- he said small indications can be masked by peened metal from the blasting process. Same response concerning needle-gun to remove the coating. How about chemical paint removal?- nope, he replied that the gel leaves a residual coating which affects the powder.
Can any of you help? In our industry, obviously we err on the side of conservatism- as we should. I just need some common sense answers. Thank you for providing this valuable tool.
Redcoat,
first if your Level II MT inspector is certified, he/she would be working to a procedure. Typically the MT procedure will give clear direction on paint removal. (I know ours do) That is where I would look first. If nothing is there, then I would throw it back at her/him to recommend a suitable process for removing the paint. I agree, sandblasting and needle-guns can be problematic. Power wire wheels and or grinding can work.
I wouldn't worry about grit blasting if you are performing MT.
Al
By Jim Hughes 
Date 02-08-2019 12:40
Edited 02-12-2019 11:33
Redcoat,
Al is correct, with this one caveat. ASME Sec V Article 7 considers surface prep as an essential variable. So it goes back to looking at the procedure and see if they qualified it using a blasting process, such as sand or grit blasting. It's been my exp. that sand blasting can mask small discontinuities. So a lot of this in contingent on what code and any internal SOP's you might be working to. Again, as I mentioned in my last post, throw it back on the Level II, he/she should be working to a procedure.
