MPI or Penetrant dye for ASME VIII

[dbday]

Hi,
Can anyone help me understand where ASME VIII Div 1 tells me how to select MPI or penetrant dye examination of welds on a non-heat treated vessel.

From my college days I seem to remember these two techniques differ a bit in what they can find, however, everything I see with respect to coded pressure vessel construction just seems to regard them as surface crack detection techniques, is this right ?

Any help is appreciated

Thanks

 

[Weldmedic]

MPI and penetrant examination are interchangable on ferromagnetic alloys. Penetrant inspection would be indicated where a magnetic field could not be induced into the part.

Steve

 

[metengr]

From my college days I seem to remember these two techniques differ a bit in what they can find, however, everything I see with respect to coded pressure vessel construction just seems to regard them as surface crack detection techniques, is this right ?

Yes, this is basically correct. The Code does not get into process detail requirements nor does it prefer one NDT method over another, when it comes to surface or volumetric test methods.

 

[stanweld]

Refer to ASME VIII, Div.1 UG-93(d)(3), UHT-57(d)&(e) as well as answers by Weklmedic & metengr.

MT with suitable field strengths can find subsurface discontinuities but Code only views it for the purpose of locating surface discontinuities. PT can only locate surface discontinuities.

 

[dbday]

Thanks,

So if I have a non heat-treated vessel manufactured with materials that are not impact tested operating at ambient temperatures then I don't see anything in the code that compels me to use PT or MPI on the welds other than my own good practice.

Am I correct ?

 

[stanweld]

Either MT or PT can be used on ferromagnetic materials. PT only is permitted for non ferromagnetic materials. Heat treatment or impact testing has no bearing on the question of use.

 

[dbday]

Thanks Stanweld, but I am not being very clever today, does ASME VIII compel you to use MPI or PT.

My problem is that I just don't see in the code paragraphs where it says after welding that you must inspect with MPI or PT in the same way in does for x-ray and ultrasonic.
Thanks

 

[stanweld]

Yes, but only where defined therein (see my previous post) and UW-42, UW-50, UCS-56(f)(3), UHT-83.

 

[dbday]

gotcha, thanks

 

[weldtek]

Add UHA 34.