Positive Material Identification (PMI)
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MPI of martensitic stainless steel
MPI of martensitic stainless steel
We have placed order for 13%Cr tubing (API 5CT L-80) which has premium threads cut on both sides of it.
As per our specification, it calls for wet fluorescent MPI of threads. Now, vendor has come up with clarification that wet florescent MPI would cause contamination of iron oxide particle with stainless material. They are now proposing Liquid penetrant inspection (LPI) in lieu of MPI.
As far as we know, 13%Cr material is a martensitic stainless and it still attracts a fair magnetism since it is ferromagnetic in nature and moreover, wet florescent MPI is more sensitive than LPI for threaded area.What we believe that LPI costs less compare to wet florescent MPI and that’s why, they are proposing LPI. Does MPI cause contamination on 13% Cr material ?
Please advise your comments
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