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00:07 Jan-10-2004

Raúl Navarrete

Consultant, teacher ndt inspector
METAL-MET, C.A.,
Venezuela,
Joined Jul 2000
8
Re: PMI - definition ----------- Start Original Message -----------
: PMI (positive material identification) to me is sorting of materials to be sure there has not been any mixing of components/materials. If you expect that your vendor may supply you with bad material, i.e. not according to spec (out of spec. we have a world market these days), this is a quality control, but not a PMI? Do anybody have comments on this?
------------ End Original Message ------------


PMI will certainly serve you as quality control, because you are able to distiguish between any type of material, inclusive for their components. The most of the PMi instruments in the market, as the one sold by METOREX, gives you the alternative of having a PMI in around 3 seconds or having an element espectrum in some other seconds. The question is what you mean with BAD. It can be, bad surface finish, bad hardness, but materail specs????. You has to be more specific when you use the word BAD.




    
 
09:10 Jan-12-2004
sigbjø
Re: PMI - definition ----------- Start Original Message -----------
: : PMI (positive material identification) to me is sorting of materials to be sure there has not been any mixing of components/materials. If you expect that your vendor may supply you with bad material, i.e. not according to spec (out of spec. we have a world market these days), this is a quality control, but not a PMI? Do anybody have comments on this?
:
: PMI will certainly serve you as quality control, because you are able to distiguish between any type of material, inclusive for their components. The most of the PMi instruments in the market, as the one sold by METOREX, gives you the alternative of having a PMI in around 3 seconds or having an element espectrum in some other seconds. The question is what you mean with BAD. It can be, bad surface finish, bad hardness, but materail specs????. You has to be more specific when you use the word BAD.
------------ End Original Message ------------


The PMI-instruments are improving in quality and can give you impressive results.
My question was more on the understanding the term PMI. I have seen PMI as a tool to find mix-ups, often this may be type 316 and type 304 austenitic steels.
The other way of interpreting PMI is that it may qualify the composition according to the sertificate. Is the Ni or Cr-content within the specs/sertificate of the material. Especially these elements may give some uncertainty both because of uncertainties in the measuring method and due to the fact that methods used often are surface analysis methods (xray/spark emission)
Some people may order PMI and expect to receive a certificate of the material. This is by my opinion a wrong expectation.
I see that from John O'Brians reference, API:
"3.13 positive material identification (PMI) testing:
Any physical evaluation or test of a material to confirm that the material which has been or will be placed into service is consistent with the selected or specified alloy material designated by the owner/user. These evaluations or tests may provide either qualitative or quantitative information that is sufficient to verify the nominal alloy composition."
I understand this also in the way that PMI does not give a certificate. Even in the quantitative form I feel the sorting aspect is most important?




    
 


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