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Positive Material Identification(PMI)

Positive Material Identification(PMI)

Positive Material Identification(PMI)

Dear All,

Just want to ask something about PMI.I recently used a PMI machine or tool,to identify sets of pipes and plates stocked in our facility.
I found out that the machine will identify the stainless steel properly,with the grade and alloy percentage displayed on the screen.
Now when it comes to ferrous materials,it will only gives me the percentage of the content and the grade it says "O6" or sometimes when I pressed it for about 10-12 seconds it will identify it as "C10xx".What Im expecting is it will display like SA36,SA135,etc..
With the percentage of content alone,how can I identify what grade is it?
Any one having an idea kindly point me to a good reference.

RE: Positive Material Identification(PMI)

PMI instrument is not suitable to identify grade of carbon steel materials.
You may require to send sample for detail chemical analysis at laboratory.

RE: Positive Material Identification(PMI)

XRF based PMI instruments are not capable of analyzing low atomic number elements like carbon. boron, lithium, etc. There are optical emission PMI instruments that can.

RE: Positive Material Identification(PMI)


I agree with weldstan, XRF cannot "see" low atomic number materials like carbon, which can make identification of low allow steel grade impossible. However, a quick answer to your question, do an internet search for the steel composition. I did a Google search on "A36 chemical composition" and got good hits. Of course anything posted on the internet must be used with caution but it may help you through your problem.


RE: Positive Material Identification(PMI)

Will XRF machine identify 2205 materials and give percentages of chem composition including ferrite percentage?

RE: Positive Material Identification(PMI)

Yes for Cr, Ni, Mo, etc. but not Nitrogen or %ferrite.

RE: Positive Material Identification(PMI)

Thank you weldstan, I was not familiar with the XRF PMI guns.

We presently use a Fischer feritiscope for production welding of 2205.

RE: Positive Material Identification(PMI)

That is only good for measuring ferrite levels. It cannot confirm Alloy 2205 or other Duplex and Super duplex stainless steels.

RE: Positive Material Identification(PMI)

I greatly appreciate your replies.

I'm in trouble here to be honest with you guys.Our metallurgist had left the company and often I was tasked to this PMI job.(which I did not expected)
I'm actually testing our materials here in our facility just to see if our instrument is working fine and because I'm suspecting there is something wrong in it because it cannot identify ferrous materials.
Prior to what I'm doing here in our facility,my company had a client earlier.A petrochemical company here in the Middle East.
We provide supervision services for an on going testing and inspection of a pressure vessel.One of the scope was to identify the material make and to verify if it conforms to the specification on the drawings.(the vessel was an old one purchased from a nearby plant).So we did conduct a PMI.I got the results and compare it to what was there in the plan.It turned out that what was given by the instrument is not the same as what was in the plan.I consulted ASME II but cannot find any equivalent.I told the client that I cant find it in the ASME code so we better have it searched in the internet.He was stunned that I'm suggesting the internet rather than the code books.I explained that I cant find it in ASME II.Things turned out to be different and eventually we had a heated argument.

I'm not an expert in this field and so I'm consulting any one.An example of the material in the drawing specs was 13CRMO44.
The instrument displays other than this.
Many thanks to all of you!!

RE: Positive Material Identification(PMI)

Your XRF, PMI instrument should have no problem with the analysis for Cr and Mo. What alloy did it display? If the instrument has an analytical mode, what was the %Cr and % Mo?
Suspect that it may need recalibration by the manufacturer.

RE: Positive Material Identification(PMI)

I'd like to give you the percentage of the alloy contents but unfortunately I don't have the instrument now.
Yes you are right maybe it needs calibration since the instrument looks very old already and not sure when was the last time
it was sent for re calibration.
Thanks a lot!

RE: Positive Material Identification(PMI)

There are a number of NDE service contractors who provide PMI services.
None of the PMI equipment available will be able to pinpoint a carbon steel specification like SA-285, SA-515, SA-516, etc. because chemistries overlap. The best optical spectra emission devices can provide an effective quantitative analysis that you could use to verify purchased low carbon steel materials and AISI/SAE low alloy steels.

RE: Positive Material Identification(PMI)

As per API RP-578, below techniques are adopted :-

1. X-Ray Fluorescence Method (XRF) - Can detect all major elements, except lighter elements like "C" and a few others. (XRF technique can detect only element with atomic number greater than 21)
2. Portable Optical Emission Spectroscopy (OES) -This technique can detect all major alloying elements including "C".

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