PMI test 1

[MirjafariSM]

Hi dears
i have a question .
what is the PMI test normaly acceptable tolerance?
(in copmare with astm or other standards)

 

[SMF1964]

Are you referring to "Positive Material Identification" such as using a portable alloy analyzer to identify the alloy?

 

[SJones]

Within the measurement error of the measuring device against the criteria set by nominated material standard.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[MirjafariSM]

yes SMF1964
my intent is that.

 

[MirjafariSM]

I hear that some of equipment for PMI can't analysis light element such as C, P, S, etc.

 

[SMF1964]

Instruments that use an x-ray tube operate like and SEM's EDS detector and typically cannot measure elements at or below Silicon in the periodic table. I have seen product literature on new designs that attempt to go lower in the periodic table but have no experience with these, although the science and engineering is sound. My current unit is one of the ones that cannot measure carbon, phosphorus, silicon, etc.

There are other devices that use a spark and optical emission spectrograph rather than x-rays and x-ray fluorescence and can measure carbon, etc. I have one of these also, but it is not what I would consider portable.

 

[EdStainless]

PMI is to verify grade, not actual composition. As long as the material looks more like the required grade than another grade it passes.
If you want actual chemistry that is another issue all together.

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Plymouth Tube

 

[MirjafariSM]

Thanks all
I searched and understood that Spark UV equipments can measure light element with acceptable tolerance. (About +-0.002 percent for some element such as carbon)