PMI

Positive material identification — an on-the-spot alloy verification by X-ray fluorescence or optical emission before despatch.

Mixed grades are the most common and most dangerous error in a fittings package, because a 304 elbow in a 316 chloride line looks identical and fails early. PMI checks the actual chemistry of the finished item against the marking and the certificate; on alloy and stainless packages it is done on 100% of pieces rather than on a sample.

Related terms

Heat Number
Marking

Where this applies

butt-weld-fittings, flanges

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