Inspection method · PMI
Positive material identification (PMI)
Confirm on the part itself that the alloy is what the certificate says it is.
01How it works
PMI determines the alloy composition of a component non-destructively or with minimal surface preparation. Handheld X-ray fluorescence (XRF) analysers identify most alloying elements quickly. Optical emission spectrometry (OES) creates a small spark burn and also measures light elements such as carbon, which XRF cannot measure reliably.
Results are compared with the composition ranges of the specified grade.
02Typical industrial applications
- Stainless and duplex steel components
- Alloy steel pressure parts
- Nickel alloy and special materials
- Bolting and fasteners
- Weld metal verification
- Incoming material verification
03Benefits and what it detects
- Prevents material mix-ups
- Fast results on site
- Covers finished components
- Supports traceability
04Limitations
- XRF cannot reliably measure carbon, so L grades and carbon steels need OES
- Surface preparation affects accuracy
- Identifies alloy, not mechanical properties or heat treatment
- Spot measurement only
05Specifying and reviewing the method
Specify the extent (100% or sample), elements to verify, method (XRF or OES) and acceptance relative to the grade standard. API RP 578 is a common reference for PMI programmes in process piping.
Other references: API RP 578, ASTM E1476
06QUALITAS TR role
Witnessed and reviewed by QUALITAS TRPMI is performed with the supplier's or a contracted analyser and operator; QUALITAS TR witnesses measurements, checks instrument verification and evaluates results against the grade.