XRF and OES: what each can tell
| Handheld XRF | Portable OES (spark) | |
|---|---|---|
| Damage to the part | None | A small burn mark; the surface must be ground clean |
| Measures | Most alloying elements: chromium, nickel, molybdenum, copper, lead | The same, plus carbon and other light elements |
| Cannot do | Measure carbon, so it cannot tell 316 from 316L | Replace a full lab analysis on prepared specimens |
PMI confirms grade identity. It does not prove mechanical properties, heat treatment or freedom from internal flaws; those come from the mill certificate, lab tests and NDT. ASTM E1476 is a guide for metal identification, grade verification and sorting, and API RP 578 sets out material verification programmes for piping.
Worked example: 316 valves with a 304 body
An order of ball valves specifies grade 316 stainless steel, whose standard composition includes about 2–3% molybdenum; grade 304 has none added. The factory tests every valve body by XRF while the inspector watches, on bodies the inspector picks from finished stock. Twenty-nine read about 2.1% molybdenum. One reads 0.2%. That body is 304, probably from a mixed casting batch. It is set aside, the batch's heat records are pulled, and the remaining bodies from that heat are all tested before packing.
How Clear To Load uses it
We do not own XRF or OES analysers. Where your order calls for PMI, the inspector witnesses the factory's analyser on parts the inspector selects, checks the instrument's calibration or check-standard reading, and records each result with photos. For a disputed result, samples go sealed to an ISO/IEC 17025-accredited lab through lab testing coordination. See industrial valves and stainless steel cookware.