What Is Inspection?
PMI verifies by composition analysis that a component really is made of the alloy specified. It is carried out on site with a portable XRF or optical emission spectrometer (OES), without damaging the part.
Why Is It Done?
The aim is to prevent material mix-up. A pipe or flange made of the wrong alloy may corrode unexpectedly or lose strength under design conditions; such events have led to serious accidents.
Which Equipment Is Covered?
- Stainless and alloy steel pipes, flanges and fittings
- Weld seam and filler metal verification
- Pressure equipment components
- Valve and pump bodies
- Incoming material acceptance inspection
Legal Basis and Interval
NDT has no interval of its own; how often it is applied follows the inspection programme it serves. In manufacturing the governing factor is the coverage required by the product standard and the specification (e.g. a given percentage of welds); in operation it is the asset integrity or risk-based inspection programme.
Scope of Inspection
- Percentage of main alloying elements (Cr, Ni, Mo, Mn)
- Conformity of the material with the declared grade
- Compatibility of the weld filler metal with the base material
- Carbon content (with OES; XRF cannot measure carbon)
- Detection of material mix-up
- Traceability: part marking and records
Related Standards
- ISO/IEC 17020
- ASTM E1476
- ASTM E572
- ASTM E415
- API 578
- ISO 9712
Method and Equipment
- Portable XRF analyser
- Portable OES (spark) analyser
- Certified reference materials (CRM)
- Surface preparation equipment (grinding, cleaning)
- Labelling and record-keeping system
Inspection Process
- 1Selection of Method and TechniqueThe type and location of the discontinuity sought and the material properties are assessed to select a suitable method and technique; a written procedure is prepared.
- 2Verification of Personnel and EquipmentThe level and industrial-sector qualification of the operator under EN ISO 9712 and the calibration records of the equipment are checked.
- 3Surface PreparationThe inspection surface is prepared as the method requires; coating, rust and contamination directly affect the sensitivity of the method.
- 4Calibration and Sensitivity VerificationA reference block or control specimen is used to demonstrate that the system can detect the discontinuity sought.
- 5Performing the InspectionScanning is carried out according to the procedure; indications are recorded and located.
- 6AssessmentIndications are evaluated against the applicable acceptance standard to determine whether they are defects; they are sized.
- 7ReportingMethod, technique, equipment, calibration, findings and acceptance criteria are reported together.
Nonconformities
The measured composition is compared with the elemental ranges the material standard (e.g. ASTM/EN) defines for that grade. A result outside the range means the part is not the declared material, and the part is isolated and investigated.
Inspection Report
- The inspection body and the personnel's EN ISO 9712 level and sector
- Method and technique applied and the written procedure number
- Part and weld examined, with a location sketch
- Equipment, consumables and calibration records
- Surface condition and inspection conditions
- Indications recorded, with their location and size
- Acceptance standard applied and the result of the evaluation
- Accept / reject decision
Accreditation
Non-destructive testing is carried out as an accredited inspection activity under ISO/IEC 17020. The second decisive factor in NDT is personnel qualification: the operator must be certified under EN ISO 9712 for the method, level and industrial sector concerned. An examination performed with a method outside the scope of that certificate is not valid. EUROLAB holds internationally recognised accreditation under ISO/IEC 17020, granted by accreditation bodies that are signatories to the ILAC mutual recognition arrangement.
Scope and authorisationsRelated Inspections
Frequently Asked Questions
What is the difference between XRF and OES?
XRF is fast, portable and does not damage the surface; however, it cannot measure light elements such as carbon, sulphur and phosphorus. OES analyses by producing a spark and can measure carbon, but leaves a small mark on the surface and requires surface preparation. If carbon content is critical, OES is required.
Why is PMI requested when I already have a material certificate?
The certificate belongs to the production batch; it does not show that the part has not been mixed up in storage or during assembly. PMI verifies the identity of the physical part on site. For critical services, both the certificate and PMI are required together.
Is the weld seam also subject to PMI?
Yes, and it is often the most critical point. A weld made with the wrong filler metal becomes a starting point for corrosion or cracking even if the base material is correct. For this reason, specifications require the weld metal to be verified separately.
Who may carry out the inspection?
NDT personnel are certified under EN ISO 9712 by method, level (1, 2, 3) and industrial sector. Level 1 performs the examination, Level 2 evaluates it and writes the report, Level 3 prepares procedures and selects the method. An examination performed in a method or sector outside the certificate is not valid.