PT Penetrant

Penetrant testing relies on a low surface tension liquid drawn by capillary action into surface-breaking discontinuities; the excess is removed and a developer is applied that pulls the liquid back out to make the indication visible.

The aim is to detect surface cracks and porosity too fine to see with the naked eye. On non-magnetic materials — stainless steel, aluminium, titanium — the method is the most common choice for surface flaws.

• Stainless steel and aluminium welds
• Castings and forgings
• Titanium and nickel alloys
• Ceramics and glass (non-porous)
• Aerospace and pressure equipment components

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.

• Surface-breaking cracks
• Surface porosity
• Lap and seam defects
• Cold lap and lack of penetration (where surface-breaking)
• Weld-seam surface discontinuities

• ISO/IEC 17020
• ISO 3452-1
• ISO 3452-2
• ISO 3452-3
• EN ISO 23277
• ISO 9712

• Penetrant, cleaner and developer consumables
• Darkroom and UV-A lamp (for fluorescent systems)
• Light meter and UV intensity meter
• Reference (control) test block
• Cleaning and drying equipment

1. 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.
2. 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.
3. 3Surface PreparationThe inspection surface is prepared as the method requires; coating, rust and contamination directly affect the sensitivity of the method.
4. 4Calibration and Sensitivity VerificationA reference block or control specimen is used to demonstrate that the system can detect the discontinuity sought.
5. 5Performing the InspectionScanning is carried out according to the procedure; indications are recorded and located.
6. 6AssessmentIndications are evaluated against the applicable acceptance standard to determine whether they are defects; they are sized.
7. 7ReportingMethod, technique, equipment, calibration, findings and acceptance criteria are reported together.

Indications are classified as linear or rounded and assessed by size against the applied acceptance standard (e.g. EN ISO 23277). Linear indications, being suspected of being cracks, are generally subject to stricter limits.

• 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

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.

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