VT Visual

Visual examination is the systematic assessment of discontinuities visible on the surface by eye or with optical aids. Though it looks like the simplest method, it is the first and mandatory step of every NDT programme: a VT not performed before the other methods weakens the validity of those examinations too.

The aim is to detect surface flaws and geometric deviations before moving to costlier methods, and to confirm that the surface is in a suitable condition for the other NDT methods.

• Weld seams (before, during and after welding)
• Cast and forged part surfaces
• Internal and external surfaces of pressure vessels and tanks
• Pipeline and structural connections
• Coating and paint surfaces

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, porosity and slag residue
• Undercut, overlap and lack of penetration
• Weld geometry: width, height, transition angle
• Spatter, arc strikes and mechanical damage
• Pre-weld joint preparation, cleanliness and tack-weld quality
• Deformation, distortion and assembly deviations
• Traces of corrosion, erosion and wear

• ISO/IEC 17020
• EN ISO 17637
• ISO 9712
• EN ISO 5817
• ISO 17635

• Weld gauges and calipers
• Magnifier (typically 2×–10×)
• Endoscope / borescope (inaccessible areas)
• Light meter (to verify illumination level)
• Mirror, measuring rule and torch

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.

Findings are assessed against the quality level applied under EN ISO 5817 (B, C, D). A crack is unacceptable at every level; for other discontinuities, size limits vary by level.

• 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.

• PT Penetrant
• MT Magnetic Particle
• UT Ultrasonic
• RT Radiographic
• ET Eddy Current
• PAUT
• TOFD
• Leak Testing