Hardness Measurement

On-site hardness measurement determines hardness with portable instruments, without damaging the part or leaving only a very small indentation. Unlike laboratory hardness testing, it can be applied to the existing structure without cutting a specimen.

The aim is to verify that the material is in the expected heat-treated condition, to check whether excessive hardening has occurred in the weld and heat-affected zone, and to detect material changes that arise in service.

• Weld seams and the heat-affected zone
• Pressure equipment and pipeline components
• Post-heat-treatment verification
• Large cast and forged parts
• Components suspected of service damage

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.

• Base-material hardness
• Weld metal and heat-affected-zone hardness
• Verification of post-weld heat-treatment effectiveness
• Hardness distribution and locally hardened areas
• Compliance with the hardness limits of the specification

• ISO/IEC 17020
• ISO 16859 series
• ASTM A956
• ASTM A1038
• ISO 6506
• ISO 6507
• NACE MR0175

• Portable hardness tester (Leeb / UCI method)
• Certified hardness reference blocks
• Surface preparation equipment (grinding, polishing)
• Calibration verification rig

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.

The measured hardness is compared with the maximum value prescribed by the material standard or service specification. For example, NACE MR0175 defines maximum hardness limits for sour service; exceeding this limit means a risk of stress corrosion cracking and may require post-weld heat treatment.

• 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.

• VT Visual
• PT Penetrant
• MT Magnetic Particle
• UT Ultrasonic
• RT Radiographic
• ET Eddy Current
• PAUT
• TOFD