Leak Testing

Leak testing verifies the tightness of a closed system. The method is chosen according to the leak sensitivity required: the bubble method finds relatively large leaks, whereas a helium mass spectrometer can measure very small ones.

The aim is to prevent loss of fluid, environmental pollution and release of hazardous substances, and to safeguard the function of systems operating under vacuum or pressure.

• Pressure vessels and pipelines
• Heat exchangers and condensers
• Storage tanks and underground tanks
• Vacuum systems
• Refrigeration circuits and gas systems

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.

• Tightness at weld seams and connection points
• Tightness of flanges, gaskets and valves
• Measurement of the system's overall leak rate
• Determination of leak location
• Pressure-drop monitoring

• ISO/IEC 17020
• EN 1779
• ISO 20485
• ISO 20484
• EN 13184
• ASME BPVC Section V
• ISO 9712

• Helium mass spectrometer leak detector
• Bubble (foam) solution and vacuum box
• Pressure-drop measuring rig and calibrated pressure gauges
• Tracer-gas mixing and supply equipment
• Ultrasonic leak detector
• Calibrated leak standards

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 acceptance criterion is the system's maximum permitted leak rate and is defined in the specification. In the bubble method, acceptance is usually 'no bubbles observed'; in the mass spectrometer method, a numerical leak-rate limit is applied.

• 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