PAUT Weld Inspection & Focal Law Calibration Guide
Comprehensive Field Procedure for ASME Sec V Article 4 & ISO 13588 Compliance
Key Technical Takeaways & Execution Rules
- Configure Sectorial Scans (S-scan) from 40° to 70° with 0.5° angular resolution for full volume weld coverage.
- Perform Time Corrected Gain (TCG) calibration using IIW Block V1/V2 and side-drilled holes (SDH) at 3 depth targets.
- Encoder calibration tolerance must be kept within ±1% over a 500mm scanning distance.
- Set amplitude threshold at 20% DAC/TCG for indication recording and 50% DAC for evaluation.
Step-by-Step Field Execution Procedure
Probe & Wedge Verification
Inspect probe element array (e.g. 5 MHz 32-element array) for dead elements using pulse-echo check. Verify wedge angle (e.g. 55° shear wave wedge) and measure wedge delay.
Velocity & Wedge Delay Calibration
Couple wedge to IIW Block V1 radius (100mm). Calibrate material velocity (5920 m/s for carbon steel longitudinal, 3240 m/s for shear) and adjust wedge delay across all focal laws.
Sensitivity & TCG Curve Construction
Scan calibration block containing 1.5mm SDHs at T/4, T/2, and 3T/4 depths. Normalize peak amplitudes to 80% Full Screen Height (FSH) to generate a smooth 3-point TCG curve.
Weld Overlay & Scan Plan Setup
Input weld bevel geometry (V-bevel, J-bevel, thickness) into instrument beam simulation. Verify complete coverage of weld root, toes, fusion line, and cap.
Data Acquisition & Defect Characterization
Perform automated or semi-automated raster scan. Evaluate A-scan, B-scan, C-scan, and S-scan views to characterize volumetric defects (porosity, slag) versus planar defects (lack of fusion, cracks).
Probe & Wedge Selection Specs
- 5L32-A11
- 2.25L32-A12
- 7.5L64-A10
Code Acceptance Criteria
ASME Sec V Art 4 Mandatory Appendix VIII / ASME B31.3 Table 341.3.2: Cracks, lack of fusion, and incomplete penetration are strictly rejectable regardless of length. Volumetric indications exceeding 50% TCG evaluated against max length limits.