Ultrasonic Indication Acceptance on a CJP T-Joint
A 1-in A992 web-to-flange CJP T-joint is examined by ultrasonic testing using a 70° angle beam. The examiner calibrates on a reference block and scans from the flange surface. The report lists a single indication 1.1 in long, with a signal amplitude of 60% of the reference level, located about 0.35 in from the fusion face and within the weld thickness. The report concludes: 'Recordable but acceptable; amplitude is below 80% of reference.' The fabricator wants to apply primer and close the area. The contract drawings require AWS D1.1 acceptance criteria and 100% UT of CJP groove welds. You are the special inspector reviewing the UT report.
1. Is the examiner's amplitude-only acceptance conclusion valid? Explain.
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No. Amplitude alone is not the D1.1 UT acceptance criterion. D1.1 ultrasonic acceptance is based on the indication rating relative to the reference level and on the indication length compared with the allowable length for that rating. An indication can be below a particular amplitude and still be rejectable if it is long enough or if its classification places it in a rejectable category. The report gives a length and an amplitude but does not show the rating, the reference level, the classification, or the comparison with the acceptance table. The statement that '60% is below 80%, therefore acceptable' is an incomplete criterion. The inspector should not accept the weld on that basis and should not allow primer until the UT report is corrected and the indication is evaluated against the governing acceptance criteria.
2. What variables and documentation should you verify before accepting or rejecting the indication?
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Verify the examiner's qualification and the UT procedure, including the probe angle, frequency, calibration block, and scanning technique. Confirm that the reference level was established correctly and that the indication amplitude is reported in the correct units relative to that level. Check the indication length measurement method, the location measurement, and whether the signal is from the weld or from a geometric reflector such as the backing, root, or fusion face. For a T-joint, verify that the scan coverage included the web-to-flange fusion faces and that the 70° probe was appropriate for the thickness. The report should classify the indication and compare it with the D1.1 acceptance table using both rating and length. Also check that the examination was performed after the required waiting period and before primer. Missing calibration or coverage information is a reason to require re-examination, not to accept.
3. What is your disposition, and what should happen before the area is painted?
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Treat the indication as unresolved and do not permit painting. Require the examiner to provide a complete evaluation: reference level, indication rating, length, classification, and the specific acceptance comparison. If the indication exceeds the D1.1 acceptance criteria, reject the weld and require a repair procedure. The repair should be excavated to sound metal, rewelded under the approved WPS, and re-examined by UT. If the indication is acceptable, the report must show why under the correct criteria, and the inspector should verify that the examination coverage was adequate. The fabricator should not rely on the 'below 80%' statement. Document the hold, the corrected report, and the final disposition. Only after the UT record is complete and acceptable should the surface be prepared and painted.