T9074-AS-GIB-010/271 Rev 1
require sensitivity compensation (e.g., through the use of non-conductive shims). The standardization process shall provide a means to ensure that the sensitivity remains consistent between the performance verification reference block and the surface to be inspected, regardless of paint thickness and type. When the non-conductive coating thickness increases to a point where sensitivity between the uncoated performance verification reference block and the coated surface to be inspected can no longer be maintained (see 7.5), the coating thickness shall be reduced before resuming inspection. Inspection of coated surfaces greater than 0.040 inch requires NDT Examiner approval. Inspection procedures that allow inspection of coated surfaces greater than 0.050 inch requires approval by the authorized representative of NAVSEA. 7.6 TEST TECHNIQUE. Inspection shall be performed such as to avoid rocking or tilting the probe (see figure 7-1 for optimum positioning). Unless otherwise specified, the inspection zone for welds shall include the weld and ½ inch of adjacent base material on each side of the weld, where possible. 7.6.1 Toe of Weld Scan. With the probe oriented to scan parallel to the weld longitudinal axis, scan along each toe of the weld. Ensure that the probe is maintained at a constant attitude to the toe of the weld, keeping the working face of the probe in full contact with the weld. Monitor the weld condition by noting the response on the instrument display. 7.6.2 Weld and HAZ Scan. With the probe oriented to scan parallel to one weld toe and keeping the working face of the probe in full contact with the weld, scan the weld for the desired distance. Repeat this scanning process such that the entire weld and heat affected zone is covered. The weld shall also be scanned in the transverse direction, unless the probe has been verified to be able to detect both longitudinal and transverse indications with one scan. 7.6.3 Inspection of Surfaces Other Than Welds. With the probe oriented at a consistent attitude to the work piece, keep the working face of the probe in full contact with the work piece at all times during scanning. To ensure detection of linear indications having axes in any direction, not less than two separate scans shall be made in each area. The second scan shall be at right angles to that used in the first, unless the probe has been verified to be able to detect both longitudinal and transverse indications with one scan. 7.6.4 Indexing. Each scan of the probe shall be indexed not greater than ⅛ inch from the previous scan. Indexing greater than ⅛ inch may be used when approved by the Government Inspector, provided adequate defect detection for a particular type of equipment and geometry has been demonstrated. 7.7 EVALUATION OF TEST RESULTS. Evaluate surface conditions by monitoring the signal response produced. Any portions of the item that produce a flaw signal response equal to or greater than the signal response from the notch in the performance verification reference block shall be inspected by magnetic particle inspection (for ferromagnetic materials) or liquid penetrant inspection for (non-ferromagnetic materials). The accept/reject criteria for the magnetic particle/liquid penetrant inspection shall be as established by 1.3. Since not all eddy current signals represent a flaw, local procedures should provide guidance for evaluating flaw signal responses. A flaw signal response would be typical of that from the performance verification reference block. This signal is separated from lift-off and has a quick response time.
7-3
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