T9074-AS-GIB-010/271 Rev 1
ultrasonically sound. They shall be capable of providing constant reference sensitivity levels for all angles of search unit and inspection depth. The standard reflecting surface shall be a 3 ⁄ 64 -inch diameter hole drilled through a 1¼-inch wide block. The surface of the test block shall be approximately 125 Ra microinches as compared to surface finish standards. See figure 6-7 for a typical calibration standard. An additional 3 ⁄ 64 inch diameter calibration hole at a depth of ⅛ inch shall be added to the standard for the inspection of flush ground welds. 6.6.4.2.4.2 Detection of Lack of Penetration in Full Penetration Tee Welds. The calibration standard shall be the through member upon which the inspection is being performed.
6.6.4.3 Specific Requirements for Butt and Corner Welds and the Volumetric Inspection of Tee Welds.
6.6.4.3.1 Instrument. The instrument shall have circuitry to provide a continuously increasing amplification with respect to time. This circuitry compensates for the signal losses with depth as a result of sound beam divergence and its attenuation in material.
6.6.4.3.2 Transducers.
6.6.4.3.2.1 Size. The maximum dimension of the transducer's active element shall not be greater than: a. ½ inch for plate thicknesses less than ½ inch. b. 1 inch for plate thicknesses equal to or greater than ½ inch.
6.6.4.3.2.2 Frequency. The nominal frequency shall not be less than: a. 4.0 MHz for plate thicknesses less than ½ inch. b. 2.0 MHz for plate thicknesses equal to or greater than ½ inch.
6.6.4.3.2.3 Angle. The transducers used for shear wave inspections shall be affixed to suitable wedges designed to induce shear waves in the material at the following recommended angles. The beam angle should be based on the thickness of the plate as follows: a. For plate thicknesses ¼ to, but not including, ½ inch: a 70-degree angle.
b. For plate thicknesses ½ inch to, but not including, 1½ inches: a 60 to 70-degree angle. c. For plate thicknesses 1½ inches to, but not including 2½ inches: a 45 to 60-degree angle. d. For plate thicknesses 2½ inches and over, a 45-degree angle. e. For tee weld volumetric scanning from the through member, a 45-degree angle.
Other angles may be used to complement or substitute for the angles recommended above to obtain 100 percent coverage when otherwise precluded by configuration, or for the evaluation of indications. 6.6.4.3.3 Calibration. The instrument range and delay controls shall be adjusted to display signals from the calibration holes on the viewing screen for the range of depths to be inspected. The attenuation-correction controls shall be adjusted to compensate for the signal losses due to depth. 6.6.4.3.3.1 Class I Welds. The instrument gain shall be adjusted to peak all signals within the range of test at not less than 80 percent of full screen. The corresponding depth and location of the peaked signals from the calibration standard shall be noted along the base line of the viewing screen. The screen shall be divided by two horizontal lines at 20 percent (the DRL) and 80 percent (the ARL) of full screen height. 6.6.4.3.3.2 Class II and III Welds. The instrument gain shall be adjusted to peak all signals within the range of test at not less than 80 percent of full screen. The corresponding depth and location of the peaked signals from the calibration standard
6-9
Made with FlippingBook - Share PDF online