T9074-AS-GIB-010/271 Rev 1
CHAPTER 6 ULTRASONIC TESTING
6.1 INTENDED USE. The ultrasonic test method is used for the detection of discontinuities throughout the volume of material, measurement of wall thickness, and evaluation of bond characteristics in most types of material and in basic geometric configurations. Appendix B, Requirements for Ultrasonic Characterization and Sizing Inspection of Embedded and Surface Connected Discontinuities, addresses special flaw characterization and sizing requirements and are applicable only when specifically invoked. 6.2 DEFINITIONS. The standard terminology for ultrasonic examination as described in ASTM E1316 shall apply to this section, except as noted below. 6.2.1 Acoustically Similar Materials. The same type of material as that to be inspected or another material experimentally proven to have an acoustical velocity within plus or minus 3 percent for thickness testing, and for amplitude comparison tests, the back reflection amplitude from equal thicknesses of material shall be within plus or minus 1 decibel (dB) of each other as measured on the instrument display. This test shall be conducted on samples having equal contour and surface finish for both the sound entrant and reflective surfaces. 6.2.2 Amplitude Rejection Level (ARL). The horizontal level on the instrument display which is established as either a percentage of full screen height or as a dB level based on the peak amplitude of the signal received from the applicable reflective surface in the calibration standard. 6.2.3 As-Welded Condition. The condition of weld metal, welded joints, and weldments after welding and removal of slag, spatter, and so forth, prior to any thermal or mechanical treatment. 6.2.4 Calibration. Adjustment of the ultrasonic system to give desired indication height and position from known reflecting standards as required for the inspection being performed. 6.2.5 Calibration Reflectors. Ultrasonic reflectors, such as side-drilled holes, flat-bottom holes, or notches, that are permitted by applicable documents to be used for calibration. 6.2.6 Calibration Standard. A sample of material acoustically similar to the material to be tested, containing known reflectors with which the ultrasonic system is calibrated and reference levels are established. 6.2.7 Class of Weld. Weld Classes I, II, and III are used to differentiate between critical and less critical welds and relate to acceptance criteria. Weld classes are defined by applicable fabrication documents. 6.2.8 Continuous Scan. A scanning practice in which each pass with the transducer overlaps the previous pass by not less than 25 percent. 6.2.9 Disregard Level (DRL). The horizontal level on the instrument display established at a given level below the amplitude rejection level (ARL). 6.2.10 Full Screen Height. The highest point on the instrument display used for evaluation and recording purposes, designated as 100 percent or scale 10.
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