T9074-AS-GIB-010/271 Rev 1
6.2.11 IIW Block. A standard test block designed by the International Institute of Welding (IIW) to check the operation of the ultrasonic system and search units or transducers. 6.2.12 Instrument Display. Device used to show results of the ultrasonic examination. The device can be cathode ray tube (CRT), liquid crystal screen, segmented digital display, or other appropriate device. 6.2.13 Peak Indication. The maximum height or amplitude of an indication received from any one reflective surface using a constant gain setting.
6.2.14 Ultrasonic Test Sensitivity. The sensitivity at which the test will be conducted.
6.2.15 Ultrasonically Sound Material. A material capable of exhibiting an 80 percent of full scale reflected signal amplitude from a specified reflector with no more than 20 percent of full scale extraneous signal amplitude (noise). 6.2.16 Weld Heat Affected Zone (HAZ). Base material that is included in the weld inspection zone. The HAZ for ultrasonic inspection is measured from the base material surface to which weld metal will be applied, and follows any beveled weld preparation. If the exact location or angle of the beveled weld preparation surface is not known, a straight line shall be used, which connects the opposite surface weld toes. 6.3 PROCEDURE AND TEST METHODS. The following test methods apply to the inspection of forgings, castings, rolled or extruded shapes, bar stock, plate, weldments, pipe and tubing, bonded materials, and metal sheet. As described herein, the procedures are largely manual. Automation, however, may be applied to these methods when it serves to minimize operator-induced variables; this relates only to testing, not to analysis. Techniques such as phased array, time of flight diffraction, and computer-assisted analysis in any form requires specific NAVSEA approval. Traditional C-scans and B-scans, and ultrasonic instruments using “g ates ” are not considered to be computer-assisted. Neither are such devices as “ digital thickness gauges ” or “ data loggers. ” Testing can be performed more easily and reproducibly on parts which have simple geometries associated with early stages of fabrication. Inspection methods other than those specified in this section may be used, provided approval is based on procedural qualification obtained from the authorized representative of NAVSEA. All tests shall be performed in accordance with a written inspection procedure approved as specified in 1.7. 6.3.1 Test Method Selection. The method or methods required for inspection of a component is specified by the equipment or material specification or other fabrication document. Selection of a test method or combination of methods shall be based upon the configuration and the orientation of expected discontinuities in the items to be inspected. 6.3.2 Surface Finish. Surfaces of material to be inspected shall be clean and free of dirt, loose scale, loose paint, or other loose foreign matter. Unless otherwise specified, the test surface may have one coat of primer (not to exceed 0.004 inch in thickness). Surfaces to be inspected shall have a finish of not greater than 250 Roughness Average (Ra) microinches and be free from waviness that may interfere with the test. Unless specifically permitted herein, the surface finish of the calibration standard shall not be any smoother than that of the material to be tested (except for thickness inspections, see 6.7.3). 6.3.3 Testing Speed. Rotation or speed of the part or search unit shall be controlled as closely as possible and shall be consistent with operator readout capability. In any case, the test speed shall not be greater than the maximum speed at which the calibration standard can be scanned to produce a clearly resolved indication. 6.3.4 Couplant. A couplant shall be used which causes acoustic coupling between the transducer and the part being inspected. This couplant shall not be injurious to the material. Glycerin, glycerin mixed with water, and glycerin mixed with alcohol are some materials that may be used as a couplant. The couplant shall be removed from the part at the completion of the inspection. 6.3.5 Calibration. Prior to any inspection, the equipment shall be calibrated, using the proper calibration standard, and shall be rechecked no less than once per 8-hour shift, and at the completion of testing. If the recheck indicates that instrument sensitivity has dropped by more than 1 dB, all items tested since the last instrument check shall be reinspected. During
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