T9074-AS-GIB-010/271 Rev 1
testing, any realignment of the search unit or any change in search unit, instrument settings or scanning speed from that used for calibration shall require recalibration. (Note: For thickness measurement only, the gain setting may be modified without requiring recalibration.) 6.4 EQUIPMENT. The instrument and accessory equipment shall be capable of generating, receiving, amplifying, and displaying electrical pulses at frequencies and pulse rates necessary for the intended inspection.
6.5 GENERAL REQUIREMENTS.
6.5.1 Equipment Requirements.
6.5.1.1 Basic Instrument Qualification - A-Scan Display Instruments. A single transducer shall be used to perform all of the instrument qualification operations of 6.5.1.1.1, 6.5.1.1.2, 6.5.1.1.3, and 6.5.1.1.4. 6.5.1.1.1 Vertical Linearity. The vertical linearity shall be within plus or minus 10 percent (in the range between 20 percent and 80 percent of full screen height) as measured in accordance with ASTM E317 or other approved method. Instrument settings used during inspection shall not cause variation outside the 10 percent limits established above. 6.5.1.1.2 Horizontal Linearity. When the time-distance relationship (horizontal linearity) displayed on the sweep of the instrument display is a function of the test, the horizontal linearity shall be within plus or minus 3 percent, as measured in accordance with ASTM E317 or other approved method. 6.5.1.1.3 Resolution. The system shall be capable of resolving the calibration holes within the range of T m to be inspected using the calibration block(s) specified, as described in ASTM E317, or other approved method. 6.5.1.1.4 Attenuation. A calibrated gain or attenuator control, if used in a procedure, shall be evaluated according to the requirements of ASTM E317, or by converting dB to an amplitude ratio using the relationship:
The calibrated gain or attenuator shall be accurate to plus or minus 20 percent of the nominal amplitude ratio.
6.5.1.2 Basic Instrument Qualification - Thickness Gauge. Readings shall be made on each of a series of test blocks representative of the ranges of the instrument. A sufficient number of readings shall be made to accurately determine the thickness testing characteristics of the instrument. Readings shall be within plus or minus 3 percent of the true value. For thicknesses less than 0.150 inch, the readings shall be within plus or minus 0.005 inch of the true value. 6.5.1.3 Frequency of Basic Instrument Qualification. The basic instrument qualification shall be performed and documented at intervals not greater than 6 months or whenever maintenance is performed which affects the equipment function. 6.5.1.4 Shear Wave Transducers. Shear wave search units shall have a refracted angle within the limits of plus or minus 3 degrees of the designated angle at 68±10 °F, as determined by an IIW or similar block. 6.5.2 Inspection Procedure. The ultrasonic inspection procedures shall contain, as a minimum, the following information: a. Materials, shapes, or sizes to be tested or to be exempt from test. b. Automatic defect alarm and recording equipment or both. c. Special search units, wedges, shoes, or saddles. d. Rotating, revolving feeding mechanisms and indexing method.
6-3
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