Significance and Use
Industrial phased arrays differ from conventional monocrystal ultrasonic transducers since they permit the electronic control of ultrasound beams. The arrays consist of a series of individual transducer elements, each separately wired, time-delayed and electrically isolated; the arrays are typically pulsed in groups to permit “phasing,” or constructive-destructive interference.
Though primarily a method of generating and receiving ultrasound, phased arrays are also a method of scanning and imaging. While some scan patterns emulate manual technology, other scans (for example, S-scans) are unique to phased arrays. With their distinct features and capabilities, phased arrays require special set-ups and standardization, as addressed by this practice. Commercial software permits the operator to easily make set ups without detailed knowledge of the phasing requirements.
Phased arrays can be used in different ways: manual or encoded linear scanning; and different displays or combinations of displays. In manual scanning, the dominant display will be an S-scan with associated A-scans. S-scans have the advantage over E-scans that all the specified inspection angles can be covered at the same time.
The main advantages of using phased arrays for ultrasonic weld examinations are:
Faster scanning due to multiple angles on display at the same time,
Better imaging from the true depth S-scan,
Data storage, for example, selected reflectors, for auditing, and archiving.
Rapid and reproducible set-ups with electronic instruments.
All personnel responsible for carrying out examinations, analysis and reporting results using this standard should be appropriately trained and qualified in accordance with a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNT CP-189, SNT-TC-1A, NAS-410, or a similar document and certified by the employer or certifying agency, as applicable. Additionally, there should also be training or knowledge and experience related to phased array equipment and techniques. Personnel performing examinations to this standard should list the qualifying credentials in the examination report.
1.1 This practice describes ultrasonic techniques for inspecting welds using phased array ultrasonic methods (see Note 1).
1.2 This practice uses angle beams, either in S-scan or E-scan modes, primarily for butt welds and Tee welds. Alternative welding techniques, such as solid state bonding (for example, friction stir welding) and fusion welding (for example, electron beam welding) can be inspected using this practice provided adequate coverage and techniques are documented and approved. Practices for specific geometries such as spot welds are not included. The practice is intended to be used on thicknesses of 9 to 200 mm (0.375 to 8 in.). Greater and lesser thicknesses may be tested using this standard practice if the technique can be demonstrated to provide adequate detection on mockups of the same wall thickness and geometry
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
Note 1—This practice is based on experience with ferrous and aluminum alloys. Other metallic materials can be examined using this practice provided reference standards can be developed that demonstrate that the particular material and weld can be successfully penetrated by an ultrasonic beam.
Note 2—For additional pertinent information, see Practices E 2491