Phased Array Ultrasonics
Phased array technology an ultrasonic method with the capability of setting beam parameters such as angle, focal distance, and focal point size through software. Phased arrays allow the replacement of multiple inspections and mechanical components. Inspecting parts with variable-angle beams maximizes detection regardless of the defect orientation, while optimizing signal-to-noise ratio.
Phased array/TOFD AUT approach for inspection of welds has been accepted by ASME for in lieu of radiography, ASME CC 181 and CC 2235-9. However, it is the new technology that makes it commercially viable. If phased array AUT approaches were not cost effective, then they would not be used.
Advantages of Phased Array for pipe welds:
- Auditable, repeatable results (i.e. full data storage)
- High quality inspections, especially for planar defects
- Rapid
- Much cheaper than RT overall
- No safety (i.e. radiation) issues
- No disruption of production
- Adaptable to many different configurations and applications
Sample of Method Comparison:
| Based on a 2" Butt Weld .200" MWT & 100% access to circumference | ||||||||
| Method |
Crew Size |
Scan/ shot time |
Set-up time |
Welds per hour |
Production Interruption |
Safety Hazards |
Report format |
Auditable Results |
| RT | 2 man | 5 min |
5 minutes per weld |
6 to 10 | 100% | 100% |
Image of Weld |
Yes |
|
Manual UT |
1 man | 10 min |
5 minutes per weld |
4 to 6 | 0% | 0% |
Hand Written |
No |
|
Mech. PA |
2 man | 30 sec |
3 minutes per weld |
10 to 20 | 0% | 0% |
Image of Weld |
Yes |
| ASSUMPTIONS | ||||||||
|
1. Amounts are based on averages, results will vary. 2. RT: Assumes 2 exposures with 50 curie source 3. Manual UT: Assumes minimum scanning requirements as per ASME. 4. Set up time is based on typical accessibility and work plan. NOTE: Does not include time and or cost for film processing, reporting, re-shots, etc. |
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AUT can be Cost-Effective
- No radiation licenses and no headaches moving isotopes.
- No radiation hazard, so no evacuating the area and disrupting production.
- No moving components to far locations to perform RT for new construction.
- AUT is effectively real-time; no waiting for weekends and evenings to discover defects and last-minute repairs.
- Process control by AUT reduces repeated weld defects, especially for automated welding.
- AUT permits the use of Engineering Critical Assessment, which typically allows larger defects. (Overall, combined process control and ECA should produce lower reject rates.)
- Storage cost for AUT data is minimal, certainly compared with RT film.
- AUT permits faster construction and inspection due to no disruption of production and operations.
EXAMPLE:
For large storage tank construction companies, they can save several days in production due to more weld lengths scanned and no downtime from Radiographic operations.