Rather than have multiple curved arrays, a manufacturing compromise was made. The modeling was performed on 5- and 10-MHz arrays; in practice, we chose a 16-element, 7.5 MHz array. The two curvatures selected as optimum were 30 mm for diameters less than 25 mm, and 40 mm for diameters above that. A compromise radius of 35 mm was chosen. Along with a 60-deg natural angle wedge for high angles, this became the standard for the new scanner (Ref. 6). Scan Results Figure 7 shows a typical scan of a weld from both sides using the new system. The pipe was 115 mm in diameter and approximately 12.7 mm thick. The ultrasonic parameters were slightly varied to illustrate possibilities. As with all the company’s phased array inspections, considerable detail can be viewed in the tables in Fig. 7, e.g., defect depth, amplitude, and position. In addition, cursors can be used to box in a defect for measurements (Ref. 1). The angle of maximum amplitude can be determined using the cursor, and displayed as an A-scan for those who prefer such views. Overall, there is the usual choice of views available: A-, B-, S-, and C-scans. These more than fulfill code requirements. In contrast, Fig. 8 shows very small, thin pipes: 25-mm (1-in.) diameter and 3-mm wall. The pipe in Fig. 8A is carbon steel; a stainless steel pipe is shown in Fig. 8B. Note that the carbon steel notches show better than the stainless steel, but this is primarily due to the problems with ultrasonic inspection of austenitic steels. Conclusions 1. A novel, semiautomated smalldiameter pipe scanner has been produced with two major features: Low profile for clearance, and focused arrays to minimize lateral beam spread (and hence overcalls). 2. The scanner has a number of useful features. It is adaptable from 21- to 115-mm diameters; offers one-side access scanning; and works on both carbon and stainless steel. 3. The experimental results confirm that using the scanner and focused arrays produce significantly better defect length estimates. References 1. Introduction to phased array ultrasonic technology applications. August 2004. Published by Olympus NDT. 2. Chizen, K., and Moles, M. 2007. Phased array for piping inspections using ASME B31.3. Proceedings of the 4th Middle East Conference on NDT, Bahrain. 3. ASME B31.3 CC 179, Use of ultrasonic examination in lieu of radiography for B31.3 applications for materials ½” and less in wall thickness. June 28, 2006. 4. ASME B31.3 CC 181, Use of alternative ultrasonic examination acceptance criteria in ASME B31.3. Jan. 23, 2007. 5. Zhang, J., Labbé, S., and Moles, M. 2006. Improved lateral focusing for thin-walled gas pipeline girth welds using phased arrays. Proceedings of IPC 2006 International Pipeline Conference, Sept. 25–29, 2006, Calgary, Alb., Canada. Paper no. IPC2006-10238. 6. For wedge and probe details, see www.olympusndt.com/en/probes/; for COBRA, see www.olympusims. com/en/scanners/cobra/. MICHAEL MOLES (Michael.Moles@olympusndt.com) is senior technology manager, Olympus NDT, Waltham, Mass. Inspection Trends / Winter 2011 23 Official Interpretations: D17.1, Specification for Fusion Welding for Aerospace Applications Subject: Qualified Thickness Range Code Edition: D17.1:2001 Code Provision: Paragraph 4.3.3.1 AWS Log: D17.1-01-I04 Inquiry: Paragraph 4.3.3.1 (1) defines the qualified thickness range based on a test weld thickness of t. It also defines that 2 test welds qualify welds with intermediate thickness. It is, however, unclear on the qualification range when 2 unequal thicknesses are used in a fillet test weld. This can be interpreted in several different ways. Take the following for example: a.) 0.67t of thinner member to 4t of the thicker member b.) 0.67t to 4t of the thinner member c.) Range of thinner member to thicker member thicknesses Proposed reply: Define qualified thickness range if unequal thickness members are used in fillet weld tests for welder qualifications. Response: The answer is 0.67t to 4t of the thinner member. Subject: Special Application Qualification Range Code Edition: D17.1:2001 Code Provision: Paragraphs 4.3.7.5, 4.3.3.1 AWS Log: D17.1-01-I05 Inquiry: When the “Special Application” provision of paragraph. 4.3.7.5 is invoked, can the provisions of paragraph 4.3.3.1 “Qualified Thickness Range” (0.67T – 4T) be applied? Response 1: No.
Inspection Trends - January 2011 - Winter
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