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A team of four SGS experts took part in the International Institute of Welding (IIW) Congress in Johannesburg from November 6-8 where Norbert Trimborn, Strategic Business Leader Advanced NDT, held a presentation entitled “Phased Array and TOFD in Lieu of RT Fabrication and In-Service” on the recent SGS development of a weld inspection system designed specifically for testing boiler tube welds. The presentation illustrated phased array (PA) performance by using an example in which radiography (RT) had been replaced by PA.
The International Institute of Welding (IIW), founded in 1948 by welding institutes and societies of 13 countries, considers it crucial to make global progress in science and technology more rapid. Currently boasting a membership of 56 countries representing 5 continents, the IIW is universally recognized as the largest worldwide network for welding and allied joining technologies.
Phased Array and TOFD in Lieu of RT Fabrication and In-Service
The only presenter to address testing weld strength, Mr. Trimborn discussed replacing radiography with phased array (PA) and time of flight diffraction (TOFD) and shared information on inspection requirements for pre- and in-service inspections. The phased array inspection system developed by SGS to test boiler tube welds is based on the requirements outlined in the presentation. Mr. Trimborn discussed cases in which this new system could be most advantageously used and gave an overview of the differences in the detection and sizing of various types of defects.
To learn more about this topic, you can download and read the entire paper submitted by Mr. Trimborn – “Phased Array and TOFD in Lieu of RT Fabrication and In-Service” (PDF 125 KB).
The SGS-developed inspection system for boiler tube welds uses the phased array technology to perform successful comprehensive and productive pre-and in-service testing. As restrictions in the use of industrial radiography have increased over the years, the need for alternative weld inspection methods and techniques such as PA has become more evident. In general, new developments in non-destructive testing (NDT) are driven by improved performances and the associated cost reduction of those techniques. Administered correctly, PA deliver performance superior to that of radiography resulting in a higher level of confidence in the structural integrity of PA tested products. Although PA inspection costs are typically higher than those of conventional RT, there can be significant savings associated by preventing disruption to productivity in the testing area due to an absence of dangerous radiation when using these advanced techniques. Additionally, PA offers fast, accurate testing and shortens the overall inspection time. Using these more accurate inspection methods can lead to a higher repair rate due simply to strict acceptance criteria while protecting asset values.
The SGS system covers pipes from 21.3 mm (0.84 in) to 114.3 mm (4.5 in) OD and operates within the 13mm (0.5 in) clearance on all standard pipes permitting inspections in limited access areas. The system is able to hold two PA probes for complete weld coverage in one pass and can be configured to make one-sided inspections for pipe-to-component evaluations. The system is designed to provide stable and constant pressure around the full circumference of the pipe and the spring loaded scanner may be used on ferromagnetic and non-ferromagnetic pipes. The system boasts an encoder resolution of 32 steps/mm and two encoders on the scanner.
There are no health and safety implications with using ionizing radiation, allowing other work in the vicinity to continue during inspection and eliminating the need for implementing radiation protection measures. With the SGS system, 100% coverage of the weld enables inspectors to characterize and size diverse defects in inspections done in close to real time. The system offers two dimensional sizing, direct post-test assessment and the possibility to produce both hard- and soft-copy results. Furthermore, the system guarantees equal or superior reliability when compared to RT and yields high savings in associated testing costs.
The SGS system requires tube wall thickness to be more than 4.5 mm for the detection and characterization of defects and demands that bore chamfering be handled carefully. Although highly accurate, the system may not be suitable in every case for the detection and characterization of inclusions and gas pores. Operators skilled in the cutting-edge SGS inspection technology are not yet in abundance due to the fact that the technology is so new.
SGS was pleased to participate in the 2012 IIW Congress, a perfect place to present its new system developed specifically for the inspection of boiler tube welds, and looks forward to attending this respected event again in the future.
For further information, please contact:
SGS Group, Industrial Services Norbert Trimborn Strategic Business Leader Advanced NDT Malledijk 18 Spijkenisse t: +31 181 693 611 Website: www.sgs.com/ndt
SGS is the world’s leading inspection, verification, testing and certification company. SGS is recognized as the global benchmark for quality and integrity. With more than 70,000 employees, SGS operates a network of over 1,350 offices and laboratories around the world.