RELATIVE ADVANTAGES AND WEAKNESSES OF RADIOGRAPHY VS ULTRASONIC, TWO COMPLEMENTARY TECHNIQUES Ultrasonic and radiographic examination methods are complimentary and are not directly comparable or equivalent. Depending on flaw type (i.e., volumetric or planar) and orientation, ultrasonic examination may be superior to radiography or vice versa. Radiography is most effective in detection of volumetric type flaws (i.e., slag and porosity) and detection of planar type flaws (i.e., lack of fusion and cracks) that are oriented in a plane parallel to the x-ray beam. However, radiography is limited in detection of planar flaws not oriented parallel to the beam. In contrast, ultrasonic examination is very effective in detection of planar type flaws that are not oriented in a plane parallel to the sound beam .... Finally, ultrasonic examination is capable of detecting volumetric type flaws such as slag or porosity but is limited, compared to radiography, in ability to characterize volumetric flaws. The proposed alternative ultrasonic examination requirements and provisions address the known limitations of the ultrasonic method to ensure both planar and volumetric flaws in all orientations are detected and properly evaluated. First, examination using two angle beams (i.e., 45 and 60 degree nominally) or a procedure qualified on 100% of the weld volume in accordance with the performance demonstration methodology of Section XI, Appendix VIII is required. Second, examination scans in two directions perpendicular to the weld axis and two directions parallel to the weld axis or examination scans as qualified on 100% of the weld volume in accordance with the performance demonstration methodology of Section XI, Appendix VIII is required. Third, to ensure laminar type flaws are detected, a supplemental examination using straight beam is also required. Finally, if an indication, such as slag or porosity, is not characterized as volumetric, the indication will be characterized as a planar type flaw and evaluated in accordance with the acceptance criteria of NC-5330. The acceptance criteria of NC-5330 specify acceptable lengths of indications only and do not differentiate between planar and volumetric type flaws. Most importantly, planar type flaws such as cracks, incomplete penetration, and lack of fusion, which are rejectable by NC-5330 for any size, are more readily and properly characterized by ultrasonic examination. In addition to the effectiveness of the proposed alternative, use of ultrasonic examination in lieu of radiography will provide a significant reduction in personnel radiation exposure during refueling outage maintenance work. Also outage duration and costs will be reduced by allowing parallel path work to progress uninterrupted during examination of welds. Finally, the personnel safety risk of inadvertent or accidental exposure and also the normal anticipated exposure associated with transporting, positioning and exposing a source for radiography is eliminated. Source: D. Naujock et al. (NRC Office of Nuclear Reactor Regulation), http://www.nuclear.com/archive/2003/07/13/20030713-002.html Callaway-1 10-yr pipe test ISI - UT approved in lieu of radiography , nuclear.com info nugget 20030713-002, July 1, 2003] Tahir Bilge Ölmez International Welding Engineer
On Friday, July 4, 2008 9:53:26 AM UTC+3, vhr...@gmail.com wrote:
-- On Friday, July 4, 2008 9:53:26 AM UTC+3, vhr...@gmail.com wrote:
Dear All,We awared Hydro power project. There is specifically requirments of NDT method RT for all weld joint ( i.e for all class of joint ).We never used RT in normal practice for all project. Now for convince to client We required comparision sheet between RT & UT to justifying UT is better than RT.Request to send Comparision of RT & UT. Please send comparision & revert back soon. We have to submitt QAP urgentely.Regards,Vikas Rana
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