05:26 Aug152007 Re: curved probes in ToFD  Start Original Message  : what is the criteria for choice of curved probes in TOFD? : suresh  End Original Message In addition to the reply of Ed Ginzel with respect to the referenced standards: CEN/TS 14751:2005 Use of timeofflight diffraction technique (TOFD) for testing of welds in 7.2.2 asks for the matching of probes according to EN 1714. EN 1714:1997 (2002) Ultrasonic testing of welded joints in 6.3.3 gives the equation referenced by Ed Ginzel. But this equation is not correct. EN 1417 is under revision now and will be published again soon. The correct equation (when the max gap is smaller than 0.5 mm, which can be tolerated for 4 MHz), is Dobj < (D)squared/ 2 mm, where Dobj is the outer diameter of the object, and D is the dimension of the transducer parallel to the curvature. The same correction has to be made to the respective equations in 3.4.1 and 3.4.2 of EN 5832:2001 Ultrasonic testing  Part 2: Sensitivity and range setting (The above equation with squared transducer diameter is correct) Best regards Udo Schlengermann GE Inspection Technologies GmbH Huerth, Germany Chairman of CEN/TC121/SC5/WG2 (UT of welds) Chairman of CEN/TC138/WG2 (UT)
