The graph provided by Ashfaq comes from a study by the Dutch Welding Institute (NIL) - Stelwagen, 1995. Its often shown in the literature, e.g. Charlesworth and Temple - Engineering Applications of ultrasonic time-of-flight diffraction 2nd Edition, Fig. 8.14.

No need for any change as the ToFD blocks are as specified by Appendix III Fig.III-432.2.1.(a) and (b).

Pulse-echo relies on full skip, requiring (for piping) reflection from the internal (curved) surface leading to beam profile alteration beyond the half-skip. ToFD does not rely on beam profile ...

At long last the straightjacket of ASME V Article 4 para T-434.3 Piping Calibration Blocks requiring a section of pipe the same nominal size and schedule as the pipe weld to be tested has been removed by the issue of the above Code Case on January 20, 2010. Now the same tolerances and range on block ...

Golden Rule: When re-testing AFTER PWHT, ALWAYS use the same method as used BEFORE PWHT, otherwise its highly probable you will land yourself in the situation you are in now.

If this was ASME work was the TOFD carried out strictly in accordance with Section V Article 4 Mandatory Appendix III? If ...