New ASME Code Case 2638 Alternative Piping Calibration Block

[ndeguy]

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 curvature as for vessel welds are allowed, see Fig.-434.1.7.2. Additionally thickness, T, may be + / - 25% of the component thickness.

Flat calibration blocks are still only acceptable for pipe diameters >20" diameter, therwise it should be a section of pipe as per Fig. T-434.3

However all depends on whether the AI is up to the game. What experiences have any UT techs had of the strict or not appliation of Article 4 when performing UT of ASME welds?

[ashfaqanwer]

Thats a news for me.
It has been an extensive effort of arranging calibration blocks in the same nominal diameter and thickness as the component pipe.
Now the new tolerance of +/- 25 % would be cutting down this tedious effort to a large extent.
In addition to the effort requiring in getting the blocks ready, UT teams have to calibrate their systems again and again for varying thicknesses affecting the overall progress of inspection. Construction teams were have to put in a lot of effort to compile the welds of same thickness in order to improve the efficiency of UT inspection. Good news!!!

Is there any update regarding TOFD calibration block? As for TOFD, requirements listed in T-434.3 are not applicable as per ASME V Article 4 Mandatory Appendix III-434.3.

[ndeguy]

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 for defect sizing - it is not a reflection technique, discontinuity indication is by diffraction, sizing by time-of-flight measurement and therefore the curvature of the test item (for pipes) cannot affect the direct diffracted signals. No need for different test blocks when testing pipes/piping.

[ashfaqanwer]

We are about to implement Pulse-echo technique now at our site and from your news, we would be getting some relaxation regarding calibration blocks as per ASME code case 2638.
Can you share your experience regarding the technique limitation especially when scanning pipes in thicknesses from 6mm - 12mm?