21:21 Jan-12-2009 Stan Banner NDT Inspector, Canada, Joined Jan 2009 31
ASME V Article 4 Calibrations
I have a few questions regarding how to choose a what part of the ASME V Article 4 is appropriate for a given weld examination, and the calibration block requirements:
1 - Do all of the rules for Flat ASME calibration blocks apply to Curved Nonpiping calibration blocks, e.g. the need for both slots and side drilled holes and how are circumferentially drilled holes handled, and do slot depths need to be 2% as stated for nonpiping blocks or 10% as stated for piping blocks. If 2% is the case, that means that a non piping block made of 2.5" s80 pipe would need slots <0.006" deep, which seems to me quite extreme, and the side drilled hole would be around 1/3 the pipe thickness.
2 - When examining a pipe welded to a vessel, e.g. a weld on the the drain pipe welded on the bottom of a tower, but not actually welded to the vessel envelope, is the appropriate cal block a piping cal block, or a curved nonpiping block.
3 - When examining a branch connection weld on a piping system, e.g. a 4" 'Cat D' weld onto a 10" pipe, which of the two cal block specification come into play.
To sum up the last two points, when examination is to ASME VIII, are only nonpiping cal blocks used, while when examination is to ASME B31.3, are only piping cal blocks used.
Re: ASME V Article 4 CalibrationsIn Reply to Stan Banner at 21:21 Jan-12-2009 (Opening).
The 2007 ASME Code, Section V Article 4 contains Fig. T-434.3 which will answer many of your questions from #1. In summary, there are no side-drilled holes that you are familiar with from the Flat Non-piping blocks. Also, the depths of the 4 EDM notches are nominally 9.5% deep (8 to 11% of nominal wall is specified), not the 2% called out on the flat block.
Just a couple of observations on ASME Section V and piping versus non-piping weld examinations.
It is interesting to note that the function of the notches on the piping calibration blocks is in fact to set sensitivity. These are nominally 10% of the wall with some tolerance actually noted as a range from 8-11%. Setup using a phased-array S-scan using this notch configuration is problematic at best due to the reflectivity effects from a vertical face.
When we move to plate inspections (including curved plate) it is worthwhile noting that although the Figure of the Basic Calibration Block in T-434.2.1 includes a surface notch 2% of the wall thickness, its function is rarely used (and generally poorly understood). The function of the 2% notch in the Basic Calibration Block is described in the Non-mandatory Appendices. Appendix B in Sec. V Art. 4 describes the initial use of the notch in B-464.4. The first application is simply to note the position of the surface during the position calibration of the A-scan display. B-465 describes the second use of that 2% notch. As I noted above, the issue of calibrating sensitivity on a notch in piping is problematic. This problem is described in B-465 suggesting that the response from the 2% surface notch in a 45° beam may be 6dB more sensitive than the response from the SDHbased DAC. Yet the same notch may be 6dB less than the DAC for a 60° beam. ASME describes that a correction is required in order to be equally critical of such an imperfection. However, this is not compatible with the treatment of responses in the normal workmanship-style acceptance criteria used in ASME referencing Sections. I.e., although this Appendix acknowledges that the response from a corner reflector will be angle dependent it still requires reporting based solely on amplitude response so the instructions are (seemingly) useless as you are obliged to record all responses (regardless of beam angle and corner effects) exceeding a specified amplitude.