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Technical Discussions
Chris Bland
Chris Bland
00:10 Sep-13-2002
ASME calibration

I have carried out a great many ultrasonic examinations in accordance with ASME B & PV codes but have to confess that I have never calibrated for distance (or Sweep Range, as ASME calls it) using the methods recommended by ASME V, Article 4, Appendix B, since I was taught to use the IIW block to calibrate an ultrasonic instrument and only use the ASME basic block to establish sensitivity. It has been my experience that responses from basic blocks vary considerably, depending on the skill of the machine shop that fabricated them, and this alone can impact the accuracy and repeatability of inspections.

I would be interested to know if it is common practice by others to use the ASME calibration procedure and how practical it is to work with. Since the screen is calibrated in arbitrary units (e.g. 2 on the baseline represents 1/8 of the beam path)how are accurate measurements recorded on the report? Furthermore, how can one take adventage of the trig functions built into digital flaw detectors, that make it so simple to calculate surface distance, depth etc?

About the only advantage I can see of relying on the basic block is that it would make it possible to calibrate for distance using contoured wedges - something that is impossible to do on a flat block - or does anyone know any tricks for doing this?


    
 
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ayman ahmed
ayman ahmed
07:56 Oct-30-2002
Re: ASME calibration

: I have carried out a great many ultrasonic examinations in accordance with ASME B & PV codes but have to confess that I have never calibrated for distance (or Sweep Range, as ASME calls it) using the methods recommended by ASME V, Article 4, Appendix B, since I was taught to use the IIW block to calibrate an ultrasonic instrument and only use the ASME basic block to establish sensitivity. It has been my experience that responses from basic blocks vary considerably, depending on the skill of the machine shop that fabricated them, and this alone can impact the accuracy and repeatability of inspections.
.
: I would be interested to know if it is common practice by others to use the ASME calibration procedure and how practical it is to work with. Since the screen is calibrated in arbitrary units (e.g. 2 on the baseline represents 1/8 of the beam path)how are accurate measurements recorded on the report? Furthermore, how can one take adventage of the trig functions built into digital flaw detectors, thatmake it so simple to calculate surface distance, depth etc?
.
: About the only advantage I can see of relying on the basic block is that it would make it possible to calibrate for distance using contoured wedges - something that is impossible to do on a flat block - or does anyone know any tricks for doing this?
.and ihave not standred thk.of the range example:
ihave 29mm.thk. as acalibration block, are that cover26mm.thk.?



    
 
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