Hello All - I'll dive right in with this, bear with me on the explanation:
AWS D1.1-06 6.23.1, 1st sentence, states that the IIW block is to be the standard used for distance and sensitivity calibrations.
The next sentence (still in 6.23.1) states that other portable blocks may be used provided there is an adjustment to achieve the equivalent of what you get with the IIW block.
Using the DSC block as an example, Annex H (H2.4.1) says to use the maximized signal from the 1/32 slot to get the reference line height indication.
H2.3.3 says use the decibel reading from that as the reference level "b" on the report sheet.
A "former Level III-UT" was here today, doing UT with a new company as a Level II, and said that the "equivalence" in 6.23.1 is established by the fact that the IIW and DSC blocks are made and certified to meet D1.1 requirements; so nothing else needs to be done. Essentially, you could choose to use either block and be OK (he wasn't saying one is identical in response to the other)
Is there any need to calibrate on the IIW block and then validate the response from the DSC block?
If yes, how is that done?
Chet,
The guy's full of it. Calibrate on the 1/16 hole on the IIW. Then without changing gain put your ducer on the DSC. Now change the gain to get the same screen height that you got with the IIW (I know, the sound path is a bit different but ignore that - D1.1 doesn't use a DAC so there's no convenient way to make up for that. Besides, the difference in sound path isn't all that much anyway if I remember right). Make note of both gain settings.
Now when you're out in the field you can verify your calibration at the specified interval by using the DSC at the corrected gain level. Then when you're done for the day you can throw your ducer on the IIW quick just to verify.
Mankenberg
Kipman is right thats how i was taught by a competent level III.
I agree with Kip and Trap as well. Maybe thats why he is a "former level III-UT"?
AWS D1.1 Sect 6.23.1 is pretty specific stating that the IIW ref. block "shall be the standard used for both distance and sensitivity calibration".
Gentlemen,
Thank you very much for your response. I suspected that was the case but being very new to UT I wasn't sure.
LOL...I feel silly, I don't use the DSC block that I have in my cabinet...I still lug the IIW block around after all these years. I suppose if I were to need to UT out on the jobsite that would change quickly, but here in the shop the IIW block just rides along in the bottom of my UT until I need it.
John, do you have large pneumatic tires as an accessory for your UT equipment? No wait...you're in the shop, you have a large capacity crane available.
Actually, I usually use the IIW block as well. I usually calibrate on my office table because the shop is small and most work is relatively close. However, lately I've had to fill a 5 gallon pail with my gear, put on my fall harness and other gear, and hike out to the work. The DSC block is appreciated for those excursions.
Chet, Just imagine how fast I will be able to run when I shed that IIW block in a few more years for a DSC block...it all in the training Chet ;-)
Topic American Welding Society Services / Technical Standards & Publications / UT calibration blocks
