Basic Tips for Thickness Testing with a Flaw Detector

Trying to do a thickness gauge job on a flaw detector budget? Lucky you! Lots of things can go wrong, but let's try to boil it down to the bare minimum shall we? For this video, we're talking mainly about carbon steel at ambient temperatures. If you're working at really high temps, there's a high temp video for that. And if you're working through pesky coatings and want to be as accurate as you can, there's an echo-to-echo video on the channel.

[@santiagocruz9060]

Useful

[@raddadothman]

thank you for this refreshing learning video, i need to aske about the impact of using J flank mode in accurate measurements using echo- echo technique, and i prefer always to calibrate the machine on a piece that identical ( same manufacturing condition)with the piece i need to test, the client should provide this , especially when you taking second readings using other machine brand than what has been used in first readings

[@enyaziz3107]

Hi Mr Paul!!like to see all of your UT lesson, anyway sorry for out of this video topic,if you can share a video on a Angle/shear wave twin crystal probe calibration on standard block for it suitable velocity,angle,setting etc. it would be so appreciated!!thank you..

[@hollowayndtengineeringinc.5201]

Hi Eny, unfortunately I don't own any twin crystal shear wave transducers. There are some offshore though, maybe I'll try next hitch out.

[@enyaziz3107]

@@hollowayndtengineeringinc.5201 ok sure! appreciated it!Anyway thanks 😊

[@mateuszwlodarczyk1929]

why to pick first negative lobe?

[@haroldishoy2113]

Are Zero Offset and Probe Delay the same function? Haven't used a Panametrics unit in years but have the USM Go+ now. Thanks.
P.S. Where do I buy the Wave T-shirt you are wearing?

[@hollowayndtengineeringinc.5201]

They are indeed the same thing. I got my shirt from the friendly folks at Sonatest.

[@re-geargarage]

I understand using the pre set velocity. As known values. What’s not known is the affects of scale coating etc… also you say you don’t mind on long distances, but velocity is a minor change on 5900 metres per second. Is that not a long value that a small change wouldn’t matter

[@hollowayndtengineeringinc.5201]

Calibrating for velocity on your calibration block means you can perfectly measure thickness.... on your cal block. As soon as you take it off and put it on your test piece, all bets are off. Velocity can change 0.1%, or even 1% between calibration and test surface. All other things we can control, but velocity variance we cannot. Also, coating thickness can be negated with echo-to-echo, or compensated for by adjusting the zero offset and getting 1st BWE to match E-E on a nearby area with similar coating thickness.

[@re-geargarage]

@@hollowayndtengineeringinc.5201 thanks for the reply. I don’t know what type of surfaces you scan. 98% of what I scan is corroded pipe, vessels etc.. very rare do the clients want to know how thick something brand new is.
I do scan with a flaw detector. I just feel that the minute adjustment the machine is making isn’t worth even mentioning.
.2 of a mm is .008” we can be that accurate but I think a better way would to have the actual piece.
Also the louder (gain dB) of one gate to the other to make a surface readable changes your final reading. The machine knows nothing that you don’t tell it

[@re-geargarage]

@@hollowayndtengineeringinc.5201 I hope you don’t t think I’m being critical of you. It’s difficult to put yourself out there.
I think there are a lot of people who look up to you. Rightfully so. I think there are lots always lots of variables. I’d like people and I’ll say UT1’s for the sake of naming a group. Just think about what you’re seeing, best practices are good to always employ. I’d argue repeatability from tech to tech is probably our greatest problem as UT guys

[@hollowayndtengineeringinc.5201]

I need to do a video on gating techniques. I wrote a paper on it years ago.