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Technical Discussions
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 528

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
528
01:39 Apr-09-2009
Low Temperature Thickness measurement

One of our customers is asking about the possibility of thickness measurement in a LOW temperature application on metal at around -100C (170K)

Not one I've come across before. , has anyone else any experience of this .

I'm looking for ideas on Couplants, How well it worked, and whether standard probes lasted/worked OK.

(I don't think its a delayed April Fool, although it did cross my mind...)

 
 Reply 
 
TomNelligan
Engineering,
retired, USA, Joined Nov 1998, 390

TomNelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
14:58 Apr-09-2009
Re: Low Temperature Thickness measurement
In Reply to Joe Buckley at 01:39 Apr-09-2009 (Opening).

We too get asked about that sort of thing on occasion, typically involving corrosion testing of pipes and tanks in cryogenic systems, and the big problem is finding a viable couplant that remains a liquid or gel at such low temperatures. Most high temperature dual element transducers that are designed to work on surfaces at plus several hundred degrees Celsius will tolerate short-term contact with surfaces at minus a hundred degrees, so the transducer doesn't have to be a limitation. The same design considerations that protect high temperature duals from thermal expansion effects would normally protect them from thermal contraction as well. But we don't have a couplant to recommend. I have suggested to customers that they might look into exotic lubricants to see if there's anything that might work (other than graphite lubricants, which aren't a good acoustic couplant), but to date no one has ever gotten back to me with a suggestion.

 
 Reply 
 
Jim Kovarik
Engineering
Lixi, Inc., USA, Joined Nov 1998, 39

Jim Kovarik

Engineering
Lixi, Inc.,
USA,
Joined Nov 1998
39
16:21 Apr-09-2009
Re: Low Temperature Thickness measurement
In Reply to Joe Buckley at 01:39 Apr-09-2009 (Opening).

Are you limited to ultrasonics for acquiring the thickness measurements?

 
 Reply 
 
R Duwe
NDT Inspector, API-510, 570, 653
MISTRAS, USA, Joined Jan 2009, 148

R Duwe

NDT Inspector, API-510, 570, 653
MISTRAS,
USA,
Joined Jan 2009
148
18:17 Apr-09-2009
Re: Low Temperature Thickness measurement
In Reply to Jim Kovarik at 16:21 Apr-09-2009 .

Couplant: Have you tried silicon oil? Another possible ULT couplant is alcohol. At dry ice temps, isopropyl has a moderate viscosity, should work well. Hopefully, your calibration block is also at the low temp.

 
 Reply 
 

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