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- since 1996 -

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Technical Discussions
John O'Brien
Consultant, -
Chevron ETC , USA, Joined Jan 2000, 278

John O'Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
278
04:03 Aug-13-2008
NDE/Inspection Twisted Heat Exchanger Tubes

Does anyone have any experience, methods they can share for the examination of twisted tubes in twisted tube heat exchangers. Pasisng internal devices down the tubes seems a problem but wondered if anyone had tried long range UT or other methods.


    
 
 
Ingo Becker
Engineering, NDT Inspector & Sales
ec-works GmbH, Germany, Joined Apr 2000, 29

Ingo Becker

Engineering, NDT Inspector & Sales
ec-works GmbH,
Germany,
Joined Apr 2000
29
08:46 Aug-14-2008
Re: NDE/Inspection Twisted Heat Exchanger Tubes
Hello John,

I'm working in an eddy current service company and two years ago we have developed und used special designed probes for the inspection of a twisted tube heat exchanger (stainless steel tubes, OD 1 inch, about 6000 mm tube length). From our point of view is the proper internal cleaning of the tubes still the main problem.

Please contact me directly for further details.


    
 
 
Thomas Vogt
R & D, - -
Guided Ultrasonics Ltd, United Kingdom, Joined Apr 2007, 22

Thomas Vogt

R & D, - -
Guided Ultrasonics Ltd,
United Kingdom,
Joined Apr 2007
22
00:24 Aug-14-2008
Re: NDE/Inspection Twisted Heat Exchanger Tubes
John

we have on-site experience testing twisted tubes using our internal GWUT system. The key, as usual, is to get the theory right (as guided wave propagation is considerably different than in 'plain' tubes), but we have a pretty good handle on this. There are still some unknowns which need to be addressed (e.g. effect of fouling, types of defects and sensitivity to them), so it is not yet an off-the-shelf product. Let me know if you are interested to know more, I can send a case study.

Tom


----------- Start Original Message -----------
: Does anyone have any experience, methods they can share for the examination of twisted tubes in twisted tube heat exchangers. Pasisng internal devices down the tubes seems a problem but wondered if anyone had tried long range UT or other methods.
------------ End Original Message ------------




    
 
 
Sang Kim
Consultant, NDT Trainer
Guided Wave Analysis LLC, USA, Joined Feb 2008, 44

Sang Kim

Consultant, NDT Trainer
Guided Wave Analysis LLC,
USA,
Joined Feb 2008
44
06:27 Aug-15-2008
Re: NDE/Inspection Twisted Heat Exchanger Tubes
John,

We proved that the long range UT using MsS Technology can find defects in twisted heat exchanger tubes. For the feasibility testing with MsS guided-wave system, Southwest Research Institute tested a twisted tube having four different types of defects: two circumferential grooves of 9- and 18-percent CSA, a notch of 5-percent CSA, and 0.125-inch-OD hole of 4-percent CSA. The operating frequencies of guided wave were 150 and 250 kHz. The MsS probe that covers the whole circumference (360 degree) of tube can generate and receive pure torsional mode with the same way as the long-range guided-wave inspection in pipe. All defects were clearly detected with high signal-to-noise (S/N) ratio. For checking the signal, its S/N ratio, and frequency response of data, please refer to this website (http://www.gwanalysis.com/heat_exchanger_tube.html) and then select ¡°Long-Range UT of Twisted Heat Exchanger Tube¡± at the bottom of the page. If anyone needs demonstration with MsS system, please contact me at skim@gwanalysis.com. Because the MsS system is also used for guided wave monitoring with excellent repeatability, we can reproduce the result any time!

Thanks,

Sang Kim

----------- Start Original Message -----------
: John
: we have on-site experience testing twisted tubes using our internal GWUT system. The key, as usual, is to get the theory right (as guided wave propagation is considerably different than in 'plain' tubes), but we have a pretty good handle on this. There are still some unknowns which need to be addressed (e.g. effect of fouling, types of defects and sensitivity to them), so it is not yet an off-the-shelf product. Let me know if you are interested to know more, I can send a case study.
: Tom
:
: : Does anyone have any experience, methods they can share for the examination of twisted tubes in twisted tube heat exchangers. Pasisng internal devices down the tubes seems a problem but wondered if anyone had tried long range UT or other methods.
------------ End Original Message ------------




    
 
 
John O'Brien
Consultant, -
Chevron ETC , USA, Joined Jan 2000, 278

John O'Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
278
07:44 Aug-17-2008
Re: NDE/Inspection Twisted Heat Exchanger Tubes
To produce a summary for members on repsonses to this posting.

Thanks for the data from both Long Range UT Sources I already have the data from both SWRI and GUL. Both of these technologies show promise in limited trials but would require additional development work to confirm their application and reliability.

I also had some data from limited trials from an eddy current approach.

Summary appears to be at this time ther eis no confirmed reliable NDE approach and the problem requires R&D investment to provide a solution. We will now be considering our path forward.

Many thanks to those who took time to respond.


    
 
 

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