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Technical Discussions
Michael Trinidad
Consultant,
LMATS Pty Ltd , Australia, Joined Jan 2003, 138

Michael Trinidad

Consultant,
LMATS Pty Ltd ,
Australia,
Joined Jan 2003
138
03:06 Mar-02-2000
UT versus RT weld inspection on butt welds

An ispection requires a 100% UT inspection of an 80-90mm butt weld in steel plate followed by a re-test of the same weld by 10% RT.

The re-test by 10% RT is because the clients do not 'as always happens' trust the little green squiggly lines on the UT set or the operators.

The only gamma source available in this country is IR192 so RT of this joint is stretching the capabilities and there are other problems, backing strip, access etc. The weld will be FCAW with multiple passes which I believe will have a common decfect of lack of inter-run fusion which RT on this thickness will be unlikely to fix.

My suggestions to the clients in this case has been to scrap the RT and to ensure confidence in the UT operator's ability, have them perform a practcal test.

My question is I know of codes that prefer the use of UT on thicker weldments instead of RT but does anyone recall of any papers related to the probability of detection of defects RT versus UT?

I need as much ammunition as I can find.


Kindest Regards


Michael Trinidad


    
 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1252

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1252
03:53 Mar-02-2000
Re: UT versus RT weld inspection on butt welds
Michael:
You are encountering a common problem in NDT.
Olaf Forli has done POD examples for thinner wall materials.
see the article at http://www.ndt.net/article/0498/forli/forli.htm
Mech UT and TOFD do quite well.

As of 1996 ASME Code Case 2235 has allowed UT to be used in lieu of RT on all components over 4 inches (100mm).
This year the Code Case 2235 is due to be revised and lower the alloed thicknesses to around a half inch. The Code Case even allows the use of nonamplitude based UT (i.e. TOFD).

It is not clear from your discussion topic if the UT to be done is manual or not.
My greatest problems have arisen when trying to adapt a mechanised techique to a Code written for manual UT.

The addition of a 10% spot check RT would not really add much to the quality confidence level.
I did a quick calculation using a D4 (class 1) film and 100Ci of Ir192 through 100mm of steel (90mm wall plus backing bar). Exposure time would be on the order of 350min. to get a density of 2,5.

In the same 5-6 hours you could do a lot of TOFD and add a lot more confidence to the POD than 10% RT could EVER hope to do.

Ed

: An ispection requires a 100% UT inspection of an 80-90mm butt weld in steel plate followed by a re-test of the same weld by 10% RT.

: The re-test by 10% RT is because the clients do not 'as always happens' trust the little green squiggly lines on the UT set or the operators.

: The only gamma source available in this country is IR192 so RT of this joint is stretching the capabilities and there are other problems, backing strip, access etc. The weld will be FCAW with multiple passes which I believe will have a common decfect of lack of inter-run fusion which RT on this thickness will be unlikely to fix.

: My suggestions to the clients in this case has been to scrap the RT and to ensure confidence in the UT operator's ability, have them perform a practcal test.

: My question is I know of codes that prefer the use of UT on thicker weldments instead of RT but does anyone recall of any papers related to the probability of detection of defects RT versus UT?

: I need as much ammunition as I can find.

:
: Kindest Regards

:
: Michael Trinidad




    
 
 
Dent McIntyre
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 248

Dent McIntyre

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
248
03:59 Mar-02-2000
Re: UT versus RT weld inspection on butt welds
: An ispection requires a 100% UT inspection of an 80-90mm butt weld in steel plate followed by a re-test of the same weld by 10% RT.

: The re-test by 10% RT is because the clients do not 'as always happens' trust the little green squiggly lines on the UT set or the operators.

: The only gamma source available in this country is IR192 so RT of this joint is stretching the capabilities and there are other problems, backing strip, access etc. The weld will be FCAW with multiple passes which I believe will have a common decfect of lack of inter-run fusion which RT on this thickness will be unlikely to fix.

: My suggestions to the clients in this case has been to scrap the RT and to ensure confidence in the UT operator's ability, have them perform a practcal test.

: My question is I know of codes that prefer the use of UT on thicker weldments instead of RT but does anyone recall of any papers related to the probability of detection of defects RT versus UT?

: I need as much ammunition as I can find.

:
: Kindest Regards

:
: Michael Trinidad


This is a favorite topic of mine.
You are obviously aware that RT and UT are not interchangeable. They are sensitive to different types of flaws by the laws of physics.
We are in the nuclear business here and our customers demand 100% RT and UT on all welds in that thickness range.
Given your big picture and all the details, if I were your customer I would also insist on RT. The major reason is the FCAW process is prone to rounded indications like slag and porosity.
I have seen some huge pores in FCAW with RT that UT hardly sees. The second reason is the backing strip will likely cause UT some heartache.
UT may find some of these but likely would not reject them. I have many experiences (30+ years)in this area and have learned the hard way.

Regarding RT of this thickness with Iridium 192. I was stationed in China for several years and there they were absolutely against Cobalt.
We had some work that was 110 mm thick so I told them that we needed to buy a Cobalt source.(My knowledge and experience at that time said it could not be done with Iridium.) No way was that going to happen.
so they shot it with Iridium and showed me that they could in fact do it. (Showed 2-2T) I still did not believe it so I watched the whole process closely. Nothing special was done it just took a long exposure.
Maybe Chinese Iridium has more punch???

Dent McIntyre
NDE Manager
B & W Canada




    
 
 
Uli Mletzko
R & D, Retired
Germany, Joined Nov 1998, 89

Uli Mletzko

R & D, Retired
Germany,
Joined Nov 1998
89
05:00 Mar-02-2000
Re: UT versus RT weld inspection on butt welds
: An ispection requires a 100% UT inspection of an 80-90mm butt weld in steel plate followed by a re-test of the same weld by 10% RT.
: The re-test by 10% RT is because the clients do not 'as always happens' trust the little green squiggly lines on the UT set or the operators.

The application of different NDT methods in general is improving the reliability. Therefore, if the customer requires two methods (and pays for two methods), there is not too much to say against.

: The only gamma source available in this country is IR192.

Co 60 (using steel intensifier screens) or linear accelerator (MINAC) would produce a better image quality. Nevertheless, according to the European standard EN 444, Ir 192 can be used up to 90 mm even in the high quality testing class B. Again, no much reasons to say something against.

: I need as much ammunition as I can find.

The main problem (which could lead to an economic decision) is the problem of exposure time. Asumme a source activity of about 3 TeraBequerel (according to about 75 Curie in the good old times), a source size of 3 mm, 90 mm wallthickness, film D7 with lead screens, minimum density 2.0, source-film-distance of 700 mm. This will lead to an exposure time of about 90 minutes (1.5 hours !!!).


Uli Mletzko
NDT group,
State Materials Testing Institute (MPA),
University of Stuttgart (Germany)



    
 
 
Andy Cunningham
Consultant, NDT/QA QC/R&D
ASNT,PCN, Canada, Joined Feb 2000, 14

Andy Cunningham

Consultant, NDT/QA QC/R&D
ASNT,PCN,
Canada,
Joined Feb 2000
14
08:49 Mar-02-2000
Re: UT versus RT weld inspection on butt welds
if you need "ammunition" you are arguing or that implies you client is
loosing trust.
he is paying the bills.
so if he wants 10% or 100% gama post ut. that will show nothing (but the
largest of voids) that is what he gets. (not your problem)
you are correct in your assessment RT v UT
step back it is not a battel of the intellects
remember customer client thing
YOU CAN NEVER WIN AN ARGUMENT WITH A CUTOMER.
keep on probing
all the best
andy cunningham

-----------
: An ispection requires a 100% UT inspection of an 80-90mm butt weld in steel plate followed by a re-test of the same weld by 10% RT.

: The re-test by 10% RT is because the clients do not 'as always happens' trust the little green squiggly lines on the UT set or the operators.

: The only gamma source available in this country is IR192 so RT of this joint is stretching the capabilities and there are other problems, backing strip, access etc. The weld will be FCAW with multiple passes which I believe will have a common decfect of lack of inter-run fusion which RT on this thickness will be unlikely to fix.

: My suggestions to the clients in this case has been to scrap the RT and to ensure confidence in the UT operator's ability, have them perform a practcal test.

: My question is I know of codes that prefer the use of UT on thicker weldments instead of RT but does anyone recall of any papers related to the probability of detection of defects RT versus UT?

: I need as much ammunition as I can find.

:
: Kindest Regards

:
: Michael Trinidad




    
 
 
Michael Triniad
Michael Triniad
04:48 Mar-03-2000
Re: UT versus RT weld inspection on butt welds
Uli Mletzko
Dent McIntyre
Ed Ginzel

Thanks as always for your thoughtful input, I will explain further about this particular situation so you can see how ridiculous it is.

Andy Cunningham

Sorry to single you out but in this case your wrong. I am the client’s third party representative so I can win an argument with a client. I will discuss further the debacle.

Initially the clients request was for 100% UT followed up by 10% RT on two areas on an enormous structure. One of the areas would never be be possible to be inspected by RT namely a 100mm ‘T’ Butt the second area is a 100mm splice butt joint. We played around and found the same that a 5-6hour shot was required but this is in the workshop. The component will actually be swinging in the breeze from ground level up to around 400m of the ground. Geomentry includes internal rebars stiffeners and backing strips. Anyway with all this in mind I advised the owners that RT was if not impossible highly impracticable leaning more towards the impossible.

The owners then changed the 10 % spotcheck of the 100% UT to another 10% UT of the previously 100% scanned area at of all things a less stringent acceptance criteria! When it was pointed out that this was a waste of time one guy which I refer to affectionately as the RT parrot started wanting RT all over again.

I do not even have to perform this impossible test but I will be the guy enforcing the specification sensitivity requirements on the sub-contractor NDT companies which I believe will be hard to achieve, even without the geomentry, access etc etc. My request for ammunition was to help out the NDT sub-contractors.

Given the nature of NDT and the lack of knowledge of most clients or customers ‘the customer is always right’ is not applicable. I see the biggest problem is these one day NDT awareness courses that produce instant experts who think NDT is easy and can be done by any trained monkey.

I apologise for the lengthy story but I thought some of you might relate to similar incidents where reality was not an issue.

Kindest Regards


Michael Trinidad



    
 
 
Jacques Parent
Jacques Parent
03:24 Mar-06-2000
Re: UT versus RT weld inspection on butt welds
I agree, RT and UT should be considered complementary and not "traded" one for the other.
I have been in many situations where the use of both has uncovered "interesting" indications.
I am normally on the client side of the equation and I always try to get some of both.

I was involved in one instance where RT was impossible. (Thick TKY's). In order to increase POD and decrease client concerns toward UT, we agreed to the following.
-100% UT
-10% UT crosscheck, different operator, different instrument, blind to the previous results.
-If 100% match...end of story
-If any discrepancy...investigate and resolve case by case

Good luck
jp



    
 
 
J. Mark Davis
Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama, USA, Joined Mar 2000, 85

J. Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
05:35 Mar-15-2000
Re: UT versus RT weld inspection on butt welds
Dear Michael,

I hit the wrong key in case you get two responses from me.

I agree with the others. However, if the client has a problem with green squiggles, then perform a automated or semiautomated UT examination. Then a, b and c scans can be presented for better understanding of what is down under. Also, archivibility is a key advantage. Evaluation is more effective also.

Another consideration is digital radiography.

One technology is to scan and digitally enhance the radiographic film. My company, Digital Imaging Servcies, has scanned film and enhanced and imaged cracks like IGSCC for many of the nuclear power and petrochem plants here in the US.

Another technology is Phosphur Plates or Amorphous Silicon which are filmless technqiues. This are great for defect evaluation. Generally the human eye can see about 125 to 200 shades of gray. 4096 shades of gray can be viewed in film scanning or digital radiography.

Will you be at the Spring ASNT Conference? I am the Host Chairman and I can discuss some of these ideas with you.

Good Luck,

Mark Davis


: An ispection requires a 100% UT inspection of an 80-90mm butt weld in steel plate followed by a re-test of the same weld by 10% RT.

: The re-test by 10% RT is because the clients do not 'as always happens' trust the little green squiggly lines on the UT set or the operators.

: The only gamma source available in this country is IR192 so RT of this joint is stretching the capabilities and there are other problems, backing strip, access etc. The weld will be FCAW with multiple passes which I believe will have a common decfect of lack of inter-run fusion which RT on this thickness will be unlikely to fix.

: My suggestions to the clients in this case has been to scrap the RT and to ensure confidence in the UT operator's ability, have them perform a practcal test.

: My question is I know of codes that prefer the use of UT on thicker weldments instead of RT but does anyone recall of any papers related to the probability of detection of defects RT versus UT?

: I need as much ammunition as I can find.

:
: Kindest Regards

:
: Michael Trinidad




    
 
 
Jane
Jane
07:56 Mar-06-2001
Re: UT versus RT weld inspection on butt welds
I am very interested in linear array inspection system by RT.



    
 
 
Troy Foster
Engineering, X-ray Inspection Systems
Willick Engineering Company, USA, Joined Feb 2000, 6

Troy Foster

Engineering, X-ray Inspection Systems
Willick Engineering Company,
USA,
Joined Feb 2000
6
06:44 Mar-06-2001
Re: UT versus RT weld inspection on butt welds
: I am very interested in linear array inspection system by RT.
.
I Can supply significant information on this subject. We have been experimenting with linear detectors for RT inspection of butt welds of both EB and inert gas. The 55 micron detector we have been using can resolve down to less than 0.002 inches in 0.006 wall. Our current experiments are with a 27 micron detector. As we improve the scintillator material we expect to achieve better spatial resolution at similar scan rates. Please e-mail me at troy@willick.com for further information on this process.

Troy Foster.



    
 
 

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