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Technical Discussions
Charlie Belt
Charlie Belt
04:30 Dec-25-2009
POD using Phased Arrays

Hello,

Can some here give me the way to find some POD & POS study, work etc… with Phased Arrays?

Happy Holidays !

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
14:06 Dec-25-2009
Re: POD using Phased Arrays
In Reply to Charlie Belt at 04:30 Dec-25-2009 (Opening).

Charlie:
Nearly all such reports are the result of qualification trial nowadays. Therefore, the reports are not published information.
Your request was specific for Phased-Array POD and Probability of Sizing (correctly). Separating phased-array from the standard ultrasonic assessments is again a problem. Many inspection techniques can be done using both phased-array and conventional UT.
Further, your request seemed generic...yet PODs have not been well known outside the pipeline girth weld applications (and some nuclear projects). Pipeline girth welds now use zonal discrimination almost exclusively, so comparing this technique to rastered manual phased-array or mechanised S-scan techniques would be totally inappropriate. A great report on the general NDT use of PODs is found at http://www.hse.gov.uk/RESEARCH/rrpdf/rr454.pdf
This is a useful report in that it points out the limitations of mixing parameters.

The concepts as applied to zonal discrimination are found in http://www.ndt.net/article/ecndt02/morgan/morgan.htm
Further dicsussion is seen in Insight Volume: 51 | Issue: 5 Cover date: May 2009
Page(s): 266-270

Regards

    
 
 Reply 
 
Charlie Belt
Charlie Belt
05:46 Dec-26-2009
Re: POD using Phased Arrays
In Reply to Ed Ginzel at 14:06 Dec-25-2009 .

Thank you very much Mr. Ed, excelent material !!!

    
 
 Reply 
 
Srinual
NDT Inspector
Thailand, Joined Dec 2009, 1

Srinual

NDT Inspector
Thailand,
Joined Dec 2009
1
13:02 Dec-27-2009
Re: POD using Phased Arrays
In Reply to Ed Ginzel at 14:06 Dec-25-2009 .

Reading trough those papers brings up a question about Focused Phased Array Probes.

Can a Phased Array probe's elements be focussed (curved) and can it still be used for Sectorial Scans?

    
 
 Reply 
 
Ed Ginzel
Ed Ginzel
14:52 Dec-27-2009
Re: POD using Phased Arrays
In Reply to Srinual at 13:02 Dec-27-2009 .

Yes, the curving of the elements in the passive plane was used to improve flaw length sizing the effects are reported by Moles in three papers all on NDT.net:
http://www.ndt.net/article/wcndt2008/papers/82.pdf
http://www.ndt.net/article/insight/papers/insi.50.5.253.pdf
http://www.ndt.net/article/panndt2007/papers/146.pdf
This just required that I enter the words "curved phased array" in the search box here on NDT.net! The serach engine on NDT.net is a great way to get answers to NDT questions. With nearly 7000 papers on NDT it must be the largest database of NDT information.... and all freely accessible!

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

John O'Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
278
16:15 Dec-28-2009
Re: POD using Phased Arrays
In Reply to Ed Ginzel at 14:52 Dec-27-2009 .

Ed's response is very appropriate and I am glad he posted the link to the Olympus paper on sizing approaches with focussed probes. We have conducted numerous in-house qualification and POD determination trials primarily for pipeline girth weld examination but also some for general vessel and piping inspection. These reveal that in most cases PA has great repeatability and low inaccuracy in through wall sizing dimensions however the trade off is that people forget about focussing in the other axis and come up with significant inaccuracies in the order of 10+ mm on length sizing. Selection of the probe as with all ultrasonic techniques is key and simply selecting PA does not change this.
POD is a function of the technique and all its parameters and will vary depending upon what component of the flaw is critical for you.

    
 
 Reply 
 
Michael Moles †2014 *1948
, Joined ,
20:48 Dec-29-2009
Re: POD using Phased Arrays
In Reply to John O'Brien at 16:15 Dec-28-2009 .

Focusing phased arrays in the passive direction is no longer limited to high-end pipeline applications. Olympus NDT recently commercialized the COBRA small pipe scanner which uses focused arrays. For small pipes, focusing is critical as the beam naturally defocuses on entry, and the smaller the pipe, the bigger the effect. This is one factor that has kept AUT from becoming widely used in pipe welds. Another factor is the low physical profile of the inspection system, required to pass between the numerous pipes in many applications.

    
 
 Reply 
 
Carlos
R & D, - -
UCV & EGROUP, Venezuela, Joined Oct 2008, 120

Carlos

R & D, - -
UCV & EGROUP,
Venezuela,
Joined Oct 2008
120
18:48 Dec-30-2009
Re: POD using Phased Arrays
In Reply to Michael Moles †2014 *1948 at 20:48 Dec-29-2009 .

zoom image
Hello Michael, Has the last version of the COBRA system the capability to be attached in a pipe to code weld joint? Taking account the unfavorable curvature of the code. As you can see in the attached image.

Happy New Year !!!!
    
 
 Reply 
 
Michael Moles †2014 *1948
, Joined ,
17:03 Jan-08-2010
Re: POD using Phased Arrays
In Reply to Carlos at 18:48 Dec-30-2009 .

zoom image
Yes, the COBRA can be dismantled and attached to the pipe, on one side only. See attached photo.

Legally, the codes (like ASME) require inspection from both sides of the weld if possible. The COBRA arrays/mechanics are 50 mm long, plus half the width of the weld. So, if your bend is sufficiently far from the weld, you could use the COBRA on both sides. If not, you should modify your Scan Plan to make sure you get 100% coverage on the far side of the weld (as per Code requirements).
    
 
 Reply 
 
massimo carminati
massimo carminati
20:33 Jan-08-2010
Re: POD using Phased Arrays
In Reply to Michael Moles †2014 *1948 at 17:03 Jan-08-2010 .

If case of one only side inspection, without weld cap accurate flat removal, how can you say you can address the far upper half weld part with favourable direction? In my opinion, no scan plan review can overcome this problem, without flush grinding the cap.
This appear to me to be the main real problem of on site weld inspection of piping. In any case, on side PA is better than no recording at all. Hope this would raise the interest.

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
22:14 Jan-08-2010
Re: POD using Phased Arrays
In Reply to massimo carminati at 20:33 Jan-08-2010 .

Massimo:
You are correct in noting that cap removal may be required. But this is in accord with ASME as well. Section V Art. 4...T-471.5 explains that the surface shall be prepared as needed if the weld or base metal interfers with the examination. T-472.2 goes on to further explain that welds that cannot be fully examined from two directions are considered areas of restricted access and these shall be noted in the report.
One sided access is not as good as two but I have seen large non-fusion defects on the one side that was accessible being detected by UT after RT had cleared the weld as having no defects at all.

    
 
 Reply 
 
Michael Moles †2014 *1948
, Joined ,
14:12 Jan-11-2010
Re: POD using Phased Arrays
In Reply to massimo carminati at 20:33 Jan-08-2010 .

If you do grind the caps, you can run on top of them. If so, you should be able to adapt your Scan Plan and beams to get excellent coverage from both sides, depending on the dimensions available. If you can't grind the caps, then good coverage will be a problem ... ageeed, but it may be the best that you can do.

    
 
 Reply 
 

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