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Technical Discussions
Hamid Reza
,
Canada, Joined Oct 2016, 68

Hamid Reza

,
Canada,
Joined Oct 2016
68
11:48 Nov-04-2016
Phased Array vs Radiography in the long term.

Dear Friends,

I attended a seminar held by TWI in our region about Advanced NDT methods in Oil & Gas and Aerospace industries. The speaker was a professional in various NDT methods with more than 30 years background as a Chief Technician (Airframe and NDT) in UK royal air force and another 10 years as an NDT project manager, advanced NDT technical product Specialist, Advanced market manager and principal project leader at companies such as Olympus, TWI, Ashtead and UK MoD. He is a very nice guy!

He mainly covered PAUT (Phased Array UT) and ECA (Eddy Current Array). During the talk, it was drummed into the audience that PAUT is not a potential rival for Radiography anymore, and it has already surpassed in capabilities. He mentioned that many contractors have already phased out radiography and have started using PAUT and they are very happy about their decision. Also C-Scan is a form of permanent record that is comparable to radiography and offers a permanent record.

He also mentioned that sometimes customers and contractors switch back to radiography because they do not want to see the flaws. They think radiography is better because it is not that sensitive to find small flaws. I can understand why they make those decisions.

I searched NDT.net and I didn't find any thread that directly discusses this. So I thought it was a good idea to start this thread and invite you professionals to discuss the future of radiography and PAUT in oil&gas and aerospace in the next 30 years.

I would be thankful if you could share your ideas.

    
 
 Reply 
 
James Scalf
NDT Inspector,
Royal Canadian Air Force, Canada, Joined Oct 2012, 273

James Scalf

NDT Inspector,
Royal Canadian Air Force,
Canada,
Joined Oct 2012
273
13:02 Nov-04-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Hamid Reza at 11:48 Nov-04-2016 (Opening).

Eager,

You ask if Phased Array Ultrasonic Technology will make Radiography obsolete in the next 30 years. I don’t think it will as there will always be structures and inspection requirements such that the application of Ultrasonics is just not conducive to achieving the desired results. I grant you that PAUT is a very powerful tool in the NDT Arsenal however it still has the same limitation that conventional UT has regarding voids, air gaps and attenuation. Therefore I don’t see RT disappearing completely from the requirements for oil and gas, power generation and/or aerospace.

What I do see happening and what may be phased out completely over the next 30 years is the use of conventional UT as the transducers for PAUT get smaller and smaller (this added with guided wave technology) as well the use of conventional film radiography. Digital Radiography is faster, requires less energy for excitation and produces repeatable and reliable results. This coupled with the fact that most of the systems now available are DICONDE Certified means that they can be used for almost all applications. The advantage to Digital RT to the companies is that over all the costs are lower you can by phosphor imaging plates in most cases for less cost than a box of film and if the plate is handled correctly you can get as much as 1000 images from a plate which would be 10 boxes of film. You don’t have to worry about chemical disposal, raw and/or processed film storage, the images can be saved and sent as high resolution JPEGs and the exposure times are less.

As far as PAUT, given that you get better coverage, can focus the beam to specific points in the part under inspection, and make it fully automated I can see this taking over most if not all conventional UT inspections in time.

The same applies to Eddy Current Array technology. I think what has limited the growth in the application of these technologies is the cost and added training required to fully understand and apply the technology. As with anything new though, the cost of the technology is coming down as more companies by into the systems so we will see more and more use of them as the costs get lower. A side effect of this will be that broader use will give the technologies more exposure to more clients which in turn will also drive the demand for their use.

So do I think RT will be phased out by PAUT or other technologies? No I don’t however I do think the conventional systems and applications we are used to seeing from the 70’s through the 2000’s will be replaced by these modern technologies.
Cheers…

James

    
 
 Reply 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1096

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
13:09 Nov-04-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Hamid Reza at 11:48 Nov-04-2016 (Opening).

Eager Beaver

AUT (Automated Ultrasonic Testing) with zonal discrimination has taken over from RT for inspection of pipeline welds. For long sections of welded pipeline it is worth the expense of engaging professional consultants to calculate tolerable defect height against length of planar flaws in an Engineering Critical Assessment (ECA) approach to formulate alternative acceptance criteria to the standard RT approach as used in API 1104 'Pipeline Welding'.

The abiliıty of AUT to detect through-thickness flaws and with acceptable accuracy (+/- 1mm) to determine their height is a considerable advantage particularly for narrow-gap auto-GMAW welds is proven and well-documented through many trials.

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1266

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1266
22:00 Nov-04-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Hamid Reza at 11:48 Nov-04-2016 (Opening).

Eager,
I disagree with your premise.

Your thread seems based on a notion that PAUT has surpassed RT capabilities and will ultimately replace RT. This presents NDT methods as being in a competition. That is clearly not the case. NDT is simply your "toolbox" and you would typically pull out the tool appropriate for a particular job. And sometimes you even need more than one tool to do a job well.

The goal of NDT is not always to find all flaws in a component. Sometimes it is merely to spot check a process. Depending on the process, one may find one NDT method preferable over another (for cost, type of flaws being sought or the ease of application). In some cases the NDT is specified as a code or specification requirement. In some cases the goal of an examination is to obtain the best measurement of a condition that can be achieved. In that case we may end up using 3 or 4 NDT methods and try to make a judgement as to which of the measurements seemed to be the most reliable.

In the case that Nigel described where zonal discrimination is used on new pipeline construction, it is merely to provide an alternative to RT. When the acceptance criteria is based on workmanship instead of fracture mechanics, the function of NDT is to punish welders for not paying attention and has nothing to do with size or number of flaws they put in the joints. Either volumetric method (UT or RT) can provide this function, and you see Codes like ASME B31.3 making provision for either to be used.

And why only consider RT and PAUT as the "competing methods"? Neither is particularly great at locating randomly oriented surface flaws. For that we prefer MPI, LPI and eddy current. I have found far more cracks using MPI than I ever did using PAUT.
Why do you think PAUT is not the preferred tool for ultrasonic newly pilgered small diameter heat-exchanger tube inspection? Because spinning the tubes past an array of individual spot or line-focussed probes is far more practical, and it is not a function that RT is suitable for.

Irregular-shaped forgings, castings and now 3D printing (additive manufacturing) of intricate critical aerospace components can be virtually impossible to place a UT probe on (either mono-element or PAUT) or totally impossible to get a useful UT beam into the material due to crystal structure and anisotropy. These items can still require volumetric examination and radiography using gamma, X-ray or microCT-X-ray is the best option.

RT and PAUT are not in a competition where one is eventually going to replace the other. Looking back over the past decades I have seen new technologies develop and become popular and some have found niches that were previously the sole domain of older technologies. But I have not seen any of the NDT "methods" disappear. Indeed, some of the technologies used in the methods may no longer be used (e.g. you will not likely find a UT instrument with a cathode ray tube in it, you are not likely to find anyone using the old "Probe-a-log" as an eddy current instrument and quartz probes with the spring-loaded ground-pin are hard to find even in NDT museums).

No doubt the "nice guy from TWI" was presenting his case in favour of PAUT because his presentation to the audience was about PAUT and ECArraays. However, you will note that in the past 10 years TWI has not dropped any of its RT training courses nor its RT certifications in the CSWIP scheme.

    
 
 Reply 
 
Shane Feder
, Quality Co-ordinator (SubSea)
Thailand, Joined Dec 2014, 86

Shane Feder

, Quality Co-ordinator (SubSea)
Thailand,
Joined Dec 2014
86
13:50 Nov-05-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Ed Ginzel at 22:00 Nov-04-2016 .

Whatever process is used the code committees whether they be ASME or BS/EN need to get their act together.
I was recently on a Sub-Sea project with large bore, heavy wall SDSS piping.
10 x circumferential welds were radiographed to B31.3 NFS and all passed.
Those same 10 were manually UTed and 3 x failed.
A proposal was but forward to PAUT but the removal of reinforcement was going to be time consuming and not cost effective so was canned.
Would have probably been more than 3 x failures if PAUT was involved.

If any of you are involved in B31.3 work have a look at the difference between the UT acceptance criteria and the RT acceptance criteria - they are chalk and cheese.
I put in a Request for Change to the B31.3 committee over a year ago but it came to nothing.
Regards,
Shane

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1266

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1266
19:04 Nov-05-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Shane Feder at 13:50 Nov-05-2016 .

Shane, I think your concern is separate from the thread topic of one NDT technology eclipsing another in the next few years. .
Acceptance criteria, when based on workmanship, are arbitrary. For several years I was tasked with identifying detection achieved by each of UT and RT and separately I identified rejections achieved by each. Often (but not always) both could achieve similar detection. More often, the items rejected by each were different. In the end it was agreed that EITHER RT or UT was suitable for the purpose intended (i.e. to provide a check against careless welders). When the goal of the acceptance criteria is to ensure fitness for purpose then different details must be considered for the NDT methods used.

    
 
 Reply 
 
neil cox
United Kingdom, Joined Sep 2016, 8

neil cox

United Kingdom,
Joined Sep 2016
8
17:20 Nov-06-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Ed Ginzel at 19:04 Nov-05-2016 .

Tofd is a far superior method for detecting smaller discontinuities in welds than PAUT

But it's never about what system is the best, because manufacturors will try and push the least sensitive system they can to it's customers to have a lower repair rate and less fuss and less questions asked about quality

This is the thing people just never seem to get with NDT and inspection, it's always a compromise

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1266

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1266
18:53 Nov-06-2016
Re: Phased Array vs Radiography in the long term.
In Reply to neil cox at 17:20 Nov-06-2016 .

Neil, I do not think that your blanket statement concerning TOFD is accurate. TOFD is merely a forward scatter ultrasonic technique. In order to detect the diffraction signals in forward direction one tends to use significantly more amplifier gain than is used for spceular reflections typically associated with pulse-echo (either phased-array generated or mono-element). Typically there is about 20-30dB more gain used in TOFD compared to pulse-echo tests where sensitivity is based on the response of a reflection from a Side Drilled Hole. However, it is just as feasible to collect tip diffracted signals that are backscattered. This is typically used for tip sizing (PAUT or mono-element) and some of the qualified weld examination procedures used in the nuclear industry.
It is not always as you posted that "manufacturors will try and push the least sensitive system they can". Using excessive sensitivity will usually result in false calls (e.g. identifying grain boundaries as defects). Unnecessary repairs can compromise a material's intended function by changing its mechanical properties.
Beaver's post suggested that the new PAUT technology would replace the old RT method. A similar suggestion was made of TOFD over 40 years ago when it was introduced...TOFD has become just another tool in the NDT toolbox. And as other tools, it has its place and its limitations.

    
 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 738

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
738
04:03 Nov-08-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Hamid Reza at 11:48 Nov-04-2016 (Opening).

PAUT is good but not a magic bullet. I have seen PAUT inspectors making blunders - missing flaws or calling flaws when there is no flaw. PAUT is only effective if the process is qualified and there is oversight of the inspection.
The main advantage of RT is that client has easy access to review film with just a simple viewer. PAUT companies do provide UT data but reading such data requires special software and some level of training to see the various scans (B-, C-, D- etc).
So bottom line is keep an eye on what is going on with PAUT or RT.

    
 
 Reply 
 
Dr. Uwe Zscherpel
Director,
BAM Berlin, Germany, Joined Jan 2010, 80

Dr. Uwe Zscherpel

Director,
BAM Berlin,
Germany,
Joined Jan 2010
80
09:31 Nov-08-2016
Re: Phased Array vs Radiography in the long term.
In Reply to Hamid Reza at 11:48 Nov-04-2016 (Opening).

Dear Eager,
The question if any UT testing method will replace in future RT is discussed since the beginning of UT testing after Second WW. But up today the NDT film market on a worldwide scale is still growing and since about 20 years we also have digital industrial radiology, which even improved the limits of detectibility of the old film radiography by at least another order in contrast sensitivity. RT has a tradition of about 100 years is industrial usage.
In classical shipyards industry manual UT testing of the thin walled welds was replaced very successfully by digital radiography using battery powered equipment.
So in my understanding any forecast that UT (or PAUT) will replace RT completely is just non-serious. UT and RT have totally different interaction physics and are both volumetric testing methods for internal material flaws. Therefore each method has there own advantages and disadvantages and will also be used in the next 100 years!
Greetings
Uwe Z.

    
 
 Reply 
 

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