where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -
1065 views
Technical Discussions
Md. Mahabubur Rahman
Engineering,
Chevron , Bangladesh, Joined Oct 2015, 1

Md. Mahabubur Rahman

Engineering,
Chevron ,
Bangladesh,
Joined Oct 2015
1
04:23 Jul-29-2019
AUT vs PAUT Hydroform

Dear All,

We have performed (Raptor) AUT on Vessel shell (Nominal 22.50mm) and got one pin point location Around 17.35mm. Later we performed PAUT Hydro form (Omni scan MX2) in same location but didn't get that pin point location where we got 17.35mm by AUT. In PAUT we got thickness around 22.50mm which is close to the nominal.

My question-01: which data is reliable AUT or PAUT ?
Question-02: By using which technic we can get the actual & reliable data ?

Regards,
Md. Mahabubur Rahman

 
 Reply 
 
Levi
R & D,
Dacon Inspection Technologies, Thailand, Joined Jan 2017, 48

Levi

R & D,
Dacon Inspection Technologies,
Thailand,
Joined Jan 2017
48
10:35 Jul-29-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

Hi Md. Mahabubur Rahman,
It is possible to see a defect with conventional AUT (single or duel element transducers) and miss it with PAUT.

Lets consider the differences in the two inspections:

AUT: One transducer size, with flat focusing being most common.

PAUT: Variable transducer size, with focusing.

Now lets consider the following scenario:

AUT: An inspection with a 6mm diameter Dual element transducer (14.13mm^2 active area) with no focusing is performed on a vessel with a nominal thickness of 22.5mm. The gain required to set the first backwall at reference may be quiet high, as this is a small transducer. This will make the chances of finding small inclusions, pin holes, and other small indications likely.

PAUT: A 64 channel probe is used with an aperture size of 12 elements. At 1mm pitch, this creates a 12mm X 7mm probe (84mm^2) or 594% larger square area than the duel element 6mm diameter probe. The backwall of the part will give a much higher amplitude signal than a point indication, as the gain required for reference will be low. Add to this the extra variable of focusing (in or out of focus ) and it may be even more difficult to see a point indication.

Please note that I am not saying that traditional AUT is more sensitive or more likely to find small indication. This is dependent on many variables and I beleive when PAUT is performed in optimal settings it has many advantages in comparison to traditional probes.

To directly answer your questions:

"My question-01: which data is reliable AUT or PAUT ?"

[Levi]- It is not possible to answer this without knowing the parameters of your inspection.

"Question-02: By using which technic we can get the actual & reliable data ?"

[Levi]- Both techniques can give you accurate and reliable data.


 
 Reply 
 
bommakanti srinivas
bommakanti srinivas
11:26 Jul-29-2019
Re: AUT vs PAUT Hydroform
In Reply to Levi at 10:35 Jul-29-2019 .

mr. mmahabaubur rehman

please clarify my doubt

you said 6 mm size means i hope it is high frequency. naturally for high frequency penetration will be less and hence higher gain may be required to produce an echo of appreciable amplitude

but with high frequency s sensitivity increases how come we miss small flaws?


 
 Reply 
 
Martin
R & D,
Fraunhofer-Institute for Nondestructive Testing (IZFP), Germany, Joined Nov 2016, 4

Martin

R & D,
Fraunhofer-Institute for Nondestructive Testing (IZFP),
Germany,
Joined Nov 2016
4
13:25 Jul-29-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

Hi,

PAUT is a little bit more complex. Many things can go wong here in parameterization. With the wrong parameters you can supress even big flaws.

An effect for flaw detection is also the probe frequency, is there a difference in both systems.
As Levi mentioned before without the testing parameters a good answer is not possible.

Have you a reference standard with knowing flaws that you can use for calibration your systems? Or can you test both system with the used inspection parameter with the standard?

Kind regards
Martin

 
 Reply 
 
Edward Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1286

Edward Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1286
14:13 Jul-29-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

Md. Some clarification is required to adequately answer your question. You state that you compared detection from a Raptor AUT system and a phased array Omniscan MX2. Although AUT abbreviates Automated Ultrasonic Testing, in most pipeline applications AUT has come to mean the inspection of pipeline girthwelds (usually using zonal discrimination) using a line scan parallel to the weld axis with beams directed at specified angles to provide a maximum echo from a FBH angled at the bevel angle. So do you mean that you compared a zonal system to a non-zonal system? The only "Raptor" ultrasonic system I could find referenced online was a small unit that addresses only 2 monoelement probes. Phased-array systems are now usually used for AUT because a single PA probe can be used to direct the required beams at all the zonal targets.
You provided no details on the angles and targets used so it is difficult to provide accurate rationale.

You referred to a "vessel shell" so it seems you are not inspecting pipeline girth welds by AUT as most would associate the term AUT. Therefore, it may be possible that the "Raptor" system was using a fixed angle that happened to be directed at the "pin point" flaw at the ideal angle to provide the ideal response and the Omniscan setup was using a sectorial scan scanning at a fixed standoff. Then it is possible that the PAUT angle that swept through the volume where the "pin point" flaw had been detected was not using the exact same angle and pulse shape that the Raptor system detected it.
I suspect that there will be other indications where the PAUT system will detect flaws above the evaluation threshold that the Raptor system did not detect.

Both your questions ask about the reliability of the results. If you are truly worried about reliability of an NDT technique or system you should set up a reliability test. A good set of reliability assessments is provided in DNV OS F101 in Appendix E.
But if you are actually worried about "reliability" then you should also consider using fracture mechanics acceptance criteria and determine the critical flaw size and assess the sizing accuracy of the techniques as well as their probability of detection. (you may then find that your "pin point" flaw is not very significant).

 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 218

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
218
14:36 Jul-29-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

What scanner was used with the Raptor? I assume you used the NDT Systems Raptor here:

https://www.ndtsystems.com/raptor

… but not sure what scanner you used.

Was the pinpoint reading with the Raptor repeatable, or was it just a single scan and you found the point while reviewing the data later? Corrosion scanning and data analysis can be notoriously noisy. The closer you look, the more you will find. If there was no trending around the low point (adjacent pixels showing some wall loss), then I would tend to think it was simply an inclusion or a rogue water bubble.

What was your index and scan resolutions for both systems? What aperture did you use with the HydroFORM? Did you focus (I hope not) with the HydroFORM?

 
 Reply 
 
Kenneth Shane Walton
Consultant,
USA, Joined Feb 2011, 7

Kenneth Shane Walton

Consultant,
USA,
Joined Feb 2011
7
16:36 Jul-31-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

There are many variables that could have caused your issue. Could a small inclusion or lamination or some other signal like bubbles or electronic noise have crossed your gate? Was the automated corrosion mapping system using an edge/ threshold gate while the hydroform was using a max peak gate? Did the technician truly analyze the data or did he just take whatever reading the software gave? Was an A-scan with the minimum area checked out to ensure it was a valid indication? Was any manual UT prove up performed? What sort of focusing and apertures/ diameters were involved?
Automated detection with any UT system, paut or conventional, relies on gates to measure signals that cross them, and many signals can cross our gates, giving many false indications. It's up to the operator to analyze the data and rule out relevant vs non- relevant indications, just as with any other NDE technique. Conventional UT and PAUT can be both extremely accurate and extremely inaccurate. It depends on many variables, one of the biggest being the skill of the operator.

 
 Reply 
 
Steve Prince
NDT Inspector,
Bureau Veritas Asset Integrity & Reliability Services, Australia, Joined Aug 2005, 6

Steve Prince

NDT Inspector,
Bureau Veritas Asset Integrity & Reliability Services,
Australia,
Joined Aug 2005
6
00:01 Nov-07-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

Dear Md. Mahabubur Rahman,

I would be interested to know if you used a twin-crystal normal incidence transducer with the Raptor, and if the vessel that your were testing was susceptible to microbiological induced corrosion attack (MIC), which is a distinct possibility as I note that you work for Chevron.

If both of the above are true, then the Raptor may have detected a single MIC pit of needle like form.

MIC pits generally offer very little or no reflective surface when testing at normal incidence, which HydroFORM does when used as a zero degrees linear scan.

A twin-crystal transducer transmits and receives at slightly off normal incidence angles and can often reflect off the the side face of MIC pits. This is the benefit of the dual linear array probes for corrosion assessment.

 
 Reply 
 
John O’Brien
Consultant, -
Chevron ETC , USA, Joined Jan 2000, 280

John O’Brien

Consultant, -
Chevron ETC ,
USA,
Joined Jan 2000
280
03:56 Nov-08-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

I would recommend you send this to the Chevron ETC NDE experts Mseiwald@chevron.com where you will get a Chevron expert opinion and assistance. In each case did you store the ascan data that the experts can review.

 
 Reply 
 
Miguel Diaz
Director, Inspector, Professor, Training
Integrity & NDT Solutions , Colombia, Joined Aug 2015, 2

Miguel Diaz

Director, Inspector, Professor, Training
Integrity & NDT Solutions ,
Colombia,
Joined Aug 2015
2
14:17 Nov-09-2019
Re: AUT vs PAUT Hydroform
In Reply to Md. Mahabubur Rahman at 04:23 Jul-29-2019 (Opening).

Hola, espero que al traducir puedas tener un concepto que aclare tus dudas.

Como todo ensayo no destructivo, es primordial conocer el tipo de discontinuidad que queremos detectar y estudiar, y hasta que punto queremos estudiarla... Si solo es detectarla o si queremos dimensionar su altura, longitud etc.

Dicho lo anterior, la MIC tiene una morfología que no beneficia los resultados del ultrasonido por haz normal, sea convencional o Paut, puede observar 2 cosas, una, que se pierda la señal de fondo, lo que ya es un indicativo de que hay algo en el material y segundo, si es muy pequeño una atenuación en el eco de fondo pero sin dar un resultado que indique la presencia de la discontinuidad.

Por el otro lado, la técnica dual, que usaste con el Raptor, puede llegar a interactuar con la discontinuidad por focalizar diferente y porque no tiene zona muerta ni campo cercano, toda la energía interactua con la discontinuidad y hay mejor reflexión hacia el elemento receptor que en muchos casos se fabrica de un piezoelectro de mejores características para la recepción de señales de menor amplitud.

En cuanto a la diferencia de espesor pueden estar pasando 2 cosas, la primera que la calibración de dual no esté en el rango adecuado y la segunda que la corrosión tenga su inicio a 17.5mm

La técnica que mejoraría el registro es el Dual lineal array en el caso de querer mezclar lo mejor de ambas técnicas y si quieren caracterizar muy bien su corrosión, prueba con barridos en la zona con tofd, tomando barridos desde zonas sanas hacia las zonas con corrosión para tener una imagen clara de la pérdida

 
 Reply 
 

Product Spotlight

Sci Aps Z-Series Portable Handheld Analysers

The world’s only handheld analyzer that measures carbon content in stainless (yes even L-grades),s
...
teels, and cast irons. Also accepted for low Si analysis for sulfidic corrosion analysis, and is widely used in the power industry for Cr analysis, for flow accelerated corrosion applications.
>

NEW - TD Focus-ScanRX

The NEW Next Generation Advanced UT platform, TD Focus ScanRX - Also available as a card stack solut
...
ion. Key Improvements 1. Data acquisition is significantly faster than current design 2. Better aesthetic – closely aligns with HandyScan RX 3. Improved IP rating (Target IP66) 4. Ruggedized housing 5. Connectors are protected from impact and ingress 6. Integrated stand and separate retractable handle easy to keep clean) 7. Touchscreen with ruggedized display glass 8. 3-Axis encoder input
>

Ultrasonic Testing Immersion Tanks with Unmatched Scanning Features

TecScan’s non-destructive testing Ultrasonic Immersion Tanks & scanners are designed for high pe
...
rformance and demanding NDT testing applications. Our Scan3D™ line of High Precision Immersion Tanks are specifically designed for automated ultrasonic testing of complex composites parts used in aerospace and industrial applications.
>

NDT.net launches mobile-friendly design

NDT.net has revamped its website providing a mobile-friendly design.The front page received a comp
...
letely new design and all other sections are now reacting responsively on mobile devices. This has been a major step to make our website more user- friendly.
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window