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Technical Discussions
Aadesh Karmjit
Aadesh Karmjit
18:42 Feb-06-2020
PA Evaluation

Hello.
Kinde request for help.
I have to scan one-sided welds on flanges. My question, do you have any tips for the evaluation of indications behind the axis, which can give an echo behind the weld or on the border of fusion? How do I approach this, I have double scans made for two indexes but only from one side. I never done this before. Thank You

 
 Reply 
 
Anmol Birting
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 785

Anmol Birting

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
785
12:59 Feb-07-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 18:42 Feb-06-2020 (Opening).

Then you should remove weld cap to scan the opposite side

 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 227

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
227
21:40 Feb-07-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 18:42 Feb-06-2020 (Opening).

Anmol's suggestion is the optimum solution. But if this is not possible, you may be required to do a performance demonstration on flawed samples.

 
 Reply 
 
Aadesh Karmjit
Aadesh Karmjit
14:40 Feb-08-2020
Re: PA Evaluation
In Reply to Paul Holloway at 21:40 Feb-07-2020 .

Hi,
there is no possibility to remove cap. I made simple sample on weld 22.2 mm thick by grinder. I made simple cut on one side of root and cap and I scaned from two offset, from one side. All of echos I had was in weld overlay. Scans wich I have to evaluate have echos in HAZ or on weld line behinde the CL. I was thinking about not precise index offset and why I dont see anythink at 3 halskip at far offset?
thx

 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 227

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
227
16:07 Feb-08-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 14:40 Feb-08-2020 .

zoom image



Scanning in the 3rd leg is tricky, usually only necessary on really thin welds if they refuse to take the cap off. You have to make sure you have no water or couplant on the surface in front of the probe, and be aware that part of the beam is entering the cap, even if the center of the beam isn't.

Are you really doing a 3rd leg inspection on a 22mm weld? Even with a V-prep at 37.5 degrees, the cap shouldn't be more than 50 mm wide (and that's with some forgiveness for extra passes). You should be able to get full coverage with just 2 standoffs (see image).

What is the weld geometry according to the WPS? I have run into this before with simple 9.5 mm welds where the welder superseded the WPS and thought they were being "helpful" by adding extra passes and making a prettier cap. Ultimately it prevented us from being able to perform PAUT, which in retrospect I think was probably the welder's plan all along. They ended up doing RT instead.

You could also try scanning from the flange. There's a bit of a tilt and you'd have to plan it out but it works. You might not be able to encode but your procedure may permit manual UT as a supplementary technique.
 
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Aadesh Karmjit
Aadesh Karmjit
16:36 Feb-08-2020
Re: PA Evaluation
In Reply to Paul Holloway at 16:07 Feb-08-2020 .

zoom image



zoom image



It's misunderstood, I dont wan evaluate third skip, I just read about this approach on evaluation. Third skip should be perpendicular to other side of V prep and thats why expected some reflections. My sample 22.2 mm thick is only my sample which I cut for me. Other things are scans which I need to evaluate. Both my sample and scans are on V prep. I paste type of echo (from both distances) which is disturbing me, its close to fusion line but out of weld. I though we should evalutae this region but also its out of weld.
 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 227

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
227
16:54 Feb-08-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 16:36 Feb-08-2020 .

Few things:

1) Be very careful when looking at the 3rd leg. It's valid only if it's the portion of the beam which has not yet reflected off any weld surface. You may very well be looking at something which has bounced off the cap (so the signal is therefore irrelevant)

2) It could be that your beam is hitting the root and what you are seeing is a reflection bouncing up to the cap, or a mode conversion, or a combination.

3) Can you share your scan plan?

4) The images look like you are using a 16-element aperture, but the standoff looks like you might be using a large 32 or 64 element probe. What size of probe are you using? I don't find the size of the A2 or A12 style probe very useful in many cases unless the welds are huge. I get most mileage out of the A10 for small stuff, A31 for midrange, and maybe the A2/A12 or A32 for really big stuff. I find it best to use the lower angles as much as possible. The effective aperture decreases at higher angles and makes the "red banana" look all stretched out (in layman's terms!)

5) Is your group set up to focus?

 
 Reply 
 
Aadesh Karmjit
Aadesh Karmjit
18:13 Feb-08-2020
Re: PA Evaluation
In Reply to Paul Holloway at 16:54 Feb-08-2020 .

zoom image



Scan plan above or it's more scan positions. Weld is 22 thick and angle bevel 30 degree. You are right it's 16 element probe but I have no info about focusing I assume not. Scan offsets are 40 and 70 mm.
How should I consider echos out of wled overlay, as imperfection or geometry or fake echo? What do You mean that effective apperture is decreasing, its about biger beam spread and beam size hence the reflection will be biger as You wrote "red banana" look all stretched out"? First I would like to know from what I am struglle, is there any sence consider it as a defect. Later I can try to size this. Its easy when I have echos inside weld overlay, I treat it like defect but out of overlay...
 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 227

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
227
18:28 Feb-08-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 18:13 Feb-08-2020 .

With the scan plans you've presented, I would not look at anything in the 3rd leg. The sound path is too long and there is no advantage.

In regards to effective aperture, the 70 degree beam looks uglier than the 45 degree because as the beam angle increases the aperture decreases. And when aperture decreases, beam spread increases. There's a good illustration in this paper: https://www.ndt.net/article/ndtnet/papers/VariableAperture-Phased-array-NDT.net.pdf

Again, which probe are you using? Can you not get any closer to the weld toe?

 
 Reply 
 
Aadesh Karmjit
Aadesh Karmjit
18:47 Feb-08-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 18:13 Feb-08-2020 .

The probe is SA105L16 with SA10N55S wedge, and excuse me I got info about focusing, It was unfocused.
No other positions no other posibilities - it's just scan to interpreate.
Ok I agree with third skip, there is no at scan position and it's to hard to interpretation, ther is no sence to continue this theard.
Thanks for publication looks interesting.

 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 227

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
227
19:47 Feb-08-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 18:47 Feb-08-2020 .

Note for next time, you should always try to hit the root with the lowest angles possible. The closest scan offset was 40 mm, and judging by the scan plan it probably could have been done at 25mm.

The most problems are at the root, and it's awful to try and make heads or tails out of long, fuzzy root signals with nothing but a few high angles at the upper edge of the S-scan.

Perhaps a 3rd standoff would have helped in this case.

Best regards,
Psul

 
 Reply 
 
Aadesh Karmjit
Aadesh Karmjit
21:24 Feb-08-2020
Re: PA Evaluation
In Reply to Paul Holloway at 19:47 Feb-08-2020 .

What i remember from conventional UT (here evaluation will be from amp.) for LOP best angle was 70, for side LOF better was 60, so I think You mean about one side acces scanning or this is general rule? Tomorow I will make test at my sample.
Of course third scan would give us more info but now it's impossible. My idea it's to evaluate, behinde the CL, only what I see inside overlay of weld or what is on fusion line or strict HAZ. Other way, farther signals, are to guess. Maybe its no good approache but I have no better idea.
Thanks

 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 227

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
227
22:18 Feb-08-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 21:24 Feb-08-2020 .

There is really no "best angle". That being said, for notch-like reflectors you will lose a lot of sound as the beam nears 60 degrees (30 deg. incident on vertical reflector) due to mode conversion. But real weld flaws are fractal and irregular, so what makes sense in a text book will show up a lot different in the real world.

You could say the corner trap on a crack will show up best at 45 deg, but what if the crack is tilted? You would only know that 45 deg is best if you know the crack is straight up and down. And when we're inspecting welds, we're (usually) going in blind. It could be tilted towards you, away from you, or straight up and down. You just don't know.

With encoded PAUT, it's always best to try and hit the areas of interest with the center of the sectorial, so if you pick anything up you'll at least have room on either side (angle +/-) to watch the signal take form. Of course this is rarely the case on thinner welds where you can just barely hit the root with the highest angles, but we do the best we can with the laws of physics

 
 Reply 
 
Ali
NDT Inspector,
Iran, Joined Mar 2013, 109

Ali

NDT Inspector,
Iran,
Joined Mar 2013
109
18:00 Feb-13-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 16:36 Feb-08-2020 .

Aandesh,
Paul is right about the scan plan.I have some questions more.
Is the PAUT done during construction or in servise ?
Have you checked internal surface of the pipe ?

 
 Reply 
 
Gokul Hrishikesh
Consultant, AUT Specialist
India, Joined Jul 2013, 75

Gokul Hrishikesh

Consultant, AUT Specialist
India,
Joined Jul 2013
75
19:06 Feb-13-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 18:42 Feb-06-2020 (Opening).

Hi,

Considering the fact that the cap could not be flush ground.

TOFD could make your life easy.
Is there no chance to add a pair of TOFD.
TOFD will not see upper part, but PAUT will get some corner trap reflections for defects closer to or the one breaking to OD surface.

You cannot measure accurate depth with TOFD since there is an inclined surface but the POD will shoot upwards.

You could not do a 100% inspection without getting that cap flushed.
Any way TOFD can add some power to your inspection.

Kind Regards,
Gokul

 
 Reply 
 
Andrew crawford
Andrew crawford
05:20 Feb-18-2020
Re: PA Evaluation
In Reply to Aadesh Karmjit at 18:42 Feb-06-2020 (Opening).

I have used TFM on these configurations and would use TTT and mode conversion to give some clarity.

 
 Reply 
 

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