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Hi-Spec Systems
we are specialised in the design, development and manufacture of Phased Array and Time-of-Flight Diffraction (ToFD) ultrasonic inspection systems.
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Technical Discussions
behrouz
NDT Inspector,
Iran, Joined Oct 2012, 12

behrouz

NDT Inspector,
Iran,
Joined Oct 2012
12
09:51 Feb-19-2013
TOFD indication
zoom image

TOFD Indication

Dear All,

What kind of indication could be? Welding method GMAW, 20.6 WT, J bevel configuration.(result capture by AUT PipeWIZARD)
Length 54mm, phased array and mapping channels show weak signal.
Thanks

 
 Reply 
 
Bob
Bob
12:41 Feb-19-2013
Re: TOFD indication
In Reply to behrouz at 09:51 Feb-19-2013 (Opening).

Is this a repaired area? I have seen similar indications when inspecting weld repairs on J bevels. My theory is that it a function of the shape of the excavated area because the length usually corresponds to the excavation length. Sometimes it is both sides of the excavation as well. Is it a location of weld stop starts if it is not a repaired area? I can't think of any other explanation possible but I would like to know if anyone has has some ideas. If you really want to know and it is not a critical weld then macro section it. I have never seen a macro of an indication like this and it is the only way to know for sure.

 
 Reply 
 
Patrick Bergalonne
R & D, Engineering/services
Comex Nucleaire, France, Joined Feb 2007, 7

Patrick Bergalonne

R & D, Engineering/services
Comex Nucleaire,
France,
Joined Feb 2007
7
13:11 Feb-19-2013
Re: TOFD indication
In Reply to behrouz at 09:51 Feb-19-2013 (Opening).

Hi

it's look like surface breacking defect, see the lateral wavejuste before the defect signal.
Best regards
Patrick

 
 Reply 
 
Mal Hill
United Kingdom, Joined Jun 2012, 14

Mal Hill

United Kingdom,
Joined Jun 2012
14
13:42 Feb-19-2013
Re: TOFD indication
In Reply to Patrick Bergalonne at 13:11 Feb-19-2013 .

We had Transverse cracking indications like this in on TOFD top scans in thick sectioned sub arc welding-Have you manually scanned the area Longitudinally and transversely (with a 4mhz small 45 degree on a smooth cap they were detectable)

 
 Reply 
 
behrouz
NDT Inspector,
Iran, Joined Oct 2012, 12

behrouz

NDT Inspector,
Iran,
Joined Oct 2012
12
07:58 Feb-20-2013
Re: TOFD indication
In Reply to Mal Hill at 13:42 Feb-19-2013 .

Guys

It is not the repair area, we did repair on that anyway, It wasn’t happen just one time and we have seen this indication 4 or 5 times , we had transverse crack detection and we are sure it is not the crack but it is open to surface and possible to see by MPI.
We are looking to case of the indication when we have automated welding! I mean we have 4 stations to complete a weld and stop-start point is different.

 
 Reply 
 
Bob
Bob
10:39 Feb-20-2013
Re: TOFD indication
In Reply to behrouz at 07:58 Feb-20-2013 .

Is this indication usually at the same place in the weld? 12 oclock , 9 oclock etc? Are you using tiger torches instead of induction heating for the preheat?

Another theory I had is that localized uneven heating would cause the metal to be cooler than the rest of the metal so it.

I think it is caused after the root pass by the next welders stop start. the indication is then welded over and it travels up with the welding until it reaches the surface. I believe it is an overgrinding or lack of grinding caused by the welder at the stop starts.

This is just an opinion while seeing these indications when doing AUT and trying to figure out the problem. I think that the welders do not see the indication that is present (or do not care) to grind their stop starts in a high production environment.

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1300

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1300
19:30 Feb-21-2013
Re: TOFD indication
In Reply to behrouz at 09:51 Feb-19-2013 (Opening).

zoom image



Behrouz, I have seen similar indications in TOFD. The asymmetry suggests the flaw is at some angle. It may or may not actually be connected to the surface, it is difficult to say when the upper tip is lost in the lateral wave. I have made a quick Civa model of your setup and you can see that there is a similar (but not identical) pattern to a planar flaw with about a 10x10mm at 40° tilt located 3mm from the test surface. In the simulation we see a double arc from both the upper and lower tips. A typical AUT setup for a transverse flaw using 2 probes skewed at 45° in pitch-catch would probably not detect a signal from this orientation.
1
 
 Reply 
 

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