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- since 1996 -

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Technical Discussions
andre ribeiro
NDT Inspector,
Self Employed, Brazil, Joined Apr 2008, 18

andre ribeiro

NDT Inspector,
Self Employed,
Brazil,
Joined Apr 2008
18
22:53 Aug-24-2011
Ghost echo on wedge.

I have been experiencing a sort of a malfunction on 3 GE wedges, 0.5 - 3/4 - 1 inch.

There is a ghost signal appearing on the handy scan screen when tracing the TCG curve, but the strange thing is that when you damp the right upper corner with the finger, this ghost disappears.

The is no lack of couplant or bad attachment on the kit.

Other than those ones, the rest of the wedges aren´t showing the same problem.

Any thoughts about it?

Cheers.

 
 Reply 
 
P V SASTRY
R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D, India, Joined Jan 2003, 195

P V SASTRY

R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D,
India,
Joined Jan 2003
195
21:51 Aug-25-2011
Re: Ghost echo on wedge.
In Reply to andre ribeiro at 22:53 Aug-24-2011 (Opening).

Dear Ribeiro,
This can happen because of geometrical reflections from inside the wedge where your right upper side of the wedge is also taking part.
These ghost echoes also appear because of the surface waves generated because a particular wedge geometry is facilitating them. Particularly the probability of surface waves being generated is more with slightly worn out wedges and/or while testing on curved surfaces. Sometimes you find these so called ghost echoes travelling even when you are not moving the probe.
We also found a strange phenomena of these ghost echoes being generated after about 20 to 30 minutes of operation of the machine and it is somewhat related to pulse repletion setting (USIP-11 had a three position manual setting apart from the automated selection).
You did not specify where exactly you are damping – on the upper right hand corner of the wedge or the test surface near the right upper corner of the wedge.
If it is the first, most probably it is the geometrical reflections from inside the wedge. If it is the second case it may be due to surface wave generation.
Best wishes
P V SASTRY

 
 Reply 
 
andre
NDT Inspector,
Self Employed, Brazil, Joined Apr 2008, 18

andre

NDT Inspector,
Self Employed,
Brazil,
Joined Apr 2008
18
00:12 Aug-26-2011
Re: Ghost echo on wedge.
In Reply to andre ribeiro at 22:53 Aug-24-2011 (Opening).

I´ve made a mistake, the wedges ARE NOT GE .


Sorry about the mistake.

 
 Reply 
 
Lalit Mohan Kothari
Consultant, -
On ..IOCL and BARC(Bhabha Atomic Research Centre).etc, India, Joined Jan 2003, 128

Lalit Mohan Kothari

Consultant, -
On ..IOCL and BARC(Bhabha Atomic Research Centre).etc,
India,
Joined Jan 2003
128
09:00 Aug-26-2011
Re: Ghost echo on wedge.
In Reply to andre at 00:12 Aug-26-2011 .

Andre Ribeiro,
This is generally happened in old wedge and this is common in Indian Probe which is very good for those who want to research on UT as old probe particularly Indian where you have to prove Ist its angle as its index point and angle changes regularly and without proving angle you can not scan if do result may wary in calculation.
On this point Mr S K Shrma Gm in 1995 at ISGEC of Lloyd already discussed in Mukut Pipe in the year of 1995 and e s agree with me in all points .
To avoid this problem just put an obstacle on the front side of probe .
Thnks & Regard
Lalit Mohan Kothari

 
 Reply 
 
massimo carminati
Consultant, AUT specialist
IMG Ultrasuoni Srl, Italy, Joined Apr 2007, 691

massimo carminati

Consultant, AUT specialist
IMG Ultrasuoni Srl,
Italy,
Joined Apr 2007
691
14:32 Aug-31-2011
Re: Ghost echo on wedge.
In Reply to Lalit Mohan Kothari at 09:00 Aug-26-2011 .

One option could be the disbonding of the adsorbing resine which is in the front part of the wedge; you can have a good guess by just touching with the finger with couplant before and increasing pressure then; if the echo disappear by just touching, then it is not disbonding. In this case, try with adhesive rubber tape in the position where you touch. Hope this explanation is clear enough.

 
 Reply 
 

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