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- since 1996 -
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Technical Discussions
Tuong
NDT Inspector, PV EIC NDT
PV EIC NDT, Vietnam, Joined Mar 2014, 19

Tuong

NDT Inspector, PV EIC NDT
PV EIC NDT,
Vietnam,
Joined Mar 2014
19
07:08 Sep-12-2016
What Indication on C-scan
Download What Indication on C-scan

Dear Sirs,
I just C-scan to check corrosion of piping system, the condition of surface has coasting, thickness is 12.7 mm ,carbon steel material and i use the hydroform equipment, It has indication as attachment.
I would like to know what indication it is?
I hope to receive your soonest reply
Thanks for your help!

 
 Reply 
 
Mark
,
Zambia, Joined Jun 2016, 49

Mark

,
Zambia,
Joined Jun 2016
49
17:31 Sep-12-2016
Re: What Indication on C-scan
In Reply to Tuong at 07:08 Sep-12-2016 (Opening).

Tuong,
Make sure about the surface of object in that area. add little more dB and rescan the area.

 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 747

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
747
20:38 Sep-12-2016
Re: What Indication on C-scan
In Reply to Tuong at 07:08 Sep-12-2016 (Opening).

check with a dual probe

 
 Reply 
 
Dancho
,
Macedonia, Joined Dec 2013, 1

Dancho

,
Macedonia,
Joined Dec 2013
1
05:11 Sep-13-2016
Re: What Indication on C-scan
In Reply to Tuong at 07:08 Sep-12-2016 (Opening).

Tuong,

You are using Hydroform probe and your gate setup is flank T(B/1 - A/1). Try changing to peak or narrow the gates.You are catching the small peak before the 2nd backwall and the result is the red area in the C-scan.
I think this peak it is just a noise because the dB in this area are increased from the manually constructed TCG line with 3-4 points.




 
 Reply 
 
Tuong
NDT Inspector, PV EIC NDT
PV EIC NDT, Vietnam, Joined Mar 2014, 19

Tuong

NDT Inspector, PV EIC NDT
PV EIC NDT,
Vietnam,
Joined Mar 2014
19
07:40 Sep-13-2016
Re: What Indication on C-scan
In Reply to Dancho at 05:11 Sep-13-2016 .

Dear Dancho,
As you said,
If has corrosion, must be have indication before first backwall echo?
Thanks for your help

 
 Reply 
 
Diego Mora
Diego Mora
22:40 Sep-19-2016
Re: What Indication on C-scan
In Reply to Tuong at 07:40 Sep-13-2016 .

This is not corrossion, but it is interesting to know exactly why this signal (false indication) appears in that position, normally is at 1.4 times the thickness.

I have two questions: 1. Do It happened in all the tubes inpected?; and 2. is it shown in the same relative depht allways?

 
 Reply 
 
John Pitcher
Consultant,
Sonomatic Ltd, United Kingdom, Joined Apr 2003, 14

John Pitcher

Consultant,
Sonomatic Ltd,
United Kingdom,
Joined Apr 2003
14
17:20 Sep-20-2016
Re: What Indication on C-scan
In Reply to Diego Mora at 22:40 Sep-19-2016 .

I believe the signal you refer to is due to a sound path of long wave in one direction and shear wave in the other. There is debate on how and why a shear wave is produced but the numbers fit when analysing the possible time paths.
Maybe the edge of the beam creates a radial beam creating a shear wave.
This signal varies in strength depending on probe type and manufacturer.

 
 Reply 
 
Shane
Shane
18:30 Oct-07-2016
Re: What Indication on C-scan
In Reply to Tuong at 07:08 Sep-12-2016 (Opening).

That is a mode converted shearwave created by the angled, focused Lwave occuring before the 1st critical angle and releasing an unusable shearwave. C-scan is pickling it up because the signal is crossing gate b, and you are reading edge to edge. A peak to peak c-scan would eliminate it.

 
 Reply 
 

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