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- since 1996 -
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Technical Discussions
dp_paul_dp
NDT Inspector
NDT Services, United Kingdom, Joined Dec 2009, 6

dp_paul_dp

NDT Inspector
NDT Services,
United Kingdom,
Joined Dec 2009
6
16:46 Dec-27-2009
DGS the simple way

Its been a while since I last used the DGS system for lamination examination of steel plate. Does anyone have a simple explanation of how to go about it. ( an idiots guide)

    
 
 Reply 
 
Toni Hakkarainen
Director, Technical manager of industrial services
Bureau Veritas Branch Office Finland, Finland, Joined Jun 2006, 4

Toni Hakkarainen

Director, Technical manager of industrial services
Bureau Veritas Branch Office Finland,
Finland,
Joined Jun 2006
4
20:04 Dec-27-2009
Re: DGS the simple way
In Reply to dp_paul_dp at 16:46 Dec-27-2009 (Opening).

If you have a equipment with DGS option, define the reflector type to Back Wall Echo and take the BWE. Thats it.

If you don´t have the DGS option, then you need the printed DGS- curves for your probe. Calibration is similar.

    
 
 Reply 
 
wasawelder
NDT Inspector
NDT Services, United Kingdom, Joined Dec 2009, 6

wasawelder

NDT Inspector
NDT Services,
United Kingdom,
Joined Dec 2009
6
22:06 Dec-27-2009
Re: DGS the simple way
In Reply to Toni Hakkarainen at 20:04 Dec-27-2009 .

Thanks Toni, trouble is that I don't have a digital set just the old analog, so I really need a step by step guide.

    
 
 Reply 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 522

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
522
23:36 Dec-27-2009
Re: DGS the simple way
In Reply to wasawelder at 22:06 Dec-27-2009 .

If you don't have a digital set then you MUST have the appropriate curves for the transducer you are using, preferably in the form of a scale for your set.

DGS is a great system, used properly, If you don't use it properly the results can be worse than useless, even with a digital set, In particular, You do need to understand how to compensate for the transfer correction and the material attenuation (which can be significant, especially in shear wave tests) If you don't have the right numbers for this (and for the probe) you wont get the right results.

The Best guide i've come across aimed at technicians is in John Drury's book , Published by Silver Wing, available from them, or from BINDT, as well as many other sources. Its probably still not completely what you are looking for though.

    
 
 Reply 
 
wasawelder
NDT Inspector
NDT Services, United Kingdom, Joined Dec 2009, 6

wasawelder

NDT Inspector
NDT Services,
United Kingdom,
Joined Dec 2009
6
21:17 Dec-28-2009
Re: DGS the simple way
In Reply to Joe Buckley at 23:36 Dec-27-2009 .

Hi Joe,
Thanks for the reply, I do have a copy of John Drury's book, I'll have to dig it out.
Cheers
paul

    
 
 Reply 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 522

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
522
00:59 Dec-29-2009
Re: DGS the simple way
In Reply to Joe Buckley at 23:36 Dec-27-2009 .

One point I should add is that if the material to be tested is such that you can use it as a calibration piece (which a piece of plate might well be if it is thick enough that the back surface is out of the near field zone) then the transfer loss can be ignored, and For compression wave testing the material attenuation may also be low enough to ignore.

    
 
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