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Technical Discussions
SK AHAMMED ALI
SK AHAMMED ALI
09:43 Oct-14-2014
Atenuation Factor

The “Attenuation Factor C on the test report shall be attained by subtracting1 in.
[25 mm] from the sound-path distance and multiplying the remainder by 2. This factor shall be roundedout to the nearest dB value. Fractional values less than1/2 dB shall be reduced to the lower dB level and thoseof 1/2 dB or greater increased to the higher level.


Can anybody explain this?

 
 Reply 
 
Jon Wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

Jon Wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
07:24 Oct-15-2014
Re: Atenuation Factor
In Reply to SK AHAMMED ALI at 09:43 Oct-14-2014 (Opening).

Attenuation is 'absorption' of your sound in a particular material. Some materials attenuate more than others. Think of a light beam in clear dark air (fine grain low alloy carbon steel) and compare this with the same light beam in fog (course grain high alloy carbon steel).
When using the DGS system, you need to compensate for attenuation and specific materials have an attenuation factor that needs to accounted for when UT testing. This is because echo comparison is between a flat bottom hole in fine grain low alloy material (clear air) and your workpiece (unknown). This problem doesn't present itself with side drilled hole based comparisons as the comparison block should be made from the same material as the workpiece.

 
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GOWRISANTHOSH PALIKA
NDT Inspector,
Royscan engineering pte ltd, Singapore, Joined May 2008, 52

GOWRISANTHOSH PALIKA

NDT Inspector,
Royscan engineering pte ltd,
Singapore,
Joined May 2008
52
09:33 Oct-16-2014
Re: Atenuation Factor
In Reply to SK AHAMMED ALI at 09:43 Oct-14-2014 (Opening).

hi
for every inch of sound travelling through the steel, there will be a loss of 2dB. It is correct when you use equipment that all stated in AWS D1.1.

 
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