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- since 1996 -
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Technical Discussions
Peter
Singapore, Joined Jan 2012, 119

Peter

Singapore,
Joined Jan 2012
119
05:14 Feb-04-2016
RT-DEPTH OF UNDERCUT
zoom image

Dear Specialist,


I found undercut during RT interpretation. Refer to the attached ASME B31.3 requirement. How it is possible to measure the depth of undercut in RT film? Is that will be accurate if we measure based on density variation?


Peter

 
 Reply 
 
collin maloney
NDT Inspector, - Plant Inspector
Applus RTD, Australia, Joined Nov 2000, 147

collin maloney

NDT Inspector, - Plant Inspector
Applus RTD,
Australia,
Joined Nov 2000
147
05:51 Feb-04-2016
Re: RT-DEPTH OF UNDERCUT
In Reply to Peter at 05:14 Feb-04-2016 (Opening).

unless you used an undercut shim with your exposure, you cannot determine depth, even then (if you used one) it is a very subjective measurement

 
 Reply 
 
jon wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

jon wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
07:54 Feb-04-2016
Re: RT-DEPTH OF UNDERCUT
In Reply to Peter at 05:14 Feb-04-2016 (Opening).

Only the DWDI technique allows measurement of undercut to any degree of accuracy by radiography. I don't understand why B31.3. requires this discontinuity to be assessed by radiography instead of visually, which is the case in other norms. External undercut is easily measured physically, internal is more difficult. A general rule of thumb that used to be applied was to check the density of the undercut and compare it to the density of the parent material, if the undercut density was less then reject - not very scientific but with the lack of any other practical method of looking at internal undercut it served its purpose.

 
 Reply 
 
N. B. RENGARAJU
NDT Inspector, NDT Level-III/Radiation Safety Officer(RSO)
Marine and Heavy Engineering Company, MALAYSIA., India, Joined Sep 2014, 106

N. B. RENGARAJU

NDT Inspector, NDT Level-III/Radiation Safety Officer(RSO)
Marine and Heavy Engineering Company, MALAYSIA.,
India,
Joined Sep 2014
106
14:53 Feb-04-2016
Re: RT-DEPTH OF UNDERCUT
In Reply to Peter at 05:14 Feb-04-2016 (Opening).

Dear Peter,

With respect to your basic question, depth of undercut cannot be measured in a RT Film. All other things are subjective or appropriation.

Regards
Rengaraju

 
 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
16:03 Feb-04-2016
Re: RT-DEPTH OF UNDERCUT
In Reply to jon wallis at 07:54 Feb-04-2016 .


Dear Sir,

From your reply "if the undercut density was less then reject"

Am I missing some thing.

Best wishes

P V SASTRY

 
 Reply 
 
jon wallis
NDT Inspector, -
Netherlands, Joined Feb 2010, 626

jon wallis

NDT Inspector, -
Netherlands,
Joined Feb 2010
626
16:07 Feb-04-2016
Re: RT-DEPTH OF UNDERCUT
In Reply to P V SASTRY at 16:03 Feb-04-2016 .

Quite right, I meant "density greater" which means less thickness of course.

 
 Reply 
 
Shankar Arumugam
Other, NDE Engineer
India, Joined Oct 2013, 39

Shankar Arumugam

Other, NDE Engineer
India,
Joined Oct 2013
39
05:28 Feb-05-2016
Re: RT-DEPTH OF UNDERCUT
In Reply to P V SASTRY at 16:03 Feb-04-2016 .

Dear Sir,
We can’t judge the undercut’s severity through RT film. Practically while interpreting RT film it found the undercut severity is very high in the Film. But while visual checking the undercut found very less. So undercut cannot be measured in RT film by its density means. Only visual inspection is good for undercuts.

 
 Reply 
 
Peter
Singapore, Joined Jan 2012, 119

Peter

Singapore,
Joined Jan 2012
119
07:17 Feb-05-2016
Re: RT-DEPTH OF UNDERCUT
In Reply to Shankar Arumugam at 05:28 Feb-05-2016 .

zoom image
Hi,

I found this statement from ASME B31.3 old version saying that density differential shall not be use to evaluate undercutting.

Peter
 
 Reply 
 

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