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Technical Discussions
Shahid Bangash
Shahid Bangash
10:29 Dec-07-2009
Acceptance rejection criteria for UT & RT

Dear Forum members
Acceptance and rejection criteria of welds are similar for RT and UT w.r.t length in different ASME codes. It was observed practically that a slag traced out in RT was declared rejected according to Code but when ultrasound tested the defect echo was found intermittent and had amplitude much lower than that prescibed by code.The situation was observed many times. Although the response echo depends largely on defect geometry but such things should be incorporated into the code to cope with such unseen problems.
Can anyone please help in this regard to find actual problem with a consensus of different techniques.

Best Regards
Shahid Bangash

 
 Reply 
 
ezio
Other, Retired ex Laboratory Technical Manager
OMECO Research Centre, Italy, Joined Sep 2008, 276

ezio

Other, Retired ex Laboratory Technical Manager
OMECO Research Centre,
Italy,
Joined Sep 2008
276
12:13 Dec-07-2009
Re: Acceptance rejection criteria for UT & RT
In Reply to Shahid Bangash at 10:29 Dec-07-2009 (Opening).

Dear Shahid,
my opinion is that in the Code you can find many of these uncertainties, but they are accettable if you consider all other uncertainity elements.
In your case I think that you must apply the part of code that is in the contract.
Ciao, Ezio

 
 Reply 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1096

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
14:27 Dec-07-2009
Re: Acceptance rejection criteria for UT & RT
In Reply to Shahid Bangash at 10:29 Dec-07-2009 (Opening).

Hello Shahid

Sorry, I admit that I do not understand your last sentence so my answer is based on the rest of your post.

I agree with Ezio - if RT is the stipulated contractual NDT method then acceptance/rejection is decided by that method. Sometimes if there is doubt over indication characterisation or depth location then a good UT tech can be asked to provide support information only. The RI can choose to use that information for re-evaluation or not but he should be prepared to field awkward questions from any second view, e.g. Authorised or Third Party Inspector. But I would challenge an assessment on the basis of a supplemental test method when, as in the case described, it contradicts the original method.

Imagine if UT were the primary inspection method, and an unacceptable indication located which was then RT'ed and deemed acceptable on the basis of the RT. Though I expect it may have already occured!

 
 Reply 
 
JB Goradia
JB Goradia
14:31 Dec-09-2009
Re: Acceptance rejection criteria for UT & RT
In Reply to Shahid Bangash at 10:29 Dec-07-2009 (Opening).

Shahid Bangash,
Your experience is at present one side of the coin. One day you will find a lack of fusion or crack not detected in RT will give rise to high UT indication.
To Code-committees this is not an unseen problem.
Best approach is to fulfill contractual obligations.
"the response echo depends largely on defect geometry" is true "but such things should be incorporated into the code to cope with such unseen problems." is not technically true.

 
 Reply 
 
ezio
Other, Retired ex Laboratory Technical Manager
OMECO Research Centre, Italy, Joined Sep 2008, 276

ezio

Other, Retired ex Laboratory Technical Manager
OMECO Research Centre,
Italy,
Joined Sep 2008
276
23:35 Dec-09-2009
Re: Acceptance rejection criteria for UT & RT
In Reply to JB Goradia at 14:31 Dec-09-2009 .

Bravo Goradia,
very appropriate your answer
ezio

 
 Reply 
 

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