NDT after repairs

[DekDee]

Gents,
I was involved in a duplex tank project in the Phillipines a few years ago as the Clients Representative and a written response from API to a Technical Inquiry was used by the contractor to justify their repair methodology.
I could never understand the reasoning behind the response - hopefully one of the forum members can clarify.

As per Section 6.1.2 spot radiography is performed and a weld defect is found that extends off the end of the film.
A "tracer" shot is then taken adjacent and this also contains a weld defect that runs full length of the film.
A second "tracer" shot is then taken and this is found free of defects so the area of defective welding has been identified.
This area is then repaired.
The question was addressed to API as to how many shots were required in the repaired area and APIs response was as per 6.1.7.2 the post repair inspection procedure is to be spot radiography as per the original requirements.

My confusion is how can you confirm the defects have actually been removed if you do not radiograph all the repaired area ?

Any clarification greatly appreciated,
Regards,
DD

 

[fegenbush]

It is my opinion that once you are aware of a defect, you are required to act to correct said defect. Thus, the number of radiographs required after a repair is the same as the sum of the radiographs that it took to isolate the defect. In your example, that quantity would be three.

Perhaps the wording of the standard is unclear, but I believe the intent of the standard is to inspect completely that the repaired region is free of defects.

 

[DekDee]

fegenbush,
Thank you for your response - that was my understanding as well.

However,the interpretation seems to differ.

10th - Nov. 1998

650-I-10/02

Question:

For repaired regions made after spot radiography detects defective welding, is it correct that according to 6.1.7.2 that only the original spot radiography requirements apply no matter the number of original spot and tracer radiographs taken?


Reply:

Yes, because the post-repair inspection procedure is spot radiography as was the original inspection requirement.

So, hypothetically I could have 6' of defective welding and yet I only have to radiograph 6" (1 x spot weld)of that on completion of repairs - seems a bit strange ?

Regards,
DD

 

[fegenbush]

I now more clearly see your confusion. In some other standards, if a weld is considered defective based on a single spot radiograph or a single spot plus tracers, the entire weld must be removed an reexamined. Such is not the case in API 650. 8.1.7.2 of API 650 (12th Edition) clarifies the intent as you have described where the "original examination procedure" for the tracer shot areas is radiographic inspection.

 

[DekDee]

Thanks for the clarification fegenbush.
Regards,
DD