B31.3 RT requirement (5% Random) for girth welds 1

[nichols7007]

I'm looking for clarification for interpriting what 5% random sample requires.

For example: If you have a project with a total of 12,000 girth welds under NFS, and there are 22 welders working on that project. Does the code require 5% random sample from each welder/welder operator or does that matter? Is that up to the owner?

Please advise

 

[ApC2Kp]

nichols 7007,

ASME B31.3 (b) 1. states,
" Not less than 5% of circumferential butt and
miter groove welds shall be examined fully by random
radiography in accordance with para. 344.5 or by random
ultrasonic examination in accordance with para.
344.6. The welds to be examined shall be selected to
ensure that the work product of each welder or welding
operator doing the production welding is included."

Of course you need to get a minimum of 5% of each welder's work. For the 12,000 welds you will want to do more exams early to weed out any problem welders. If you find defects then more follow up progressive exams of that welder's work is a reasonable consequence, but not necessarily by code, but by owner decision.

Note that the Code now accepts ultrasonic exam for the 5% random exams. Be sure to get Owner agreement for UT exams. It is a cost savings as well as less disruption to ongoing work. Radiography would usually done at night when area is cleared of personnel. If two shifts are working, then it is difficult to schedule the radiographic exams.

 

[paavainathan]

I agree with Nichols 7007
Each welder and Each size the 5 % random sample will be applicable.

 

[humbug]

Gentlemen,

The referenced paragraph in B31.3 states that each welders work must be represented. That does not neccessarily mean that it is 5% of each welders work. With that you could have one or two welders have the majority of the required radiographs and have the balance of the welders only have a minimal amount to get to the 5% requirement. This way all of the welders have been represented. This of course is not the most practical way to ensure the quality level that you are looking for.
Usually the client/owner will require that both the 5% is relevant to the welder and not just the job, which in most cases when you radiograph per the welder you will exceed the code requirement.
Along the lines of progressive sampling (341.3.4): When a weld reveals a defect then 2 additional samples of the same kind (by the same welder) must be examined. For further info continue reading that same paragraph. There is a logical step by step sequence to follow.


Humbug

 

[PAN]

If the code asks for "not less than 5%", you may indicate more such as 10% for each welder's work...

Code may give minimum requirement to you. Final decision should be the decision of project team. This depends on optimization among quality, SHE, cost and schedule...

 

[BigInch]

Humbug's right.

Besides, 5% of all welds with 5% on one welder would be NO welds remaining to be checked for any other welders.

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[ndeguy]

nichols7007

Sorry for not being alert to your post. Is a month too late?

Please follow the link to an excellent article on random radiograpy in The Fabricator:

http://www.thefabricator.com/TestingMeasuring/TestingMeasuring_Article.cfm?ID=1129