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samuelo00 (Marine/Ocean)
9 May 07 15:52
Hi all,

I am recieving from the engineering company some data confusing to me. For a carbon steel pipe with approx. 100°C op. temp. and 300#, in some cases we have to do 100% radiography to the welds and in other cases only 33%, in prefabrication.

I have check the code (344.5 of B31.3, which applies), and it seems that this is not necessary, although it is not clearly enough to me.

So the question is: when is mandatory to perform 100% radiography to a welding union of pipes or pipes and accesories?

Advanced thanks
samuelo
metengr (Materials)
9 May 07 16:04
samuelo00;
I reviewed ASME B31.3, Section 345.5. It seems clear to me regarding RT of girth and miter groove welds. Also referenced in this section is random RT and spot RT.

The Engineer involved with the design of this project has final say above and beyond minimum Code requirements for nondestructive testing.
metengr (Materials)
9 May 07 16:05
Correction above, Section 344.5.1 and 2.
imctmga (Petroleum)
9 May 07 19:51
Hi samuelo,

May be because the fluid is hazardous, i think that a inspection of 100% radiography in welds can be with some product like H2S e.g.

Usually in refineries the lines with H2S are made in carbon steel with TT, so you must radiography all the welds before (or not is your problem) TT and post ever.

It´s only my opinion
samuelo00 (Marine/Ocean)
10 May 07 8:24
Yes imctmga, that's also my opinion,

I don't see the point in making radiographys to lines handling non hazardous fluids, but if a girth weld is not well done, then there can be problems with corrosion cracking, and hence the 100% radiographs.

Thanks for your valuable answers.
samuelo
Helpful Member!  BigInch (Petroleum)
10 May 07 8:46
Well actually there can be a lot of points in favor of 100% radiography.  Nonhazardous fluid lines are often 100% radiographed to minimize risk of poor weld quality for the simple fact that explosions of any kind can be deadly.  Even though a non-hazardous fluid, that could even be ingested like CO2 for example, can be extremely hazardous if encountered in large quantities, as would probably be the case in a high pressure dense phase CO2 pipeline girth weld failure.  Just the risk of a high pressure explosion of any kind in a populated area might be sufficient justification for 100% to most people.  Furthermore it can simply be cost effective, as in the case of an offshore pipeline, where 1 bad weld can cost hundreds of thousands of $$ to go out there and physically fix it, to say nothing of the lost sales of product from the consequential shutdown which could easily reach millions of $$ per day.



http://virtualpipeline.spaces.msn.com

STYMIEDPIPER (Mechanical)
10 May 07 9:15
AS BigInch has stated--it usually is very expensive to fix a problem (bad welds) in the field.

As metengr has stated--the design engineer can specify requirements that exceeed Code requirements.

The welders in the fab shop are considered experienced and thoroughly tested by their employer.  If a bad weld is detected in the fab shop then the examiner will review other welds by the welder in question.

The available pool of field personnel may be considered sub-par or not as experienced in a local job market depending on the site location.  If a welder hired at the job site successfully completes a weld coupon does not necessarily mean that his next weld will suffice.  Some construction jobs have a high turnover rate hence, weld consistency is an issue.
BigInch (Petroleum)
10 May 07 10:09
These things are not all necessarily always the welder's fault.  Some crew bosses just simply want to keep on going when they really shouldn't, even when there's salt spray, blowing dust and sand, high humidity and cool pipe...



http://virtualpipeline.spaces.msn.com

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