Deisgn of pipeline to CSA Z662 vs B31.3

[Helium41]

Hello;

We have a bit of a problem here: we have a pipeline designed to CSA Z662 (date ±1972). Some repairs were made to the pipeline and the spool fabrication was made to ASME B31.3 because everyone forgot to mention to the shop that material and welding should be to Z662. During installation of the spool, the Z662 welding procedures were used. Whe did 3 things: a)repaired a 5 ft portion with a dent somewhere in the middle of the line b) cut out a bend and replaced it with a "T" and some fittings in order to install a pig launcher - this is also in the field at the main branch-off c) installed a pig receiver at the end of the line - this is within the refinery.

My question is: could a design half B31.3 and half Z662 be acceptable? What do I need to check specifically to maintain the Z662 "certification"? I can not do a hydro test because of the length of line (generates to much water) and was planning on accepting welds based on the concept of "closure welds" which can be X-ray only. Can't seem to find if this is OK in Z662...

Thanks for your help.

 

[Helium41]

I Forgot to mention: I have already read the CSA Z662, article 7.2.5 and I know that the shop fabrication according to B31.3 is allowed. My question is to the new field weld on the existing pipeline. Should this new weld be CSA Z662 or B31.3?

 

[vpl]

I would generally take it that the spool piece is a component, fabricated to an acceptable code, that is then installed in the pipeline to an acceptable code. If spool piece fabrication was acceptable, then you need to install it using the required installation codes. I saw four questions being asked:

1) Could a design half B31.3 and half Z662 be acceptable?

It doesn't appear that you have a "half and half system" -- the pipeline is designed to CSA Z662 with a spool piece fabricated under B31.3 (which you say is ok under article 7.2.5 of CSA Z662.).

2) What do I need to check specifically to maintain the Z662 "certification"?

I don't really understand this question. Installation should be to CSA Z662 so that's what you need to check.

3) Is it ok under Z662 to accept welds based on the concept of "closure welds" which can be X-ray only?

No idea. However, I'm not sure that it is ok to use B31.3 as a basis for acceptance as your pipeline isn't designed and constructed to B31.3.

4)Should the new field weld on the existing pipeline be CSA Z662 or B31?

It should be CSA Z662 -- which you said you did: "During installation of the spool, the Z662 welding procedures were used."

From the description of work done, it sounds like there may actually have been more than one weld made to the pipeline. If that's the case, how are you treating all the other welds and what is the justification for use of anything other than CSA Z662? "Too much water" sounds like an excuse -- but then I don't know what is normal for pipeline testing.

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[SNORGY]

I wouldn't panic yet.

CSA Z662 will usually allow weld procedures qualifed and conforming to ASME Section IX. It would require a more "competent" welding specialist or metallurgist than me to tell you for sure, but I believe that the differences in film interpretation come down to different acceptance / rejection criteria for certain defects. There may be some considerations in sour service, but otherwise I would suspect that you are probably OK. If in doubt, if you still have the films, have a certified inspector re-evaluate them against the Z662 criteria.

With respect to materials (I assume that someone used A-106 B or A-333-6 instead of Z245.11 or something like that). From your brief scope of work description I am assuming that the line sizes are not very large (below 12" OD probably?), in which case you would probably find that such material substitutions will be allowed without further qualification. You would need to evaluate hoop stress versus Pipe Threshold Stress Value (this concept is defined - at least - in the later editions of the CSA Z662 code), but I strongly suspect that you can make an A-106-B substitution for most Z245.11 linepipe for up to 50 metres between fittings, for example.

With respect to the new welds, again I am making assumptions, but you can probably use an ASME IX WPS / PQR with interpretation to Z662 criteria; on the issues of hardness and notch toughness it is unlikely that P1-G1/2 to P1-G1/2 welds per ASME IX would not meet CSA Z662 acceptance criteria, leaving only the examination of the film for defects as cause for concern between one Code or the other.

Whether or not a "closure weld" examination in lieu of pressure testing is acceptable is probably driven more by the local Regulations than the Code.

Regards,

SNORGY.

 

[dcasto]

I thought it was a pipeline, not plant piping? B1.3 is for plant piping and B31.8 is for pipelines. They have different standards for construction & maintence.

 

[Helium41]

Thank you for all your answers. They have given me some areas to check.

After a bit more digging, it appears that Z662 art. 7.2.5 allows for "maintenance repairs" to be made to ASME B31.3 standard (for welding procedure), for all spool prefabrication. The intent is to take into account that most shops are not qualified Z662 and therefor it is easier to have pre-fabricated spools to B31.3 than to Z662. Stress calculations should still be made to Z662 to select proper materials / thickness.

Only the field weld (i.e. welding the pre-fab spool to the actual pipeline) should be to Z662 for welding inspection criterias.

The only thing not clear to me yet is if I can do only X-Ray or if the hydro test is absolutelly required. I am still searching on this and any help would be appreciated.

 

[dcasto]

The old "Golden Weld" question!!! Look that one up here, it has been dicussed many times.

You still haven't answered, is it a pipeline or process piping.