Automatic welding and DNV Supplementary D

[Dudepipeline]

Hi guys,
Is application of automatic welding machine for offshore pipeline welding (on laybarge) enforces any requirement on pipeline dimensional tolerances?
Is DNV supplementary requirement D is mandatory or at least strongly recommended to be applied if automatic welding is going to be used?

 

[SJones]

Is application of automatic welding machine for offshore pipeline welding (on laybarge) enforces any requirement on pipeline dimensional tolerances?

Under an EPCI arrangement it won't and, if you are free issuing the pipe to an installation contractor, it also shouldn't otherwise you would not get comparable bids.

Is DNV supplementary requirement D is mandatory or at least strongly recommended to be applied if automatic welding is going to be used?

What is "supplementary requirement D?" Do you mean part D of Appendix C of DNV-OS-F101? If yes, the next question has to be: are you actually needing the pipeline to be certified to DNV-OS-F101? Assuming a negative response, then it will not be mandatory. As to whether it is "strongly recommended", that would have to be down to a review of the quality and reliability requirements for the project and a review of other appropriate pipeline welding standards such as API 1104 or BS 4515-1.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Eyeoftheneedle]

Supplementary Requirement D means there are enhanced dimensional tolerances for the linepipe supplier to contend with. In terms of AUT, the tolerances applicable because of the D are just used as input to setting up the work. The tighter the tolerances though, the easier it is to line up for the welding, so quite often Supplementary D is prefered by installation contractors.

There is not a mandatory requirement for specifying linepipe to supplementary D or not, it all comes down to the bottom line (as always) of how much the buyer wants to pay for their linepipe as obviously the tighter the tolerances, the more the manufacturers are going to charge to give you that linepipe. And as above, the cost of this will be 'traded' against offshore time due to lining up the pipe ends for welding.