DUPLEX COLD BENDING
DUPLEX COLD BENDING
(OP)
Have anyone had experience with Duplex Cold Bending.
I'm working on a pipeline engineering with duplex pipe (S31803) 6"/4" thick. 4.8mm.I have to specify a limit angle for the cold bending on site. Some people has experience with 15°, someone else with 30°. There is also Company like SHELL that prohibit the cold bending of duplex.
Obviously there is a lot of parameters that influence the feasibility of this process. very important is also beending speed and method of bending. A this phase (engineering)is not possible to give an answer but rather a good practicse.
In my opinion 15° could be feasibile, but have to be considered that high pressure condition (96 barg) and very very low thickness do not permit high margine on thinning or wrinkling. Waiting for your experience on this matter.
I'm working on a pipeline engineering with duplex pipe (S31803) 6"/4" thick. 4.8mm.I have to specify a limit angle for the cold bending on site. Some people has experience with 15°, someone else with 30°. There is also Company like SHELL that prohibit the cold bending of duplex.
Obviously there is a lot of parameters that influence the feasibility of this process. very important is also beending speed and method of bending. A this phase (engineering)is not possible to give an answer but rather a good practicse.
In my opinion 15° could be feasibile, but have to be considered that high pressure condition (96 barg) and very very low thickness do not permit high margine on thinning or wrinkling. Waiting for your experience on this matter.





RE: DUPLEX COLD BENDING
The relevant parameter here is % strain, the only thing the metal understands. You need to follow ASTM and the construction Code and any technical specifications.
RE: DUPLEX COLD BENDING
https://exchange.dnv.com/Publishing/Codes/download...
And, if the transported fluid also contains H2S, then they may have a really strong aversion.
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: DUPLEX COLD BENDING
RE: DUPLEX COLD BENDING
Strain at bend outer radius (extrados) has nothing to do with bending angle; only depending on bend radius.
Doesn't matter whether bending angle is 1, 15 or 30 degr.
I always follow the requirements per piping design code ASME B31.3 + limits per ISO 15156-2 for Sour service (H2S).
I wouldn't bend in case of Sour service unless hardness is surely below ISO 15156-2 limits.
No Sour service > apply rules of ASME B31.3 (cold bending rules).
My advise is to apply a relative large bend radius; as large as possible.
Min. radius recommended 3,5 * OD pipe (if allowed by piping design code of course)
Be aware; pipe bends must be engineered as required per design code(s).
good luck