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Heat Treatment of Pipe after manufacturing
2

Heat Treatment of Pipe after manufacturing

Heat Treatment of Pipe after manufacturing

(OP)
Hi Dear Friends
As I know there are several methods for manufacturing longitudinally welded pipe like: U.O.E,U.O.C, continuous forming and Press Brake. All of these methods cause plastic cold forming.In ASME B31.4 it is written it is forbidden to use material with increased yield strength due to cold forming. As you know cold forming can increase yield Strength up to 15% .But refer to specification of Pipe manufacturing like API 5l, there is no mandatory requirements for doing heat treatment on manufactured pipes. In some instances it will be done but in others no. Also as you know when for example you use U.O.E which E stands for Expansion as final manufacturing Process your pipe shows greater yield strength on external Pressure but lower than plate material Yield Strength on internal Pressure and U.O.C which C stands for Compression shows greater yield strength on internal Pressure and adversely lower than plate material yield Strength on external Pressure. Now here are my Questions:
1) in standards Like ASME B31.3 it is Mandatory to do heat treatment on components after Cold forming like bending that exceeds specific fiber elongation. Does this requirement applies to Production of Pipe too ?
2) if answer to first question is No, why there is no correction factor for yield strength after cold forming during Pipe Manufacturing ?
3) As Stated in ASME B31.4 using increased yield strength due to cold forming is prohibited but in reverse condition like Internal Pressure on U.O.E pipe; there is no correction factor for decreasing Yield strength due to cold forming ?
you can read follwing documents if description of my question seems to be not clear:
http://www.engr.mun.ca/~spkenny/Courses/Undergradu...
Also see attached page from API 5l.
Best Regards

RE: Heat Treatment of Pipe after manufacturing

(OP)
Also only in DNV-OS-F-101 there is a correction factor named as fabrication factor which for U.O.E is about 0.85 but not in any other standards

RE: Heat Treatment of Pipe after manufacturing

1. No - the particular pipe manufacturing standard governs

2. Most pipeline design standards are predicated on mechanical property determination for acceptance being performed on pipe in the final condition?

Google "Bauschinger effect in pipe steel" and see if the results help with your question regarding DNV-OS-F101.

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.

RE: Heat Treatment of Pipe after manufacturing

B31 and API all list acceptable material specification. It is those specs that govern what alloys can be used, what production methods are allowed, and the required heat treatment and testing (mechanical and NDT) are required.
The strength of steels changes so little with cold work that it doesn't make sense to try and use it.
The greater concern is various delayed and hydrogen cracking mechanisms related to local high strain.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

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