Formulas for collapse check of corroded pipelines 2

[FilippoT]

With my colleagues we were wondering which kind of standards and formulas we should use to verify the resistance of an offshore pipeline to local buckling – collapse in case of metal losses.
As you know ASME B31.G is related to corroded pipeline for which bursting is the governing loads and also the DNV-RP-F101 (Coroded pipelines) does not report anything on buckling.

So, what if I have a pipeline originally designed for external pressure collapse due to high water depth and it shows severe metal losses. We think we should check not only the bursting capability with the corroded wall thickness (as for ASME B 31.G for example), but also the new collapse resistance with the reduced wall thickness. As far as you know is there any codes, standards or good practices that deal with collapse resistance for corroded pipelines? Or simply we have to go back to the design formulas of DNV-ST-F101?

 

[SJones]

2003 Pipeline Defect Assessment Manual

An important factor to be aware of when considering corrosion in an offshore pipeline is the
possibility of collapse due to the external pressure. The authors are not aware of any reported
collapse tests on corroded pipe. Regular or irregular wall thinning with a significant longitudinal
or circumferential extent will reduce the resistance of the pipe to collapse due to bending or
external pressure, and it will affect the geometric stiffness of the structure in the plane of the pipe
cross-section, but the effects may be difficult to quantify. Non-concentric thinning of the crosssection
will promote ovalisation (and hence collapse).

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[1503-44]

I have not noticed any check for corroded wall collapse,
You will probably have to use the external pressure collapse equation and adapt that to suit your wall loss conditions.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

Do a few FEA models is my only idea.

Or just never blow the pipeline down.

But severe metal loss in a deep water pipeline sounds like a scrap metal issue to me....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

So true.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[HTURKAK]

The title of this thread ( Formulas for collapse check of corroded pipelines )..

In this case My points and suggestions would be;

- You may look Theory of elastic stability. (Timoshenko SP, Gere JM. )

- Pls look to the book Subsea Pipeline Integrity und Risk Management ( section 2 ( Buckling and Collapse of
Corroded Pipes), 3. COLLAPSE DUE TO EXTERNAL PRESSURE , By Qiang Bai & Yong Bai)

- FEM analysis always a tool to go with,

- You may look ASME and DNV for relevant loading combinations etc.



My opinion ..






Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB