Finite Element Analysis to compute MAOP of corroded pipeline

[NATIVES]

A pipeline has lost approx 50% of all thickness. Original wall thickness was 0.625-inch. Barlow's or B31G gives MAOP much lower than desired MAOP. [Desire MAOP 5,000 psi, computed MAOP based upon Barlow's 3200 psi].

Company hired a high flying engineering consulting company with top brain to show that the pipeline is still good for 5,000 psi based uon their Finite Element Analysis [FEA]. Is FEA acceptable for pipeline design, specially corroded ones?

 

[EdStainless]

What about the applicable Code of construction?
In some cases FEA may show that it is possible, but the Code will define the rules and it may not allow that analysis.
If the attack is non-uniform them the actual strength will be much lower than Barlow's would give you.

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

 

[Metalero]

Is the loss of thickness uniform or localized?

 

[metengr]

This is an in-service pipe so code of construction does not apply, directly. Yes, FEA can be used subject to review and approval by the Owner. Third, did you review ASME FFS-1? If it passes, FFS-1 it is good enough for me.

 

[brimmer]

FEA can be acceptable, depends on the model. What kind of FEA are they doing? Has it been validated with real life results & testing? Try and run results through RStreng first to see (maybe that is what they did)? You can run it in KAPA, it is free on the Kiefner website

http://kiefner.com/.

You will need profile of corrosion to run this (as opposed to one depth & length measurement).

Barlow's or B31G???? Are you sure you are using B31G correctly then? What is the length of the corrosion?

 

[NATIVES]

EdStainless/ MarriolaV:
Code is Barlows: 30 cfr 250.1002
Corrosion is non-uniform

metengr: i will check with ASME FFS-1

brimmer: ABAQUS/Standard version 6.14.1

 

[brimmer]

Seems like this would be simulating some corrosion through a given thickness of material. I'm not sure this is reasonable, given that there are better well validated corrosion models out there being used. I have never seen this software specifically used for corrosion in a pipeline for burst pressure, only in simulation for something else, assuming a wall thickness (which may have been corroded). If your corrosion in non-uniform, not sure about this, give us the measurements of the corrosion, with diameter & grade of material. Typically one pit of 50% will pass easily, it is how long the corrosion is.

You cannot directly apply Barlows to the corrosion, the models work differently (I'm not sure if this is what you are doing).

 

[Metalero]

FEA is excessive for that assesment (in my opinion is kill ants with dynamite)

I agree: API 579-1 / ASME FFS-1 Fitness-for-Service is good enough and B31G or B31GMod (RStreng 1) (both conservative), RStreng 2. DNV RPF101 (less conservative), etc ... are recognized as accepted methods for evaluating defects of corrosion (at this moment I do not remember those contemplated in api579-1 / ASME ffs-1).

The spreadsheet recommended by brimmer is a good tool.

 

[brimmer]

Here we go. If you get this paper it would show, but I would question real life testing and application, a few tests in one laboratory one time isn't enough data to validate the model. This is the only reference to using this software for pipeline corrosion burst pressures that I have ever seen in industry.

Finite Element Analysis of Burst Pressure for Pipelines With Long Corrosion Defects
Xian-Kui Zhu and Brian N. Leis
Paper No. PVP2012-78730, pp. 945-952; 8 pages
doi:10.1115/PVP2012-78730
From:
ASME 2012 Pressure Vessels and Piping Conference
Volume 6: Materials and Fabrication, Parts A and B
Toronto, Ontario, Canada, July 15–19, 2012
Conference Sponsors: Pressure Vessels and Piping Division
ISBN: 978-0-7918-5505-8
Copyright © 2012 by ASME

 

[Metalero]

One more question: Did you make the mechanical characterization of the steel or are you assuming the properties from the nominal grade?

If you assume and use FEA, you are wasting money and computing time, better put your computer to mine bitcoin.

If you measured it, the scenario is a little different, although I insist, the models are a good approximation more or less conservative, depending on the ability of the simulator to model the component with the defect, if you have good skill, you will be able to obtain slightly higher results than with the models.

It is not the paper recommended by brimmer, but it is also from the proceedings of a recognized congress.

http://www.gruppofrattura.it/ocs/index.php/ICF/icf13/paper/viewFile/11432/10811

 

[LittleInch]

You also need to add in the accuracy of the measurements taken by the inspection tool.

Also that was then, what is the thickness today or next week? That is pure conjecture. Once you get to depths and pits of 6+mm corrosion inhibitors become less effective and pits can deepen much more rapidly than before.

I agree with the others- there are many established and recognized means of analyzing pipelines with corrosion. FEA is only valid for the particular location you're looking at - to do FEA for an entire pipeline is ridiculous.

If it's only two or three locations, just add an external sleeve and forget about the analysis or cut it out and replace it. Sometimes it can take longer and cost more to analyse it to find you've got a problem than it does to simply fix the problem in the first place.

Lost metal won't come back....

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