Flowlines vs Pipelines
Flowlines vs Pipelines
(OP)
Hi,
I need to evaluate the risks of offshore damage/losses from flowline installation, at depths say 80m (Carnarvon Basin), compared to pipeline installation. How are they different in terms of installation, material, behaviour etc? Does flowlines face lesser risk of dry/wet buckling?
Grateful for your response. Pretty clueless.
Thanks.
I need to evaluate the risks of offshore damage/losses from flowline installation, at depths say 80m (Carnarvon Basin), compared to pipeline installation. How are they different in terms of installation, material, behaviour etc? Does flowlines face lesser risk of dry/wet buckling?
Grateful for your response. Pretty clueless.
Thanks.





RE: Flowlines vs Pipelines
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Flowlines vs Pipelines
Is the D/t ratio dependent on whether it is an S-Lay or J-Lay?
I've read that a J-lay is generally for deepwater installation, however is it relative to pipe diameter as well?
Is a larger diameter flowline more robust against wet buckling?
Thanks.
RE: Flowlines vs Pipelines
For those smaller diameters, you could do either.
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Flowlines vs Pipelines
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Flowlines vs Pipelines
Flowlines can face a greater risk of buckling, since pressures can be much higher and temperatures much greater, as they often carry fluids directly from well stream conditions. Higher temperatures and pressures increase compressive buckling loads in restrained pipe segments, which is the main reason that "snake laying" flowlines has become a popular method of averting uncontrolled buckling.
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Flowlines vs Pipelines
In this case, the hotter, higher pressure pipelines will tend to buckle before the lower pressure and lower temperature lines.
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Flowlines vs Pipelines
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
I am looking at loss numbers from offshore pipe installation claims in general (but work scope mainly flowline-laying in the Carnarvon Basin), and have decided rather simplistically on 3 variables: 1) diameter, 2) depth water, 3)terrain. Regarding (3), I am assuming that the sea-bed would have been prepared with the allowable free-span etc. Assume pipe material would have been selected to enable specific service function e.g high temperature. Hence, to the designer, his/her concerns would be structural behaviour only. It then takes us to (1) & (2). Unless I am missing some special techniques during S or J-lays, I would expect higher losses resulting from small diametered pipes (flowlines) because it is generally slender, more hold-downs on the seabed(??) making it problematic. I mean a 3" is like a rope in these depths? Is it a hose of some sort?
Have I confused myself? Thanks.
RE: Flowlines vs Pipelines
It would be hard to draw general conclusions based on diameter; larger lines have more steel area (axial load), but higher radius of gyration to resist buckling and they also tend to grow axially rather than buckle, since gain in load with diameter is not resisted by the same ratio of a gain in soil friction. Smaller pipelines would not develop so much axial load, since x-sectional area is usually smaller, so can become fixed by soil friction, stopping axial growth, increasing compression load and setting up a buckling response. Water depth doesn't have much to do with the buckling problem. I think a function of operating temperature and pressure might go the farthest. Next correlate to diameter.
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
A great discourse on operational issues, but does all that apply when the pipe is hanging off the barge? Yves says 'pipe installation claims'. It's not clear who is claiming from whom, and for what specifically, but I got the impression that it's damage before completion and handover.
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Flowlines vs Pipelines
During installation the concerns become more about contractor technical abilities and matching the equipment capabilities in lift to that of the weight of pipeline plus furnishing the proper amount of tension required to hold a smooth unbuckled pipeline profile from the end of the stinger over the distance to touchdown point on the bottom. Installation factors obviously are affected by diameter and depth, as much as those affect weight and span to touchdown, additionally by D/t ratio as that affects collapse pressure from water depth pressure, but all those factors are still easily managed in depths up to 80 m, at least as long as the equipment is right for the job and the contractor does not push the limits of operating margins during storms and high currents. I'd try correlating installation buckles to Pipe diameter: wall thickness ratio, D/t, and water depth H. 80 meters is a rough depth borderline for crushing collapses. Not usually a problem for lesser depths, but can quickly become a problem for higher D/t ratio pipe at 100 meters and more.
Being that 80 m shouldn't really be much of a technical problem in laying properly designed steel pipelines from a conventional S-lay barge, it leaves me wondering how many installation buckles have been experienced in that Carnarvon field to warrent a special evaluation... and why they occured? If D/t ratios are not at extreme values, pointing at the engineer, it might finger the contractor(s) as the problem.
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
Because I am no longer in engineering, I do not have design standards for reference. :(
RE: Flowlines vs Pipelines
From "BigInch's Extremely simple theory of everything."
RE: Flowlines vs Pipelines
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Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04