design subsea pipeline 3

Thats one of those how long is a piece of string questions?

What size of pipe are you looking at. A large export line will usually be layed using either S-lay or J-lay, each having different lay characteristics and stresses on the pipework.

For a smaller pipe you could be looking a rigid reeled pipe, or a flexible. For very short lengths you might be looking at spool pieces.

What exactly do you want to design the pipe for:

1] Flow assurance characteristics. This is to ensure that the product flows in the pipeline, pressure and temperature are such that the platform or facility can accept it. Also to prevent waxing, deposition etc. Insulation requirements.

2] Corrision and protection design. Could be cathodic protection, various coatings, shrink film, paint applied etc

3] In place stability calculations. To ensure that the pressure/temperature affects dont induce upheaval buckling by expansion, short lengths may be prone to pipe ratcheting. Mattress or rock dumping design to assist in stability. Fishing gear snagging analysis. Dropped object analysis and impact analysis. Flange design, structural crossing design, Free span analysis.

4] Wall thickness, pipe stress analysis, structural characteristics of the pipe.

5] Installation anaylsis. Interaction with splashzone, plastic stress strain cycle assessment, catenary analysis, Lift analysis dynamic effects.

So as you can see, there is no one answer on how to design a subsea pipe.

In the UK we tend to us PD 8010-2:2004, Code of practice for pipelines. Subsea pipelines.

OS-F101

Steve Jones
Materials & Corrosion Engineer

look in Troitsky's "tubular steel structures" ch 11
available from J.F.Lincoln arc weld foundation

Thanks for all information,

But can we design a marine pipeline for transporting oil and/or gas similar as process pipeline, onshore and/or offshore ??

Thanks

No you cannot.

Some of the areas of differences are as detailed by Ussuri:

External pressure (not significant in 10m water but in 1000m of water equals 100 bar)
Seawater temperature and heat absorption (The product is cooled much more raidly and insulated pipelines may be needed)
Corrosion (Anti-corrosion systems - anodes, coatings are required)
Wave and current action (Mainly in shallow water and landfalls)
On bottom weight (What is the necessary submerged weight of pipe for adequaye stability (use concrete weight coating? - design concrete density 2400kg/m3 to 3400kg/m3)
Spanning and spanning correction (the seabed is not flat, the pipe is laid empty and then sags. Need to analyse allowable span
Connections at each end
Burial methods and depths (for landfalls and fishing protection)
Dropped object anlysis
Allowable installation stresses and / or fatigue. (How much of the fatigue life can the installation contractor use up during installation?
etc.
etc.

Over the last few years, I think the publication "World Pipelines" (see web portal has featured several actual offshore and shore-to-beach etc. articles/case studies etc. Perhaps some of this experience and illustrations etc. may be helpful to your understanding, if you can get access to same.

Try Subsea pipeline engineering by Andrew C Palmer.

Reel lay is basically where pipes are wound onto a large drum on the back of the boat. Ther pipe is plastically deformed when spooled on and then plastically deformed when spooled off to get the pipe back to its straight length. I think reel lay will do up to about 18". The drums will be big as the boat will take:

Technip CSO Apache

Technip CSO Deep Blue (the largest vessel at the moment)

Subsea 7 Skandi Navica

Stolt Kestrel

What's wrong with the alternative acceptance criteria approach? Engineering Critical Assessment using fracture toughness testing is an established and valid technique (and a vital one when the pipeline is already on the sea bed). On what basis do you think standard workmanship criteria were developed?

Steve Jones
Materials & Corrosion Engineer

Thanks everyone with full of information..
I will read them carefully and come back to you all.

Rgds,
wati

Max OD for reel lay is dictated by the maximum size of seamless pipe available: ie roughly 14". Also, as the pipe OD gets bigger, the pipe length on the reel gets less, so the Apache has to do more round trips to the reel base to reel on more pipe, often removing the lay rate advantages of reel laying over conventional methods (S- and J-lay).

The American codes that apply, ASME B13.8 for gas lines, and B31.4 for liquid lines, along with API 1111 will give you a good summary of what is required for pipeline design.

Also I find that when I am training new engineers the book "Pipeline Rules of Thumb" edited by E.W. McAllister is still useful.

Also regarding the lay comments, S-lay can also be used in deep water it is depending on the line size and vessel capability. To confuse you further there you may also hear "G-lay" refered to, though not often. This is basically a reel-lay where the pipe is run up and over a device that put's it into the vertical position of a J-lay.

SubseaRoy,

"PRT", (at least the edition I have) isn't much use for offshore per say. Is offshore covered in a new edition? Actually B31.4 and 31.8 are secondary to CFR 49, Part 192 and 195 and MMS design requirements have precedence offshore, where CFR DOTs do not apply (or has that changed now?) I haven't worked in the States for 15 years.) And just about anything goes in an unregulated onshore gathering system. Beef me up on the new regs please.

Going the Big Inch!