Advantages Carbon steel marine pipelines vs HDPE

[IrIngMsc]

Hi I am working on a comparative study on the use of HDPE vs Carbon Steel marine pipelines for an offshore water intake.
I am schooled as a structural steel and concrete bridge engineer and this the first time I'm on an offshore project.

I've listed all the advantages of HDPE (durability and deployment) over the use of carbon steel. Now I want to do the same for carbon steel, but I can't come up with anything other than that carbon steel is better in withstanding the impact of a ship anchor or any type of other impact.

Does someone know some other advantages of the use of carbon steel over HDPE marine pipelines?

 

[rconner]

fyi you may wish to see references and discussion at

http://eng-tips.com/viewthread.cfm?qid=177906

(plastics and steel are quite apples and oranges)

 

[StephenA]

Maximum diameter of an HDPE pipe is presently 2000mm and even that is pushing it a bit, so larger intakes would have to be concrete or steel.

Steel pipe may need a smaller trench (if buried) as the continuous collars would be thinner that that required for the PE pipe. However if "string of pearls" (continuous collars with small gaps between them) were used for the PE pipe then maybe even ship's impact would be OK.

Liquifaction of the backfill material, caused by wave action, would be another reason to use steel pipe, as the PE pipe would "pop up" through the backfill. If the PE pipe is made heavy enough not to rise in the liquified backfill it will not float during installation without additional buoyancy. Another solution would be to use an engineered backfill to eliminate liquifaction but this can be very expensive.

Stephen Argles
Land & Marine

http://www.landandmarine.com