Deep Water Pipeline

[akbari1358]

Dear all,

What are the key factors regarding steel pipeline for deep water application? Basically is there any difference between shallow/deep water or onshore pipeline material? Is it allowed to follow API 5L for offshore applications?

Best regards,
Akbari

 

[DekDee]

You are looking to install sub-sea piping and you are asking for advice on an internet forum ?

 

[LittleInch]

If you're just looking at material then not very much difference. Most of it is some sort of high strength Carbon Steel pipe.

However most subsea pipelines and especially deep ones are designed to DNV OS-F101 which includes within it it's own pipe material specification which you need to use.

Design is completely different.

As dekdee says, a very very basic question without any context or background so a pretty bland response...



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

 

[akbari1358]

Thanks for valuable response, I've not experienced offshore pipeline project however I was involved in several onshore pipeline. Of course the design is totally different! the following are the key factors in steel pipeline but I don't know weather the same for offshore or not.

(1)CV value on Charpy test (API 5L/ISO 3182 – Table 22)
(2)Share % of DWTT test (API 5L/ISO 3182 - 9.9.1 DWT test for PSL 2 welded pipe)
(3)Carbon equivalent - % of Ceq/Pcm (API 5L/ISO 3182 – Annex J – Table J.1)
(4)Specification of coating - 3LP+concrete (?)

 

[BigInch]

You can use the same API 5L pipe spec.

You can also see the sections of ASME B31 Pipeline Codes B31.4 or B31.8 relevant to the minimum design requirements for offshore pipelines. The design of an offshore pipeline is not completely different, as there are many, many similarities, however the environmental and installation stresses are far different than what you may be used to for onshore pipelines.

 

[georgeverghese]

I'm no expert in offshore pipeline design; sooner or later you may need to know when and how to design buckle triggers for high temperature subsea applications.

 

[BigInch]

Thermal buckling can also be a design consideration for high temperature, onshore pipelines, although it often can be more easily triggered in a high temperature, offshore pipeline is not buried. Otherwise there is no difference in the basic design procedure for thermal buckling of either on or offshore pipelines. The onshore buckling design procedure was derived from the same equations that were developed for offshore pipeline buckling.

 

[georgeverghese]

Some 15years ago, I was told a feeder subsea pipeline to a large offshore platform in the Java Sea (formerly called the Ardjuna Sea) was rendered unpiggable because it was badly kinked at the riser since buckle triggers hadnt been considered - this facility must have been operating for at least 10years by then.

 

[akbari1358]

Thanks guys, but responses not helping. The question is not regarding design, that's about material and or tests which is necessary to be taken care from pipe manufacturer for offshore pipeline during manufacturing of pipe. We are using API 5L X70/80 in onshore projects for dry, solid free and sweet natural gas services with the mentioned tests above I am not sure of applying the same for submarine pipeline.

 

[LittleInch]

If it's transporting the same material then the tests should be the same.

Whether you need concrete coating is dependent on the design requirements / size, wall thickness, currents, waves, trenched or surface laid etc.

Just make sure that the design code you use allows API 5L / 3183 pipe - DNV doesn't allow it and is in common use along with B 31.4/8 for subsea pipelines

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

 

[BigInch]

"dry, solid free and sweet natural gas services" does not require special materials, as such you should use API 5L. There is no difference in API 5L for on or offshore service, other than you might want to do some exta quality control, so that you can be sure that you don't waste all that expensive offshore construction time sending some of it back to the shore to be replaced.

 

[blacksmith37]

Material and design interact. I remember some lines made in Gr B or X42 to provide more weight to keep the pipe down.

 

[BigInch]

Unless you have a very unusual case, concrete weight coating is far cheaper than buying extra steel wall thickness to be used only for it's weight. And most pipe diameters 6" and above will float, regardless of wall thickness. 6" XS and thicker wall will sink, but all other 6" walls and all larger diameters will float without weight of some kind being added.