Pipeline Crossing 1

[jshaw17]

I am looking for any reference material that might help in doing analysis of pipeline crossings. We are putting in a pipeline that is about half a mile and it has 8 crossings. Any papers or books would be appreciated.

 

[rconner]

You have not noted exactly what your pipeline is, or for that matter what it is crossing (and this will probably have bearing on appropriate references). However, I am aware there is a "Pipeline Crossings" technical committee of the American Society of Civil Engineers (ASCE) who have worked on some publications over the years, including a manual called "Pipeline Crossings" (MOP No. 89 presented first at a Pipeline Division specialty conference in Burlington, VT in 1996). I'm sure there are many other arguably more specialized industry references, e.g. for water and sewer etc. the bridge and subaqueous crossing publications of DIPRA (e.g. available for download from

http://www.dipra.org/pdf/subaqueous.pdf),

as well as manufacturers literature sections e.g.

http://www.acipco.com/adip/products/Sect10.pdf.

 

[jshaw17]

Sorry for the lack of info. We are running a 12" pipeline across 8 other pipelines ranging from 4" to 8" in about 440 foot of water in the Gulf of Mexico.

 

[jshaw17]

Also it is an Oil line running API SG 30 Crude.

 

[BigInch]

Will the line be buried?
Will the other pipelines be lowered?
US Gulf or Mexico?

I've constructed cement bag pyramid structures to maintain separation.

http://virtualpipeline.spaces.msn.com

 

[GregLamberson]

There is a spoecification, VERITEC E305, "On Bottom Stability Design of Submarine Pipelines". As with BigInch, have used concrete mats to bridge pipelines. If you use the pyramid structure, you should have a minimum side slope ratio of 1:1. Also, you can use ashoalt/concrete mats and if the soil condisitons are bad you can use piled/bridged crossings.

Watch the spacing between supports so it doesnt;t exceed the new pipeline'sa maximum unsupported span length. I believe VERITEC E305 (I don't have a coipyu with me), require the design to provide a minimum safety factor of 3.0 against bearing failure of the soil.

Obviouskly, it is preferable to have the larger (heavier) pipeline to be crossed by the smaller line so that any differential settlement, whyich would be expected of the heavier line, would tend to seperate the pipelines further.

Seapartion is also required to isolate the CP systems of the two lines. Generally a final separation (after settlement) of 0.5M is recommended as a minimum.

As far as analysis, the new pipeline stresses and stress combinations that rewsulet from all load factors (weight, buoyancy, thermal effects, pressure bending, residual tension, environmental forces, etc,) are available in the applicable ASME Code (B31.4 or B31.8). Some comapny;'s have al ittle more stringent requirements for hoop, longitudinal and combined stresses at various stages (installation, testing, and ioperations).



Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[narenr]

Lay your pipeline over the existing pipelines with a separation of 300mm. This can be done either by pre installation of precast concrete mattresses or post installed grout mattress as supports for your pipeline. The supports has to be placed on either side of the existing pipelines and the pipeline configuration over the supports shall be such that it is not overstresses. The pipeline profile can be adjusted by varying the support height till the pipeline stresses are acceptable.

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[BigInch]

300 mm separation is pretty slim pickings for an offshore line.

http://virtualpipeline.spaces.msn.com

 

[narenr]

300mm separation is specified in API-RP-1111 and DnV OS F101. Note that installation of offshore crossing is expensive and any increase in support height is increments costs.

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[BigInch]

API-RP-1111 specifies the minimums.

Its more expensive to fix it than to do it right the first time.

http://virtualpipeline.spaces.msn.com