subsea pipe in pipe insulation

[heyjaehey]

Hi, I am to design pipe in pipe for transporting crude oil and I am confused to what equations & theories to use. The main criteria is to find the insulation that would bring the product to the destination at the temperature of 90F and above (starting 250F) over 55km.

Any help would be appreciated.

 

[MortenA]

Normal heat transfer thery applies here. Nothing fancy as such.

Best regards

Morten

 

[BigInch]

Given its such a hot oil, be prepared for some possibility of non-Newtonian flow and its resulting heat transfer implications, as in heat transfer during plug flow for example. Your head losses vs pipe distance could be quite nonlinear and the line may flow laminar over some portion and turbulent in others.

You may also need to define multiple pump head capacities you will need as temperature changes occur over start-up shut-downs and restarts after 1 day, 3 days, 1 week etc. shut-downs and/or if sea temperatures change during seasons.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[BigInch]

In other words, your system curve will change markedly during start-ups and shut-downs as hotter or cooler oil or a diluent mix fluid is displaced ahead or behind your normal flow temp.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MortenA]

BigI

I dont think temp changes during shut down will matter much - but you have a point about the cooled oil in the line could have different properties. Apart from this i have heard that non-newtonian flow is cooon for curdes?

Anyway his question was for steady state arrival temperature - and here i think was answer was fair! Theres no way you can specify insulation for an idefinate shut down - it will cool sooner or later!

Best regards

Morten

 

[BigInch]

Morton, try doing a start-up simulation on a crude with 1200 cP at 20ºC and 70 cP at 90ºC. Once the cold stuff is out of the pipeline, you can get rid of about half your head, or perhaps you will double your target flowrate. The crude may have slight nonN characteristics, which may be possible to ignore, but cooling is logrithmic along the length and with such changes occuring to viscosity with temperature, hydraulically similar effects are observed in any case.

Depending on the diameter and insulation start-up times to reach various flowrates after cooling to various lower temperatures over certain periods of time can be quite different. In may cases on land pipelines, full temperature stability is never actually reached due to seasonal temperature variations as well.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MortenA]

I think you have a good point, i havnt looked at start-up of long pipelines - but i know about the temperature instability - even though the danish oil pipeine from offshore is pretty stable at aroundd 20 deg C. The problem is that the data i get is usualy quite old and never taht detailed But i will see if i can get somebody convinced of doing this work some day

Best regards

Morten

 

[swearingen]

Is it just me, or is the OP's question a tad frightening?


If you "heard" it on the internet, it's guilty until proven innocent. - DCS

http://www.eng-tips.com/supportus.cfm

 

[BigInch]

Wassa' matter, don't you like petroleum supply shortage price spikes?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[narenr]

Just run a pipesim simulation with various insulation thickness till you arrive at your desired outlet temperature.



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

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