Intermediate pump station spacing

[flexflo]

Want to significantly increase capacity of an old 8" crude pipeline that is 40 miles long on level terrain. MOP 750 psi based on design strength of the pipe. Installing four intermediate pump stations plus DRA would achieve the objective more economically than looping the entire line. Is it feasible to have that many stations only 8 miles apart or would I have line up problems due to transient pressure issues? How close is too close?

 

[BigInch]

That's a totally unresonable number of stations in 40 miles of LEVEL terrain. You shouldn't need more than 1. Your velocity is way too fast and I will predict right now that you will not be able to hold transient pressures under allowables, not to mention erosive scour of internal pipe wall, OR ENERGY COST within reason. Do yourself a favor and buy some road tankers, or build a railroad, or loop the existing line. Either of those options will be far cheaper.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

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

 

[flexflo]

Thanks for the response. I know it's unreasonable to have that many stations, but I'm not certain how to prove mathematically that it's unfeasible. I'm up against people armed with a hydraulic gradient that shows it can be done. Of course, most head loss calculations are approximations based on non-compressible liquids and uniform pipe etc. Where can I find more rigorous calcs to prove their folly?

 

[BigInch]

Anything can be done. The problem comes when you have to pay for the operation and maintenance of it.

Yes I'm sure that somebody has done a gradient diagram and and can prove it works (for a month or so).

First do a velocity calculation. Pipelines should normally be kept within 3 fps and 10 fps to avoid sedimentation at low velocities and pipe wall erosion and transient pressures at higher velocities. I'm sure the velocities must be very much greater than 10 fps. That's the first killer card.

Second killer card is to calculate the cost of power needed to operate this pipeline at that high flowrate. Then add a lot of maintenance due to erosion blowouts.

Fourth killer card is to calculate the cost of installing and maintaining 4 pump stations and an old pipeline (which will probably require considerable maintenance) as opposed to just one high pressure pump station and a new high pressure pipeline (using DRA) of the correct diameter.

What is the maximum flow you are designing for now and the operating pressure of the old pipeline?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

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

 

[flexflo]

8.625" OD x 0.250" wt pipeline. MOP is 750 psi and we want to flow 60,000 bpd of 40 API crude oil (kinematic visc ~ 3 cSt). Replacing the line would cost $20 to $25 MM because of congestion, sensitive areas, etc. Pump stations would cost around $1MM each (not including power infrastructure). Velocity at 60 Mbpd = 10.8 fps. I'll look into the erosion issue you mentioned along with surge pressure risk, which might be significantly higher than normal at this velocity. Thanks again for the comments.

 

[BigInch]

OK, normally it wouldn't be so much to loop the line, but you've got a high cost there. Still something seems very wierd that you need 4 stations. Don't believe it.

Got it. I think the 4 pump stations are needed WITHOUT DRA.

Where's the DRA study? How much DRA do you plan to use?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

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

 

[BigInch]

I've run some estimated numbers and get a 12" pipeline as the most economic diameter w/o DRA. I'd guess 10" would work with, or w/o DRA.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

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