The great Alaskan Pipeline, wth ammonia heat pump radiators

3 responses to “The great Alaskan Pipeline, wth ammonia heat pump radiators”

1. 

   rocketmavericks

   Aug 28, 2017 at 11:07 pm

   How about ammonia heat pipe radiators? 🙂

   Gotta love the lost art of chemical engineering in the new digital age!!! ( Moore’s law does not apply to backhoes).

   Somehow the oil companies knew about climate change impacting permafrost layers and included compensation into the pipeline. Amazing!!!!

   How they work:
   ffden-2.phys.uaf.edu/webproj/212_spring_2015/Chase_Delatu…

   Reply
2. 

   jurvetson

   Aug 29, 2017 at 3:20 pm

   Thanks! And hope to see ya soon on the playa.

   P.S. here is a follow up email to the wew lad from our engineering guide:

   Here’s a mechanical engineering question from the CHEGG curriculum to shed more light on that pressure question you asked about. By working through the engineering problems you learn a lot about how pump station pressure, pipe pressure, and volume requirements are calculated.

   The design operating pressure of the pipeline is 1180 psi but in reality pressures even close to this are only ever experienced right at the discharge of the pump station. Typical pressures are under 100PSI, and on a slack line or downhill run the pressure is zero at the top then builds. To save energy we only input enough pressure (energy) at the pump stations to overcome friction in the pipe and to lift the oil over the terrain. You need about 1PSI for every 3 feet of elevation gain, so 1000 feet requires about 300PSI, plus you need to keep the oil moving so a little more pressure is required to overcome friction.

   The biggest accident I ever dealt with was in 2012 when a pig got stuck in the pump station 8 discharge port and the high pressure built up and blew out a strainer valve. It leaked a lot of oil because those discharge ports are about 2500+ psi, about 6000 gallons leaked from a tiny little crack in the valve, but all of it was contained inside the pump station berms and tanks. One guy got killed when it blew out.

   The biggest leak we ever had was in 2001 when a guy shot a 1.5" hole in the pipeline close to where we saw it. He used a 338, which shouldn’t have been able to penetrate but somehow did. The oil there is about 100+ to 150 PSI so about 100,000 gallons per day leaked out. I wasn’t involved in that cleanup but was pretty disappointed it took them 3 days to plug the hole. We’re a lot faster now.

   Anyway – this is a good example of how we look at pressures and forces as engineers.

   Thanks again for visiting us here!

   Fred

   Question: Crude Oil is pumped 799 miles across Alaska through a 1.22m diameter steel pipe at a potential maximum rate of 2.4 million barrels a day. A more typical rate would be 1.8 million barrels a day. Using the typical pumping rate determine the horsepower needed to pump this oil through this system.

   The temperature of the Crude Oil is 60oC
   Its density is 860 kg m-3
   And its viscosity is 3.83 × 10-3 kg s m-2
   One barrel of oil is 0.1589837 m3 (42 gallons)

   The volumetric flow rate of the oil is 3.313 m3 s-1

   V=3.313/(p ?1.22?^2/4)=2.834 ms^(-1)

   P_1/?g+(V_1^2)/2g+z_1+h_P=P_2/?g+(V_2^2)/2g+z_2+h_L

   1 and 2 represent points within the large holding tanks at each end of the pipeline. h_P . Is the pressure head provided to the crude oil by the pumps.
   Assume z_1=z_2 the crude oil is pumped from sea level to sea level.
   P_1=P_2=V_1=V_2=0 . These are very large holding tanks.
   Assume minor losses are negligible due to the relatively straight uninterrupted pipeline, which also has a large l/(D=1285591/(1.22=1.05×?10?^6 ))

   Now:
   h_P=h_L=f l/D V^2/2g

   Since the only pressure needed is to push the crude oil through the pipeline overcoming friction.

   The Reynolds number for the flow is:

   R_e=?VD/µ=(860×2.834×1.22)/?3.83×10?^(-3) =776374

   Using the tables e/(D=0.000036) and f=0.0125

   h_P=0.0125×1.05×?10?^6 ?2.834?^2/(2×9.81)=5372 m

   The power needed to overcome this friction head loss is:

   Power=?gQh_P=860×9.81×3.313×5372=150.2 MW

   W=J/s=Nm/s=(kgm/(s^2 m))/s=((kgm^2)/s^2 )/s=kg/m^3 ×m/s^2 ×m^3/s×m

   Converting this to horsepower gives:

   P=355720532/745.69987=201383 horsepower

   There are many reasons why it is not practical to drive this flow with a single pump. First there are no pumps this large. Second the pressure at the pump outlet would need to be ?gh_L and no practical 1.22m diameter pipe would withstand this pressure.

   The actual system contains 12 pumping stations positioned at strategic locations along the pipeline. Each station contains 4 pumps, 3 of which operate are any one time (the 4th is a backup emergency pump to allow maintenance etc.).
   Each pump is driven by one 13,500 horsepower motor; this therefore produces a total output of 486,000 horsepower.
   Assuming that the pump/motor combination is approximately 60% efficient there is a total of 292,000 horsepower available to drive the fluid, which compares well with the above calculation.
   The assumption of 60oC oil temperature may seem unreasonable for flow across Alaska, however the oil is warm when it is pumped from the ground and the 201,383 horsepower needed to pump the oil is dissipated as a heat loss along the length of the pipeline.
   However if the oil temperature were 30oC the viscosity would be approximately twice as large as the value used in the above calculation but the friction factor would only increase from 0.0125 to 0.014. This doubling of viscosity would result in only an 11% increase in the power needed.
   Because of the large Reynolds numbers involved, the sheer stress is due mostly to the turbulent nature of the flow. That is the value of Re for the flow is large enough, on the relatively flat part of the Moody chart so that the friction factor is nearly independent of Re (or viscosity).

   Alaskan Oil Pipeline

   1. Check the efficiency of the pump/motor combination on the Alaskan Oil Pipeline if oil is pumped at the maximum rate and:

   • Only the standard 3 pumps are used per pumping station and the 4th remains as a backup.

   • All 4 pumps are used at each pumping station.

   2. Assuming that the pump/motor combinations are 60% efficient and that the standard 3 pumps are used per pumping station and ignoring any changes in elevation, estimate the maximum horizontal distance between adjacent pumping stations.

   3. Draw a simplified longitudinal section of the route of the pipeline and determine where you would locate the pumping stations and indicate these locations on your longitudinal section. Then estimate the pressure head loss along the length of the pipeline and draw a pressure loss graph for the oil pipeline from the Artic ocean to the Valdez terminal

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3. 

   precious amount

   Sep 6, 2017 at 4:17 am

   Thanks for posting these thoughts. I saw the fins but had no idea they used anything as exotic as ammonia heat pipe systems.

   Impressive hydraulics. (Translation: beyond my comprehension.)

   Scaling it to everyday things: I think each turbine at Glen Canyon Dam is 165,000+ horsepower. Each CalTrain locomotive is 3,800 horsepower.

   You’ve probably already seen the American Experience documentary on the Pipeline. Original construction footage looks like it was shot on 16mm film. I enjoyed footage showing Motorola Micor two-way radios used on the original project.

   Best wishes.

   Reply