Hi guys,
I am an engineering intern working for an oil company this summer. My project is to design a pipeline and gathering system to transfer saltwater from 10 central tank batteries to a central disposal site. Each tank battery will have a pump. I have done a few preliminary pipe calculations and have contacted our pipe vendor to get price estimates. The sales rep I talked to scoffed at my flow calcs, though, when he heard what I wanted and was trying to do. I will list my basic calculations below. Am I missing something, or can you guys find any significant mistakes in my calculations?
Material: HDPE spoolable pipe, with a Hazen-Williams C factor of 150
Distance: 36,000 ft
Change in elevation: none (to make things easy)
Fluid density: 1181 kg/m^3 (it is a very salty brine)
Viscosity: 1.2 cP
Pipe Diameter: 3.9" ID
Requirements: 2400 BBL/DAY capacity. I figured on 150% safety net, so 3200 BBL/DAY. Once again, for ease, I assumed that 3200 BBL/DAY divided equally into the 10 central tank batteries (CTBs), thus, 320 BBL/DAY/CTB. The head engineer wants the pumps running no more than 6 hours per day. Additionally, he wants each individual pump to run no more than 2 hours per day (it could be for a solid two hours straight, or for 20 minutes here and there...the pumps will kick on and off from tank level sensors in the tanks at each CTB.)
For my calculations, I figured: 320 BBL/DAY/CTB pumped over a span of 2 hours = 160 BBL/HR/CTB
Since you have 6 hours of total pumping time and 10 CTBs pumping for 2 hours each, I figured that 3.33 CTBs would be pumping at all times in those 6 hours (3.33 the first 2 hours, 3.33 the next two, and 3.33 the final two.) 3.33 CTBs pumping at 160 BBL/HR/CTB= 535 BBL/HR. 535 BBL/HR*24 hours/day=12,840 BBL/DAY or about 13,000 BBL/DAY, which is what I told the sales rep. (I know, 13,000 BBL/DAY capacity for a pipeline only expected to carry 2400 BBL/DAY seems a little overkill.)
Anyways, 12,840 BBL/DAY = 375 gpm. In order to get a flowrate of 375 gpm through 3.9" ID pipe, over 36,000 ft, even with a super smooth pipe, is going to require over 10 ft/sec fluid velocity, with a friction-loss pressure drop of over 1300 psi, by my calculations. In order to pump that kind of pressure, its going to take one hell of a centrifugal pump (thats what the head engineer wants) and we are going to be operating too close to the maximum OP of the pipe (1500 psi), at least as far as I can tell. I recommended going to a 6" pipe, but the sales rep insisted that 4" would be fine and said he would consult his engineers to get a "real" flow calc from them. Is there something that I am seriously missing here? I have did the calculations over and over, and trust the numbers, but I agree, it just doesn't seem right to me, either. Any help on this would be greatly appreciated.
Welcome to the forum and man, they are really testing you. Without spending time on figures, 36,000ft (7 miles) seems nuts to me to try and do that with a single pump. I would be putting lower pressure pumps every mile. Size the individual tank-pumps to get the mile distance+30%. Then size the mile-pumps for the total flow to the next pump.
I think the pipe guy was just being nice by only "scoffing!"
By my Pressuredrop calculator , it will be 90 Bar , or about 1300 PSI , speed about 10Ft/sec , seem to be, your´s calcs are good .
I wonder the how big will be the pump .
Feel fre to contact me
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