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Pump Selection
3

Pump Selection

Pump Selection

(OP)
I have the following conditions and I need to select a pump that will precisely control the flow.
Liquid = Fuel Oil and various grades of oil (SAE-10, SAE 40 ,Diesel Fuel....)
Tank Size = 250 gal  Avg Specific gravity = 0.9  
Discharge size 2"
Tank is a 3'x3'x4' square tank
Controlled Flow is .004 through 150 gal per minute.
Opertating Temp 60-150 F
Flow will need to be precisely controlled for use on a viscosity calibration manifold.
The system will also need to be recirculated
I'm not sure of the pressure required nor do I think it matters.
What type of pump and control is available to complete this task

RE: Pump Selection

Hello,

my name is Chuck. I am new, and I see a whole lotta big words flyin around.....and I don’t use big words....


if pressure is of no concern, i would go with a PD pump like a mono-flow (rotating stator).  it's friggin long, as far as I am concerned, so if space is not premium, it is a good choice. Now you need a motor suitable for at least 20:1 turndown and a VFD.  You will oversize the driver to accommodate the constant torque requirements at the low RPM's. if the pump HP is 10, you will probably double it up to 20 HP.  If you run at low speeds a lot, a supplemental blower would be in order, as the shaft mount fan will put out a mousse fart for cooling.
. this is going to be tough to match the low flow requirements of .004 gpm….this is to 4 thousandths of a gallon.  
Your range is quite wide.  You will need to be able to send signal back and forth.  i would use a Allen Bradley SLC-500, or 1000, as well as accurate pressure transducers for pressure readings.   If you can elevate your tank, you can kill NPSH issues, and have the PD feed from a tap on bottom of tank.

C

RE: Pump Selection

i'm no expert on this topic, but as a suggestion, wouldn't it make sense to provide e.g. 4 pumps in parallel? to accomodate the big range of neccessary flowrates?

RE: Pump Selection

My initial suggestion would be to abandon the idea of selecting a pump to "precisely control your flow."

RE: Pump Selection

You specify the application as a viscosity calibration manifold for fuels and lubricants and that the fluid will be recirculated.
Much will depend on your process viscometer and the manufacturers recomendations.
Even though these are Newtonian fluids, flow is very critical. My experience says it must be constant.
Without knowing the viscometer you are using, i can't advise exactly.
When designing process viscosity analyser systems, including for heavy fuel oils, bitumens/asphalts and lubes, i use a gear pump with a delivery of between 10 and 20l/min. In some applications I find it necessary to use a VFD to find the optimum flowrate. For fuel oil applications i just use a 20l/min gear pump.
The main concerns i usually have are that the sample loop will be at pipeline pressure, which the pump must withstand, but the pump usually is not doing much work so the dP is quite low.
However, reading your post, are you designing some sort of calibration set up for viscometers?

RE: Pump Selection

Your flow range requires a turndown of 150/0.004 = 37500:1.
This is too high to be achieved in practice with a single conventional pump at continuous flow rate. Also you are unlikely to find a flowmeter with this sort of turndown and reasonable accuracy at the bottom end.
I agree with the other posted comments.

When I need to meter flows accurately and for test purposes, I still use a header tank with constant overflow. This gives me near enough to a constant head system. Separate outlet pipes are used for the flow. If the header tank supply pump is fitted with a bypass, then the head can be controlled tightly. You may be able to adapt the gear you have to work the same way. But you will need a header tank and suitable flowmeters. There may be some problems is you want to use highly viscous oils so you need to establish an envelope of your requirements first.

Cheers

Steve

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