Is it possible to add a 2nd coolant pump to a mini mill for extra coolant pressure?
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    Default Is it possible to add a 2nd coolant pump to a mini mill for extra coolant pressure?

    There's room for it. Or would it be better to just buy one higher HP pump?

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    I would say bigger pump....... What were you going to do with the second one? Run them in series??

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    In series there will be less pressure drop across both which will increase flow.
    In parallel it will need one way check valves on both to keep the stronger pump from backflowing the weaker pump.
    Which is cheaper, a higher HP pump or a smaller with the added connectors and hose?

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    In series the shutoff head will be the sum of the shutoff head of each pump. If the pumps are identical the flow rate will be the same as one pump.

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    I needed more pressure, and I went with a bigger pump. It worked.

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    Quote Originally Posted by CutEdge View Post
    I needed more pressure, and I went with a bigger pump. It worked.
    What did you end up going with?

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    It's not as simple as two in series gives more pressure but the same flow (assuming centrifugal pumps). Your coolant system has what is called a characteristic curve that is the flow that will occur with an unlimited volume of fluid at a series of pressures. Your pump also has a characteristic curve that is flow for a given back pressure. The point where the lines cross is where the system will run.

    Here's an example:


    The flow of a centrifugal is very dependent on rpm. You can see where the pump curve and system curve cross (red circles) at about 5 gpm for 690 RPM, 75gpm for 2070 rpm, and 135gpm for 3450 rpm. If you were to put 2 2070 pumps in series(Green line), you would get double the head at zero flow, but it doesn't do a whole lot of good for this particular pump and system characteristic. You'd go from about 75gpm to about 95gpm (based on rough pencil scratchings).

    Interestingly enough, with these pumps and system curves, if you put two pumps in parallel (blue line) you would get just about the same operating point either way.

    Please recognize that this illustration is qualitative, you would need to get the curves for your pump and your system curve to engineer the system. With a centrifugal pump, the most powerful tool is rpm, as shown by the uppermost pump curve. But the power consumption goes up as the cube of the rpm.

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    More pressure and higher HP pump may not belong in the same sentence.
    A 20 HP pump may give you tons more flow if can be used but no more pressure than a 1/4 HP.
    Much depends on outlets an flow ability and then if two in line it is a booster pump setup.
    You are asking for more pressure and not flow, different animals so the above chart not a lot of help.
    High pressure coolant is not high flow rate or high GPM coolant.
    Do you want more coolant on the parts (flow) or more pressure in the stream (PSI out)?
    I know this is confusing but apples and oranges.

    High pressure coolant is often in the 800+ PSI range, sort of like a quarter fed car wash hose. These break chips and blast anything out of the way. Stick your finger in front of the output and you will be sorry.
    No amount of centrifugal pumps in any horsepower or arrangement will get you there.

    I do not know if you just want more coolant or lots more pressure.
    Bob

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    It was part of a filtration system by Ebbco, but I don't know the model of the pump itself off-hand. It was 20gpm at 40psi.


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