Automatic Centralized Coolant Tank Maintenance System - Page 2
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  1. #21
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    Quote Originally Posted by kunalv View Post
    Agreed. Refractometers cannot be provided on each machine. What we have decided so far is we will draw a certain quantity of coolant from each machine into our 'Measurement tank' where a refractometer would analyze the concentration & feed to the PLC. The PLC would then actuate valves & a pump to deliver appropriate quantity of coolant & water to the tank to maintain concentrations at desired levels.

    Having said that, I have a few queries which I would really appreciate if you guys could throw some light on :-

    1. Drawing liquid from the machine coolant tank into my measurement tank will require a pump. Now I am not sure if I have to install a pump next to each coolant tank (cumbersome), or my centralized unit will have a pump that will draw liquid from number of machines (what about the suction head? as the machine may be a good 50 feet away!). Which type of pump would be suitable for such an application?

    2. After measuring the concentration, I have to feed coolant at appropriate concentrations back to the Coolant tank. I guess delivering pre-mixed coolant (coolant mixed with water at required concentration) would be better than delivering coolant concentrate & water separately into the coolant tank right?

    3. How do I measure & control the flow rate of liquid? Flow-meters are expensive.

    Any help would be greatly appreciated. Thanks
    Take care as to how you introduce your coolant concentrate. Some coolants are picky as to how they need to be mixed.

  2. #22
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    Apologies for the long hiatus.

    We're still working on the project and have now encountered a new problem. So, the coolant concentrate & water mixture has to be fed to the machine tank in a mixed, emulsion form at a particular concentration as per the requirement of the process.

    Now I have been trying to find out ways to do this, and all I could find so far are these Venturi Proportioners / Mixers that work purely on Venturi principle. But for this to work, you have to manually turn the knob to set the desired concentration.

    I was wondering if there is a way to automatically set the required concentration by a PLC on a valve/pump that meters the desired concentrate as per the set concentration.

    Any help would be appreciated. Thanks

  3. #23
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    Quote Originally Posted by kunalv View Post
    Apologies for the long hiatus.

    We're still working on the project and have now encountered a new problem. So, the coolant concentrate & water mixture has to be fed to the machine tank in a mixed, emulsion form at a particular concentration as per the requirement of the process.

    Now I have been trying to find out ways to do this, and all I could find so far are these Venturi Proportioners / Mixers that work purely on Venturi principle. But for this to work, you have to manually turn the knob to set the desired concentration.

    I was wondering if there is a way to automatically set the required concentration by a PLC on a valve/pump that meters the desired concentrate as per the set concentration.

    Any help would be appreciated. Thanks
    Venturi proportioners can be problematical The length of the discharge hose will affect the mix. A longer discharge hose causes backpressure and changes the percentage of the mix. A piston type displacement pump does not have this drawback.

  4. #24
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    You could use the fixed-orifice / pressure flow-rate method for mixing quantities.

    You would need a large vessel to hold the mixture, top vented to be at atmospheric pressure. Basically, two solenoid valves introduce the two different liquids, each through a known orifice size. You would have to test the flow-rate beforehand: the longer your sample size ( time-wise ), the more accurate the result.

    For instance, one pump supplies coolant concentrate from a reservoir, at, for instance, 10 psi through a 0.250” orifice. Accurately measure how much fluid is dispensed in a 1-minute time frame. Now you have a time/volume relationship. Same for the water. Then, when your micro controller reads the inline refractometer value, and calculates a certain ratio to correct it, said micro controller actuates those two solenoids to fill the mixing vessel with the appropriate quantities. Micro controller activates another relay for an agitator / mixer motor, run for a prescribed duration, and you have your mixture.

    Or maybe that’s dumb. I’m sure someone will let me know if it is.

  5. #25
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    If the system develops a bad leak, would it continue to pump coolant on the floor?

  6. #26
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    Quote Originally Posted by kunalv View Post
    Also, the formula used for calculating the make-up quantity & concentration of coolant to refill the tank due to evaporative & drag out losses makes use of a very important factor - existing quantity of liquid in the tank!

    How do I determine that in an automated process?
    easy...weight, not easy...how to weigh it

  7. #27
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    You say centralized coolant tank but you seem to be talking of filling and maintaining a tank at each machine.
    How about using humans? A water fill valve and a raw coolant fill on on a cart with a metered dispenser.
    Daily concentration checks are done and written on your layered audits.
    No fancy automation needed, just a training of your work force.
    Ask yourself why you need this.

    Bob


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