Calculating coolant concentration when adding coolant

1. RJT
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## Calculating coolant concentration when adding coolant

Is there a handy way to calculate this? Say I have a 100 gallon tank that is 20 gallons low and has a 12% concentration. At what concentration do I mix the 20 gallons I'm adding to get it the 100 gallon tank back to 8%? Or a 30 gallon tank at 6% that is five gallons low, at what concentration should I mix the 5 gallons to get it up to 8% ? Sure would be nice to have a chart, or formula, but there's a lot of variables. We just kind of estimate, but I would like to be more precise. We have 10 different size tanks we are trying to regulate, trying to maintain 8% for all. What method do you use?

2. Cast Iron
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An interesting problem in elementary mathematics.
No doubt somebody will jump in before I manage to pull my thoughts in order at this late hour (2230). Will follow this thread and if no proper answers, I will give it a try.
Hope you're not running out of coolant in the meantime!
Regards, fusker

3. Originally Posted by RJT
What method do you use?
If it's too lean, I add 20% mix.
If it's too strong (usually the case due to evaporation) I add straight water.

The formula you would use depends on several factors, which makes the formula a bit cumbersome, but OK ...

Vi = How many gallons the tank currently has
Vf = How many gallons you want in the tank after adding mix
Ri = Current concentration
Rf = Target concentration

(I think ...)

Regards

Mike

4. I think the hard part is knowing exactly the volume of MIXED coolant you need to add to get
the tank full..

If you want to make it simple.. Its

The Amount of Concentrate in a FULL TANK

minus

The Amount of Concentrate IN the tank

equals the amount to put in..

You WANT 100 gallons at 8%, 8 gallons of concentrate in the tank.

You have 80 gallons at 12%.. 9.6 gallons of concentrate.

You need to add 20 gallons with NEGATIVE 1.6 gallons of concentrate.

2nd example.

30 gallons at 8% is 2.4 gallons of concentrate

You have 25 gallons at 6%. 1.5 gallons of concentrate.

You need to add 0.9 gallons of concentrate when you top it up..
That's a MUDDY mix.

In the first example, you can't make a concentration that is negative, unless you have
DARK coolant... Though if DARK coolant touches regular coolant, it turns to pure energy
and we all die.

Second Example. .9gallons divided by 5 gallons equals 18% mix.

5. Hot Rolled
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Originally Posted by Bobw

In the first example, you can't make a concentration that is negative, unless you have
DARK coolant... Though if DARK coolant touches regular coolant, it turns to pure energy
and we all die.
And that is why I never miss a day checking this forum. Thanks I tip my hat.

6. Titanium
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Adding straight water to correct too high a concentration is asking for coolant problems as it destroys the water/oil emulsion. Better to add a 1 or 2% solution and work that toward your goal than adding just water. If ya RTFM, it usually tells you this. Just sayin.

7. Plastic
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We've been having plenty of trouble with our coolant and pretty sure it is down to us managing concentrations poorly so we've been trying to think of a way to manage this better. I am interested to see how others manage.
As shown above it's relatively easy calculate how much coolant needs to be added if you know your volumes. Knowing the volume needed to get back to full on different machines is the tricky part in my book.

What i'm planning on doing is picking an appropriate point on the gauge/tank of each machine and marking this as your refill point.
Then, using the 5 gallon bucket, figure out how many buckets it takes to get you back to full.
Now you know the volume you are adding and its the same every time.
Perform some math wizardry as shown above and print yourself off a pretty chart for each machine with current % and how much coolant to add to the fixed no. of buckets.

Works in my head anyways but have yet to implement.

8. Dump some water in it and leave few inches for coolant concentration....mixture be damned but the question is as well

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Originally Posted by Dan from Oakland
Adding straight water to correct too high a concentration is asking for coolant problems as it destroys the water/oil emulsion. Better to add a 1 or 2% solution and work that toward your goal than adding just water. If ya RTFM, it usually tells you this. Just sayin.
Unless you're running Oemeta Hycut. Straight water is ok with that coolant.

I find my guys are surprisingly accurate just guessing. One of them will test the additive and oil concentration first thing in the morning, then add whatever mix he thinks he needs after the machines are up and running. We are never more than 1/2% off. Don't over think this.

10. Diamond
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Originally Posted by Bobw
I think the hard part is knowing exactly the volume of MIXED coolant you need to add to get
the tank full..

If you want to make it simple.. Its

The Amount of Concentrate in a FULL TANK

minus

The Amount of Concentrate IN the tank

equals the amount to put in..

You WANT 100 gallons at 8%, 8 gallons of concentrate in the tank.

You have 80 gallons at 12%.. 9.6 gallons of concentrate.

You need to add 20 gallons with NEGATIVE 1.6 gallons of concentrate.

2nd example.

30 gallons at 8% is 2.4 gallons of concentrate

You have 25 gallons at 6%. 1.5 gallons of concentrate.

You need to add 0.9 gallons of concentrate when you top it up..
That's a MUDDY mix.

In the first example, you can't make a concentration that is negative, unless you have
DARK coolant... Though if DARK coolant touches regular coolant, it turns to pure energy
and we all die.

Second Example. .9gallons divided by 5 gallons equals 18% mix.
I hope you're correct, that makes more sense than trying to derive the equation I can never remember

11. Hot Rolled
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I think the important question is do you have a refractometer so you can test how the concentration is changing from evaporation and carryout on parts?

12. Diamond
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I don't put that much worry into it. I check with the refract, and if it's too high, I mix some water with just a splash of coolant, to bring it down. Pour it in, run it and see where it went from there. If you want to run at 8%, don't fret too much if it winds up at 9 or 7. Much more important things to worry about.

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14. RJT
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I agree, knowing how many gallons it will take to fill the tank is an estimate. Some machines get used daily, others may sit for a week idle. Everyone mixing their own will ad more variables, maybe one guy should do it all the time for more consistency, but to really get a handle on it,looks like it should be done daily with each machine. How often do you check / add coolant?

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Originally Posted by RJT
I agree, knowing how many gallons it will take to fill the tank is an estimate. Some machines get used daily, others may sit for a week idle. Everyone mixing their own will ad more variables, maybe one guy should do it all the time for more consistency, but to really get a handle on it,looks like it should be done daily with each machine. How often do you check / add coolant?
We check / add every morning as part of starting up the shop, no exceptions.

16. Cast Iron
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Originally Posted by [email protected]
Don't over think this.
Quite right. It took me a few hours to construct the equations and nobody would pay me for time and effort. Quite funny, though. I felt quite clever, long as it lasted.

fusker

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18. RJT
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Mike,
Using your calculations, what happens when you come up with negative number?

Vi = How many gallons the tank currently has 85
Vf = How many gallons you want in the tank after adding mix 100
Ri = Current concentration 10
Rf = Target concentration 8

Vadd = Vf - Vi =15
Radd = (Vf*Rf) - (Vi*Ri) / Vadd Radd = (100 x 8) - (85 x 10) / 15 = -3.33

Mix at 3.33 % ??

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R

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Mike,

The only way to get negative concentration to add is if the amount of coolant in the water is already more than should ever get in the full tank.

If that happens, it means you added too much coolant at some earlier time. Flush some amount of the mix, recalculate, repeat as necessary until you get a non negative ratio.