[Terry G]

Hi,

I've been trying to figure out what is going on with my coolant. Can't seem to find any scenarios like this so I thought I would ask.

I had quite a bit of tramp oil floating on my coolant, so I installed a Zebra tube skimmer. I ran it for about a week for a few hours a day and it removed the oil slick. Though coolant was now looking a bit light in color. I guess the oil skimmer will also remove the oil mixed in to the coolant making up the proper 5% mixture. Is this true?

After running the skimmer I checked the coolant with my refractometer, and it was only at 1.5% (should be 5%). Coolant was also on the low side, so I went ahead and filled it up and brought the mixture to exactly 5% again. It looked perfect in color, and smelled right. Checked with the refractometer again the next day, and still perfectly at 5%.

I ran the machine for a few more days with the new coolant, then it sat for about 12 days without running. During this time I did not run the skimmer since the coolant was fresh and the mill was hardly run.

Today I checked on the coolant and there was a thin yet solid oil slick over the entire tank (except where the bubbler was bubbling). I have no idea where this oil came from since the machine is clean with fresh coolant, and there is no way that much oil could have come from the ways after a few hours of running.

Using my chip scraper, I mixed the coolant up in the tank and got rid of the oil slick pretty quickly. Though the color was not the clean blue it was before, again it looked light in color (and a little green). I checked the mixture with the refractometer and it was at 2%.

This is what is puzzling me. Does soluble oil coolant start to separate after it sits? Is this where the oil slick is coming from, and why my mixture ratio reads so low?

I loose about 2 to 3 gallons a week from evaporation, so I would imagine the mixture level would go up, not down. At this point, it seems I would have to mix another double batch or 10% ratio coolant for the 2nd time in a row to bring it back up to 5%. But it just doesn't add up.

The refractometer has been calibrated and checked with fresh water, and fresh batches of coolant before it gets mixed in and it reads perfect every time. Must be missing something obvious.

Any thoughts or comments on this?

Thanks.

[Machineit]

Yes, coolants can separate. Some of it depends on how you mix it to begin with.

Believe it or not, you don't just put the two together. Most coolants today are added to the water slowly. A mixer is the best way to do this, but they can be expensive. Some in the past were mixed by adding water to the coolant. One way the water molecules surround the oil molecules and in others the oil molecules surround the water.

Bottom line, check with the manufacture and get the detailed mixing instructions. From what I was told, once mixed wrong, it can't be fixed.

Best to run the machine for a few minutes each day just to keep the coolant mixed and bacteria free.

Mike

[txcncman]

Some of the chemicals in the coolant/water mixture can evaporate. They can evaporate differently due to atmospheric conditions (heat, humidity, etc.). If the alcohols of the coolant evaporate first, you will end up with the lower numbers. If the water evaporates first, you will end up with higher numbers. I do not think any of the machine tool builders or the coolant manufacturers recommend you let coolant sit in the sump for 12 days. Might want to follow their recommendations. It does not take much way lube to coat the top of the coolant. I would recommend that you run the coolant pump, skimmer, and bubbler about 15 minutes every day or two, even if you have no plans to use the machine. You probably could wire these up in parallel with a 24 hour timer that could run them for you, whether you remember to or not. As noted above, coolant begins to separate when sitting over time. Running the coolant pump periodically helps keep it mixed. I do not buy into the water first-then coolant or coolant first-then water ideas. If this was ever recommended by a coolant manufacturer, I never saw it on any instructions for use I have read. I have done it both ways and have never had additional problems with coolant as long as the machine is properly maintained.

[haastec]

Yes, coolants can separate. Some of it depends on how you mix it to begin with.

Believe it or not, you don't just put the two together. Most coolants today are added to the water slowly. A mixer is the best way to do this, but they can be expensive. Some in the past were mixed by adding water to the coolant. One way the water molecules surround the oil molecules and in others the oil molecules surround the water.

Bottom line, check with the manufacture and get the detailed mixing instructions. From what I was told, once mixed wrong, it can't be fixed.

Best to run the machine for a few minutes each day just to keep the coolant mixed and bacteria free.

Mike

Well said!

Water quality will play a big roll with this also. If you have very hard water, the minerals and solids will stay in the tank after evaporation. To many solids in the water will hinder the binding process between the water and oil.

Good luck!

[Matt@RFR]

One thing I know for sure is that it's not your Zebra. I run mine 24/7 and have no problems.

Like Mike said, I find that mixing your coolant properly is a huge help. I run Blaser and bought their mixer. I went from having issues like you state, to having zero issues with my coolant. I also found that it takes MUCH less concentrate to get to my 8% with their mixer than it did by hand mixing it. I think that is very telling. I haven't changed my coolant (80 gallons in total) in over 3 years, and it looks like it'll be good for another 3 years atleast.

[underthetire]

+2.

Mixing it correctly is key. Adding water on top of concentrate is bad. It sets off the biocide in the coolant and cooks it. Also never add straight concentrate to a tank if you can avoid it, and never add straight water to the tank.

[Terry G]

Thanks for all the great replies.

I'll add a bit more info based on some of the comments.

I mix my coolant 5 gallons at a time until it reaches the light blue color of the Cimperial Blue 1070 coolant I use. Then I add it to the machine. I have only ever used RO water with the machine as well.

I have been using this mill and coolant for about 1 1/2 years, and since then have cleaned the machine twice. Once due to an oil spill from some plugged oil holes in the Y saddle, (had never been cleaned before), and once after about a year just to bring the level back to normal.

It is only a 25 gallon tank, so it evaporates pretty quick and I keep it fairly fresh.

This is by far the longest the mill has ever sat without running. I do run my bubbler 24/7, but it just bubbles in the corner. I could add some more line and bubble around the tank if it would help.

At this point it looks like the oil separated from the coolant. I added 10 gallons of fresh coolant and brought my mixture back to 5% about 2 weeks ago. I ran the mill a few hours and it was perfect. I kept an eye on the coolant for about 1 week and it stayed perfectly blue with no tramp oil floating. And typically with tramp oil I notice is starts to float pretty quickly.

Then over the next 4 days I was out of town, when I came back it had a full oil slick. I mixed it by hand for a few minutes and measured the ratio at 2%. Not all that much water had evaporated either since it has been fairly cool in the shop.

Only problem now is that the tank is still pretty full, so I can't just add more water and coolant to bring the mixture back.

From now on, I'll make sure to run the coolant for a little while every other day or so when the mill is not in use. It is not that common for it to sit this long, but now I know!

Thanks again.

[Matt@RFR]

You could try running your Zebra 24/7 like I do, or atleast for a few hours every day (on an automatic timer) and see if that is enough agitation to keep things in line. If that works, it'll do it whether you're there or not.

[Terry G]

I do run the skimmer on a timer usually 1 hour a night along with my bubbler which runs 24/7. But if the mill is going to sit for a little while and the coolant is already clean. I usually just turn off the skimer. Though this time the coolant sat for almost 1 week without any tramp oil. It was very clean. Then within a few days after that, a full oil slick.

I spoke with the coolant manufacturer and what has happened is the oil simply separated from the coolant. This is why 1 1/2 weeks ago I had a nice clean 5% mixture. And now I have an oil slick with a 2% mixture, with the machine just sitting there.

The manufacturer stated this should not happen and they are looking into any reasons this may have happened.

[garylb]

i had the exact same problem with a coolant that i used. I assumed that if anything the concentration would get stronger with evaporation but the opposite was happening which caused rust inside my machine. The coolant used was a "general purpose" coolant. I now use a better quality coolant which is more stable

[haastec]

I mix my coolant 5 gallons at a time until it reaches the light blue color of the Cimperial Blue 1070 coolant I use. Then I add it to the machine. I have only ever used RO water with the machine as well.

Are you mixing the coolant into the water or the water into the coolant?

[Terry G]

The coolant I use is the standard stuff all the machine shops use in our town. I have been using it for the last 1 1/2 years since I acquired this mill. For the first 10 months I had 0 issues. No oil slicks for the first 10 months using the same coolant. Just topping it off as necessary.

I picked up a new 5 gallon bucket in April or so, and this is when the problems started. May just be a coincidence. Though I did post another thread about having a huge oil slick overnight. I thought it was all the tramp oil stuck in my y saddle (since it had never been cleaned and was blocked up), but I am now thinking it was this new batch of coolant. Happened right when I started using it.

As far as mixing the coolant, I have always added my coolant to the water then mix very well. I do this in 5 gallon buckets, then add to the machine. Same method I used all last year without any issues. It dilutes very quickly. But if it makes more sense to add the water to the coolant, I can do this too. I haven't seen any mention of this from the manufacturer.

I've been running the skimmer and have already pulled out over 1/2 gallon of oil. Pretty much pulling out all the oil I just mixed in 2 weeks ago!

I may have to pick up another bucket of coolant and see if it was just a bad batch. I'll wait to hear back from the manufacturer before I do anything else.

Thanks

[garylb]

the correct way is to add the coolant to the water

[Terry G]

the correct way is to add the coolant to the water

Thanks!

[haastec]

Thanks for clarifying.

I will be interested to hear what the manufacturer has to say. Hopefully it's just a bad batch like you mentioned.

Good luck!

[Terry G]

i had the exact same problem with a coolant that i used. I assumed that if anything the concentration would get stronger with evaporation but the opposite was happening which caused rust inside my machine. The coolant used was a "general purpose" coolant. I now use a better quality coolant which is more stable

Forgot to ask. Being that the concentration was getting less, were you developing an oil slick on top of your coolant?

[garylb]

Forgot to ask. Being that the concentration was getting less, were you developing an oil slick on top of your coolant?

yes i was, it was horrible stuff. The coolant just seemed to seperate and the oil would sit on top. I even tried adding neat coolant to the sump to bring the concentration up but it didnt work

[txcncman]

I have not seen where you are running the coolant pump, allowing the coolant to circulate through the system, while doing all of this mixing, adding coolant, and skimming.

[Machineit]

i had the exact same problem with a coolant that i used. I assumed that if anything the concentration would get stronger with evaporation but the opposite was happening which caused rust inside my machine. The coolant used was a "general purpose" coolant. I now use a better quality coolant which is more stable

If you are making a lot of chips, oil will be taken out of the mix. It coats the chips and then the water evaporates, leaving the oil on the chips. As you remove the chips you will loose oil. Think of the oil on your table and vises etc. The difference is that you reuse the table etc, and the oil is added back into the mixture.

If you are cutting parts, but mostly just spraying coolant everywhere, you will evaporate more water and leave the oil in the machine. Then your mixture can get more concentrated.

You just need to check it often. I had been very busy and had not checked mine recently and then about a week ago, I came in and I had rust on my vises. I fixed that and then I have been making a lot of spray in the last week and I can feel it is too strong now. I have to adjust again.

Just remember that what it looks like is not a good way to judge the mixture. Machining different materials like I do, plastics, aluminum, SS, Starboard and everything else under the sun, the mixture will get cloudy and look strong. I too use Blaser and it is white when mixed, very had to tell when right without a refractometer.

Mike

[garylb]

If you are making a lot of chips, oil will be taken out of the mix. It coats the chips and then the water evaporates, leaving the oil on the chips. As you remove the chips you will loose oil. Think of the oil on your table and vises etc. The difference is that you reuse the table etc, and the oil is added back into the mixture.

If you are cutting parts, but mostly just spraying coolant everywhere, you will evaporate more water and leave the oil in the machine. Then your mixture can get more concentrated.

You just need to check it often. I had been very busy and had not checked mine recently and then about a week ago, I came in and I had rust on my vises. I fixed that and then I have been making a lot of spray in the last week and I can feel it is too strong now. I have to adjust again.

Just remember that what it looks like is not a good way to judge the mixture. Machining different materials like I do, plastics, aluminum, SS, Starboard and everything else under the sun, the mixture will get cloudy and look strong. I too use Blaser and it is white when mixed, very had to tell when right without a refractometer.

Mike

Yes I agree with this but I had the problem on both my mini mill and sl10, there was definitely an issue with the coolant I was using as now I'm using a better coolant I haven't had an issue. The coolant I used before was a milky white and like you say you can not judge it by looking at it. I didn't expect the concentration to reduce and only found out when using a refractometer after finding rust on the inside panels of the sl10. My new coolant is translucent and is definitely more stable. I now have to top up with water to keep the concentration at 5%