View Full Version : Coolant Evaporation?

08-22-2009, 07:14 PM
After a few months, my Rustlick soluble oil mix coolant has evaporated to the point where there is about 2/3s of it left. It's in a one gallon bucket. Is this normal? Does the oil evap? or just the water?

Also, what is the best way to skim such a thing-drag stuff through it imitating mechanical skimmers?

08-22-2009, 07:17 PM
The water evaporates off as far as I know. It's best if your not using it every day to drain it and put it in a closed container. I did that with my valve grinder.

08-22-2009, 09:53 PM
Yes had the same problen . with lathe ,mill and surface grinder . the trick os to seal the bucket . Made tight fitting tops of 1/2 inch plywood and tight fitting holes for lines to pass through. Mill sat for 2 years with out use checked a few weeks ago bucket still full. so is surface grinder . Lathe lost some because of use and slinging off chuck. So seal your buckets . I know that works.

08-22-2009, 10:35 PM
It has been hitting over a 100 in the shop here and something like 115 inside my vmc by the end of the day and I have been having to add about 5 gallons of water every morning to the machine and a half gallon of straight coolant about once a week. It is insane how much water evaporates in this heat.

08-22-2009, 11:45 PM
Don't forget the amount of coolant that clings to chips being thrown away.
Those chips have alot of surface area.

08-23-2009, 01:11 AM
It's mostly the water evaporating. Some coolant does get discarded with the chips.

A few years back, we had a machine with a 250 gallon coolant tank. It was used sparingly, and after a few months, the coolant was down to about 150 gallons. To get the coolant level back up with the same original 9% concentration, we added 1.5 gallons of coolant and about a hundred gallons of water.

The best way to skim oil on the cheap is to use a shop vac. Home Depot sells nice $30 shop vacs every Black Friday.

Mark Hockett
08-23-2009, 01:48 AM
My coolant supplier told me to use a 100 to 1 ratio when adding coolant to compensate for evaporation. I have a 55 gallon drum of coolant with an adjustable mixer in it. I just turn the dial to the correct ratio, stick the hose in the machines coolant tank and turn it on. I use a refractometer to check the ratio. Enco sells refractometers fairly cheap. If you use coolant they are a good idea to have. Theres nothing worse than letting the ratio get weak and finding rust on your machine.

08-24-2009, 05:05 PM
The less exposed surface area of the coolant the less evaporation. You cant do much about the area around the cutting area but you can in the resovoir. In our application we had what looked like ping pong balls floating on the coolant to reduce exposed surface area. They were a bit heavier that ping pong balls. What about a closed cell foam or styrofoam float cut as close as possible to the size of the resovoir? This would float on the coolant and greatly reduce exposed coolant.

08-25-2009, 03:34 PM
For homeshop quantities (my tank is about 20 L) I top up by taking a 1/2 L (a pint) and putting in a 5 L container (close to a real gallon) filling the container 2/3rd full and shake it vigourly for a minute then return it to the tank, stir and remeasure with the refractometer.

08-25-2009, 06:26 PM
For skimming on the cheap, I use papertowels, just lay them on top of your oil slick and it sucks the oil right up. If your sump is nasty as mine usually are it may take quite a few paper towels, but if you spend 30 seconds every morning, keeps 'em nice and clean(I need to take my own advice more often).

I've found shop vacs to be messy, and me and disc or belt skimmers don't mix. I turn them on, forget about them and end up with an oily mess on the floor, or I get really smart, put a timer on them, forget to empty the dump bucket and still end up with an oily mess on the floor.

Oh, and get a refractometer, they are handy and honestly a necessity if you've got some money tied up in coolant, already been said, I'm just agreeing.