How to avoid stinkin' coolant?

[ESjaavik]

This is concerning a small (apx. 1000Kg.) toolroom mill, but now only used intermittently as a hobby machine.

I have torn down and built up my mill. This included cleaning the coolant tank, which is actually the lower part of the main casting. I scrubbed it as good as I could using a strong caustic solution that is used on walls before painting. There was a lot of slimey goop in there, and I tried to get everything out.

Is there anything more I can do to avoid that goop to get back to life when I put in coolant?

The last coolant used (don't remember name) allowed this goop to grow. The previous one called Zeronite did not. But on the other hand it was not very nice to the paint. Can anyone tell us what different "families" of soluble oil coolants there are, and the pros/cons.

Should I drain the coolant tank during periods of little or no use, and store coolant in an airtight container? I guess these aliens need oxygene to breed.

[Bloy2004]

In my limited reseach, I've learned that maintenance is a big part of "storing" coolant. There are "skimmers" that take the impurites off the surface of the coolant, which I believe are the promoters of the "spoiling" of the coolant. Basically, keeping the coolant clean as best as possible seems to allow a longer shelf life(intermitant use).
Please... anyone with experience...please correct me if I'm way off...

[HuFlungDung]

Bloy is right It is the thin film of machine oil that provides the medium for slim bacteria to munch on. And keeping the coolant in an air-tight just aggravates the problem, because anerobic action is also part of the stink. I suppose not enough air penetrates the oil slick, or a slime skin once formed.

I got sick of cleaning the machine sump as Einar wrote about, so I simply use a five gallon pail as a sump now. It is easier to rig up a skimmer and also easier to dispose of the coolant and to disinfect this kind of sump.

Unfortunately, I think it is impossible to eliminate slime bacteria no matter how much you scrub. So it becomes a matter of replacing coolant regularly. This is the most affordable for the infrequent user.

The synthetic coolants last quite well, but I still only get maybe 3 months of use before I change it. The weaker dilutions, although cheaper, have a shorter life. But it may make more sense to just mix up a little bit of weaker solution and be happier to dispose of it more frequently. Again, the pail sump allows you to mix up less coolant and yet still have sufficient depth to cover a small submersible pump.

[nervis1]

I have a 40 gal sump that was rotting every month or so but since I got a skimmer I've had the stuff in there for 3-4 months without any problem. That little guy just skims all the goop right off the top along with floating chips and the occasional scorpion or grasshopper if you live in AZ.

[Mouldmaker]

If you have bacteria in your coolant system, try using a cleaner which is added 24 hrs to the coolant prior to it being replaced. This will clean your coolant system (coolant system includes pump, pipes, etcc... not only your sump) and kill all the bacteria present in your coolant system. Your coolant supplier should be able to supply you with this system cleaner.
Another important aspect of coolant maintenance is the usage. Do not leave it for long periods without being used. If possible, use it on a daily basis, for example, starting the coolant pump for 30 min daily.

[dcook]

There are numerous germicides available to put in your coolant. Also many coolants have germicides in them. Low use/stagnant coolant, especially with an oil film will become rancid at some point. A skimmer is your best buddy. It is unfortunate but most germicide-based coolants will take the paint off of a machine. Epoxy based paints resist this the best. Alcohol based paint (Japan) will come off within a few days. Keeping the machine as clean as possible is good insurance.

[ESjaavik]

Thanks for several good advices.

It seems the Zeronite must have been a germicide-based coolant, because it stayed fine for a long time and attacked paint (and seemingly also rust!). Would it help if I apply car-wax when cleaning the machine? I will probably see if I can hunt down a can of the same stuff again. It was given to me because the machinist didn't like the smell of it. It did however smell a lot better than the goop!

Does anyone here recognize the name? I tried to google for it but did not come up with anything useful. So I don't know where to call to get it.

[Mouldmaker]

I dont think applying car wax will help as it will contaminate the coolant even worse. Keep the coolant as clean as possible to keep it free from bacteria.

[bob1371]

In my little hobby machine that I never have time to mess with I started by adding a skimpy brand skimmer. Every other week or so I just add a cup of household bleach to the tank. Pretty cheap and So far I dont believe it has affected the usable life of the coolant and it keeps the nasty stuff from growing.

Bob

[ESjaavik]

Bob,
I Googled the skimmer you mentioned. How does it work? Does all return oil have to pass over it, or is it just like a cat's tongue licking off any oil that happens to pass it. If so: do you leave it on for some time even if not actually milling?

And what are those germs? Or rather how harmful are they? I still don't know if there is life on Mars, but there sure is in my coolant tank. Is it out to get me?

[dcook]

The bacterium that grows in a coolant tank can become very harmful. Skin rashes and/or burns from the bacteria are common. Eye irritation and in severe cases blindness can occur. If you find yourself especially allergic to poison ivy watch out. You can build your own skimmer from common items. There are several styles commercially available. Two of the most common are belts and discs. A belt hangs into the coolant tank below the top of the coolant and slowly rotates; the oil will stick to the belt and is scrapped off into a container. The disc skimmers work the same way but normally use a UHMWPE disc partially submerged vertically in the tank and again the oil is scrapped off. I like the disc skimmers better. They seem to do a better job. The disc skimmer is the easiest to make yourself.

[oldguy]

Avoid coolants with "biodegradable" on it. May not be politically correct, but that is just another term for "it rots." Check compatability, but perhaps an antibacterial additive could stop it. Never tried it, but chlorine bleach, a small amount, might work to stop it from starting, but it wouildn't reconstitute the rotted stuff. Just a thought.