[Driftwood]

So we have a small CNC shop, 1 mill and 1 lathe, and we haven't had to replace the coolant in the machine until now...

In the lathe in particular, all the lube oil from the ways drains into the coolant tray, so its gotten pretty nasty in there since there's no oil skimmer...

So we've drained the coolant into a large drum, have let it sit for a week and it looks like all the oil has separated to the top, and hopefully any solids have sunk to the bottom...

So I'm wondering what to do with this coolant now... if we skim off all the oil, is it good to go back in the machine? If not, what do you typically do with it / how do you dispose of it?

And how frequently should coolant be replaced?

Thanks...

[Rich 72]

We store our coolant in large totes and have it disposed of by an outside company, I don't know if it should be reused, if you get a lot of fungus you will have health issues down the road. Depending on how much the machine is used is what we base our coolant changes on, usually 4-6 months depending on how much oil gets mixed in the sump

[HuFlungDung]

Driftwood,
You could reduce the volume of the old coolant by boiling it off. If the smell is too rank, you could mask it by simultaneously boiling off Fat Bastard's stool sample at the same time

[DareBee]

Pretty rude HU - really funny - but rude.

Driftwood
It costs us about $50/barrel to dispose of through OSS.
Initial set-up for disposal is a bit lengthy (lots of paperwork) but what you gonna do? (gov't eh)
Safety Kleen is another company that will take waste.
Do not re-use it please.
I have also been told that it is against our law to store containers of waste for more than 6 months. If it is a partial container it is not considered storage because you are still de-canting into it.

Considering the size of your business, this is likely your best option. Treatment systems (to reduce the amount being disposed) are very expensive and will not pay for itself with a business the size of yours (or mine).

I strongly recommend that you run skimmers in each tank to remove the tramp oil. I also found that adding aeration to my tanks doubled the coolant life.

[Eurisko]

Our shop uses 3 methods to deal with used coolant.

1) A coolant recycler, which consists of a centrifuge and filtering stages. The used, filtered coolant is then mixed with water and new concentrate.

2) An evaporator (as HU suggested) is used for the really rank stuff. The liquid evaporates out and the sludge is hauled away. Cheaper than disposing of liquid coolant. Less volume.

3) The pit is well, a pit. Nasty old coolant is dumped into the pit. When the pit is full, a waste removal firm empties it. Big $$$. Only used if the evaporator is full and the coolant can't be recycled.

Ideally, coolant should be changed every week. This is not an ideal world, and production pressures may keep the coolant in the machine for a month or more.

Google "contact dermatitis"

[JMECKES]

We use Safety Kleen also, and the cost is fairly minimal when you consider gov't regs and the like. However, we recently made the switch to Houghton HoCut coolant. Best I've ever seen as far as keeping any tramp oil on top for skimming. And skimming is a must. As far as changing, the stuff never seems to degrade. We just top off the tank periodically and watch our concentrations.

[littlerob]

However, we recently made the switch to Houghton HoCut coolant.

Keep it off your hands, I don't know that I would blame the Hocut, but I got a real nasty case of Dermititis while it was in the machine. While I am aware that all coolant has fungus and bacterias, we changed to a different brand two years ago never recurred.

Robert