Dry sump coolant system ?

I have been wondering if anyone has a dry sump system for their mill or lathe ?
I imagine a system like this working like this: The coolant drains from the machining area / chip conveyor into a filter of some sort to stop small chips and other crap. Then into a dry sump where a pump pumps everything into a sealed holding tank, for example a chip blaster high pressure system.

Sometimes a machine sits idle for some time, and it would be nice to have all the coolant sealed off so it wouldn't evaporate. There could/should be an oil skimmer and aerator inside the thank. It would be much less work to clean the system too since there would be only one holdingtank for crud to accumulate.

Panza said:

I have been wondering if anyone has a dry sump system for their mill or lathe ?
I imagine a system like this working like this: The coolant drains from the machining area / chip conveyor into a filter of some sort to stop small chips and other crap. Then into a dry sump where a pump pumps everything into aN INCUBATOR, for example a chip blaster high pressure system.

Sometimes a machine sits idle for some time, and it would be nice to have all the coolant sealed off so it wouldn't evaporate. There could/should be an oil skimmer and aerator inside the thank. It would be much less work to clean the system too since there would be only one holdingtank for crud to accumulate.

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Coolant does not evaporate, the water in it does. Aerator will cause the water to evaporate too.

I know what evaporates, no need to nit-pick. The water will not evaporate if it is in box with a lid. Or: it won't get out of the box.

Yeah, kind of. It drains out of the mill into a 2 gallon trough that catches the bulk of the chips. It then is pumped through a 5 micron bag into a holding tank for storage. The storage tank has the air bubbler and skimmer. No baffles make these much more efficient. I have no tramp oil in the morning. Another big advantage with this type of system is how little coolant you really need to have. I can get away with 5 gallons but useally run 7-8 for safety. Makes it real nice when cleaning out for a fresh charge, not much to deal with. Here are some photos that show the flow of coolant at the tool, a dirty filter, the filter/storage tank, and the dry sump. Just need a little auger in it!

Another note- I started rinsing off my chips with the old water from rinsing off parts and fixtures and dumping this back into the machine. I drain them anyway so dumping the water on them as they drain doesn't add much work. I estimate this is saving around 90% of my concentrate usage. I run a full synthetic at 6-7% and cut mostly aluminum. Anyone else rinsing their chips off to save the coolant? Shits expensive!

The reason I made this coolant system is the one that came with the machine was 80 gallons and way too big for my little shop and goes right to the floor flush in front of the machine so that is where your toes stop when reaching into it to swap parts. The table doesn't get very close to the door so this alone was a deal killer since I will be the one running the machine. This isn't the smallest version, the trough is the smallest version, and worked for the most part.

DavidScott said:

......Anyone else rinsing their chips off to save the coolant? Shits expensive!

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I used to rinse all my aluminum and plastic chips and use the rinse mix for my make up coolant. Did not seem to get too much off the aluminum so stopped rinsing them. Still rinse the plastic (mostly ABS, acetal, polycarbonate, and acrylic) as they seem to hold lots more coolant than aluminum.

I'm familiar with automotive dry sumps, so I'm pretty sure I'm following your train of thought here. I never thought about it in these terms, but the system I have on our Haas is essentially what you're talking about, except the "dry sump tank" is the factory sump, and the "oil pan" is an additional 15 gallon tank with a sump pump in it.

Coolant is diverted to the additional sump and through a 200 micron bag filter. You can see the sump pump and a check valve:


Then through a 25 micron, then 10 micron bag filter. The return line to the main sump has a ball valve to throttle flow, only to introduce pressure in to the system so I can have gauges to tell me when filters are plugging up.


The flood pump then pumps through a 5 micron filter, and the TSC pump is either 5 or 2 micron depending on what we're doing.

Replacing the Haas sump with a 55 gallon drum or similar is intriguing. It would have the added benefit of essentially decanting the coolant over the weekends, and be much more portable for maintenance or cleaning. Or if you were so inclined, you could have each machine pump back to a central tank and play like the big boys do.

DavidScott said:

Anyone else rinsing their chips off to save the coolant? Shits expensive!

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On the list to do Some Day is get a place to build small centrifuges for smaller shops. Cuttin' erl costs even more than coolant and it doesn't drain off the chips very well.

Vancbiker said:

I used to rinse all my aluminum and plastic chips and use the rinse mix for my make up coolant. Did not seem to get too much off the aluminum so stopped rinsing them. Still rinse the plastic (mostly ABS, acetal, polycarbonate, and acrylic) as they seem to hold lots more coolant than aluminum.

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I probably add 10 gallons of rinse water before I need to add any concentrate and I keep it at 6-7% testing enough to ensure this. Perhaps the differences we see is the coolant?

Matt, is that a 5 gallon paint strainer bag?

Nice thing about the 55 gallon, or 30 gallon, is it will have far less surface area to skim the tramp oil from.

DavidScott said:

Matt, is that a 5 gallon paint strainer bag?

Nice thing about the 55 gallon, or 30 gallon, is it will have far less surface are to skim the tramp oil from.

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David, that bag is this guy here: McMaster-Carr And I mispoke, I'm using 100 micron bags, not 200. I bought 10 six years ago and haven't thrown one away, they are amazingly tough.

I'm really liking the thought of a vertical storage tank. Pumps and filters mounted on the outside so the entire system is portable. I'll have to think on this.

Try a water well jet pump with the separate jet, put it down in the primary sump.

digger doug said:

Try a water well jet pump with the separate jet, put it down in the primary sump.

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If I'm following you, the whole point for me is to filter the coolant before it gets to the main sump, not after.

Sump pumps rated for solids do a great job for this. There is no reason for this system to be high pressure, and it just needs to flow reliably over however much all your coolant pumps combined can flow. Mine only makes 4psi through 1-1/2" hose. So as far as water pumps go, it's a very low performance system. This pump here has been doing a great job for me, and it's cheap: CountyLine Cast Iron Submersible Sump Pump with Vertical Switch, 1/2 HP at Tractor Supply Co.

Panza said:

I know what evaporates, no need to nit-pick. The water will not evaporate if it is in box with a lid. Or: it won't get out of the box.

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You blow air into the coolant in the tank/box to aerate it. Where does that air pressure go? Air bubbles evaporate a lot of moisture. Yes? Put a small air blubber in a tank of coolant. You will see a fog forming and rising up and out of the barrel, ready for you to breath.

Matt@RFR said:

If I'm following you, the whole point for me is to filter the coolant before it gets to the main sump, not after.

Sump pumps rated for solids do a great job for this. There is no reason for this system to be high pressure, and it just needs to flow reliably over however much all your coolant pumps combined can flow. Mine only makes 4psi through 1-1/2" hose. So as far as water pumps go, it's a very low performance system. This pump here has been doing a great job for me, and it's cheap: CountyLine Cast Iron Submersible Sump Pump with Vertical Switch, 1/2 HP at Tractor Supply Co.

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Sump pumps don't like to run DRY.....DUH

And no, the rest of what you assumed is NOT what I was getting at.

digger doug said:

Try a water well jet pump with the separate jet, put it down in the primary sump.

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Didn't read it correctly. Why a jet pump and not just a centrifigul pump? Jet pumps are for lifting water out of the well.
And I run my first stadge pump dry all the time, pretty much every cycle.

digger doug said:

Sump pumps don't like to run DRY.....DUH

And no, the rest of what you assumed is NOT what I was getting at.

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You go girl!

Submersible pumps like linked above will toast the seal that keeps liquid out of the motor if run dry. Typical machine tool centrifugal pumps have the motor above the fluid level so not a problem.

A jet pump sits above the fluid level and uses a venturi created vacuum to draw fluid from a shallow well and pump it to a tank. Never seen that used with anything other than a water well so don't know how it would work with dirty coolant. If the well goes dry on a jet pump system or otherwise draws air into it, the jet pump loses its prime and will quit pumping. This reason makes me think it would not be a good choice for a "dry sump" coolant system.

Vancbiker said:

Submersible pumps like linked above will toast the seal that keeps liquid out of the motor if run dry. Typical machine tool centrifugal pumps have the motor above the fluid level so not a problem.

A jet pump sits above the fluid level and uses a venturi created vacuum to draw fluid from a shallow well and pump it to a tank. Never seen that used with anything other than a water well so don't know how it would work with dirty coolant. If the well goes dry on a jet pump system or otherwise draws air into it, the jet pump loses its prime and will quit pumping. This reason makes me think it would not be a good choice for a "dry sump" coolant system.

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I had a typical machine tool centrifugal pump in mind, as in what I am using. I think seals and plastic impellers are to be avoided with the first stage pump. Also a good idea to mount it in a well in the tank so you can pump it dry at the end of the day.

I have a jet pump on my stone coolant system, by accident. I used to go through ceramic seals every 1-2 years when I just used 5 micron bag filters. About 11 years ago I switched to pleated and started filtering to 1 micron. Haven't had the seal go out since. I know it would not like pumping any chips.

Matt, I have used those same level switches for your sump pump. After the contacts went bad in my first one I now just use it for the low voltage signals for a relay.