Tramp oil in coolant won't skim

Kapster · Jun 18, 2019

I have a C thru oil skimmer on a few month old machine, I installed it soon after it arrived after realizing how much way oil it uses. Coolant is Trim microsol 690XT and the way oil is Shell Tonna S3 M68 on the factory tank, Shell Tonna S2 MX68 is what I've refilled with several times.

I can't seem to get the coolant skimmed. It looks great when the oil skimmer is running but If I shut it off it goes back to an oil/cream slick on top. I've tried running for a week at a time. Tried running it a day, shutting it off to let the oil rise again, and restarting it but no matter what I do it just returns.

Has anyone seen this before? I've done some tests and the Shell S2 MX68 does seem to emulsify more then Vactra 2, maybe the C thru can't separate emulsified oil? Would a belt skimmer work better, I've never used one?

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Bluesux01 · Jun 18, 2019

I’m not familiar with that type of skimmer how is the oil supposed to be removed? I can see how that would actually work I would suggest a belt style skimmer . The surface tension differences allows the oil to be removed and the coolant to stay . Tried and true method just gotta clean the wiper periodically.

Dan from Oakland · Jun 18, 2019

Another option is a disc type skimmer- looks like you have room for one.

Bluesux01 · Jun 18, 2019

After I looked up how the 3 ball style works I understand, is the hose too long eg coiled up in the pan ? Is the oil escapes route higher than the coolant level? That system relies on gravity to evacuate the oil so the hose has to have a drop in elevation all the way to the end to work properly.

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guest · Jun 18, 2019

That coolant looks pretty good to me- I'd be happy if my machines all looked like that.

How much oil are you getting from the reservoir?

I think those coalescers work best if you run them overnite. Running them during the day when the machine is running just pumps coolant through the thing.

Also pickup location is important, too low and you just get coolant through. If you're running aluminum, make sure the screens are not plugged by fines.

Ziggy2 · Jun 18, 2019

That skimmer appears to be working fine.

You could probably rise the weir slightly to reduce the total flow through the gravity separator.

One thing to keep in mind when observing a coolant tank while the machine is operating is that there is a significant amount of homogenized tramp oil in the coolant that will not be visible to the naked eye until the coolant is allowed to sit without agitation for a period of time.

That is why you are noticing the tramp oil in the morning. J. is spot on about running the skimmer at night.

Kapster · Jun 18, 2019

These photos were both taken with it not running, I run it while the machine is running but also overnight. This machine doesn't get run all day everyday so has plenty of time to separate out. But even still, as soon as I stop the skimmer it goes back to oil on top.

I have the pickup for the skimmer under the chip conveyor area. The area where the coolant pump is located is blocked off on top so oil can't get to the pickup from there. I purchased a second three ball float and pump to pump over to the chip conveyor side to be picked up by the skimmer.

It seems very efficient at getting the oil, but almost like it's just mixing it up and not removing it.

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gregormarwick · Jun 18, 2019

Ziggy2 said:
You could probably rise the weir slightly to reduce the total flow through the gravity separator.

That's the key.

From your photos, it seems like the inlet is a bit further below the surface than it should be and that it's got quite a lot of flow. Separators need to have very little turbulence otherwise the suspended oil just stays suspended and goes straight back into the tank again with the coolant return.

The inlets on our separators float closer to the surface, and they naturally cycle by pumping until the inlet rises out of the coolant, takes a gulp of air, and then settles back below the surface. It then takes about 30 seconds or so to push the air bubble through the system, before it starts pumping coolant again. The pump-pause-pump-pause cycle keeps the flow down and the turbulence inside the separator at a minimum.

If I force them to pump continuously, they behave just like yours. Pristine tank when it's running, but lots of suspended oil remaining in the coolant.

Insert · Jun 18, 2019

I have that same skimmer and get excellent results.
For what its worth, here is what I did, don't know if it will make a difference. (could just be the compatibility between oil and coolant).
I have it on a timer, runs 3 times a day for 30 min, with two of those times being at night.
My tank is the shape of a C, I have the intake balls at one and and the return at the other, this helps it create a nice flow. Intake does a good job sucking, but if your return is somewhere in the middle, facing the opposite direction, it might not allow a good flow.

When I turn mine on, you can see a nice flow moving across the entire surface towards the intake.

Your second pic looks good.
Are you catching any oil in the clear tank ? Mine typically has a nice layer of oil sitting when the pump is off.

Kapster · Jun 18, 2019

Thanks for the tips! I'm encouraged that you guys had similar issues with this skimmer and were able to tune it out. I will definitely try raising the ball float and could also simulate running it 30 minutes several times a day to see if a timer would solve my problem.

I am catching oil in the tank but not enough for what I'm putting in the way lube tank. It does catch a good amount behind the covers in a container but still, there is quite a bit unaccounted for.

Does aluminum mess up the efficiency of the c thru seperator, do I need to clean the plastic mesh? I ran one aluminum job and did notice it sucking up a bunch of floating aluminum.

Bogart999 9 · Jun 18, 2019

Insert said:
I have that same skimmer and get excellent results.
For what its worth, here is what I did, don't know if it will make a difference. (could just be the compatibility between oil and coolant).
I have it on a timer, runs 3 times a day for 30 min, with two of those times being at night.
My tank is the shape of a C, I have the intake balls at one and and the return at the other, this helps it create a nice flow. Intake does a good job sucking, but if your return is somewhere in the middle, facing the opposite direction, it might not allow a good flow.

When I turn mine on, you can see a nice flow moving across the entire surface towards the intake.

Your second pic looks good.
Are you catching any oil in the clear tank ? Mine typically has a nice layer of oil sitting when the pump is off.

I agree, we have the three style skimmers described above and this style in my opinion is the best of them. but proper placement is key

Insert · Jun 19, 2019

Kapster said:
Does aluminum mess up the efficiency of the c thru seperator, do I need to clean the plastic mesh? I ran one aluminum job and did notice it sucking up a bunch of floating aluminum.

I run 95% Aluminum, and have no contaminants in my separator(or coolant), but I run paper filters in my chip pans to prevent any chips from going into the coolant.(I'm pretty anal about keeping coolant clean, as I really do not want to deal with the smell of bad coolant and then having to clean the entire machine with a toothbrush)

DavidScott · Jun 19, 2019

Try reducing the flow as much as possible but still suck the oil off the coolant, the lower the flow the better the oil will separate in the tank. I run mine for 15 minutes every 6 hours but disable it when I am running my mill. I also have an aerator that comes on with the pump. The air stone is opposite the pickup for the pump which helps push the oil over to the pump.

I find that my coolant emulsifies a lot of the way oil, at least for the first 10 days, then after that a lot of way oil goes out with your chips. The finer the chips the more oil, and coolant concentrate, they will take with them. If you machine polyethylene then those chips take out all the oil, which makes sense since the media in the coalescers is polyethylene.

tdeutmeyer · Jun 19, 2019

OP, I would drop in an aquarium aerator in your sump also along with your skimmer. (opposite end to prevent skimming up coolant bubbles)

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