Cleaning forepump oil out of a turbo

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ian_krase
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Cleaning forepump oil out of a turbo

Post by ian_krase »

I run my system with a turbo pump, because it was what was available to me.

Unfortunately, an indiscretion with shutdown/venting resulted in several milliliters of (clean) forepump oil getting sucked into my turbopump's foreline connection. The pump had its axis in a horizontal position, and as far as I can tell it migrated through all the drag and turbo stages.

The pump still turns *smoothly* but with far too much resistance.

Is it possible to clean this without needing to disassemble or rebuild? Most professionals I have talked to think that rebuilding this specific turbo without dynamic balancing capabilities is a doomed project. If it is just the pump stages being full of oil that is keeping it from working, can I use the commonly cited procedure of immersing the lower half of the pump in isopropanol that is just deep enough to not quite reach the bearing?

Has anybody ever succeeded in getting rebuilds done for cheap?
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Re: Cleaning forepump oil out of a turbo

Post by Jerry Biehler »

Just pour some solvent down the pump and let it flow out and wash the oil out. Mineral spirits will be fine. IPA does not dissolve oils worth a darn.

What kind of turbo?
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Re: Cleaning forepump oil out of a turbo

Post by ian_krase »

To be clear is a Varian grease lubricated one -I think the kind used in Varian mass specs and the like. By "pour down" you mean put the inlet flange and rotors facing up, and just pour in the top? Do I need to worry about removing the liquid parts of the bearing grease?


I keep seeing IPA being described as able to remove oil. Is it something that will dissolve only a little, so good for residue but not bulk?
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Dennis P Brown
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Re: Cleaning forepump oil out of a turbo

Post by Dennis P Brown »

This is where a manual is essential or call the company.

My extremely old turbo has instructions for doing this procedure. For this TP-150 unit one can immersion it in a solvent - I believe acetone (but don't have the manual here.) Then, one then needs to dry the pump via vacuum and low level heat (under 100 C - they suggest a dry nitrogen purge, too) and after this, add a cc of TP oil to the bearing oil port, (it has a rather strange 'wick' system.)

So, the procedure can be a bit involved depending on the pump.

If all else fails (no manual or input from the mfg.) one could remove the main body exposing the blades. Then cleaning the body and blades without harming the bearings is rather straight forward.
Last edited by Dennis P Brown on Sun Oct 08, 2017 6:00 am, edited 1 time in total.
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Re: Cleaning forepump oil out of a turbo

Post by Jerry Biehler »

The bearing are not exposed to the solvent when you pour down. It would have to work it's way up the shaft tunnel to get to the top bearing and that's just not going to happen. You just need enough to thin out the oil that is stuck in the drag stage, that's probably where it is causing the issue. There is not much space between the surfaces and the surface tension of the oil will drag things down.

Solvents have polarity, from non-polar to polar. Water being the most polar and you want non-polar solvents to get rid of oils and greases. IPA sucks for this, it is pretty darn polar. It also introduces water into the system which just means more pumping time.

Acetone is kind of in the middle and is much better than IPA but it still does not mix with oils that well.

Mineral spirits could be one of a number of heavier hydrocarbon solvents but it usually toluene which is a great solvent for oils. It also is a nice heavy molecule which pumps out pretty easy. When cleaning out one of my system I usually use acetone and then finish wiping down with mineral spirits.

Here is a list of solvents from non-polar to polar. http://murov.info/orgsolvents.htm#TABLE%202
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Re: Cleaning forepump oil out of a turbo

Post by Silviu Tamasdan »

You can buy xylene at hardware stores such as Home Depot and Lowes - in the paint department. It's pretty close to toluene in properties, and cheap. Alternatively, starter fluid (comes in spray cans, it's meant to be sprayed into the air intakes of engines to help starting on very cold days) is a mixture of heptane and ethyl ether. It has the disadvantage of being very volatile and an explosion risk because it's what it's designed to do. But it dissolves oil pretty well.
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Re: Cleaning forepump oil out of a turbo

Post by Rich Feldman »

Too bad we can't buy carbon tetrachloride at the hardware store any more. I have some in a pressurized household-fire-extinguisher can.

In a quick look at the table in Jerry's link, I didn't see trichloroethylene or trichloroethane. Both around for decades after CCl4 was phased out, and equally nonflammable. One would expect them to be polar, but they are darn good degreasing agents. These days, their names come up mostly in the context of contaminated soil Superfund sites.
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Re: Cleaning forepump oil out of a turbo

Post by Jerry Biehler »

trichloroethane is actually slightly polar but still does not want to mix with water. trichloroethylene is pretty non-polar. There are other charts out there, I just cant find the one I usually use. Here is another. This one shows what is miscible in what: http://www.finarchemicals.com/pdf/hplc_ ... _table.pdf
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Re: Cleaning forepump oil out of a turbo

Post by Sarvesh Sadana »

Hexane may work to dissolve the oil. Also, keep in mind that a fair amount of these solvents (xylene, toluene, benzene, etc.) are very toxic. Make sure to take safety precautions before working with them.

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Re: Cleaning forepump oil out of a turbo

Post by John Futter »

When I used to service stirling engine cryocoolers the best degreaser is Di ethyl ether followed by Methylene Chloride (dichloromethane) which is not infammable or explosive like ether. And there is a funny story as to why we changed from ether to methylene chloride which involved an electric hot air Blower that was used to fully dry the regenerator from ether remains. The Hot air drier went kapput and got send out for repair at a motor re-winders, when it can back it was a sucker not a blower nobody noticed until a regenerator was started to be dried where the sparks from the drier motor brushes ignited the ether fumes and the hot air drier exploded with metal shrapnel going in all directions nobody hurt but some damaged cars in the car park where drying took place because of the ether fumes.
New Drier and a change to methylene chloride made things safe and we could do it inside
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Re: Cleaning forepump oil out of a turbo

Post by ian_krase »

See also the great frustration about the unavailability of Freon TF, and the unsuccessful search for substitutes that are not gasoline-tier flammable.

(The maintenance manual for one Varian leak detector actually said to clean the blades of a turbo by partial immersing in Freon TF. Not gonna happen now.)

This is where a manual is essential or call the company.

I haven't had any luck getting maintenance manuals but I did have some luck talking to someone who works at Ideal Vacuum Products.

The user manual for this pump has a cutaway drawing. Assuming it's accurate, I should be able to soak the pump to a depth that will get the drag stages but not the bearings. However, the bearings don't look like they are protected by a "shaft tunnel" unless you know for sure.

In any case, I think I have an idea of a path forward.
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Re: Cleaning forepump oil out of a turbo

Post by John Myers »

D-limonene is used as a solvent and might be a usable and less flammable/toxic alternative.
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Re: Cleaning forepump oil out of a turbo

Post by John Futter »

After reading the fact sheet for D-limonene I certainly would not put it anywhere near a high vacuum system -- too many long chain slightly polar molecules that will stick much worse than our friend water which is bad enough for most on this site
Methylene Chloride is non flammable (not too good for the ozone layer but better than freon TF as a solvent and much much better to the ozone layer)

But be careful it is so good that nearly all plastics except teflon are dissolved by it
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Re: Cleaning forepump oil out of a turbo

Post by Jerry Biehler »

Plus Methylene Chloride is pretty easy to get, it is used as a cement for acrylic.

You dont need to dip the turbo. Just pour a little bit down the inlet to wash the excess oil out and let it drain out of the backing port. You dont need to go crazy with this, it is really not that big of a deal.
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Re: Cleaning forepump oil out of a turbo

Post by Dennis P Brown »

Jerry has a good idea; also, but I would like others to weigh in before you try this - one could use an electronic tuner spray cleaner can (get these online or possibly a hardware store.) Just spray the blades vertically down through the upper throat . Allow a small pool of liquid to collect (2mm at most) at the base and then pour this contaminate liquid out the lower port. You might get the blades to turn by spraying - if not, try gently to get the blades to turn a little to expose new surface. The back surfaces should collect some of the vapor. Do this one or two more times so the lower blades see clean fluid. The bearing shouldn't 'see' any liquid. Maybe. Allow to air dry, then pull vacuum on it.
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Re: Cleaning forepump oil out of a turbo

Post by Jerry Biehler »

Its not the oil on the blades. It is the oil in the drag section. The clearances are small in this section and the surface tension of the oil will cause drag. Just need to wash that out and everything should be fine again.
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Re: Cleaning forepump oil out of a turbo

Post by ian_krase »

Got some mineral spirits that I'm going to try. The hardware store didn't have any toluene or xylene but they had mineral spirits, paint thinner, mineral spirits paint thinner, paint thinner (mineral spirits) and low-VOC paint thinner.
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Re: Cleaning forepump oil out of a turbo

Post by Jerry Biehler »

mineral spirits is generally just toluene, sometime has some xylene in it, kind of a potpourri of hydrocarbons. Either is fine, you just need to thin the oil out enough and wash it away. Its just a good non-polar solvent to have on hand for cleaning things and pumps out of the system fast.
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Re: Cleaning forepump oil out of a turbo

Post by Rich Feldman »

>> Hexane may work to dissolve the oil. Also, keep in mind that a fair amount of these solvents (xylene, toluene, benzene, etc.) are very toxic. Make sure to take safety precautions before working with them.

It's the aromatic hydrocarbons that are most toxic.
For volatile aliphatic hydrocarbons (e.g. hexane), the IDLH levels (Immediately Dangerous to Life or Health) of the vapor are generally the same as the Lower Explosive Limit. :-)
Same for isopropanol, ethyl ether, etc. https://www.cdc.gov/niosh/idlh/intridl4.html

Nonflammable solvents are less of a fire hazard, but generally their vapors are more toxic. Water is a notable exception.
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Re: Cleaning forepump oil out of a turbo

Post by ian_krase »

There's also Propylene Carbonate, an aprotic polar solvent notable for destroying most chemical resistant plastics and rubbers (except Kalrez and simple polyolefins) while being very safe and nontoxic.
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Re: Cleaning forepump oil out of a turbo

Post by Jerry Biehler »

That stuff is more polar than isopropyl, you're going the wrong way. Polar is bad, it helps introduce water into a vacuum system as well as not going to thin out the oil.

Found the list I usually use:

http://macro.lsu.edu/HowTo/solvents/Pol ... 0index.htm

Mineral spirits is not going to kill you, not even close. Just have good ventilation and you will be fine.
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Re: Cleaning forepump oil out of a turbo

Post by ian_krase »

I wasn't going to use propylene carbonate in my vacuum system. Just thought of it since it's something I ran into on my day job.
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Re: Cleaning forepump oil out of a turbo

Post by ian_krase »

So, I cleaned the turbo with mineral spirits as proposed. This seemed to work to get the forepump oil out of the drag stages and the controller now is willing to start spin-up.

However, I am nervous about running it. The solvent cleaning looks like it left some particles sticking to some of the stator blades, which doesn't seem good, and didn't really fully dry or drain -- I have it under forepump vacuum now, but I seem to be having a hard time getting under 1.8 torr -- is that just massive amounts of evaporating heavy fractions of mineral spirits and oil residue? Should I warm it with my bakeout heater?
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Re: Cleaning forepump oil out of a turbo

Post by Dennis P Brown »

If you have a low vapor point liquid remaining (maybe still some of the old oil), pumping will do little. Rather, try using the solvent again and do two or three rinses )using as little new solvent as possible.) This might help remove the particles (but if any still remain and are very low mass, the spinning blades should "throw" these off. You will know if this is an issue when it starts to spin up in a big way; if significant vibrations occur - trouble and turn it off. If it spins up smoothly, then they aren't an issue.)

A single (or even two) rinses doesn't always fully clean even a glass with a bit of dirty liquid in it - a turbo might be a bit more difficult still ...lol.
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Re: Cleaning forepump oil out of a turbo

Post by ian_krase »

As it turns out, my foreline was full of water and other contamination in the crevasses - was getting cold from that boiling off.
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