Turbo Pump Cleaning

[Chris Trent]

Ok, I just recieved the Balzers TPU-100 turbo pump I picked up off eBay for $30, (sorry for not posting it guys).

Here's the rub though, I removed the cover blank and was blasted by the smell of machine oil. The blades look good, but it looks like someone prepped this for storage by drenching the internals. There's a coating of oil over everything.

The blades will move through the full 360 but with some resistance through part of the rotation. There doesn't appear to have been any sort of crash and there are no shavings evident at the foreline connection.

It looks like overhaul time baby.

I'm about to pull the whole thing apart and break out the acetone and isopropyl, but lacking the service manual is there anything I should know before I do?

[UG!]

i had a very similer problem with my turbo, though that was due to backstreamed oil from the roughing pump. in my case i found that most of the nasty brown smelly stuff had collected in a small cavity under the lower bearing, that was accsessable by removing a small pannel on the underside of the pump and cleaning the cavity. after doing that the situation has been steadly improveing.

i would be much more worried by any resistance to rotation. the blades on mine seem to spin absolutly freely on casuial inspection, you can walk in a circle with the thing and the blades will retain there origanal position with respect to north, but it still sounds like a jet plain takeing off when its getting up to speed

the bearings will most likely have internal grease lubrication, which it would be a very bad idea to remove, so don't dump them in solvents, unless you reely know what your doing.

Acetone is not actuialy very good at removing heavy oil contamination. you would be better with petrolium ether, zylene or even something chlorinated (i use dichloromethane when all else fails) but keep solvents (including acetone) away from moter windings and such as it may strip the enamiling.

you realy want yo have everything you might need (like nasty solvents, vac grease for o-rings etc) ready beffore hand and do a througher job as there is nothing more anoying than haveing to go through it all again as your first effort wasn't good enough (i speek from experance )

hope that helps

Oliver

[DaveC]

Chris -

Try VERY hard to get the Balzers Service Manual before trying various solvents. Second best plan is to contact a "local" vacuum pump rebuilding service, and get their advice.

An older Varian pump manual states that use of solvents like Acetone and other Hydrocarbons will VOID the warranty and probably damage the pump stator and bearing seals.

There are motor stator windings in there, whose insulation is in the vacuum These could also be coated with the oil scum you see on the rotor. The Varian manual spoke of using a "Freon" liquid bath to clean the pump innards safely.

Perchorolethylene (very similar to 1.1.1 Trichloroethylene ) is routinely used to clean HV transformers in the XRAY mfr and rebuilding business. It is quite compatible with many insulations.
But I do not know if it could be used in the Turbo.

You just don't want to go from a gummed up but salvageable pump to junk in a few minutes.

Even if it needs new bearings or at least bearing flushing...you could have a really nice unit with a little patient cleaning.

All the best...

Dave Cooper

[Chris Trent]

Thanks for the tips guys.

I've done some cleaning with alcohol and gotten some of the oil out. The resistance through part of the rotation is now clearly blade against stator. It makes a soft rythmic whisking sound as I turn the blades. If I spin the rotor it will revolve two or three times before stopping, a great improvement so far.

I also found a few tiny metal filings and a bit of silverish dust while cleaning, most likely confirming some sort of contact. Now I need to take apart the blade stack but don't see any obvious way to do it.

There is a ring around the axle at the top with various threaded holes spaced around it. There are screws recessed at various depths in these holes, presumably for balancing.

I have removed all of the external screws on the case but have not ascertained a way to seperate the pieces without damaging the blades or stators.

The screws are now back in by the way.

Any suggestions on how to dismantle this pump?

BTW I Called Pfeiffer and they are researching the manual. They don't know if they have one.

And yes, I know the pump is probably worthless at this point. But I'm going to learn something from this one that I might use later. Besides, there's still hope yet.

[DaveC]

Chris,

If you get the rotor blade stack apart, you may be finished... kaput...dead in the water... with regard to getting it back together and re-balanced.

The light drag, and metal bits, suggests a possible vacuum loss and partial atmospheric pressure surge. This causes large forces on the high speed rotot blades, bending them so they contact the stator blades. You might be able to straighten the bent blade(s) if the deformation is not severe, but this gets really delicate... with regard to metal fatigue and the like. Still you can treat the whole thing as education, and it is an invaluable opportunity in that regard.

Hopefully, you can get a manual. You still should also try to find some place that rebuilds turbos. They should be willing to share a few tips on rebuilding and teardown, with a serious experimenter like yourself.

Dave Cooper

[Tom Dressel]

For what it is worth, I am posting the cleaning instructiong for a TPU-40.
Also I have found the guys at A & J Vacuum Services helpful. Talk to Jersey. http://www.ajvs.com/.

Tom Dressel