Turbo pump grease

[Jeremy Adams]

Hey I was wondering if you could lend some advice on how to grease a turbo pump and what grease to use.

My Sargent-welch turbo pump is still having a rotor lock failure even under a solid dual stage roughing pump backing. Basically the turbo pump will only run for one minute and then have a rotor lock failure. I'm pretty sure this failure is caused by lack of grease because in the manual it states that the if current monitor on the control panel does not rise gradually it could indicate lack of grease. And when I run the pump, the current shoots up pretty quick. Also my pump is fairly old, and probably needs new grease. It spins smooth so the bearing seems well for now, and the roughing pump is definitely low enough to get this turbo running.

So what grease should I use? It is a sargent-welch 3131. The manual has no specification on what exactly should be used. I found some turbo pump grease online and it was very expensive for just a syringe ($150+). Do you have any recommendations that would be preferably less than $100 and still get the job done?

I am also wondering how to actually grease the pump. It says in the manual grease can be applied while the pump is running- this is confusing- how could you apply grease it if the pump is running in a low pressure system sectioned off by steel flanges? Is anyone familiar on how to grease an older sargent welch turbo pump?

Jeremy

[Dennis P Brown]

I can only answer your last question and only partly - many turbo's have an 'access' screw that when removed, allows oil to be injected even if the pump is running (but with a roughing pump only - not high vac). Whether your pump uses such a 'screw' only a technical repair manual would show. Hopefully someone here might know. I have never seen a turbo that uses grease (have heard of those) - all I've seen have oil filled bearings (a few dozen different types and of turbos sizes.)

Aside: Turbo pump oil is expensive (it is very special oil) so not too surprising the grease is costly; that said, there may be alternatives but that I do not know.

[Richard Hull]

Not to be flippant but ....you go with high-end vacuum solutions, you need to be prepared to pay high-end prices. Turbos are classically expensive. A full system with cable and controller at surplus will forever be expensive! Many of the operational items needed around it are also expensive. I now have two functional turbo's with controllers and all cabling for both, but remain on my no moving parts $40.00 air cooled diff pump. If I ever tear down fusor IV, the turbo will be attempted. (note, I bought my diff pump back in 2003 at the HEAS fleamarket. It was laying forlorn in the grass of my side yard by its seller's car. I gave it a home.)

Mind you...I will design the next system such that if the turbo fails, a mindlessly easy replacement path back to the 12 year reliability of my old diff pump will be made!

Richard Hull

[Jerry Biehler]

You need a grease that will not outgas at roughing pressures. Krytox makes some, Kluber might too. It is expensive stuff. I need to order some oil for one of my pumps and it is something like $150 for 50ml, it is a fomblin.

But the big problem is you cant mix grease chemistries, bad things can happen.

[prestonbarrows]

As others have mentioned, turbos are super high performance pieces of gear and are generally not conducive to home-user second-hand maintenance.

Beyond all that preamble, Krytox or fomblin are the classic lubricants suggested at turbo pressures. I have had great success with both for lubrication under UHV, but have never seen anyone but the manufacturer successfully service a turbo bearing without quickly leading to a complete failure.

Usually when a turbo bearing needs replacing, it is due to physical wear on the bearing faces which no amount of any magical lubricant will fix.

[Jeremy Adams]

Thanks for the info. I contacted Kryox and also found some greases in the links below. I get that the grease might not work in our pump, but trying something to get our pump to work is better than not.

http://store.tmcindustries.com/CHRISTO- ... p_405.html

http://store.tmcindustries.com/CHRISTO- ... p_383.html