Removing Turbo Pump Rotor

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Jackson Oswalt
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Removing Turbo Pump Rotor

Post by Jackson Oswalt » Thu Feb 08, 2018 12:15 am

Hello all,

Some of you may remember a previous post of mine in which I inquired about a turbo pump I picked up off of eBay. Since then I have figured out the issue: the bearings. Whether they are just gummed up with the oil that spilled out the pump during shipping or are just worn down, I do not know. However, I do know that the friction caused by the bearings is causing the pump to pull to much current from the controller, causing the fuse to blow. So, I have taken off each and every stator blade and set them in pure IPA in order to clean them. In case you're wondering, they are all labeled.
Now the only thing standing in between me and the bearings is the rotor, which I have absolutely no idea how to remove.
image.jpeg
image.jpeg
I was able to remove a bolt and a thick washer from the hole you see. It seems like it might require a tool like what this person used:
https://m.youtube.com/watch?v=jL0fXUZ4wFQ
[skip to 16:15]

Any suggestions are greatly appreciated!

-JO

Jackson Oswalt
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Re: Removing Turbo Pump Rotor

Post by Jackson Oswalt » Thu Feb 08, 2018 11:24 pm

Strangely, after sitting with the stator blades off, the pump has been able to drain some of the spilled oil. The rotor now spins much more freely, but still needs improvement.

Jerry Biehler
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Re: Removing Turbo Pump Rotor

Post by Jerry Biehler » Fri Feb 09, 2018 9:05 am

See if it spins up to speed without the rotor.

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Dennis P Brown
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Re: Removing Turbo Pump Rotor

Post by Dennis P Brown » Sat Feb 10, 2018 12:09 pm

If you think it is "gummed up" then try cleaning it. Acetone is often recommended for some turbo's. Then a rinse with absolute (or close) alcohol. If it is the upper "floating" bearing, then you are done. If it is a lower bearing, then one needs turbo pump bearing oil to re-lubricate the bearing.

Do not know if your unit has its bearing pressed on - my lower bearing was and does require a tool (read this from the manual I found on line.) Pulling such a bearing can be done but you should find a manual on your turbo to see what is really required. My upper bearing allowed the shaft to be removed but was pressed into a upper housing. The manual said nothing about that units removal.

Since you say there is spilled oil, then I assume your turbo uses an immersion bearing? Then rather essential to replaced lost oil. Are you saying oil from a mechanical pump got into the unit? Then cleaning the turbo with acetone may be required (again, what my turbo pump manual recommends.) That, of course, then requires that the lower bearing be re-oiled.

I am lost on why you must remove the bearing? If it is bad, then yes. But you indicate it might not be - just needs cleaning, which can be done without removal. Also, do you then have a replacement? If not, removal is pointless until you do.

If you do want to remove it (you know it is no good), that should not be too difficult if it is pressed in. From the looks, simply placing the rotor blade assembly onto the top of a metal surface with a hole large enough to just pass the bearing. Then use a brass shaft just big enough to enter the hole and cover the outer bearing ring. Then gently tap with a hammer. Should drive the bearing out but it then needs to be replaced. That requires pressing in a new bearing - a drill press or a vice can do that but it needs to be done slowly with a steady force - no impacts.

This all assumes the main drive motor isn't involved. If so, then a proper press would likely be required. Your picture does not show me enough information to know. If the motor case is involved, one could possibly make their own tool using on hand stuff but more details would be needed - a side and rear pic, for instance.

prestonbarrows
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Re: Removing Turbo Pump Rotor

Post by prestonbarrows » Sat Mar 17, 2018 3:12 am

I have not seen a modern turbo from the past 20 years with 'wet' lubrication. That is to say, none that require actively flowing oil or even macroscopic quantities of oil. Used market turbos often come from fab houses that use corrosive gasses that can cause all sorts of problems, you should really be using gloves and a respirator if you are handling the innards of a turbo from unknown origin.

Typically, there are one or two bearings mounted to the rotor shaft. Almost always, it is the 'rear' bearing mounted towards the high pressure side furthest from the intake that goes bad.

Servicing typically involves removing the outer cylindrical casing axially, removing the internal stator segments axially, removing the rear bearing plates, pulling out the rotor assembly, pulling the bearings off the rotor shaft, replacing the bearings and reversing the disassembly.

The trick is 'approved' bearings are almost always only available for the newest pump line and only guaranteed if the manufacturer installs them at a cost comparable to a new pump.

If you want to wing it, you absolutely want full ceramic bearings rated to well above the operating RPM of the pump. Adding a dash of high performance turbo lubricant such as Krytox is usually beneficial and a standard part of 'real' refurbishments.

All that said, self-servicing of turbos is always a crap shoot even for experienced dudes. The cost per risk of failure ramps up dramatically with radius slash pumping speed. The little 50 l/s guys are basically idiotproof but getting up to >1000 l/s is just asking for your wallet to be broken.

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Re: Removing Turbo Pump Rotor

Post by Jerry Biehler » Sat Mar 17, 2018 3:25 am

Pfeiffer still uses wet systems, their larger pumps use them, around 1000l/s up. I have one of these that uses a fomblin variant for lubrication and there is a little gear pump in the base of the turbo that pumps oil into a well where it travels up the tapered bearing nut to the bearing. one pfeiffer turbos use TL011 which is a hydrocarbon based oil. I almost went that route but found some of the real stuff on ebay cheap thanks to someone pointing it out on youtube in one of my videos.

https://www.ajvs.com/library/Pfeiffer_V ... Manual.pdf

Most semiconductor fabs have very stringent contaminated article procedures and anything that is contaminated with something toxic immediately goes to scrap and is not surplused out. They are very serious about this stuff. My friend deals with a lot of the high tech companies around here surplus wise and nothing gets out without it being written off as decontaminated.

There is a chance you could get something that is bad but if it came from a major corp, probably not going to happen unless someone found it sat a scrap yard.

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Re: Removing Turbo Pump Rotor

Post by prestonbarrows » Sat Mar 17, 2018 3:35 am

Jerry Biehler wrote:
Sat Mar 17, 2018 3:25 am
Pfeiffer still uses wet systems
Do you have a good explanation of why? I routinely use competitors pumps with significantly larger pumping speeds using 'dry' bearings (at least no active flow within the lifetime of the pump)

Fomlin or equivilent is still common in higher pressure mechanical pumps we have seen, but there should be no need for it in turbos.
Jerry Biehler wrote:
Sat Mar 17, 2018 3:25 am
Most semiconductor fabs have very stringent contaminated article procedures and anything that is contaminated with something toxic immediately goes to scrap and is not surplused out.
Agreed, one of the reasons for the rising cost of second hand turbos. But honestly, you dont want gear slimed with methal-ethel-death, that is all the rage at fabs these days.

Jerry Biehler
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Re: Removing Turbo Pump Rotor

Post by Jerry Biehler » Sat Mar 17, 2018 5:56 am

My guess is they handle contamination a lot better than a greased bearing, probably lasts longer too. Grease just holds contaminants in place where oil dilutes the contaminant in a greater volume. Also greased bearings run hotter than oil bearings. More friction, that's why high speed spindles on milling machines use a air/oil mist. This is actually probably a major point because the larger the bearing is lower max RPM you can run it with grease. The bearing in the 1001 was pretty decent sized, I think 15mm ID and like 27mm OD. I found a place in Cali that was able to get me a ABEC 7 grade ceramic ball bearing to replace the one that was bad, so far so good.

The oil in the turbo is still exposed to whatever gas you are pumping, if you are pumping O2 or corrosives you are going to want fomblin or one of the other PTFE based fluids.

Rising prices of turbos? Heck, they are cheaper than they ever have been, I picked up a real nice 700l/s leybold with built in drive for a sputter system at work for something like $650. Came out of a mass spec so nice and clean. You just got to keep an eye out.

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