Servicing a Varian V200 Turbo Pump

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Steven Sesselmann
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Servicing a Varian V200 Turbo Pump

Post by Steven Sesselmann »

Hi all,

Turbo pumps are the way to go when you are building a fusor vacuum system but for many of you the price tag might mean you settle for an old diffusion pump instead, but you can be lucky and find a second hand turbo on eBay often for sale because the bearings are gone and servicing can cost a lot of money. The important thing to look out for is that the rotor and turbine blades are undamaged.

So for the freshmen on the forum I herewith document the servicing of my V200 Turbo. The bearings became damaged after I ran it for too long without water cooling causing the bearings to become too hot and the grease to run out, totally my fault, because I never had a manual with the pump, so I never realised the two tapped holes were for the water cooling nipples.

This pump is a Varian V200 Turbo
Bearing Part Numbers
CER-2280ZZSD602SBM3C77P58LY683UB
CER-101ZZSD629SBM3C70P58LY683P

Expect to pay around $200 each for the bearings, expensive but still a lot cheaper than sending the pump for service.

First step is to prepare a clean bench to dis assemble the pump, in this case I used clean brown wrapping paper to cover the bench. Make sure you have all the tools you are going to need and a pair of clean latex gloves. The pump is hopefully clean inside and you don't want to get any fingerprints inside the pump as these could be a source of virtual leaks later.
Some acetone and lint free rags come in handy too. Last but not least some silicone vacuum grease.
First step
First step
Start by removing the easily accessible parts, clean each part including the rubber o'rings with acetone. Try to place the parts on the table in the same order you disassemble the pump, this will make it easier to reconstruct.

Here I am removing the bottom bearing cover.
Varian-V200 - 2.jpg
After removing the 6 screws underneath the pump, the whole top part of the pump slides off, the fit is extremely precise and it is quite impressive how it just slides off.

Inside the pump on the picture below you can see how the turbine is constructed in layers.
Varian-V200 - 3.jpg
The turbine consists of a multi layered rotor with interleaved static (stator) blades. The stator blades are D shaped and fit perfectly together with minimum tolerances between blades. Each stator blade is held in position by a ring.
Varian-V200 - 4.jpg
Remove the ring and the stator blades one by one and lay them out on the table in the order you removed them, they have to go back in the same order thy came out. Here you can see how the manufacturer has engraved a number on each pair.
Varian-V200 - 5.jpg
Once the turbine has been dis assembled, the brass motor housing can be removed, this pulls the shaft out of the bearing so it might be a bit tight. I used a few small wedges to gently pull the shaft straight up.

Note: At no time must any pressure be put on the turbine blades, these are extremely fragile and will be rotating at 60,000 rpm. and needless to say your pump will be useless if you bend a blade.
Varian-V200 - 6.jpg
Here I am removing the bearing cover and the old bearing. In this old V200 there are some oil wicks surrounding the old bearings, these are no longer needed as the new bearings are sealed and do not need oiling. So I removed the old wicks and cleaned out the bearing housing with acetone to remove the old oil before fitting the new bearings.
Varian-V200 - 7.jpg
There seemed to be a 3 mm gap between the bearing and the cover which might mean that a spacer or a spring has been lost here, so I machined a small bushing from Teflon to hold the new bearing in the right position.
Varian-V200 - 8.jpg
To change the top bearing it is necessary to remove the shaft and to do this the motor rotor has to be removed, and it requires a special tool which I did not have on hand, so it was time to put on the thinking cap and dig in my box of scrap.
Varian-V200 - 9.jpg
The best I could find was a 30x30 mm square steel pipe, so I brought out my hacksaw and started making a tool from it. As it turned out this tool worked perfectly and the screw came off without a single bad word being mentioned.
Varian-V200 - 10.jpg
The re-assembly was pretty straight forward, and the only hold up was the bottom bearing which was a bit of a tight fit on the shaft, but placing the top of the shaft on a firm surface and using a copper bar as a pusher I was able to gently tap it on using a small hammer.
Varian-V200 - 11.jpg
Here is the pump fully assembled again and spinning freely. Note: during the re-assembly all rubber o'rings were first cleaned with acetone and heavily greased with vacuum grease.
Varian-V200 - 12.jpg
The job took me most of the day and by the afternoon I had the pump back on the rig and running. But I still had several hours work to carry out the proper running in procedure.

According to the manufacturer, new bearings need to go through a running in period according to their instruction sheet.
Varian-V200 - 13.jpg
Here is the typical running in instructions for the bearings, it consists of 1 minute on 4 minute off running for several hours followed by longer and longer on periods. This method allows the grease to distribute itself properly and makes the bearings last longer.
running-in.png
So if any of you guys ever have to replace a bearing, I hope this will give you the confidence to give it a go, and whatever you, don't run your turbo without cooling water if it was designed for it.

Last but not least, thanks to CGB Precision Products Pty Ltd in Melbourne for excellent customer service and for helping me locate the right bearings for my old Varian V200 Turbo.

Steven
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Dennis P Brown
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Re: Servicing a Varian V200 Turbo Pump

Post by Dennis P Brown »

Outstanding article! I've open two turbo's that had bent blades (one still had a bolt stuck between some lower blades!) and bent them back. Both turbo's work great now. Just if one decides to do this, remember the blades are brittle and will bend but break all too easy. Yet, getting them back into alignment was very easy - that surprised me a great deal - especially the one with the bolt; those blades were really bent (forty to sixty blades.)
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Re: Servicing a Varian V200 Turbo Pump

Post by Jerry Biehler »

Alpine Bearing has a good selection of turbo pump bearings, http://alpinebearing.com/bearings/turbo-pump/

I was looking for bearings for a pfeiffer 1000l/s pump I have and found a picture on PTB Sales of one of their turbo bearing kits and zoomed in and was able to read the number on the bearing package which lead me to Alpine Bearing. The bearings are significantly cheaper there. Though for this pump it uses a special fomblin oil and a small oil pump that circulates the oil though the bearing. It is a single bearing pump, the top end of the pump is supported by a permanent magnet bearing.

For that pump I ended up getting a new bearing from a company in california that makes ceramic bearings, only about $50 shipped. The bearing was a standard off the shelf size just with a special ball separator. I was able to pop the old one out and snap it in the new bearing easily. Still need to order oil for the pump to test it out.

I have another 500l/s pump that I need to do too, but unfortunately it is an odd bearing so I am going to have to get it from Alpine.
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Re: Servicing a Varian V200 Turbo Pump

Post by Rex Allers »

Interesting stuff on Turbo bearings by both Steven and Jerry. Having no direct experience myself, I'm curious how one knows the bearings need attention? Is the main symptom noise or other stuff?

Do turbo bearings tend to fail gradually? Do you guys have any other input about spotting problems and how fast one needs to respond?

I snagged a small turbo a while ago (Edwards EXT75). It's neat in that all it needs is a DC supply and a serial connection to run - no external drive controller required and there are commands for both control and status monitoring. So far all I have done is hook it up to a roughing pump and spin it up with the input blocked off. I still need to make a manifold to measure vacuum but it seems to spin up OK.
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Re: Servicing a Varian V200 Turbo Pump

Post by Steven Sesselmann »

Rex,

In my case the bearings got too hot causing the grease to run out, and it came to a halt pretty quickly, I could see the speed was dropping and then it came to a complete halt, which caused the thermostat switch to cut out. When I opened the pump the shaft was difficult to turn.

The more common reason for a turbo to fail is a catastrophic leak, usually someone venting the system accidentally (turning the wrong tap), this causes air to rush into the pump and usually the momentum of the blades hitting the gas causes the rotors and stators to collide into a nice aluminium salad.

Steven
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Re: Servicing a Varian V200 Turbo Pump

Post by Rex Allers »

Thanks, Steven. Yeah, that catastrophic failure mode is not a bearing issue. I think I'd notice that pretty fast. Time to shop for a total replacement, I'd think. Hope I never see something like that.
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Re: Servicing a Varian V200 Turbo Pump

Post by Jerry Biehler »

Noise is the first sign. You will hear a gravely sound when it runs. A pump in good condition should be almost silent. Vibration can also be a sign. Pumps can die from sudden air ingestion and can also just spontaneously self destruct. A guy I knew that worked at intel had a 18" diameter turbo suddenly seize up, ripped itself right off the mounts of the machine. A friend at PSU also had one just decide to shred itself one day. There is one hell of a load on those vanes...

Most pump can be ran without water supply at low gas loads. At most you just need a fan. When you get into higher gas loads you need more active cooling.

A lot of the newer pumps have the drives built in which is very nice. Though that 1000l/s pump is kind of annoying, it wants 140vdc, not exactly a common voltage.
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Re: Servicing a Varian V200 Turbo Pump

Post by Rex Allers »

Thanks, Jerry. That's the kind of info I was looking to hear. Pretty much what I expected about how they normally fail, but good to have confirmation.

With the crazy RPMs these things spin at there has to be a lot of energy stored in there that has to go somewhere if it crashes, especially on a big one. I saw a youtube vid of someone who built their own controller for a turbo and was testing it. It seemed to be working (it spun up to some extent), but they just had the turbo sitting on a table with no roughing pump and nothing sealing the inlet. It made me cringe for several reasons.

The little Edwards I have only needs 24 VDC at several amps. I tested it with a pretty small 24 V, 200 W switcher supply.
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Re: Servicing a Varian V200 Turbo Pump

Post by Rich Feldman »

Great thread. I still check ebay for turbopump deals from time to time, in spite of already having one (as well as an air-cooled diff pump) sill never vacuum-measured by me.

Strictly speaking, in a crash the rotor's _kinetic energy_ is easily dissipated internally, by bending / tearing / slightly heating metal parts. It's the _angular momentum_ that has to "go somewhere". The cringeworthy unsupported little pump could roll itself off the table. As Jerry mentioned, big guys (as with serious ultracentrifuges and energy-storage flywheels) can break their mounting bolts and unleash hell in the lab.
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Re: Servicing a Varian V200 Turbo Pump

Post by Steven Sesselmann »

I noticed one thing that hasn't been mentioned in this thread yet, and which may not be obvious to the first time turbo owner.
  • NEVER move a running turbo pump!
While running it may look like an inertial object just sitting on the table, but it has a huge angular momentum and the gyroscopic effect is extremely powerful so moving the pump will put strain on the shaft and the bearings, this applies even when it is mounted on a cart with wheels as it is in my case. I have fallen for the temptation to move my cart a few inches to get in behind it, and seen how the frequency of the turbo falls right off, indicating how it's struggling.
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Re: Servicing a Varian V200 Turbo Pump

Post by Richard Hull »

All turbo's, no matter how small, need to be rigidly fixed in space! Read that as bolted firmly down in a fixed rack or struture that is effectively immovable when active.

We all have friends and science buddies in th' biz who have shared "campfire stories" about turbo pump death rattles, self-destructs and related stupid moves that took out a turbo. Based on their price and mechanical complexity, turbos are not toys or casual components in any modern vacuum system.

I have had a working turbo, matching controller and all the proper cables, but have refused to use it only because the small diff pump I have on fusor IV does great with few worries, since 2004.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Servicing a Varian V200 Turbo Pump

Post by Frazer Monks »

I am very impressed that you tackled this yourself and had a successful outcome. I used to work in the vacuum industry so I have some idea of how much precision is required to properly service a turbo. They are simple in principle but so easy to damage with careless use or poor maintenance.

Perhaps you can help me though in explaining why so many go the turbo route? I am in the early stages of building having just sourced a rather juicy stainless vacuum chamber that was doing service as a coffee table and I intend to build around an old Edwards E04 diff with a matching baffle and trap rather than a turbo. I know a turbo is the way to go for an ultra-clean setup and the power consumption is low but turbos do have some key weaknesses: high cost, susceptibility to mechanical damage, finite lifetime, high service cost, poor hydrogen/deuterium pumping performance relative to a diff, vulnerability to plasma damage (esp. maglevs).

Sure, a diff drinks power (though with a little experimentation you can use a temperature controller to drop that quite a bit), they have a tendency to back-stream if operated with no baffle and the startup and shutdown is slow but they are comparatively cheap and go forever. For an equivalent size a diff easily outperforms a turbo with lighter gases and they are pretty much immune to plasma damage.

Of all the disadvantages, back-streaming is potentially the worst but it is seldom an issue at the sort of operating pressures in a fusor, even with no cooled trap or baffle and provided that you aren't using silicone based diff fluid even cleaning the chamber out every year is not too onerous. Given the pressures, pumping time, overall cleanliness and just plain performance that most of us will get I just can't see why I would want a turbo other than it looks cool.

And if you think back-streaming is a deal breaker you should see what a mess a turbo winding failure can make in a vacuum rig!
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Re: Servicing a Varian V200 Turbo Pump

Post by Richard Hull »

Today, for a consumate scrounger, good electronics guy and the mechanically adept, a turbo can be quite inexpensive, but only to those mentioned here. Where there is a will there is a way. For the vacuum head to whom a fusor is just another vacuum project, they surely already have a turbo in their current system where cleanliness is paramount.

Diff pumps are virtually zero maintenance, ultra cheap for a "one-time vacuum project builder who is a decent scrounger. Plus, they don't have a mechanical or complex electronic failure mode. The power to operate them is not worth consideration and never is part of the equation. (unless you are a tree hugger). As I have noted before, I have a deal with my local power company....they offer to sell me all the power I want, as long as I pay the bill. A diff pump of the size a fusor needs will cost about 5 cents for each full continuous hour of operation in my state. I will not let 5 cents per hour of juice out a wall outlet stop me from fusing and I doubt anyone else would squeal at such an expense either.

On the other side, what may be the last of the nice surplus, air cooled diff pumps are thinning out, just as the first and second generation turbos are being retired or replaced in good, still usable condition. No one should ever buy a brand new diff pump or turbo pump unless their heart demands it and their cash pile is flush. Even used, fully cleaned and reconditioned diff pumps from Duniway are very expensive. Sadly, Diff pumps will slowly go the way of the doe-doe bird.

The word turbo hits a lot of folks as "cutting edge" ( I prefer the "bleeding edge") and there are those who want the very best without knowing or are willing to accept the risks and costs. Sadly, most turbo pumps on the surplus market are found with no controller and or cables!! This makes them an unknown quantity regarding operational condition.

Both turbos and diff pump have operational issues and rather nasty failure modes if stupid mistakes are made by a neophyte operator who doesn't learn the issues for their particular choice prior to operation.

You asked why so many choose turbo's over diff pumps? All of the above...... Why do people still choose diff pumps? all of the above.

You pays your money and you takes your chances.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Servicing a Varian V200 Turbo Pump

Post by Dennis P Brown »

My fusor has a diffusion pump (water cooled) and my "Ion Gun" has a turbo; it is a question of cleanliness. A DP with a good (read very cold) trap is every bit as good as a turbo for a fusor but that trap cooling for high vacuum issue is a bear. For me (since access to water never was an issue) the DP is hands down better (do need a good gate valve but that is true for both systems.)

Long term, a DP has advantages; a turbo will need servicing and can have both electrical and mechanical failure modes that are minor to very serious (lose the unit, no repair) and this is just not possible for a DP (worse case, replace the heating elements and clean it out (that anyone with even just a little skill can make the heaters themselves using hand tools.))

Even with the chance to getting a second turbo (fairly cheap) this never crossed my mind to do for the fusor. I like my DP pump (and turn around almost as fast as a turbo. My heating unit in the DP has separate water cooling access and this has been setup by me to work. Cooling the oil down is just fifteen minutes and the unit can see air.) This DP (with a manual gate valve) AND a small access chamber that has four ports cost about $120 (w/shipping) and can couple (as it does) to a larger chamber through the small chamber. Can't see that such a device is anything but superior to a turbo (even the working unit I got with the controller for $10 (not w/shipping.))

My two cents; of course, with these units getting harder to find, Richard's point may matter far more.
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Re: Servicing a Varian V200 Turbo Pump

Post by Jerry Biehler »

I replaced the DP on my SEM with a turbo for a couple reasons, one, that was the only part of the SEM that needed water cooling, with a turbo it does not need cooling. Also it is way cleaner, I no longer need to clean apertures because of back streaming. Combining that with the oilless scroll pump backing it I have a very clean system. I had installed a RGA on the SEM to see if it worked and I showed visually no oil in the system.

Also turbo's start up so much faster. I have a CHA/Veeco evaporator with a 18" jar and 6" diff pump. If this 1000l/s turbo works it is going on there ASAP, yes, I loose ~1000l/s over the diff but not have to worry about back streaming makes a huge difference and I can just start up the machine to do a quick coating instead of waiting nearly a half hour for the pump to come up to full temp.
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Re: Servicing a Varian V200 Turbo Pump

Post by Bob Reite »

The main reason I bought a turbo for my system is finding one for ten cents on the dollar complete with backing pump and controller. Otherwise I probably would have gone with a diff pump.
The more reactive the materials, the more spectacular the failures.
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Re: Servicing a Varian V200 Turbo Pump

Post by Richard Hull »

Smart money, at a super good price, goes for the best thing they can find. Nice buy Bob!

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Servicing a Varian V200 Turbo Pump

Post by Marko Kuzmanovic »

I have a V80a. Looks the same. I'm assuming the method would be the same for changing the bearings.
Any tips on getting the nut loose that requires the special made tool? How did you secure the shaft without touching the blades?
TIA!
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Re: Servicing a Varian V200 Turbo Pump

Post by Dennis P Brown »

Marko, start a separate new thread so your post doesn't get buried here. More likely to get help with the issue.
Never place any force on those blades - they are weak and easily bent. In all likelihood the bolt has some type of anchoring system (mine used two holes like Steve's) for a tool. See Steve's home made tool that did the trick at the start of the post. I used a Lens spanner tool (these are even sold on Amazon.)
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