Turbomolecular pump controller and bearing oil

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Connor Givans
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Turbomolecular pump controller and bearing oil

Post by Connor Givans »

Hello all. It's been a long while since I or Cameron posted, so I decide to take this opportunity to state that, alas, Mr. Key is no longer attempting to construct a fusor and I am the only remaining member of that 'partnership.' That large CF chamber has been replaced by a cylindrical vessel of my own, the diffusion pump with, what this topic is focused on, a massive and somewhat problematic turbopump. It requires enough bearing oil to fill the cup to fill line (visible in images below.) On top of requiring this bearing oil, I also need to devise a controller for this unit. I lack funds to purchase the only unit I have been able to find, and it costs 1,000 dollars. I know the pump runs at 400Hz and the pump has a 3 pin connector on the bottom. I do not know the voltage, current, or internal wiring of the pump. I also need to find a way to significantly choke this pump down to a smaller size fit for valving and connecting to the vacuum vessel, suggestions are more than welcome. It also has a foreline connector on the bottom I am unfamiliar with, what would I use to connect that to the rough pump? The turbo's OD is 11", ID is 8", it weighs ~62 lbs.
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Re: Turbomolecular pump controller and bearing oil

Post by prestonbarrows »

It looks like both vacuum ports use some type of semi-custom o-ring seal. You will need to machine/weld up some sort of adapter plates to a more standard fitting most likely.

Making a home-brew controller is a doable, but very significant electronics project. It is probably out of reach unless you are very skilled in electronics, have access to a very skilled mentor, or have detailed schematics of what you need already sourced.

Big beasts of turbos like this one are also quite dangerous and need to be anchored very securely. Something this size when fully spun up can store kinetic energy on the order of partial sticks of dynamite. If unsecured, a seized turbo of this size can put a hole through a wall or break your leg easily. It is much much more than you need and I would only think about using it if it was already working and/or free.

Are you 100% sure this even works? Even a freely spinning rotor does not guarentee the internals work or the bearing will hold at full speed or the oil glands aren't gummed up from being shelved to long etc. Given the missing parts and apparent age, it seems likely you scored it second hand surplus from some place. Though sometimes things like these get stashed in working order, most often they stop being used because something went wrong with them. Best case scenerio, prepare to spend a few hundred dollars on flanges and oil and electronics plus a few hundred hours getting this thing into fully working condition.

In any case, I would keep half an eye out for better options if you choose to work on it.
John Futter
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Re: Turbomolecular pump controller and bearing oil

Post by John Futter »

I bet the roughing port is KF25 or KF40 and is used with a custom retainer like a lot of the modern pumps do like Leybold.
the centering ring of the KF arrangement sits in the hole and two plates pickup on the 4 bolt holes to keep the backing line in place..

the oil is just good mechanical backing pump oil as used in direct drive pumps. the oil is only present in the pump at the backing pressure end.
Jerry Biehler
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Re: Turbomolecular pump controller and bearing oil

Post by Jerry Biehler »

Wow, that is an oldie. Airco pretty much disappeared in the early eighties being bought out by other companies.I think I saw this guy on ebay?

I think the roughing connection is the pretty-generic 4 bolt flange that airco-temescal used on a lot of their valves and fittings. O-ring groove in one flange and it squeezed against the face.

The motor should be a pretty generic 3 phase squirrel cage motor. You can *probably* get away with using a generic VFD to drive it, a lot of VFDs will go to 400hz. I would run in v/hz mode and slowly bring up the voltage parameter till the motor actually reaches full speed at 400hz since we have no idea what the winding actually want. Set the acceleration for a slow ~5min ramp up.

I am going to guess the two white fittings are for water cooling.

The 3 pin connector is a generic Amphenol MS connector. If you look at the insulator it should ave two numbers which designate the shell size and pin configuration.

First thing I would do is take a good ohm meter and check the resistance between the pins, it should be the same. Then check from the pins to the case and it should read open. If this tests good and the rotor spins freely without noise then you are probably good to go. These things are not rocket science. Well the ones with non-maglev bearings are not.
prestonbarrows
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Re: Turbomolecular pump controller and bearing oil

Post by prestonbarrows »

John Futter wrote:I bet the roughing port is KF25 or KF40 and is used with a custom retainer like a lot of the modern pumps do like Leybold.
the centering ring of the KF arrangement sits in the hole and two plates pickup on the 4 bolt holes to keep the backing line in place..
Ah, I think you may be right.

Try if a KF o-ring and the metal retaining ring fits snugly into the roughing port. If it does, you will need to make up a little plate with 4 tapped holes matching the existing bolt pattern with a large hole in the center. The center hole needs to be sized so the edge lands on the tapered face of a KF fitting such as a bellows. The clamp also needs a slot with enough clearance to slip the KF fitting in; or just split the entire thing in half.

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Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

The turbomolecular pump is working according to the ohmmeter and continuity tester. Any suggestions as to the type of VFD that would be good, current-wise? I'm not sure how much TMPs usually draw, really. I would definitely secure it well were it used, and I plan to use it. For water cooling, unless some magical water chiller happens to show up for 0.99 dollars in the general fort collins area, will be just an open loop using city mains. I lack a KF O-ring but can provide dimensions tomorrow with a pair of calipers.
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Re: Turbomolecular pump controller and bearing oil

Post by Jerry Biehler »

I would probably want a vfd that was rated for at least a half HP, maybe even 1 HP. Hitachi VFDs are good, I would avoid anything chinese like the plague. And it needs to be able to have the motor voltage settable, look through the manual of a potential VFD candidate and see if there is a parameter to set the motor voltage and it goes pretty low. These will be 240v in units. If you can use a 1/2 HP vfd you can get those with 120v input.

yes, you can use city water. There is also a pretty good chance you won't need cooling at all for duty like it will see. It is only when you cycle the pump through starts/stops and high gas loads that they usually start to warm up. My Varian 301 uses 7 watts with no load on my SEM.
Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

The pump originally had 3 round metal (I presume aluminum) legs with rubber bottoms for the unit to be suspended on. I'll probably see if I can find out what kind of threading the holes for those have and just turn out 3 new ones on an engine lathe so the pump can be suspended above the ground for the foreline and water-cooling tubes (better safe and cool than sorry!) Other than just welding a frame for the pump to sit in, what would be best for securing the unit?
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Re: Turbomolecular pump controller and bearing oil

Post by prestonbarrows »

At least for modern units, they are usually designed to be mounted directly to the chamber by the inlet port with the back end hanging in the air. This requires a chamber assembly that is much more massive than the pump or securely bolted to the ground.

You should is especially cautious the first times you spin it up given that it is old and you are using a rigged controller. It will be very easy to crash it. On the first tests, blank it off and bolt it to the floor if you say it has mounts for that. Throwing a ratchet strap around it to a structural post is a good idea before the pump is proven also; think securing a pressurized gas cylinder. Whatever you do, don't spin it up while it is just sitting loose on a benchtop.
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Re: Turbomolecular pump controller and bearing oil

Post by Jerry Biehler »

On a pump this size it would be bolted to the chamber or valve and then feet would be bolted to the floor. My big pump (2000l/s) list the torque that is created when it locks up solid and it is insane. A friend recently had a smaller pump crash on him for no reason and it ripped itself right off the mount.
Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

I'm just going to have a frame built for the entire vacuum system with the rotary vane pump and turbo sitting in there. I'll have the three legs for the turbo drilled and tapped on the bottom so I can bolt it to the bottom of the chassis. I'll have the chassis secured to the ground, and atop that I'll have my chamber sit with the vacuum fittings poking through to the bottom. the legs will be ~1.5-2" in diameter and just long enough for me to run the connections on the bottom for structural stability. Either aluminum or steel, I'll have to see how things turn out there. All this will be spaced away from me either way. I should get pictures of the vacuum vessel in sometime this month, hopefully, and I can start setting up my plans for vacuum connections, feedthrough, gas feedthrough, and the viewport. I'll get a pair of calipers at my place so I can get a CAD model of this pump made to work with and I can see about getting a KF clamp-plate machined or the likes. Hopefully the pump will have legs within a week, all things going well.
Jerry Biehler
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Re: Turbomolecular pump controller and bearing oil

Post by Jerry Biehler »

Don't put the carriage before the horse. You first need to get the thing spinning. You dont even need to run it under a vacuum. You can get it up to 4-5krpm in air without an issue, just watch the motor current. The control probably has a current limit setting, who knows what it was set at. You dont want to fry the motor from overheat.
Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

This is how I plan to install the TMP in the system, as my vessel is large for a fusor but not near large enough for the full force of a TMP like that - and it can't be choked off that way anyhow.
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Adam Szendrey
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Re: Turbomolecular pump controller and bearing oil

Post by Adam Szendrey »

If I may ask, what do you mean by "not near large enough for the full force of a TMP like that" ? If your system is well sealed and it pulls a good vacuum fast, then that's good. There is no such thing as a "too powerful high vacuum pump".You backfill the chamber with the work gas through a needle valve (which you can easily control) anyway, and you have a controllable valve to adjust the flow rate. I also don't get the "can't be chocked off " part. What do you mean? You seem to have a controllable valve between your TMP and the chamber, and the TMP sure as hell won't mind if you happen to completely close that valve.
Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

I was saying that it's far better to use a KF-50 for my application considering I don't need to pump 1,800l/s is all. Versus just bolting the whole pump on with a much larger valve or the likes.
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Adam Szendrey
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Re: Turbomolecular pump controller and bearing oil

Post by Adam Szendrey »

Oh I see. Wasn't sure what you meant :) . Well yes, when you don't need that pumping speed you can get away with a smaller valve, which is a lot cheaper. Not sure about the volume of your chamber but KF50 sounds plenty (if not overkill) for the typical fusor. I actually used KF25 and it worked like a charm.
Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

The vessel is a cylinder, if I remember properly it's a bit over 1' diameter and 22" in length with the largest/longest port going to 27", so it's a bit beefy, but nothing like the vessel I was previously working on.
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Adam Szendrey
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Re: Turbomolecular pump controller and bearing oil

Post by Adam Szendrey »

About 40 liters, that's indeed a sizeable chamber, do you have a photo of it uploaded to the forums?
Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

Alas the chamber is presently in farmington missouri awaiting shipping to my residence, as I got it for $200 US and shipping will only be around $100 US. When I get it here I'll have plenty of images taken with measurements and specifications.
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Re: Turbomolecular pump controller and bearing oil

Post by Jerry Biehler »

Again, get the pump running before investing in adapters and stuff. It could turn in to a boat anchor.
Connor Givans
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Re: Turbomolecular pump controller and bearing oil

Post by Connor Givans »

I won't be buying any vacuum parts till I know my pumps work, no question there. I just like to plan ahead as I know I have little to do between now and obtaining a VFD outside of that and working on the electrical system, which is dependent on my receiving a possibly donated transformer or not, if not then my work will go to getting a beat of a cockroft-walton working.
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