TMP Diagnosis

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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Richard Hull
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Re: TMP Diagnosis

Post by Richard Hull » Fri Aug 11, 2017 5:29 pm

Turbos, especially used and second hand ones, purchased "at range", can be nothing but a pain. This is why a "no moving parts" diff pump starts off with a big advantage. Even a diff pump demands a good heater and a clean stack or you are back to more issues, still minor, compared to major turbo issues.

I have owned a perfectly functional 3" throat turbo with all cables and controller for 2 years, but will not install it as my diff pump is "plumbed in" and has worked well for 12 years in my fusor IV.
"If it ain't broke don't fix it" and "let a sleeping dog lie".

The real issue with any secondary high vacuum pump is size. Turbos are typically just the right size, (small). Diff pump offerings can be very inexpensive, but are often large, ( 4" throat or larger). These large diff pumps should be avoided.

No secondary pump should have a throat of 4-inches or larger. Plumbing adaptations on these larger offerings can be complex and costly if one is not a good machinist.

Good luck on getting the turbo to spin up

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Roberto Ferrari
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Re: TMP Diagnosis

Post by Roberto Ferrari » Fri Aug 11, 2017 5:45 pm

Adding to Richard’s wise words, I would comment on Diff pump sources.
Of course eBay is a must but keep an eye to damaged or scrapped Mass Spectrometers.
From 20 years now it is common in those systems to use small diff pumps, air cooled, of small size.
Service people following employer policy replace all the pump. So search for damaged units at universities and labs.
Basic damage is heater cartridge burned off but most of them are replaceable. Some having a glass window can get a crack on it. Just take it off and weld a blank plate.
My small lab has 3 of those diff pumps on use and 3 more on the shelf, recovered from scrap.
Good luck!

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Richard Hull
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Re: TMP Diagnosis

Post by Richard Hull » Fri Aug 11, 2017 5:53 pm

I will second Roberto's advice! Old, discarded, air cooled diff pumps off mass specs and helium leak detectors are ideal for the fusor builder. This are typically 2" throated pumps, but 3" is also common.

If you go turbo you need to be very careful in any purchase effort.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Jackson Oswalt
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Re: TMP Diagnosis

Post by Jackson Oswalt » Fri Aug 11, 2017 11:45 pm

David,

Your guess is as good as mine when it comes to the brand. There's is no doubt in my mind that Rigaku had some part in the pump. It's branded as "Rigaku" everywhere I look, so my guess they had some sort of deal with Varian that ended quite some time ago. The pump is from 1995.

As for the oil spillage, yes, it was in the vacuum inlet as well as outlet (because that's where it spilled out of). Fortunately, I've seen a few companies that could clean/repair the pump if needed, though I am trying to avoid that. I'm sure the price would be in the thousands.

Until I'm certain that the turbo is busted, I'm going to stick with it. Despite it's issues, I still believe it was a steal.

Thanks for the responses everybody. It's been a big help!

David Kunkle
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Re: TMP Diagnosis

Post by David Kunkle » Sat Aug 12, 2017 3:22 am

If oil was coming out the inlet port that connects to your vacuum chamber, I have little doubt that oil is covering your rotors and the rest of your insides, and that is your entire problem. Not quite sure how oil spilled out and "soaked" it. The oil is probably causing a lot of drag making it stumble when it tries to spin up.

And, yeah, sending a turbo in to a company is a minimum of $1500 to $2k and up. I've attempted to repair the same turbo twice with failure, while I know some here have seemingly repaired theirs successfully. Not sure how many would admit if it blew up after some too short a time period. ;) I've been known to go back to ebay and buy another used one that was compatible with the controllers I already had.

$160 is definitely a good deal........ on a good, working turbo. Apparently it was in good running order when the guy sold it to you. If you got it back in February, it's probably too long ago to complain that it was defective or packed improperly for shipping- but you could always give it a shot.

Jackson Oswalt
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Re: TMP Diagnosis

Post by Jackson Oswalt » Sat Aug 12, 2017 1:31 pm

Thanks for the help. I just have one question: Isn't the oil supposed to be on the rotors so it doesn't wear down? Or is it only in the motor? Second, although I'm sure the oil is a major problem, I still bet that the cruddy vacuum is also a suspect. Again, thanks for the help. I'll look into cleaning the pump and with any luck it will be fixed.

David Kunkle
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Re: TMP Diagnosis

Post by David Kunkle » Sat Aug 12, 2017 2:28 pm

No, the oil or grease is only supposed to be on the upper and lower bearings that support the rotor shaft. This keeps the bearings from wearing down- not the rotor. The rotors' only job is to spin quietly in a vacuum- they never actually touch anything.

Jerry Biehler
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Re: TMP Diagnosis

Post by Jerry Biehler » Mon Aug 14, 2017 7:18 am

Its probably not the oil. This pump is probably not a turbo-drag so it is going to need probably 50-100mtorr on the foreline for it to be happy.

Johan Reinink
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Re: TMP Diagnosis

Post by Johan Reinink » Mon Aug 14, 2017 10:10 pm

Even in a terrible vacuum a turbo spins up to several thousand rpm, not really like "stumbling" described by OP. Usually controllers don't blow fuses, they just push on until either a timeout (some even skip this), overheating or normal operation.

How many pins does the connector to the turbo have? If you can find the winding connections (low ohmic, significant induction) you can check if all connections are equal to find a winding problem that could blow a fuse. Since the rotor spins well I'd suspect the controller. Also, that guy of the youtube video also has this video: https://www.youtube.com/watch?v=PjOTTGOunI4 I hope that's not your turbo!

The styling of the pump looks like a Seiko Seiki unit, I'm not surprised Rigaku doesn't know about this pump, it's not their market.

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Re: TMP Diagnosis

Post by John Futter » Tue Aug 15, 2017 6:57 am

Your robinair pump is not good enough!!!!!
The controllers ramp up at a set speed and if the foreline pressure is not good enough the controller senses this and will shut down or will blow a fuse due to excess current demand from a lagging rotor
You need to know that your foreline pressure is well below 1 x 10^1 millibar or 5x 10^-2 torr before attenpting to start one of these old pumps.
even if your robinair got to the approved vacuum the spinning pump would overcome it and stall on the resulting high foreline pressure

I see you still have not corrected your earlier photos and now probably can not
it has taken me a long time to spot the upside down robinair

Take the advice
get a diff pump learn how to use that with all the needed metrology (meters ie foreline and high vac)then try to apply it to your Turbo.
secondly most turbos do not like being in storage for very long as oil drys out in the wrong places.
some turbos have a repair program built in where they vary the speed and time to try to get the lubrication circulating properly before going to full speed

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