Varian rotary vane pump lost all its oil through exhaust?

The only thought I have is that if the safety valve failed and the rotary pump was running near 1 atm for many hours, it could have dumped nearly all its oil out the exhaust. No problem with pump (or at least there wasn't). Running with low oil probably didn't do it any good.

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Hi Sam,

Thanks for the input. For all I know, the valve failed 5-minutes after I left on Friday. The solenoid overheated and all the DC wires melted. This opens a slow leak... not sure how long that "slow leak" takes to reach 1 atm... but then the RVP ran like that for up to two days until I noticed the puddle today.

Seems strange to me that this leak would take it even close to 1 atm considering the RVP should take the system to 10^ -1 quickly and easily. I'll run it again and hopefully that fixes it. The RVP wasn't making bad sounds today... so I presume it's ok. It spit out a lot of oil mist when I first turned it on but that's to be expected.

Bah, another $500 valve :(

Thanks,

-Matthew

Ah, I remember spending hours one Monday cleaning vacuum pump oil off of EVERYTHING (e.g.: dielectric coated laser mirrors). Guano happens.

How about some sort of watchdog against future disaster? Perhaps a vacuum sensor to initiate a delayed shut down of the rotary pump and some way to gracefully leak the system up to atmosphere?

Luckily this was an easy cleanup. A little bit of that kitty-litter stuff they use on oil spills and it was done.

I'd need a sensor that would signal if the pressure stayed above a certain level and then power down the rotary pump.

Problem with a sensor like that is I would need to keep the "trigger pressure" really high otherwise I'd have to clean my foreline trap all the time. The system leaks to atmosphere fine... seems like the problem is going to be powering off the rotary pump if the safety valve fails...

I suppose I just hope my next safety valve doesn't melt on me.

It wouldn't have to come up to 1 atm; it just has to be enough liters/sec to get the rotary pump misting.

It's pretty unusual for those relief valves to fail. Who made this one?

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I've run Ultra High Vacuum systems for 40 years with no serious problems !, Electron Microscopes !

My son was supervising the operation of a Mass-Spectrometer with a Turbo-Molecular pump, RVP system when a Carbon-Fiber Vacuum coupling failed on the high Vacuum side. I don't know what it cost the manufacturers for repairs , but I know the TMV pump tried to go into Full-afterburner mode and filled the Ultra-high Vacuum system with pulverized metal dust when the TMV-pump swallowed atmospheric air ! Which is why the inclusion of the "electronic safety valve" This probably saved your TMVP!

I would suspect the diaphram in the "electronic safety valve" ruptured on the roughing pump side and protected the TMVP and shut it down safely

It is ironic but a 2 stage rotary vacuum pump is not really designed to handle large volumes of air. 99% of its operating cycle is pumping at ~

10u pressure. The exhaust port is part of a reed valve set-up sealed by the flat spring-like reed which is made gas-tight by the oilbath reservoir. Normal operation has only a trickle of bubbles flowing out from under the spring, usually from bypass operation to flush moisture (condense-able vapors ) from the pump. It is only during the initial roughing cycle that a significant amount of air flows though the pump and carries a small amount of atomized Vacuum pump oil with it, hence the oil mist filter. The RVP is designed to pump down a Closed system. not an open to the atmosphere system, so it is no surprise that it flushed out its charge of oil when it was opened to the atmosphere.

BTW Philips/Ewards High Vac. now recommend using "AMSOIL" Compressor oil ISO-46 (PCI) SAE 20 for their Vacuum Pumps. Much better pump life !

Yukio YANO

I've discovered why it failed. This was a valve that I pulled from our "random extra parts" closet HPS model 145-0040K-24V

I should have pulled the spec sheet on it long ago... it required

24VAC and we were feeding it 24V DC I'm surprised it worked fine for the first week.....

As a matter of fact, most of the UHV parts I used to build this (including the turbo) were from an electron microscope that we got donated in surplus. The diaphragm didn't rupture. The solenoid that opens the valve melted. And yes, as you pointed out, failures in these valves are designed to close off the UHV from the roughing side to keep from destroying our expensive stuff.

Thanks for the info on roughing pumps though. Interesting stuff...

-Matthew

Geez, major meltdown. I'm also surprised it didn't smoke in the first few minutes.

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Well, that certainly explains it.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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