Mini Dry turbo station build

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Andrew Seltzman
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Mini Dry turbo station build

Post by Andrew Seltzman »

I'm in the process of building a miniature dry turbo station using a diaphragm pump backing a molecular drag pump. This will hopefully be replacing my current turbo station that uses a dual stage oil pump(pfeiffer Duo 1.5A) and a 55l/s turbo pump (pfeiffer TPH-055). I'm aiming at a 8"x10"x4" footprint on the new system with the option to run on battery power for portable operation, and the ability to mount directly on the fusor frame.

My backing pump will be a 4 stage diaphragm pump, KNF Neuberger N84.4 with a 24vdc brushless motor, capable of ~4.8l/min at atm and rated at 2mbar(1.5torr) ultimate vacuum. These are equivalent to the pfeiffer MVP-006, but more readily available on ebay.
SAM_5826a.jpg
https://www.knfusa.com/?type=5600&fileref=7838
Testing of the pump with the a vacuum gauge shows the pump down curve and leak rate after the pump is shut off. The pump performed better then it's rated vacuum, achieving ~500mTorr.
SAM_5837a.jpg
diaphragm.jpg
The diaphragm pump will be backing a pfeiffer TDP-011 molecular drag pump. The pump has a 10l/s pumping speed, and can discharge into a fore vacuum of 25mbar(18.7torr) and has an ultimate rated vacuum of 5E-5mbar(3.7e-5torr)
000125825.jpg
000125825.jpg (11.71 KiB) Viewed 6321 times
For comparison the TPH-055 has 55l/s pumping speed, and an ultimate rated vacuum of 1e-6 mbar.

This turbo station is loosely based on a portable TOF mass spectrometer developed at Johns Hopkins
http://techdigest.jhuapl.edu/TD/td2501/Ecelberger.pdf
Andrew Seltzman
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Andrew Seltzman
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Re: Mini Dry turbo station build

Post by Andrew Seltzman »

The molecular drag pump(MDP) arrived today, it's a nice very compact unit with a built in controller and power supply, allowing the pump to run on bot 24vdc and 115-230vac.
SAM_5853a.jpg

It's very compact, allowing both the diaphragm and turbo system to fit on a piece of paper.
SAM_5862a.jpg
A test setup was built with the diaphragm pump backing the MDP, which was connected to a vacuum gauge
SAM_5856a.jpg
The system was tested with the diaphragm pump turned on at ~10s and the MDP turned on at 60s. At 120s it reached 1e-3torr, at 350s it reached 1e-4torr. It maxed out at about 5e-5 at ~18min.
full.jpg
A closeup of the pump down curve is plotted below
down.jpg
Due to the low leak rate of the backing pump and high fore line tolerance of the MDT, the backing pump can be operated intermittently. In this test, the backing pump was turned off for 60s, then on for 10s, then off for 60s, then back on. The manual for the MDP says using a buffer volume in the foreline, such as a small tank, can reduce the pressure fluctuation and allow lower duty cycles of the backing pump.
backing-on10-off60.jpg
It has some limitations in vacuum and pumping rate over a turbo like the TPH-055, but I think it is generally suitable for fusor work, and may allow greater effective pumping rate by allowing it to be placed on my fusor frame, without the 2ft of flex-hose. Additionally, the lack of an oil filled backing pump and the compact nature make it an attractive vacuum system.
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Tom McCarthy
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Re: Mini Dry turbo station build

Post by Tom McCarthy »

That's cool. The suitcase mass spectrometer also, it's a nice, neat build.

Are you working towards a battery-powered Fusor, or mostly battery-powered Fusor that you can port around easy? It's popped into my head from your mentions of battery power and portability here.
Andrew Seltzman
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Re: Mini Dry turbo station build

Post by Andrew Seltzman »

Partially, one of the things I'm planning is to make the fusor battery powered and portable. Most everything on the fusor with exception of the HV power supplies runs in 24V, potentially adding an inverter or modifying the supply's DC link with a boost converter will allow operation off of 24V LiPo batteries.

The other is to build a small replacement for my turbo station. I'm getting close to finishing up my PhD and will likely be moving so I'm trying to build a compact replacement for my existing turbo station so I can sell it.
Andrew Seltzman
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Richard Hull
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Re: Mini Dry turbo station build

Post by Richard Hull »

Very nice work. A nice success story with solid data reported. Good luck in achieving what might be a portable apartment friendly system.

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
David Kunkle
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Re: Mini Dry turbo station build

Post by David Kunkle »

Awesome. What did it cost for the 2 pumps and other essentials ?
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
Andrew Seltzman
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Re: Mini Dry turbo station build

Post by Andrew Seltzman »

The 2 pumps cost a little over $800, still getting other parts though.

I think I can get it to fit in a pelican 1200 case
SAM_5942a.jpg
Andrew Seltzman
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Re: Mini Dry turbo station build

Post by Andrew Seltzman »

The mini turbo station build is compete, both the turbo pump and diaphragm backing pump have been mounted in the case. A hole is cut through the top of the case to allow an kf25-kf16 adapter to pass through the top. A set of studs holding the kf25 bulkhead clamps to the turbo pump also mount the turbo to the case. The cover around the motor controller on the backing pump was removed due to space constraints, and the backing pump was mounted on vibration isolators. A 6mm of hose connects the turbo to the backing pump, typical backing pressures are 500mTorr-1torr; the turbo pump is capable of running with an ~18.5torr backing pressure. The system is powered by an external 24V wall power supply. An buck-boost DC-DC converter may be added internally to allow operation off of 5-32V, or off of battery power.

Station top
SAM_5998a.jpg
Station side
SAM_5997a.jpg
With power adapter
SAM_6000a.jpg
Internal components
SAM_5996a.jpg
Pump down curve
turbo-station-down.jpg
Andrew Seltzman
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John Futter
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Re: Mini Dry turbo station build

Post by John Futter »

Andrew
I would not take that into an airport
they would probably blow it up in a controlled explosion

Nice work!!
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