Could you help me judge this vacuum pump?

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.
Martin Shahi
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Re: Could you help me judge this vacuum pump?

Post by Martin Shahi » Sat Aug 31, 2013 7:13 pm

Richard Hull wrote:Brands?! What does that have to do with anything? If it is a diffusion pump and the heater works, it's OK.

As noted in my FAQ, select an air cooled unit with a 2 to 4 inch throat. Big Belly Bob's diff pump is as good as the finest Varian. They are like just tubes with a heater and a jet stack dropped in them. Zero moving parts.

Richard Hull
Well as with most products there are brands which are more reliable than others. There are also diffusion pumps of hugely varying prices. Clearly some are more suited to this particular job than others. Such as these two:
http://www.ebay.co.uk/itm/Diffusion-Vac ... 35ca7c5fc0

http://www.ebay.co.uk/itm/Varian-VHS-4- ... 2ec8fc9cad

They probably both do a great job, but one of the two may be more suited to a fusor. I was just asking for some help, no need to be curt and short-tempered towards a complete newbie here.

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Re: Could you help me judge this vacuum pump?

Post by Carl Willis » Sat Aug 31, 2013 7:52 pm

Martin,

There is little brand variation among diffusion pumps, outside of appearance.

My advice is to pick something small. You will have to buy oil for the pump, and it is very expensive, so it pays to stay on the small size. Fusor projects almost never benefit from the high speed of a big pump anyway. I see many pumps on eBay right now that are much cheaper and smaller than the two you are looking at. I see plenty of air-cooled pumps (nice for running at home, where you don't want to run water cooling lines for your pump). You should be able to find something suitable for under £150 any day on eBay, today is no exception as I look through the listings. Check out 350858658105 for an example of what I would call an ideal air-cooled diff pump at a fair price (comes with a high-vac valve as a bonus).

Many times, diffusion pumps will be sold with extras attached. Foreline, roughing, and high-vac valves are some of the nicest extras to look for. Your first link shows a water-cooled pump that comes with a baffle, a cryogenic trap, and a foreline valve. Baffles and traps are of limited value in fusor projects, and the trap can only be operated if you have a supply of liquid nitrogen. The second pump has no "bells and whistles." Just a plain diff pump offered at an exorbitant price. Both of those sellers are typical of the career-eBayer nuisance sellers who think that everything they touch turns to gold. One always has to wade through a long list of nuisance listings to find anything decent anymore.

-Carl
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Re: Could you help me judge this vacuum pump?

Post by Martin Shahi » Sun Sep 01, 2013 6:23 am

Carl Willis wrote:Martin,

There is little brand variation among diffusion pumps, outside of appearance.

My advice is to pick something small. You will have to buy oil for the pump, and it is very expensive, so it pays to stay on the small size. Fusor projects almost never benefit from the high speed of a big pump anyway. I see many pumps on eBay right now that are much cheaper and smaller than the two you are looking at. I see plenty of air-cooled pumps (nice for running at home, where you don't want to run water cooling lines for your pump). You should be able to find something suitable for under £150 any day on eBay, today is no exception as I look through the listings. Check out 350858658105 for an example of what I would call an ideal air-cooled diff pump at a fair price (comes with a high-vac valve as a bonus).

Many times, diffusion pumps will be sold with extras attached. Foreline, roughing, and high-vac valves are some of the nicest extras to look for. Your first link shows a water-cooled pump that comes with a baffle, a cryogenic trap, and a foreline valve. Baffles and traps are of limited value in fusor projects, and the trap can only be operated if you have a supply of liquid nitrogen. The second pump has no "bells and whistles." Just a plain diff pump offered at an exorbitant price. Both of those sellers are typical of the career-eBayer nuisance sellers who think that everything they touch turns to gold. One always has to wade through a long list of nuisance listings to find anything decent anymore.

-Carl
Thank you very much for your kind advice. Also how do you search for things on ebay, since when I search "vacuum diffusion pump" I only get 4 search results returned. Clearly I am doing something wrong, but if you could tell me how to rectify my mistake then I would be very grateful.

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Re: Could you help me judge this vacuum pump?

Post by Tom McCarthy » Sun Sep 01, 2013 7:12 pm

Just look out for the voltage rating, you may already know but England and Ireland are 220v, 50 hz, unless you've got some sort of adapter which I'm not sure you can get, 110v rated pumps and equipment will be useless for you.

Just did a quick search with 'diffusion pump' and 331003911723 was at the top of the list. It's going for $99 but it's rated at 120v.

Edit: Does anybody know if it's possible to use a Variac as adapter to provide 120v to items from a 220v mains? That is if they can take the 50hz rather than 60hz if that's relevant?

Tom

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Re: Could you help me judge this vacuum pump?

Post by Martin Shahi » Mon Sep 02, 2013 6:29 am

Tom McCarthy wrote:Just look out for the voltage rating, you may already know but England and Ireland are 220v, 50 hz, unless you've got some sort of adapter which I'm not sure you can get, 110v rated pumps and equipment will be useless for you.

Just did a quick search with 'diffusion pump' and 331003911723 was at the top of the list. It's going for $99 but it's rated at 120v.

Edit: Does anybody know if it's possible to use a Variac as adapter to provide 120v to items from a 220v mains? That is if they can take the 50hz rather than 60hz if that's relevant?

Tom
Your post helped me realise why I could only find 4 results for diffusion pump; I was using ebay.co.uk instead of .com! Now when I use ebay.com I get loads more results! Thank you for this. :)

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Re: Could you help me judge this vacuum pump?

Post by Bogdan G B » Mon Sep 02, 2013 12:20 pm

http://www.ebay.co.uk/itm/170854353765? ... 1436.l2649

Similar pump, cheaper.
Would this run off single phase?

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Re: Could you help me judge this vacuum pump?

Post by charlie_mccartney » Mon Sep 02, 2013 4:23 pm

I got a Acatel 2004A with a MicroTorr 11-D diffusion pump for 300 after shipping, just wait and watch.
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Richard Hull
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Re: Could you help me judge this vacuum pump?

Post by Richard Hull » Tue Sep 03, 2013 2:58 pm

Carl was right!...........Someone would show up and quote entire previous postings within a thread!!!

Please do not quote what was just posted, Martin. Folks follow threads real good here. No need to parrot others words just posted.

Richard Hull
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Re: Could you help me judge this vacuum pump?

Post by Ross Moffett » Tue Sep 03, 2013 3:15 pm

You can run the motor on single phase, but you will need a motor drive unit. These can have some advantages, that you can speed/slow the pump at will using the controller. Three-phase motors are quiet, too, because there are no commutators. If you go this route, be careful as to not run the pump at low speed for too long because some pumps have lubrication issues there.. they may have some mechanical "fling" inside that sloshes oil around and doesn't work at low speeds. I work in the automation industry, and I can say that AutomationDirect is going to have the best prices you will find on new equipment in the USA, though there is some used and third-rate equipment available on eBay.

Here are some instructions for removing the "quote" button, Richard. I expect it will take less time to do that than you will spend warning people not to use it in the future.

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Re: Could you help me judge this vacuum pump?

Post by Carl Willis » Tue Sep 03, 2013 5:26 pm

Does anybody know if it's possible to use a Variac as adapter to provide 120v to items from a 220v mains?
In this case--a diffusion pump heater--a cheap light dimmer can be used to control power consumption. Even in cases where the nominal heater voltage rating and the mains supply are consistent, better control of operating conditions can be had with a dimmer. Different oils boil best at different temperatures.

Variacs can also be used. In general, the same transformer can be used on both 50 Hz and 60 Hz line frequencies, albeit the tap configuration may be more restrictive for 50 Hz (more turns on the core, less output range).

-Carl
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