Critique this turbomolecular pump backed by Welch 1400 setup

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Michael Bretti
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Real name: Michael Bretti

Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Michael Bretti »

For the YellowJacket Pump, which has a 3/8" male flare input, it is very easy to adapt to KF if you wanted to go this route. This pump can be a great low-cost pump if you are backing something such as a diffusion pump and you need more roughing throughput, though I doubt you will be using a diffusion pump as large as the one I have. For my system, I needed a KF25 flange for the roughing line, so I used the following parts, in order from the pump to the line:

1.) LASCO 17-5833 3/8-Inch Female Flare by 1/2-Inch Male Flare Brass Adapter - $11.77 on Amazon
https://www.amazon.com/gp/product/B008E ... UTF8&psc=1

2.) LASCO 17-6789 1/2-Inch Female Flare by 1/2-Inch Male Pipe Thread Brass Adapter - $4.44 on Amazon
https://www.amazon.com/gp/product/B008E ... UTF8&psc=1

3.) NW25 To 1/2" NPT (Female) - $23.00 LDS Vacuum
http://www.ldsvacuumshopper.com/nwto1fenpt2.html

4.) Teflon Tape (for the NPT threads only)

If you wanted to go to a KF10 flange, or any of the KF sizes, you can get KF adapters from LDS or eBay pretty cheap, and adjust your brass fittings accordingly. I used 1/2" adapter brass hardware to keep the line as open as possible to maximize throughput on the pumping side and make sure that the only limiting factor on pumping was the size of the inlet at the roughing pump. Richard Hull and myself have had good luck with this pump so far, could be something to consider if you want to get a roughing pump in new condition that will work well for your purposes. However, I agree with what Andrew Seltzmann suggested as well. Just a few different options to explore based on your system and budget constraints.
ian_krase
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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by ian_krase »

Personally I don't recommend CAD for amateur vacuum systems unless you are either rich or are building complex custom parts yourself. It doesn't go all that well with the parts scrounging strategy IMO.

While Teflon tape can work for vacuum a better option maybe the use of Loctite 290 to glue the threads together. Otherwise you should use the yellow kind of Teflon tape that's used for natural gas pipes. You can solder or braze threads if you know that you're not ever going to need to take them apart.


Dry diaphragm pumps are nice because they can have your system be completely oil-free however being oil-free isn't useful or necessary for a fusor.

Nice thing about Pfeiffer rotary vane pumps is that they are much less heavy and bulky for the same pumping speed than most other vendors of rotary vane pumps. this is useful for people who work in cramped areas.
Michael Bretti
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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Michael Bretti »

I would strongly disagree about not doing CAD for an amateur system. I am operating off an incredibly restricted budget, and CAD had been completely crucial in not only saving a lot of money, but full optimizing my system. CAD allows you to build your system ahead of time and plan without having the physical parts actually available. You don't need money to build a system in cad and see how it will turn out, or make changes on the fly. Websites like Kurt J. Lesker and Ideal Vacuum have a huge list of free cad models available for download, including just about all of the major standard vacuum components, which can easily be modified if you find variations of the component, for example, on ebay. In addition to physical planning and saving money, it has been vital for all of the vacuum engineering calculations I needed for my system, as well as thermal modeling to plan for the cooling systems for the diffusion pump, water cooled baffle, and future titanium sublimation pump. I would recommend Fusion 360 - it is free, powerful, and one of the most important software tools I have at my disposal for my vacuum projects. CAD is a very useful and powerfull skill to have in general in engineering, regardless of the type you pursue, and never hurts to learn. If you have the time to learn it, I would recommend it. I would say personally from my experience, cad is exactly the tool for someone on a very limited budget forced to scrounge. If you need help or advice with cad, feel free to reach out to me.

For the roughing line, if you use it properly, Teflon tape is more than adequate. I would not say that using permanent solutions such as locktite for the foreline is necessary, and can be advantageous for modifying your system in the future if such permanent solutions can be avoided. However, if you will never need to take it apart or dissemble it, then gluing/soldering/brazing can be a solution to explore. However, you just never know what you might want to do in the future, and having the option to disassemble and modify it can help save money further down the line. My foreline tested down to 2 x 10^-3 Torr with the Teflon on the NPT threads (the lowest the helium leak checker I used to pump and check it would go, the line should go down further), more than enough for any basic roughing line you would be operating with.
ian_krase
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Real name: Ian Krase

Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by ian_krase »

I should probably clarify. I don't disagree that CAD is a useful tool for complex vacuum systems or ones where you machine your own parts -- or even hack together enough of your own parts in restricted envelopes or the like.

However, for somebody who is mostly at the raw basic level of prototyping mostly out of scrounged parts, I think that stuff is often modular enough and you have to do enough labor just to get oddly-shaped stuff measured into the CAD program that CAD is of limited value. Meanwhile, you're often more making your project fit the parts available than the other way around.

(Unlike pen and paper, CAD is a whole separate skill that takes quite a bit of practice to be efficient at.)


So while CAD definitely has its place -- a big important place -- I don't think it's as valuable for the beginning fusioneer as commonly argued.
Jerry Biehler
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Re: Critique this turbomolecular pump backed by Welch 1400 setup

Post by Jerry Biehler »

I have one of the 071's, the older version with the 600 series drive. Pretty nice little pump.

The one thing about the pfeiffers is they are supposed to have their oil cartridge change yearly and if it has sat more then three years the bearing should be replaced. I really dont know how critical this is. I am guessing the oil starts to break down or varnish the bearing after that time period? Might be able to get away with rinsing the bearing in-situ with some filtered mineral spirits to wash out anything that might have dried before putting in a new cartridge.

Bearings are available from Alpine Bearing and you dont have to take the whole unit apart to change it. It comes out the bottom. I still need to get one for my TMU-521
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