Unfortunate Diffusion Pump Sign

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Jackson Oswalt
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Unfortunate Diffusion Pump Sign

Post by Jackson Oswalt »

Hello all!

After a solid attempt at repairing my turbo, I've officially deemed it broke and placed it in storage for when I have the chance to get it professionally repaired. So, I immediately looked into diffusion pumps on eBay. Fast forward almost a month and here we are: the pump I chose has arrived. The only problem was it came in a rather large box, about 4ft x 4ft x 4ft. I open it up and what do I find? The outlet is 9" in diameter. Now, I'm sure your wondering how I made such a drastic mistake. The answer? I was ignorant. Previous to this pump, I had been watching another pump identical in appearance to the one I have now. Unfortunately, while I was negotiating with the seller it sold for full price. So, immediately I found this one. I figured if it looked the same size it must be. Right? Wrong. It's by far the largest pump I've ever seen. Now, for the good things: 1. It's in spectacular condition. There are zero dents in the cooling line, zero broken welds, zero mangled gaskets, etc. 2. It came with a function gate valve at the top, a nice gate valve, and assortment of other fittings that probably saves me about $40 (not including the gate valves, which can be incredibly pricey. 3. The price was $200. Seemed fair when I thought it was only a 1-1/2ft tall. Seems like a steal when it's 3ft tall. Of course, shipping was a tad bit expensive. 4. This is most important; at the top attached to the outlet is a Kf25 flange, which allows me to directly hook up a hose as if it were meant to be. This also means I don't have to have a custom adapter machined for an audition $100-200. I can also return it if need be, which is why I've come to you. Should I return and continue searching for a smaller one (which have been quite a bit more expensive), or should I keep this one and live with the fact that I'm bottlenecking it beyond belief? Personally, since it's such a nice pump I'd prefer to keep it, as long as it'll work for my little chamber. Thanks for your help!

-JO
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ian_krase
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Re: Unfortunate Diffusion Pump Sign

Post by ian_krase »

I suspect that what will determine that is:

1. How much oil is needed -- since all diffpump oil is very expensive and eventually you reach the point where the small bottle you might already have isn't even one charge

2. How much power -- and what voltage -- is needed. If it can't run on whatever voltage the house wiring where you live are, then problems. If you can power it at all, then cost for power is probably not prohibitive but might be undesirably high.

3. How much foreline pump capacity is needed. I do not actually know whether this scales rapidly with diffpump size

4. Cooling water demands.
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Dennis P Brown
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Re: Unfortunate Diffusion Pump Sign

Post by Dennis P Brown »

People here have posted sites (just a month or two ago if memory serves) for low cost diffusion pump oil, so that shouldn't be a big issue. Water cooling is water cooling - if you have access, can't see that being as an issue. As for power - fusors aren't very low power devices so, unless it uses 220, or over 10 amps, that should not be an issue.

In any case, is the gate valve a manual or pneumatic?

The rather critical issue is, can it be adjusted to vary exhaust performance? If you can't throttle it down, then that pump will exhaust your deuterium tank in no time. So, as long as you can nearly close off the DP via the gate valve, the size shouldn't be an issue.

Might look rather funny, with a small fusor chamber though ... .
Last edited by Dennis P Brown on Wed Nov 15, 2017 7:21 am, edited 1 time in total.
Jackson Oswalt
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Re: Unfortunate Diffusion Pump Sign

Post by Jackson Oswalt »

The oil charge is 260ml. It's a lot, but I've got more than enough. The gate valve is manual and the heater is 210 volts and around 1360 watts. My main concern was pumping it down, but I do believe it's possible with a little extra time. As for water cooling, that's not an issue. I'm currently working on that, regardless which diff. Pump I have.
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Silviu Tamasdan
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Re: Unfortunate Diffusion Pump Sign

Post by Silviu Tamasdan »

Oil is not that expensive, it was my post a few months ago about it. You can get basic 702 oil for about $100 a quart, that would be almost 4 charges for your pump. https://diffusionpumpoil.com is where I get mine. Their website shipping calculator is a bit screwed-up but they respond very quickly to emails and fix the charges.
The heater voltage may be a bit of an issue, but not a deal-breaking one.
As long as you can deal with that, have an appropriate gate valve and roughing pump I'd say keep it. It has the advantage that you can later use it for a (much) larger system if you chose to build one.

(also if you ever want to subcontract from NASA testing of spacesuits in a full-size vacuum chamber you should be all set :) )
There _is_ madness to my method.
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Richard Hull
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Re: Unfortunate Diffusion Pump Sign

Post by Richard Hull »

I posted here in the distant past on just such a pump that a friend picked up at our local scrap yard for $40.00 It had an 18" throat and was about 3 feet tall, water cooled and had a gate valve attached with a motor drive to open and close it! Such a deal. He removed the aluminum gate valve and dismantled it and sold the huge aluminum body for scrap. What he thought was a treasure sat outside his lab as a small rain barrel for some years. I used to kid him each time I visited and saw it was filled with rain water and told him that was quite a water load for a system. He got rid of it one summer when mosquito larva and hatchlings thrived in its stagnant water.

That KF 25 fitting was a fortuitous strangling of the pump's conductance on your buy. Good luck firing up that ship's boiler.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
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Andrew Robinson
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Re: Unfortunate Diffusion Pump Sign

Post by Andrew Robinson »

Sounds like maybe Alex :)
I can wire anything directly into anything! I'm the professor!
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