CVC Diffusion Pump

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Liam David
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CVC Diffusion Pump

Post by Liam David »

I recently got a CVC diffusion pump, with both the input and output as tubes on the top. The outlet is a 5/8 copper pipe. The problem is that the inlet has a 3 foot KF hose, and I don't want to pour oil down that. Can I pour oil into the outlet of the pump, or will this cause problems?
-Liam David
John Futter
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Re: CVC Diffusion Pump

Post by John Futter »

Liam
I presume you have already had the pump apart and thoroughly cleaned all the internals
the correct pump oil DC 704 or santovac is very viscous and will need heating to get it to flow into the pump
It is important that the correct amount of oil is in the boiler of the pump
without a picture it is hard to gauge if this will be successful
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Liam David
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Re: CVC Diffusion Pump

Post by Liam David »

Well, I'm still trying to find a way into the pump, so I haven't cleaned it yet. The thing has one screw, which is just the oil drain.

Image

This is the pump...

Image

...and these are the inlet and outlet tubes.

Image

-Liam David
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Dennis P Brown
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Re: CVC Diffusion Pump

Post by Dennis P Brown »

As Mr. Futter said, heat the pump up (some - not to full temperature under air!) and drain out the oil. Maybe someone here is experienced with that design and knows a way to disassemble that DP.

Consider using alcohol (absolute) to clean out the remaining trace oil assuming others here don't consider that too damaging. I've done that to really dirty DP's with no ill effects BUT these were not enclosed DP's like yours. After air drying I bake the DP out (100 C) under a vacuum( 10 - 20 microns); add new oil and run it until out gassing isn't a problem.

I've added oil through the second stage outlet pipe in a DP - really isn't a problem but again, I am not familiar with that DP's design and others may indicate that isn't viable ... .
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Liam David
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Re: CVC Diffusion Pump

Post by Liam David »

OK, I'll try heating the pump, draining the residual oil, and and then baking it under a vacuum without oil. I'll wait for more peoples' opinions on using alcohol and pouring the oil in the outlet pipe.
-Liam David
Tom McCarthy
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Re: CVC Diffusion Pump

Post by Tom McCarthy »

You might want to also check that you won't have problems with vacuum conductance. From your Images Du Jour you said that your diffusion pump's hose is long - I'm not sure if it applies here (you seem to have a pretty small chamber), but just in case it would probably be beneficial to calculate your flow rate and see if it's up to standard.

Tom
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Liam David
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Re: CVC Diffusion Pump

Post by Liam David »

I don't know anything about the pump rate of the diff pump. It is an older CVC model that virtually doesn't exist on the internet. The small spec plate says it's rated at 200W, but that's pretty much all I know about the pump.

Does anyone know how to get into this type of pump? The old oil is taking a rather long time to drip out and I don't know the internal condition pf the pump.
-Liam David
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Liam David
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Re: CVC Diffusion Pump

Post by Liam David »

Wow, I finally found a "datasheet" on this pump. The pumping speed is 22 l/s.
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Richard Hull
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Re: CVC Diffusion Pump

Post by Richard Hull »

If you have old gummy oil, fill the pump with acetone, seal it off and shake it up like you are mixing a drink, then, let it set for a while, Shake again and dump. Use high pressure air to make sure it is all out. Repeat until acetone is water clear.

If you can't get into the pump, that is not an ideal situation. You may have to flush as best you can and wind 'er up in system with a gauge at the head of the diff pump...(not your fusor chamber), and see how low you can go. When clean, those little air cooled CVC diffs are good for a small chamber.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
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The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
qtube
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Re: CVC Diffusion Pump

Post by qtube »

Wow! Didn't know anyone else had the same questions about this unit. I had to register! I too would appreciate any information about taking the VMF-21 apart for cleaning. I have found these are 21 L/sec and hold 100cc of oil. I am ready to buy some oil and try mine but I would like to clean it first. I'm not doing fusors but just playing around with homemade vacuum tubes. Just simple stuff, not reinventing the wheel.
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Liam David
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Re: CVC Diffusion Pump

Post by Liam David »

Unfortunately, there is no way into the pump. There is just an oil drain screw at the bottom (close this when pulling a vacuum, or else you'll be wondering what's causing the massive leak in your system, *cough cough* myself). I repeatedly flushed the pump out with acetone until the acetone was clear. I just poured the oil into the pump inlet. The oil I bought was Duniway's Octoil version, 100cc, because it was the cheapest. The pump definitely works, and now I can get star mode in my demo+ fusor.

My pump didn't come with a heater plate, and I found any commercial replacements outrageously expensive for just a coil of resistance wire inside a ceramic/metal disk, so I just use a 1100W hot plate (yes, I know the pump is rated at only 200W). It heats the pump up much faster than any 200W unit, as long as I regulate the coil's temperature.

-Liam David
Last edited by Liam David on Mon Sep 29, 2014 2:44 pm, edited 1 time in total.
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Dennis P Brown
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Re: CVC Diffusion Pump

Post by Dennis P Brown »

Better be extra careful when you post
Please read the forum rules. Use your real name as your username and introduce yourself in the appropriate section.
Because someone here takes huge offense if anyone outside the "special" forum police dares to call anyone out on this rule (LOL)! Yes, someone here really is that silly. Still laughing about it.
qtube
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Re: CVC Diffusion Pump

Post by qtube »

Thank you Liam for the information on the CVC-21 That was really all I joined for as I am not building a fusor. I ran across this forum while searching for information on this unit.

Now as to real names. I don't divulge any more private information on the internet (anywhere else for that matter) than I absolutely have to until I get to know someone through PM's etc. and then reveal more over time as trust builds directly through private correspondence with them. It is just smart security sense. All information is available somewhere on anyone but you sure don't want to make it any easier than you have to. On the other hand I do try to follow rules and I see I am in violation of this sites rules. I did see that real names were requested but I just didn't believe that is what it really meant or I didn't want to believe it? I see that was just wishful or self centered thinking on my part and the rules meant what they said.

Before posting this I did a quick check of the site to see how to "de-register" and delete my account but didn't find any clear way to do that so I will request in this post to be removed (registration,posts etc.) from fusor net and also to genuinely apologize for making this trouble.

I have appreciation for the site where the vacuum information is concerned and will probably lurk in the future from time to time and search various as needed. Hope there is no hard feelings but I remain "Q".
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Liam David
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Re: CVC Diffusion Pump

Post by Liam David »

OK Dennis, I'll keep that in mind.
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