VCR Fittings a Vacuum Line Hose

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.
Post Reply
Jake Wells
Posts: 87
Joined: Wed Mar 19, 2014 1:29 am
Real name: Jake Wells

VCR Fittings a Vacuum Line Hose

Post by Jake Wells » Wed Oct 22, 2014 2:36 am

I have an alcatel vacuum pump with a nw 16 inlet port and a pumping speed of 1.5CFM @ 8 microns. I want to hook it up to my diff pump which has an nw 20 inlet port. I tried looking on ebay for some kf 25 hose extensions but they cost alot and have alot of un needed space. But, i found this kf 16- 1/4" vcr firring. Could i use this a vacuum hose to my diff pump with the right adapters? How could this effect my ultimate vacuum?
Image
“The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.”
― Nikola Tesla

User avatar
Chris Bradley
Posts: 2930
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: VCR Fittings a Vacuum Line Hose

Post by Chris Bradley » Wed Oct 22, 2014 5:45 am

My recommendation would be to buy yourself some hose adapters for either end, and use a length of heavy natural rubber hose to go in between, but not longer than necessary.

Jake Wells
Posts: 87
Joined: Wed Mar 19, 2014 1:29 am
Real name: Jake Wells

Re: VCR Fittings a Vacuum Line Hose

Post by Jake Wells » Wed Oct 22, 2014 11:53 am

I keep hearing that rubber hoses are very prone to leaking and that kf bellows hoses seal just fine.
“The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.”
― Nikola Tesla

User avatar
Dennis P Brown
Posts: 2105
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: VCR Fittings a Vacuum Line Hose

Post by Dennis P Brown » Wed Oct 22, 2014 12:49 pm

Vacuum grade rubber pumping line does not really leak when used in the micron range and works well. That all said, buying new KF stuff is expensive and I generally never do (only exception was a six way KF-25 cluster adapter but that was still rather cheap at the time) - I looked for deals all the time (and get them) by searching the companies that specialize in buying surplus stuff.

Best to get the correct adapter/connector to prevent leaking between equipment/hoses; besides, it makes life easier for connecting the system pieces together.

AS for the fore pump line, if the fitting is KF-20 on the turbo, you need to keep the line as short as possible or pumping efficiency will suffer a lot, otherwise. I have a KF-25 line and it uses a KF-25 to KF-16 adapter to my turbo. That way, my pumping speed isn't as impacted by my line length. Again, got my three point five foot SS bellows line for $25 with shipping; and both end adapter and the clamps for much less. Deals are there! Heck, I got a very high capacity, two stage vacuum pump at the same time for $10 (shipping was a deal at under $25) - this is a spare but I couldn't pass up the deal. These deals are there but you have to search and watch for them.

Jake Wells
Posts: 87
Joined: Wed Mar 19, 2014 1:29 am
Real name: Jake Wells

Re: VCR Fittings a Vacuum Line Hose

Post by Jake Wells » Wed Oct 22, 2014 1:04 pm

I dont need three-five feet of bellow line, I only need about 20"
“The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.”
― Nikola Tesla

User avatar
Richard Hull
Moderator
Posts: 12743
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: VCR Fittings a Vacuum Line Hose

Post by Richard Hull » Wed Oct 22, 2014 6:32 pm

20" is still a rather long foreline, but if you have built yourself into this long a corner, so be it. Running conductance equations vs. pumping speed would frighten the heck out of you. 8 to 12-inches would give you the more normal foreline length. Still, folks with 3 feet of foreline are able to pump a fusor due to its, often, small size and lack of needed pumping speed. Vacuum systems for a fusor only need to be good enough and need not be up to American Vacuum Society standards.

I personally prefer the heavy, thick, yet highly flexible, red rubber, vacuum rated hose as this absorbs a lot of vibration between the two pumps. I use clamped, KF25 hose barbs on each end. I can have my mechanical pump hit and hold 10 microns on the foreline with the foreline to diff pump and diff pump to fusor valves wide open.

In designing any vacuum system with a secondary pump, the general rule is to jam the mechanical pump up as close as you can to the secondary pump to keep the foreline extremely short.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Jake Wells
Posts: 87
Joined: Wed Mar 19, 2014 1:29 am
Real name: Jake Wells

Re: VCR Fittings a Vacuum Line Hose

Post by Jake Wells » Wed Oct 22, 2014 9:29 pm

I am still confused. My pump is elevated to frevent the heater from burning my table bottom. Is 20" of bellows hose too long?
“The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.”
― Nikola Tesla

User avatar
Chris Bradley
Posts: 2930
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: VCR Fittings a Vacuum Line Hose

Post by Chris Bradley » Wed Oct 22, 2014 9:39 pm

I run a metre of KF16 bellows from my 60l/s turbo, and it pumps just fine. We're not after super dooper scientific vacuums. You are more likely to find the chamber itself and plasma operations in the chamber are the limiting factors to the base pressure rather than the pressures in the foreline hose.

Jerry Biehler
Posts: 909
Joined: Tue Nov 24, 2009 8:08 am
Real name:
Location: Beaverton, OR

Re: VCR Fittings a Vacuum Line Hose

Post by Jerry Biehler » Thu Oct 23, 2014 7:51 am

No, 20" is fine, you won't have any issues, heck, my electron microscope has about 8 feet of line between the column and the roughing pump and I have no problems pumping down. And this is very common for EM's, about 8' of hose with a giant pass through weight to absorb vibration. And this is backing a 400l/s diffusion pump.

Now, using a 1/4" line will have issue. Either get the vinyl hose with a spring or red gum rubber hose and you will be fine. Or very thick was vinyl hose works, I am talking about 1/2" wall. Use the same ID hose as the diameter of the fore line on the diff pump.

Post Reply