FAQ: Lowest cost fusion capable vacuum pump setup.

[JoeBallantyne]

This FAQ is about how to get a brand new vacuum pump setup that is fusion capable, for under $200 (as of June 2024).

If you are surprised that is even possible, well I was too, but it is possible at least for now in mid 2024.

A few important points up front. If your goal is to do fusion, and you want to do it as quickly and inexpensively as possible, then you should plan on building a fusor system that uses only a single mechanical pump. No turbo, no diffusion pump, or any other secondary very high vacuum pump. Just a very good, inexpensive mechanical two stage rotary vane pump. That is all you need, as long as you get a pump that pulls a very good to excellent vacuum.

DO NOT BUY A SINGLE STAGE MECHANICAL PUMP.

Just DON'T.

It won't be able to pull low enough for you to be able to do fusion with a single pump setup.

Fortunately, you can get an AMAZING deal on a two stage pump from Amazon. The Kozyvacu TA500 2 stage pump will pull down to 4 microns or less when you use it with excellent mechanical pump oil and it is currently $120. This post will explain what you need to do in order to get your TA500 setup so that it can pull a 4 micron vacuum through a standard KF fitting.

Here is a link to the pump on Amazon.

(1) Kozyvacu TA500 Dual-Stage HVAC Vacuum Pump, 5.0 CFM
$120 https://www.amazon.com/dp/B01N0SYCL4

If you have Amazon Prime, the shipping is free, and the pump will very likely show up the day after you order it. You aren't going to buy a pump online anywhere else and have it delivered next day. (Unless you go pick it up yourself.) As far as I know, there isn't a better deal on a new pump anywhere. Certainly not for a pump that will pull down to 4 microns or less with proper preparation.

In addition to buying the pump, there are a few other things you will need to get:

(1) LASCO 17-6783 1/4-Inch Female Flare by 1/4-Inch Male Pipe Thread Brass Adapter
$10 https://www.amazon.com/dp/B008E5CUFG

(1) Female NPT/FNPT to KF16 Flange Fitting (ISO-KF KF16 QF16 NW16) (1/4" FNPT to KF16)
$19 https://www.amazon.com/dp/B06ZZRQ2ZP

(1) 1/2 inch wide roll of PTFE (teflon) tape
$3 https://www.amazon.com/dp/B00838JDRM

(1) Inland® 19 ULTRA Rough Pump Oil (1 liter bottle)
$21 https://www.sisweb.com/vacuum/sis/inland19-ultra.htm

You have to select the Size drop down box on the SIS web page to select 1 Liter to get the 1 Liter price. The page defaults to a size of 1 Gallon. But that is easy to switch.

Ideally, if you have the budget, you might also get some DOW Corning high vacuum grease, which will increase the probability of making a vacuum tight NPT joint connection. From what I can find, the grease is pretty pricy. The smallest authentic DOW Corning tube appears to be 5.3 oz and costs about $43. The grease is optional, so please DO NOT buy some other "vacuum grease" instead of DOW Corning. If you can't get the known good stuff, please DO NOT risk contaminating your setup with low quality vacuum grease that raises your ultimate pressure and which will be hard to clean out of your system. From what I can tell, many of the "DOW Corning" vacuum greases on Amazon are NOT actually made by DOW Corning. If it isn't the 5.3 Oz light blue tube that costs about $40, and comes in a rectangular cardboard box, it's probably fake, and I wouldn't touch it with a 10 foot pole, let alone smear it on parts of my vacuum setup. When you look closely at the pictures of the non tube containers of "DOW Corning" vacuum grease on Amazon, none of them appear to have the actual Dow Corning trademark on them. They just slapped the name on the product link, so you would buy some thinking it was the real thing. But it's not, so DON'T USE IT.

The two adapters will convert from the 1/4 male flare connector that is the horizontal connector on the Kozy TA500 pump to a KF16 connector. This enables you to use standard KF parts to connect your pump to your chamber. KF is very commonly used for connecting mechanical pumps to vacuum systems. KF/NW/QF parts are really easy to use, and because they use an elastomer o-ring on a centering ring instead of a metal gasket to make the vacuum seal, they are also fully reusable, unlike Conflat or VCR connections.

If you do have authentic DOW Corning vacuum grease, wipe a very thin layer all the way around the 1/4 inch male NPT threads on the LASCO adapter before you wrap them with the PTFE tape. Do NOT use anything other than real vacuum grease. If you don't have vacuum grease, then just use the PTFE tape and nothing else.

Make sure that you wrap the PTFE tape around the 1/4 inch male NPT threads in the counter clockwise direction with the NPT threaded end facing away from you. This ensures that when you screw it into the female connector, the PTFE tape is being further tightened as you screw the parts together. Make sure that you wrap the tape tightly around the threads, and keep it flat, untwisted, and tight while wrapping them. If you are using standard PTFE plumbers tape from Home Depot, then wrap at least 8 -10 times around the threads. If you are using the thicker 4mil PTFE tape linked to above, then wrapping it 5-6 times is probably fine. Then hold the part and grab the tape with your thumb and forefinger right next to the threads and just pull the tape off in the direction you are wrapping it, to break it off. This will help keep it tightly wrapped on the threads.

When you are done wrapping the threads, if you have vacuum grease, wipe another very thin layer of vacuum grease in the same direction as you wound the tape around the outside of the PTFE tape.

Then screw the two adapters together by hand to ensure they don't get cross threaded, and then use a couple crescent wrenches or open ended wrenches to finish tightening them together. DO NOT over tighten the parts. In my experience overtightening parts can actually ruin what was a vacuum tight connection, and make it start to leak. These are 1/4 inch NPT so they aren't big diameter connections. You don't need that much force to get them leak free. I usually hold the wrenches right up next to the head of the wrench, so I have as short a lever arm as possible, and as soon as I get pretty firm resistance while tightening, I stop. Probably something like 3-6 ft-lbs of torque. Again, the point is you want a vacuum tight connection. As soon as it is vacuum tight, you are done. Its not about cranking on the parts. Its about no leaks. If you don't over tighten the joint at first, you can always tighten it a bit more if there is a leak. The other thing in this case, is that one of the parts is brass and the other is stainless, and the brass is a lot softer than the stainless. So don't overdo it.

NPT connections are terrible for vacuum, and they are generally best avoided like the plague, but in this case, a single piece adapter from female flare to KF does not exist as far as I know. So, we are stuck using NPT.

The Lasco female flare adapter comes with 1 or 2 little pieces of copper in the package for the flare connection. DO NOT USE THEM. AGAIN, DO NOT PUT THE COPPER GASKET IN THE FLARE CONNECTION. It will just make the connection LEAK. You want to screw the brass female flare directly onto the brass 1/4 male flare connector that is the horizontal connector on the pump. Do this by hand. Do NOT use teflon tape on the flare threads. The flare threads should be bare. Once the flare connection is finger tight, then use a wrench to tighten it just a tiny bit more - like LESS than 1/8th of a turn. This is a brass metal to metal connection. You just want it firmly tight, NOT CRANKED. Keep your hand all the way up at the head of the wrench right next to the fitting so that you have the minimum possible leverage, and as soon as you feel firm resistance, you are done. If you crank too hard on the connector, the horizontal male flare connector on the pump may BREAK OFF. Per experience of others on this site.

Once you have the KF16 to 1/4 inch female flare adapter assembly connected to the 1/4 inch male flare pump inlet, you can then connect it to either a KF16 blank or a KF16 vacuum gauge using a KF16 centering ring and clamp. It is critical that during the initial breakin run the pump is pumping against vacuum, not against atmosphere or leaky connections. If the pump runs too long against too high a pressure it will DAMAGE the pump. If there is smoke or vapor coming out the exhaust port for more than a few seconds at the start of the initial run, you have a leak, and you need to fix it before letting the pump just run. Another option, is to just leave both ports with the plastic caps screwed on for the initial run. The plastic caps that the pump comes with are both vacuum tight, and can be easily opened and closed by hand. Those caps should only ever be finger tight. Do not use tools on them. There is no need, as both caps have o-ring style rubber seals inside them.

Next, remove the red plastic exhaust cap, and fill the Kozy with the in box oil through the exhaust vent in the top of the pump, so that the oil level in the sight glass is about 3/4 up from the bottom. There should be about 1 and 1/2 inches of oil left in the bottle that came in the box with the pump when you are done. DO NOT use the Inland 19 ULTRA oil for the first pump fill. Use the oil that came in the bottle with the pump. This initial fill of the pump is going to be discarded. After filling the pump with its first load of oil, replace the exhaust cap, and make sure the cap on the vertical vacuum connection is closed firmly finger tight, and make sure the KF16 connection is either blanked off, or connected properly to a vacuum gauge. You don't want any leaks on the pump intake.

Then fire up the pump, and let it pump against a vacuum for 2-3 hours. Ideally you do this with a vacuum gauge on the inlet, so you can verify that the pump is indeed pulling a good vacuum. The pump should get down to somewhere between 6 and 15 microns using the in box oil. The pump will usually take about 20 minutes or so to get fully up to temperature. The pump ultimate pressure may rise as the pump gets hot, this is normal. Once the pump is up to temperature, the vacuum the pump is pulling should stabilize, and it should be less than 20 microns. The Kozyvacu typically will hit its minimum pressure when blanked off or directly connected to a vacuum gauge after 5 minutes or so. Then as it gets hot, if the oil is somewhat contaminated (as it will be after the first fill) the pressure will rise somewhat. Possibly only a couple of microns, but perhaps as many as 10 microns or so up from the minimum. It depends on how much residual oil from the manufacturing process was inside the pump. The more residual high vapor pressure oil, the more the pressure will rise as the pump gets hot. On the 3 pumps I know about, when hot on first fill, one got up to 7 microns, another up to 7 or 8, and the last went up to about 15. (After completion of this setup process, all 3 pumps pulled down to 4 microns or less when hot.)

After the pump has run for 2-3 hours, shut it down. One nice thing about the Kozy TA500 is that you can use the black plastic cap on the second vertical inlet on the pump as a vacuum vent, and open it up just before shutting down the pump. If this procedure is followed religiously then you will NEVER get any backstreamed oil up into your vacuum gauge or fusor vacuum system, because the vacuum will be vented before the pump is shut off. You can tell just by the sound of the pump, whether the vacuum has been released or not. So, vent the pump by unscrewing the vertical cap, and then shut it down. After shutting down the pump, remove the red plastic exhaust cap, and unscrew the drain plug on the front of the pump and drain the oil while it is still hot into a separate container. Then tilt the pump down towards the open drain plug and turn it on, flush out most of the remaining oil by gently covering the exhaust outlet with your hand. This will forcibly blow air and oil out the open drain plug. Do that for 5 seconds or so, then shut the pump down. Note that this procedure will spray oil all over the place, so having the pump drain pointed into a large container to capture the spewed out oil is a very good idea. The oil that you drained and flushed out from the pump will likely be very slightly grey in color - it will be full of tiny metallic particles worn off from the initial run of the pump. This oil will also be mixed with higher vapor pressure residual oil from the manufacturing process of the pump. That is why the initial pump down pressures tend to fall between 6 and 15 microns. Because of residual higher vapor pressure oil contamination. That is why you do NOT want to use your fancy Inland 19 ULTRA oil on the first fill. It will just get contaminated and you will need to drain and flush it out. Then you might not have enough good oil left to fill up the pump.

This next procedure is critical to getting the ultimate pressure of the pump as low as possible. You are going to use a small amount of your fancy expensive Inland 19 ULTRA oil to flush out as much of the initial contaminated oil fill as possible. This will get the inside of the pump as clean as possible using good oil, in order to minimize contamination of the next oil fill. USE THE INLAND 19 ULTRA OIL to do the flush. NOTHING ELSE. Set the pump on its side so that the KF16 adapter is pointed straight up. Then with the pump still on its side, turn the pump on and while it is running pour about 1/4 cup (no more than 1/2 cup) of the Inland 19 ULTRA oil down through the KF16 adapter into the pump intake while it is running. That should take 2-3 seconds or so. Then with the pump still running, rotate it 90 degrees back onto its base so the KF16 connector is again on the side, and then tip the motor end up so that drain plug is down, and again cover the exhaust port with your hand for a few seconds. This will flush most of the fancy oil you just poured into the pump out through the drain plug, and should get almost all of the residual original oil flushed out of the pump as well as out of the innards of the pump mechanism. You should only need to gently plug the exhaust for 3-5 seconds or until most of the oil has blown out of the pump - it doesn't take very long. Then immediately turn the pump off and put the drain plug back in. Don't overtighten the plug. It has a rubber gasket on it, and over tightening it will just damage the gasket. Once the plug is back in, and the pump is level, fill the pump through the exhaust port with Inland 19 ULTRA oil to almost the top of the sight glass, and then replace the red plastic exhaust port cover.

Put the vacuum gauge back on the KF16 inlet port after wiping any residual Inland 19 ULTRA oil off of the KF16 connector, and turn the pump on again. Make sure the cap on the vertical inlet on the pump is closed. (Normally when I use that cap to vent the pump before shutdown, I immediately close the cap again after the pump is off. So the cap should always already be closed on startup, but it never hurts to double check that it is closed.)

At this point the pump should pull down within a few minutes to about 4 microns or less. There should be no vapor or smoky mist exiting the plastic exhaust cap. The pump should continue pulling down to about 4 microns while getting up to temperature as well as when it is hot.

You now have a vacuum pump ready to do fusion with your chamber. A Kozyvacu TA500 that pulls down to 4 microns with a vacuum gauge connected to its intake, should be able to pull a leak free 1-2 liter vacuum chamber down to 5-6 microns in 20 minutes or so. That is low enough to enable you to do fusion.

See viewtopic.php?p=101647#p101647 for the details of my use of the Kozyvacu TA500 to do fusion.

Good luck on your fusion quest.

Joe Ballantyne

[Alberto Sanchez]

Thank you very much! Very precise, helpfulf and explained

I´m jealous, in Spain you can´t find the vacuum pump nor the oil. I have a 2 stages vacuum pump that works well, but a lot more expensive.