Use of Swagelok needle valves

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Jackson Oswalt
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Use of Swagelok needle valves

Post by Jackson Oswalt » Fri Mar 09, 2018 12:41 am

Disclaimer: I'm not technically a new user, but this is a basic question that will fit in with the posts in the section.

Hello all,

In the following FAQ: viewtopic.php?f=24&t=12063, a micrometer leak valve is required in order to more finely adjust the flow of deuterium. Unfortunately, these are quite expensive so I was wondering if Swagelok needle valves (such as these: https://www.ebay.com/itm/Lot-of-2-Swage ... SwH09ZM2ty) could be used as an alternative. The reason why I'm looking for a cheap alternative is because I'm currently looking into integrating Helium-3 into my system, which requires a second leak valve. More on that later.

Thanks,
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ian_krase
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Re: Use of Swagelok needle valves

Post by ian_krase » Fri Mar 09, 2018 2:09 am

What you really want a swagelock micrometer needle valves like this: https://www.ebay.com/itm/2UNITS-SWAGELO ... 2127117144

Jackson Oswalt
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Re: Use of Swagelok needle valves

Post by Jackson Oswalt » Fri Mar 09, 2018 2:33 am

Twice as much money unfortunately. The one I currently have is of the same type.
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Re: Use of Swagelok needle valves

Post by Roberto Ferrari » Fri Mar 09, 2018 12:05 pm

I have a similar one but failed to make it leak-free.

Opened, shows two metal surfaces, no seal...

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Re: Use of Swagelok needle valves

Post by Rex Allers » Fri Mar 09, 2018 12:23 pm

In the Swagelok metering valves, for finesse control of deuterium, I think you want one of the S-series metering valves. They have the lowest flow rate. The part number will have SS-SS... like SS-SS4 where 4 is the size of the connectors.

The first one you gave is definitely not a fine control valve. The one Ian gave was a SS-4BMG, I think the M in there means it is an M-series which has a little higher flow than the S-series.

Here's one I just found:
SWAGELOK NUPRO SS-SS4 STAINLESS STEEL LOW-FLOW METERING VALVE 1/4" OD TUBE
https://www.ebay.com/itm/SWAGELOK-NUPRO ... Sw9V1aiyHk

You might want to search for the metering valve section of the swagelok catalog as a pdf.

There are other vendors that make similar metering valves but I don't have any good suggestions what to look for.
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Richard Hull
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Re: Use of Swagelok needle valves

Post by Richard Hull » Sat Mar 10, 2018 8:55 am

I still use a needle valve after 20 years at fusion. The same valve that I had in 1998! I will admit it is terrible, but the adroit hand and long-time operator status that I have behind me makes both an adventure and an artifice out of bringing fusor IV to the mega mark in fusion.

I now have two sapphire plate precision leaks ($1,000+ new), that sheer idleness has stopped me from going through the effort of adapting them to my fusor. " No excuse, sir!" as we used to say in the corps and military. (Only now I am much older, and retired, and don't have to walk any penalty tours).

I really don't have to do anything beyond breathing, eating, sleeping and evacuating, as needed. Beyond these unavoidable interruptions, I do as I please and answer to no one...Not even the wife. Truly, an idyllic second childhood, but armed with a load o' life's lessons and some knowledge and the ability to apply that knowledge with hands-on work......Should I be so moved.

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One of my two precision leaks - This is the ideal
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Re: Use of Swagelok needle valves

Post by prestonbarrows » Sat Mar 17, 2018 2:41 am

The proper tool here is a mass flow controller. These are basically a self regulated needle valve that measures the pressure drop across itself through various means and adapts to external conditions to provide a constant gas flow as measured, for example, is SCCM. Essentially, you provide DC power at, say, 12 volts and an analog control signal that is full scale at the rail voltage.

These are widely used in wafer fabs and other industry and are readily available as second hand on ebay and other sources. Ideally, you can get one calibrated for deuterium (or hydrogen), but units calibrated for other gasses are still quite usable if you apply scaling factors which are widely available online. Basically, the full-scale flow rate for a nitrogen or oxygen etc unit will just be multiplied by some constant value as the flow rate of deuterium through it for the same control voltage.

Even if you get the most garbage and abused second hand MFC, it will almost certainly give you a consistent flow rate per input voltage even if the absolute calibration is way off. That is much more then you get with a manual needle valve. Just set the command to '8.2 volts', or whatever works for your setup, and you are good to go; no need to worry about real units.

Waiting the week or two to snag a good deal and spending the extra $20 over a dumb needle valve is just a no brainer.

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Richard Hull
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Re: Use of Swagelok needle valves

Post by Richard Hull » Sat Mar 17, 2018 6:55 am

In General, mass flow controllers of the type you might obtain second hand are indeed surplus from semi-fabs and their flow rate is in the 10's of SCCM. Even with a fraction of a volt applied, you will most likely use your valuable D2 up at a rather alarming rate as you will have to open your chamber throttle valve up far beyond what a micro needle or a precision leak would need.

D2 flow in a fusor is a very slow leak situation, not a real gas, mass flow situation found in a semi-fab.

Ideally, you want an annoying micro leak of D2 and a throttle valve on the chamber to be virtually shut against the turbo or Diff pump. The more the throttle valve on the chamber needs to be open to maintain fusion chamber pressure against incoming D2, the faster your valuable D2 will be gobbled up.

Richard Hull
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Bob Reite
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Re: Use of Swagelok needle valves

Post by Bob Reite » Sun Mar 18, 2018 5:58 am

You can find 0-10 SCCM mass flow controllers on Ebay if you wait long enough. Most of my fusion is done in the 4-6 SCCM region. Then again, I'm not using expensive bottled D2. But as I recall, when Richard tried to be too miserly with his D2, he did not get really great neutron numbers.
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Re: Use of Swagelok needle valves

Post by Jerry Biehler » Sun Mar 18, 2018 9:55 am

I use Edwards 5 sccm MFCs on my ion guns. They are out there. I still need to pick up one more for my other system.

Terrible description of a MFC though, mass flow is detected thermally not using pressure and the control is via a solenoid valve.

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