Home Distiller

So, if I drill or thread a hole on the column side of the gate valve I can place the probe in the vapor channel. That makes a lot of sense. But before I go drilling holes, what "systems" do you all know of for sealing the probe? I want it to be removable and therefore am thinking a simply rubber stopper in a properly sized hole. The problem is I will be drilling into the arm of the 3/4" brass gate valve and so only have a limited space to work with. Like I said, I can thread the hole and then use a threaded compression fitting of some type if that seems best. But I am thinking the KISS principle may be best here and a drilled stopped could be a quick fix.

Suggestions, illustrations, pictures or pointers please!

I really do appreciate your help on this project. It is going to be a great piece of equipment! Thanks to all.

I just use a few turns of PTFE (Teflon) thread tape. Works like a charm. It will work a lot better if you taper the hole a bit, so it widens out towards the top.

Not sure if you will have enough room or metal thickness on the gate valve itself. You should be able to pull a gate valve apart, and braze in a thermo tube.

The problem is the gate valve is sweated in. I can remove the guts, but that is it without major re-do. I also don't have the means to braze, so maybe it makes sense to simply drill a hole that can accept a small stopper or a Teflon taped probe. the point where I would drill is fairly thick, both the brass of the valve and the sweated copper inside.

I am sure you can figure something out. Wouldn't use rubber though for the stopper. You might be able to buy a pre-drilled Teflon stopper just the right size. It would also double as a pressure relief safety valve, like the cork plug did on the original design.

That is a good idea. I think I may even have a source. I will look and see what I can find before I start drilling holes however.

what "systems" do you all know of for sealing the probe?

I came up with a nifty way to seal a probe.

I like to use the cheap kitchen thermometers with the corded probe.
I drill the pipe for 1/8" npt I screw in a 1/4" compression to 1/8" npt fitting.
I cut a 2" piece of 1/4" copper tubing and slide my cheap electronic thermistor probe into it. I solder the tube to the probe. I slide the nut and the compression feral onto the pipe and screw it onto the fitting. It can be easily removed when not in use. These are easy to solder to and the thermistor is down in the point. They are quite reliable. Just don't use too much heat when attaching the tube.

I had thought of trying about the same thing,but was afraid the soldering would damage the probe.I guess you could use a heat sink if you needed.
My setup now has the probe going through a thick #9 cork,cut in half,and inside a 3/4 inch cap.It works but your idea is a much better setup.When I get a chance,Ill try it.

I wouldn't solder the probe and would be very cautious when using compression fittings on them as well... Any pressure applied to the probe can potentially alter readings... Considering how there will be no real pressure building up behind the thermometer probe either Telfon tape or a flour and water paste mix should be plenty...

I had thought of trying about the same thing,but was afraid the soldering would damage the probe

These probes are oven safe to 750F. Soft solder melts somewhere in the neighborhood of 450F. As long as you are quick it solders in 5 seconds.
as far as changing the rating of the probe, I haven't had it happen yet having done it to at leasts 6 of these. The lcd part of all these has been junk. They consistantly read the wrong temp low by 2 degrees F.
I test each on and mark the lcd part with the adjustments.
That way I know when I hook it up it is going to be off by X amount.
The compression ring only touches the copper tubing and not the probe itself. These are electronic and not the mechanical types so there should not be any damage unless you pinch it in two pieces.

I will try to get a picture up, but I have put in the gate valve and placed a thermometer port between it and the column. I drilled and threaded a 1/4" hole and the screwed a threaded fitting into it (a 3" x 1/4" brass pipe) with a 1/4 x 3/8 adapter on the end. I have a teflon plug that fits into this that has a Polder swivel head digital thermometer through it. I think it will be a sweet set-up.

I'm thinking of building something like this myself - on a smaller scale for stove top operation. Your pics inspired me to start source parts and using the interactive calculators on the parent site

I'm not going to put in a gate valve and use a valve on on the water cooling to the 'cold finger'. I guess it would be a CM type column, where controlling the cooling would control the amount of reflux. No cooling at all to the cold finger and pull the packing and it's a pot still.

I liked the original design at the begining of the post before the modifications

- no coil to wind, simple cold finger
- no tricky plates to solder like a VM
- no expensive gate valve
- thermometer is easy to place at the tee.

I recently received Riku's new book on ARC and his opinion is that VM is the best small scale design for neutrals. He explains several attempts to automate the VM design and discovered that a valve on the bottom of the condenser was exactly what worked. It doesn't stop the flow of vapor into the condenser but slows it down dramatically.

He then automates with the use of a temperature probe and a powered valve in that location.

He does state however that the gate valve before the condenser is essential to equalize and concentrate heads before removing product. His book is not very clear or well illustrated but it certainly has sparked my interest in some areas. He does not advise on specific valves and thermostats so I'm having trouble putting it all together but I recently got my hands on 5 feet of 3" copper "free" and would like to try a VM build with it.

?? Is there a ratio of column diameter to condenser diameter?? I can't seem to find any info. I was thinking of 1/2" X 36". Anyone have an advice for me?

Don't know of any specific ratio for a VM set-up, but I can tell you that the amount of vapour that goes down the product arm during a reflux run is a fraction (no more than 20-25%) of the total amount travelling up the main column. And it is also being quickly condensed, which reduces its volume by a huge amount. Only the top inch of my Liebig product condenser gets warm.

I run a 2" VM column, with a 3/4" product arm and that works fine. I am pretty sure that 1/2" would also be fine for mine.

My guess is that 1" for a product arm for a 3" column would easily cover it, you would probably find that even 3/4" is plenty.

Also the control valve at the top of the product arm does not need to be real big either. Mine is a 3/4" and is only open a small amount during a reflux run. If I was building mine again I would only use a 1/2" valve (and overall product arm), which would save a fair bit of money (and weight).

Definitely recommend a gate valve. And stainless too. Costs more than brass, but are much better valves that have all PTFE seals, unlike brass that use rubber and fibre seals. Brass valves also have to be de-leaded.