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Dephlegmator Temperature Monitoring?

edited January 2014 in Usage

I have plenty of cool water from a deep well.My only expense is pumping it up. On the other hand I hate to waste anything.

So the question is, If you were going to monitor the Dephlegmator of a vapor management still or the water coming out of it to avoid waste, what temperature would you maintain and would you measure Dephlegmator or water exiting it?

Dephlegmator is standard SD 3" and still will run on 2500W.


  • that is a very good question.

    First to complicate matters your flow rate is also part of the equation. I work on a temperature range from my between the dephlegmator and the product condensor. I keep it below 195 F. I know that at approximately 197F ( for my rig and situation) I go into tails on my rig. That keeps me out of Tails.

    It also depends on how you want to take your product out. I try to suppress/ compress tails. It is a bit more trouble than some would want to do. I am sure there a lot of people who do this different ways depending on what your making and what your taste are.

    Also keep in mind that a temperature setting is a moving target as you proceed through the run.

  • Can I just check one thing. You said that this is a VM still.

    Do you mean that the dephlegmator is always running under 100% reflux conditions?

    If this is the case then the dephlegmator coolant discharge temperature should be in the range of 82 degC to 85 degC. This prevents over cooling of the reflux condensate which is just a waste of energy.

  • Yes 100% reflux. Thanks for the info.

  • ok could some explain over cooling on the reflux condendate? not sure I understand what is meant by over cooling?

  • It means the condensate dripping from your condensor is much cooler than the boiling point, which in theory means it makes it further down the packing before it eventually is exposed to enough vapour to bring it back up to temp. Thus negating the top few inches of your packing.

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  • How well is that dephlegmator working at 100%? I'm got a VM that I was trying to add a crossflow to because of limited space and a desire to keep the column as long as possible. I've eventually relented that I have neither the skills to do the job myself or the connections to have it built.

    I've been thinking about "Plan B" and thought a set-up like you mentioned would work just fine, but you are the first person I've seen mention one like that.

    I've got a 3" column but since height is an issue, I was thinking of using a 2" or a 4". Not sure the 2" would do the job and if I went 4", the reducer might eat up and height savings, unless a "short" reducer would clear the vapor path. Anyone have any insights?

  • when I go to an 8" system, and a 8" dephleg, I am going to put one of the thermostatic valves on it, I will have a bypass and shutoff also, but think the valve bulb/probe in the top of the dephleg or soon thereafter would allow very good control with absolute minimal water usage... However... you could have a short or inefficient dephleg and not have the knockdown power at that water usage, and to get the knockdown power you need would have to allow more water to flow, sending some product back down at a colder temp... which leads to this hypothesis: If you have to get your dephleg exit water temp colder than 'x'(with x being 82-85C) to get knockdown, you need a larger/more efficient dephleg...

    this is of course dependent upon incoming water temp also, but maybe we could rate dephlegs with the value such as: total knockdown power of - watts per liter per minute at 82C with 10C/15C/20C/25C/30C incoming water... set the flow for 1L/min, measure the incoming temp after a few minutes of flow, and ramp up the power until the temp above the dephleg breaks some threshold(maybe 75C?)

    we plot several peoples results on a chart and should come up with a curve we can come up with an equation for, and then a value to compare the different dephlegs for, and people can look at the chart and their water temp, and figure out what dephleg they should buy...

  • edited January 2014

    Horizontal reflux condenser is the way to go in a height restricted space. It can be as long as you like and the only vertical space used is the diameter of the shell.

    OK my last one is slightly off horizontal because I collect the reflux at one end, but the point is valid. Very compact in the vertical direction.


    Vapour in at the mid point, reflux outlet at one end, and atmospheric vent at the other.

    reflux tube and shell2.jpg
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  • Dependent on where you put the reflux back into the column, it is possible to have the vapour entering at the TOP of the reflux condenser/dephlegmator and passing through it. I am talking about in a VM configuration where the vapour path has already been split.

  • Should have a few samples like that in my current shipment i think Myles.

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  • Myles, that's exactly what I was trying to build, but I just don't have the tools on hand to do the job right - or even well. I went out looking for someone who could do the work but I hit a wall on that as well. I've been dicking with it for about 6 months and I'm not much closer than I was back then... it's still just a pile of parts.

    punkin, are you saying you've got some horizontal reflux condenser samples? Is this a potential future product?

  • edited January 2014

    Yes, pretty easy to do Lloyd said. Onlt problem being the factory can't get in there to polish.

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  • Oh man, I'm not sure that will work. I plan on having some very vain vapor and if it can't see itself reflected in every surface it might avoid the condensor altogether.

    Seriously though is this something that's only going to find it's way to AU/NZ? Is something like this going to make it to North America? I've got money waiting.

  • edited January 2014

    There are other ways to configure these VM heads but I like this version, with the external reflux return line.


    If Lloyd can make a version of these condensers available in 2" and possibly in 3" (although that is a lot of condensing capacity) they could be used in all sorts of configurations.

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  • There's a development thread here somewhere.

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  • edited January 2014


    Sorry guys, I dropped the ball on this one for two reasons...

    1. We were pushing hard to get 5 big sea freights out before the China lunar new year shutdown and I am also pushing hard on developing a few other goodies like the 5" Crystal Dragon.
    2. Only one sample has been made so far and the price is much higher than I'm comfortable with, about 40% more than a regular shotgun condenser and I can't get the factory to budge on the price.

    And I really don't know how long to make these condensers.

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  • edited January 2014

    @Lloyd said: And I really don't know how long to make these condensers.

    Well Harry did most of the work for you... assuming you can understand what he is saying better than I can.

    So nothing coming anytime soon, eh? So short of something being produced, do you think it would be possible for me to buy a 2" Long shotgun and have a 2" ferrule installed in it? Then I could plug the "inlet" and cap the ends like you showed in the "Loony" thread. I think the whole thing would come in under $300, not cheap, but it seems reasonable. I think I can find someone to work steel for me, it's the copper that was a problem.

    Could someone safely cut into the the shell?

  • You probably don't need to. There have been designs that use a single condenser mounted just off the horizontal with the vapour entering at 1 end. With the vapour in the tubes and the coolant in the shell. Not as compact and desirable as the other option with the coolant in the tubes, but a workable solution. And as I said before, dependent on your column design you can have the vapour entering at the top of a conventional shotgun. It depends on the column configuration. I haven't seen any proposed designs put up yet. ;)

  • edited January 2014

    @Lloyd I hope you don't mind me putting this in here, but I did think about this after proposing the crystal version in the Loony Bin.

    There is a simple modification that would allow you to market a shotgun reflux condenser KIT that would allow your customers to make their own condenser to the length that they wish, out of your existing components.

    Well nearly existing - you might need to offer a tri-clamp tube (for the shell) with either a removable plug or blank able port to provide the atmospheric vent.

    What is not in your inventory yet is a copper plate that could be sandwiched in the tri-clamp joint, like a bubble cap plate, but fitted with compression fittings - or solder sockets.

    Build the condenser out of existing components ( T, tubes etc) slide in copper tubes and tighten the compression fittings. Built to whatever length you decide from the available tubes that you choose to make the shell.

    Once assembled you could not take it apart again without drilling out the tubes on 1 end as it is semi-permanent. That's why I said it would be a kit.


    For practical purposes you might need a short tri-clamp extension tube, so you could clamp up the shell and copper plate, then solder or tighten in the copper tubes, then clamp on the end caps.

    Leave the customer to decide what length they wish to make it - you just facilitate them by providing the adaptor plates and shell components.

    SD Reflux kit.jpg
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  • I can't believe someone cannot furnace braze what we need, a modular insert that just needs a compression for inlet and outlet water... I mean putting all those fins inside of an automotive torque convertor at just the right angle is way harder... I wonder if you crimped the dephleg tubes into the end plate so the assembly was solid, then dip the end in a solder/braze pot or a wave solder setup... then leak test in a jig, then acid/electro polish, then weld/solder the assembly into the tri-clover spool... maybe a recessed groove in the spool ends maybe borrow some process from the circuit printed board folks..

  • edited January 2014

    @Myles said: I haven't seen any proposed designs put up yet. ;)

    I'm not trying anything fancy, basically just a 3" variation of the VM in Harry's book. It's evolved to be a combination of copper and stainless and is sized based on some rough calculations that I did months ago and what my OCD would let me do (3" > 1.5" > 3/4"). I was aiming for a 1500mm column, but was only able to eek out 1100mm, leaving me about 200mm for a condensor on the top, which is plenty for a jackson crossflow.



    That's as far as I was able to get with the crossflow though. I'm actually impressed I was able to get that disc as close as I did using the tools (angle grinder) and skills (none) that I have, but this isn't horseshoes.

    @Myles said: There have been designs that use a single condenser mounted just off the horizontal with the vapour entering at 1 end.

    So hang something like a shotgun off a 90 bend and the top with a slight angle so the reflux runs back down the column?

    @Myles said: you can have the vapour entering at the top of a conventional shotgun.

    I'm not sure I understand how that would work. Are you suggesting something that would feed the reflux back into the column via a separate line, sort of how a lot of offset heads are set up? I guess that how the previous idea could work as well and not require the slight angle.

    Can you show me an example of someone using a horizontal condensor like you mentioned? I'm really struggling to see how such a thing would work.

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  • Ok, I just went back and reread everything you posted in this thread and looked at the image you posted a little closer. I think I'm starting to get it.

  • Spazsquatch lets take this to PM or email so as not to derail the topic. :bz

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