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Sauron
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Kugelrohr
I am in the market for a large capacity Kugelrohr.
Aldrich used to sell a 4 L model but has discontinued this one.
They occasionally turn up on the used market.
The model Aldrich now sells is 2 L max. which means a pot charge of c.650 ml (1/3 the nominal). This is adequate but I have to have to pay for a new
one. (They are about $2500 I think w/glass.)
The same unit will of course accomodate oven flasks down to 10 ml but you need different glassware, not a big deal.
I suppose this was rationalized from the original two models (standard and large) where the standard model covered 10 to 500 ml and the large, 2 L and
4 L.
Anyone have any experience with these horizontal bulb short path setups?
Below is a photo of the 2 and 4 L older model Aldrich Kugelrohr that was discontinued sometime prior to 2000 but was still in the 1996-97 catalog.
This one has an air motor which was not shown in the catalogs of the mid 90s. I passed this set up for $1500 and just missed an identical set without
glassware for $300.
[Edited on 10-8-2007 by Sauron]
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Sauron
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The temperature controller in the photo above was a third party add-on.
The current Aldrich offering dropped the 4 liter option and rationalized the standard and large variants into a single model, with a nominal pot
capacity of 10 ml to 2 L. The motor drive is the same for all models old and new (electric only, no air drive option.) The temperature controller and
Type K thermocouple are now built in, the oven (air bath) is surrounded on three sides by a hand guard and the motor no longer requires a lab stand.
The system is rated for vacuum to 0.05 mm Hg and the oven to 200 C.
The 1 L and 2 L glassware sets are now System 45 threaded rather than 24/40 ST joints, the thread to thread couplings are PTFE sealed. The threads are
alternately right and left hand so that no joint loosens during rotation.
Bear in moind that the pot charge is 1/3 the nominal capacity so a 2 L oven flask holds only 650 ml charge.
Anyway the path is very short, making this a specialized sort of rotavap but also good for sublimations on a prep scale. ''
If I can't find a bargain on an old 4 L system I will just break down and buy a new 230V 2 L system and be satisfied.
[Edited on 10-8-2007 by Sauron]
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Sauron
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I just logged onto Aldrich and got price for this thing. THEY ARE INSANE.
About $7000 US, that's about the price of THREE Buchi rotavaps - and that did not include the large glassware yet.
They have priced themselves out of the market, in my opinion. There is no reason for the price to have triples in ten years.
Totally ridiculous!
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evil_lurker
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I totally agree. These lab companies like Aldrich, Cole-Palmer, Thomas Scientific, Parr, and Buchi think their shit is made out of fucking gold... and
why shouldn't they?
They just about got the market cornered in many repects.
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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Sauron
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The 230V Kugelrohr is 20% higher than the 115V one. Also ridiculous.
Anyway I still have two options:
1. Find one on used market
2. DIY.
An air bath is easy, even with T/C and PID.
A low speed high torque motor is easy.
The thing that requires some thought but not that much is the vacuum takeoff from rotating system. Some sort of gland I guess.
What would be wrong with a sperical ball/socket? I mean I would relocate the drive to the bottom of the flask (the old style 2 L and 4 L flasks had
glass rods attached for support and I think those can be driven.) Then for vacuum takeoff I would have a spherical ball and socket with a ptfe liner,
and an adjustable clamp, seems to me that this would be vacuum tight and still allow rotation. Easy enough to try this concept out without building
the whole unit.
Here is what appears to be the US patent for the improved current model kugelrohr, filed in 1996, issues in 1999, expires in 2016.
Apparent that air motor in the older Aldrich model shown above is an automotive windshield wiper type motor, which reverses direction after a partial
rotation.
The current model as described in patent uses a conventional low speed high torque motor operating in one direction only.
The vacuum bearing assy is quite conventional and is described in details. SS body and caps, spring loaded teflong seals and Rulon bearings.
The inventor linked the last flask and the drive tube via a short length of vacuum hose to allow for misalignment. Old lab trick used on overhead
stirrers.
Altogether I do not see why this could not be built on a DIY basis at very low cost, certainly nothing like the $7500 or so being extorted by Aldrich.
Comments?
Balseal is a company, I found their website. Rulon is a brand of PTFE polymer and several companies sell Rulon bearings of various types ex stock.
Also, Aldrich sells replacement gaskets, bushings and bearings and their web pages give OEM details...
How convenient.
[Edited on 10-8-2007 by Sauron]
Attachment: 5879516.pdf (79kB)
This file has been downloaded 898 times
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Sauron
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One of the criticisms by the inventor in the patent posted above was that the old Aldrich kugelrohr had as its air bath oven, an aluminum coffee maker
with an ungrounded heating element that screwed into a lamp socket inside the oven.
He replaced this with a SS oven body having a sealed and grounded heating element mounter in a liquid-tight manner through the floor of the oven.
Which is certainly an improvement.
I am thinking that an alternative arrangement that can be built from off the shelf components would be a horizontal SS cylinder closed at one end and
with a detachable lid at the other.
The lid and the rear of the SS oven would be fitted with PTFE bearings to support 24/40 joints. The oven flask would be same as receiver flask, e.g.,
male joint on one end and female joint at the other.
The male joint is mated to a female TS cap which is attached to a pyrex rod 9mm OD; this is coupled by a short length of vacuum hose to an Al or SS
shaft held in chick of an ordinary variable speed lab stirrer like an IKA. This is set to drive the oven flask and receiver flask train at low speed.
The final receiver bulb is fitted with a joint terminating in a hose barb and the hose barb coupled again with flexible vacuum tubing to a vacuum
takeoff similar to the one described in the patent.
Heating of the air oven is via a custom GlasCol mantle of the lace-up type or else heating tape, in either case regulated by a thermocouple and a PID
controller, preferably with digital display. The controller need not be dedicated to the Kugelrohr, when that is not in use. It is a standard mantle
controller such as sold by GlasCol or it could be an Ace temp controller, or whatever is on hand.
The advantage of this assembly is:
Low Cost!
Off the shelf stirrer motor (on hand)
Off the shelf flasks either Aldrich kugelrohr receiver flasks or any maker's chromatography reservoir flasks, or could be modified from ubiquitous
single neck flasks by addition of a second joint at bottom.
Off the shelf (or nearly) mantle. If I get lucky there will be a stock GlasCol mantle that will work. Otherwise GlasCol will build mantle to specs and
heating tape is always an option.
Only the largest (2 L and 4 L) flasks require support at rear. For smaller flasks the motor is relocated to the vacuum takeoff and drives the metal
takeoff tube just as in the patent.
I doubt this setup will cost much more than $1000, not the $7500 or so Aldrich wants.
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vulture
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Mostly it are large companies, academic or government institutions that buy this stuff. Then you can pretty much ask anything you want. When it gets
there is more important than what it costs.
What are you going to sublime anyway?
[Edited on 11-8-2007 by vulture]
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Sauron
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Something sublime, no doubt.
The thing is not primarily for sublimations, it is primarily for delicate simple distillations of higher boiling compounds that nevertheless come over
at <200 C and a good vacuum down to a twentieth of a torr.
It is not an everyday tool like a rotavap. But it does show up in the lit., and when it is useful it is very useful. I would not pay c.$10,000 for
one, but I have long coveted one and I am sorry I missed the one for $300 and was too slow on the one (pictured above) for $1500. Both of those are
within the price range of a second hand rotavap, and I regard a Kugelrohr as a specialized rotavap with functionality the Buchi does not have.
So I would spend $1000-$2000 to buy one or cobble one together
It is just another acquisition. You might as well ask what I will make with my Parr 3911, Parr 4521, Thermolyne tube furnace, or anything else. Or the
half a dozen HPLC systems presently cluttering up the place.
The only proper answer is "Any damn thing I want to make."
What is the point of having a lab anyway if not to do precisely that?
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Sauron
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Some dimensions worked out:
A 3000 L RB flask is 185 mm OD
A 4000 L RB flask is 200 mm OD
A 5000 L RB flask is 221 mm OD
So a metal cylinder, preferaby SS but Al or Cu would also work, with a 11 to 12 inch ID and similar length fitted with Aldrich PTFE flask bearings on
centerline and having a removable lid.
Heating provided by a 1400 W GlasCol 1" x 20 ft heating tape, 230V (convenient for my Powertrol controller). The top end of this tape is 400 F so
compatible with the 200 C top end of the Aldrich Kugelrohr.
The Aldrich old style large unit which was a coffee urn in its former life was 500 W. So mine is less energy efficient. So what? It is a lot more $$
efficient. The energy usage only matters for long slow procedures. The Powertrol regulates input from 5% to 100% so I am comfortable.
Now to go look for a suitable metal pot - sounds like a job for my wife!
I have requested a quote from the local GlasCol agent (who I have bought from before, they also are Kimble Kontes agent among others) for the heating
tape, and ordering the teflon bearings from Aldrich, and some glassware.
Then it is time for the trickier bit, the vacuum adapter and motor drive. The old style Aldrich unit was an automotive windshield wiper motor (see
photo above) powered by air or vacuum. I gather that such motors these days are 12V DC unidirectional ones and the reciprocating action is produced by
a gear box.
The post 1996 Kugelrohr is anyhow, unidirectional high torque low speed nonsparking and cooled by an external fan for continuous duty. I have a number
of fixed speed high torque drives intended for peristaltic pumps and one of these will serve. (Again, not necessarily even a dedicated role.)
I guess something like 10 rpm would be about right.
The design of the vacuum adapter is right from patent, and will just mean some AutoCAD time and buying spare BalSeals and Rulon bearings from Aldrich.
Those will reveal the domensions of the adapter body and caps, and the perforated drive shaft that is terminated in a hose barb one end and closed at
the other. Then a trip to the machine shop I use and we are done.
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vulture
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Sauron, I don't know if you have a copy of Organikum (the laboratory book), but if you don't, it might be worth looking into. It describes some of the
fancy old school apparatus like that and some hints & tips.
| Quote: |
The only proper answer is "Any damn thing I want to make." |
That'll soon turn into a luxury problem I suppose...
I was under the impression you were making money with your lab adventures, that's why I asked.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Sauron
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Ha, I wish I was making money instead of simply bleeding it out of every orifice. But alas, no, I am underwriting this out of my own pocket. No
grants, no nothing. It is after all - my hobby.
The corporation is left over from an aborted absinthe making business (well, abortive from my end - my partner went on and is making the stuff in
France.)
I don't have Organikum, do you have a link to a download?
Oh, I see from Google. 22 vols, and only in German. From Wiley in Germany. I wonder how much a set costs? A rather major digitizing project...
[Edited on 12-8-2007 by Sauron]
[Edited on 12-8-2007 by Sauron]
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Sauron
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The motor shown above is the pre-1996, windshield wiper type powered by compressed air or vacuum. My best guess is that the same vacuum that was used
for the distillation, powers the drive, maybe via a Y-connector and a one way valve to keep chemical vapors away from the motor. The tube protruding
from the black box has to be the drive shaft and the black box, a gear box most likely.
I'd rather go for the current style rotary drive rather than reciprocating like this but if I find one of these old ones I will buy it and then the
mystery will be sol-ved (as Clouseau would say.)
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Sauron
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Well, I found a used current model Aldrich Kugelrohr with glass for $1750 and am ordering it.
See photo. The wraparound guard is missing, so somehow I will have to remember not to put my hand on the hot over surface (DUH!)
This model has built in temp controller and thermocouple. The oven handles flasks from 10 ml to 2 liters corresponding to pot charges of 3 ml to 650
ml.
So mission accomplished.
[Edited on 13-8-2007 by Sauron]
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Phosphor-ing
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I envy your budget Sauron. More power to ya!
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Sauron
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It comes from being childless.
For example one of my friends is having to pay $6000 a year for her son's school bus. And a similar amount for his tuition.
I have a stepson but he is grown and pretty much on his own, gainfully employed.
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stoichiometric_steve
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| Quote: | Originally posted by Sauron
I don't have Organikum, do you have a link to a download?
Oh, I see from Google. 22 vols, and only in German. From Wiley in Germany. |
i have the 21st edition in PDF format...you want?
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Sauron
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Sure! Can you put this on 4shared.com?
(Sept 19)
I purchased a spare set of ptfe bearings from Aldrich, these are the pieces that mount on the side wall of the ovel and through which the flask neck
and joint emerge and ride as they rotate. These are about 3mm thick flat ptfe sheet. The one with small hole is for 14/20 joint and the larger is for
24/40 although it looks large enough to pass a 29/42. 14/20 and 24/40 are standard Kugelrohr flask and bulb joint sizes.
The two very small holes are for screw posts and the piece is retained by wing nuts. The thin ptfe is flexible enough to conform to the curvature of
the original Aldrich coffee-urn style ovens.
A rotary horizontal flask/bulb train air bath would be dead easy to fabricate.
[Edited on 19-9-2007 by Sauron]
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Sauron
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Just spotted this photo of a kugelrohr drive motor on the net.
Ought to be of interest to anyone contemplating making their own such apparatus.
[Edited on 31-3-2008 by Sauron]
Sic gorgeamus a los subjectatus nunc.
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Sauron
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I wonder why I can't edit that post?
Anyway I am now told, this is an air motor and reciprocates in a partial turn L and R. Thus it is for the older model Aldrich Kugelrohr, and there's a
photo of it with the old style air oven (like a coffee urn) at top of thread. These ovens have a capacity for flasks up to 4 L (working capacity 1.3
L) and that is double the max capacity of present model.
The 2 and 4 L flasks Aldrich sold for this purpose had a rear support (solid or hollow glass rod) at bottom integral to the flask to take stress off
of the 24/40 top joint. Not much of a challenge for a custom lab glassblower.
The partial rotation also greatly simplifies vacuum takeoff. On the current model this has to be done with a special bearing assy integral to the
motor drive. Probably part of why Aldrich wants $5000 for these.
On the old model I don't see why a conventional vacuum adapter can't be part of the receiver bulb train.
I just bought two of these (one for a friend and fellow member maybe) so I guess I'll need a small compressor and air tank.
Sic gorgeamus a los subjectatus nunc.
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Jor
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Sauron.
Can you please post pictures of your lab of you have time?
We all see you have such a high budget. I wonder how it looks there , in your lab.
http://www.sciencemadness.org/talk/viewthread.php?tid=4777&a...
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Sauron
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I now have the capability to take stills and HD video. Fume hood installation will be finished mid summer. Till them it's a large pile of assorted
equipment, instruments, glassware in boxes, cabinets full of reagents etc. and not very photogenic.
The fume hood is a major pain and expense. It has taken a long time to sort out because I wanted a large one with a scrubber to match and refused to
compromise on the dimensions. It's two meters wide, a meter deep and I could sleep in it if I wanted to, though I doubt it would be comfortable. Like
a sleeper berth on a train.
The budget goes up and down with my discretionary income. The hobby is a money pit, and one day my wife will kill me, or divorce me.
Sic gorgeamus a los subjectatus nunc.
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Magpie
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Sauron says:
| Quote: |
The hobby is a money pit, and one day my wife will kill me, or divorce me.
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My wife hates PayPal. I guess she just wanted me to take on her home improvement projects in my retirement years. 
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Pulverulescent
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| Quote: | Originally posted by Phosphor-ing
I envy your budget Sauron. More power to ya! |
The apparently high budget could just be total dedication; IMO, that's more enviable.
P
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Sauron
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Dedication or obsession?
Who dies with the biggest chemistry set, wins.
Sic gorgeamus a los subjectatus nunc.
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Pulverulescent
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Arrgh! The dreaded "Memento mori"!
I've, reverted, now, to contemplation of the meaninglessness and utter
futility of all presence on this mortal coil.
P
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