mr.crow
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How to service a Rotavap?
I managed to acquire a really old Rotavap R. All the glass is intact but its contaminated with god knows what and needs a good cleaning.
How do I remove the vapor duct from the motor? Does anyone have a manual?
Double, double toil and trouble; Fire burn, and caldron bubble
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DJF90
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I don't have a manual, but I've just recently "serviced" mine. The vapor duct should just pull out, but if its stiff a gentle tap with a rubber mallet
from the condenser side will do the trick.
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mr.crow
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Thanks, I will give it a shot later. I'm worried about damaging the worm gear!
Double, double toil and trouble; Fire burn, and caldron bubble
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Dr.Bob
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Yes, a gentle tap often works, maybe put a piece of wood against the glass, then tap the wood, to help protect the glass. If the gear breaks from
that, it is not going to hold a heavy rotating flask well either. But the motors are the hardest part to repair, so your caution is wise. Try to
clean the glass with hexane or DCM, the most common dirt is just grease and grim holding other dirt.
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DJF90
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Yes for removing grease residues use a greasy solvent like hexanes, toluene or xylene. After that, if it looks clean, give it a quick rinse with
acetone or methanol or whatever is conveniently on hand. If you're worried about the worm gear (really?) then you can remove the motor prior to shaft
removal, though it'll still be attached by the three wires to the control box. There should be two screwheads on the opposite side to the motor body,
about 1.5-2 inches apart. Remove these screws *they're long* and the motor (and worm gear) pull right out.
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DJF90
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Any questions feel free to U2U me.
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mr.crow
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Thanks, DJF90 and DrBob 
I figured the two screws held the motor on. There is also a bearing held on by 3 screws on the condenser end. By worm gear I meant the gears on the
vapor duct. I'm going to try and pull the tube out on Saturday
Double, double toil and trouble; Fire burn, and caldron bubble
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mr.crow
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I took another look at the Rotavap today. I cleaned up the vapor duct but was unable to remove it. Should be fine though. The condenser is pretty
hopeless.
Picture 1: You can see the crusty-ass condenser. This thing costs $650 new!
Picture 2: Made by Buchi, sold by Brinkmann? The speed control is actually a variable resistor. No automatic digital controls whatsoever.
Picture 3: The wrong stopcock. It was actually frozen in place, briefly heating the outer joint with a blowtorch made it pop right out.
Picture 4: The seal area is pretty corroded. Should I squirt some WD-40 in there? 3 screws hold the bearing in place.
Picture 5: The other side. There are little metal bars holding it in place. It didn't come out pulling on either end even with the 3 screws removed.
Picture 6: The seal is really crusty. Ask Dr.Bob if you want a new one!
     
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plante1999
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Have you tried boiling hot chromosulphuric acid for the condenser?
I usually put "enough" dichromate in 30% sulphuric and boil the piece in it. It has cleaned anything I tested.
I never asked for this.
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crazyboy
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Try soapy water and acetone before moving on to the harder stuff like acid. Cleaning the inside of the coils is pretty tricky I have had success with
even the nastiest coils by using a vibratory pump to push sandy water through the coils for an hour or two, although vibratory pumps are rather
uncommon. WD-40 isn't really the best, I would recommend a penetrating lubricant and after letting that sit for a while a few firm hits with a rubber
mallet. The vapor duct can stick pretty good and as long as you don't slam it it shouldn't break. Also those aren't metal bars, it's a single metal
piece with bent sides that fits in the groove. Did you get the lift as well? I don't see it in the picture.
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stoichiometric_steve
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NaOH in Ethanol. Etches the worst stains off the glass. Don't leave it in there for too long!
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DJF90
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For the condenser, consider a 10% citric acid solution to remove the hard water/iron stains. Formic acid should also work nicely
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Lambda-Eyde
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I've seen weak nitric acid been recommended for cleaning the insides of coils as well. Edit: I also have such a motor, the threads are broken and will
need some metalworking. Obviously I would also need a set of glassware.
[Edited on 15-9-2013 by Lambda-Eyde]
This just in: 95,5 % of the world population lives outside the USA
Please drop by our IRC channel: #sciencemadness @ irc.efnet.org
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mr.crow
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Thanks everyone for the suggestions.
The inside of the coils are fine, just nasty gunk in the condenser. Base bath seems like the easiest way to clean it. Of course I have to protect the
stopcock on the bottom from being damaged or popping out.
It spins just fine, I don't think I need to take it out. Maybe lubricate it a bit. Its too old to have a lift, just clamps onto the stand.
Double, double toil and trouble; Fire burn, and caldron bubble
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Dr.Bob
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I would just wash the inside of the condenser with acetone, ethanol or other solvents for now. If you have iron stains inside the water part of the
condenser, any mild acid will remove them, HCl, citric acid, or several other are good to just pump through, no need for sand or other harsher
chemicals. Once you reassemble the rotovap, just evaporate some methanol, acetone, DCM and a few other solvents to clean the organic side of the
condenser. You normally don't worry about the distilled solvents being absolutely clean, unless you are trying to recover them, and even then I
would re-distill them with a normal still anyway if you want to get them clean. Rotovaps do not usually purify solvents much, just remove them
quickly. If the steam tube is really stuck, you may want to leave it alone if it works, I have broken them before, but it takes a lot of force to do
it, or some bad luck.
If the stopcock on the condenser is wrong, the replacements are hard to find. I have a few, but most have the inner tube (designed for re-filling
the rotovap while in use) broken off. I have rarely ever used that, so not usually a problem. But those get broken often, that is the one part I
will grease often to make it work well.
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mr.crow
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I did give it a rinse with Lacquer Thinner (toluene, mek, methanol) as well as spraying soapy water. It was effective on the vapor duct because I
could scrub it off.
A broken one should be fine, I have only seen people use it to release the vacuum.
Double, double toil and trouble; Fire burn, and caldron bubble
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crazyboy
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I have two Rotovapor R's They have a lift like this
They're nice to have but not necessary.
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DJF90
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Yes, mine has a lift also. It just makes manouvering the assembly alot easier, especially with a 3L vap flask on it. The tap at the end is rarely used
on a benchtop buchi for filling/refilling, but it is essential on a 20L buchi (I use a R220 at work regularly...)
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Cloner
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What sort of grease should be used to lubricate the bearings? The motor of my rotavap is making a squeek and it is experiencing greater friction.
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DJF90
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When I took mine apart to service it the other month, I considered replaceing the machine grease. I didn't in the end as I didn't think it was
necessary, but I had intended to use Lithium grease: http://uk.rs-online.com/web/p/product/4638413/?grossPrice=Y&...
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