Roto Evaporator issues

im having issues with my roto evaporator hoping you guys can help me solve the issue.

this is my roto evap im using

https://www.amazon.com/USA-Lab-Evaporator-RotoVap-RE-200A/dp/B079WRXXV4/ref=sr_1_8?crid=UXWFKPRVR1BQ&keywords=roto+evaporator&qid=1573606575&sprefix=roto+eva%2Caps%2C248&sr=8-8

this is the pump im using

My parameters are

  • bath temp = 55c
  • RPM = 60
  • Chiller = 1c-10c

my etoh mix keeps boiling up into my collection flask. not instantly but eventually.

i had put maybe 500ml then when it was almost finished i added maybe 300 more ml of etoh mix then boom it bubbled up into my collection flask! but my main flask was only half full so i dont know why it would bubble up on me and this is the 2nd time it happened.

the next problem

i dont even know how to explain this but its almost as if my vacuum is pulling all the etoh vapor inside so it keeps filling my pump up with ethanol !

will post videos.

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What kind of vac are you pulling (depth)? Are you running a cold trap?

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im not sure what depth im pulling and no im not using a cold trap.

That pump is way overkill for a 2L roto. I would consider it my own personal hell to try to keep that from ‘bumping’ (the word you’re looking for).
Get a single head diaphragm pump, for starters. When it starts to bump, you need to open up a valve to bring vac levels back up for a second. You might have to do this several times to get past the volatiles & get it evaporating at a normal rate…

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Also, target temp on the coils should be -10c to 0c. 10c isn’t great.

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You need some sort of dry ice cold trap to catch off the boiling EToH vapors. That’ll save your pump. Do it in an EToH slurry.

Try cracking your continuous feed valve a hair. That pump is actually way overpowered for that set up let some air leak in and those should solve your issues

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Posted at the same time😂

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DO NOT USE A ROTARY VANE PUMP ON A ROTARY EVAPORATOR. That’s how you catch yourself on fire. That small of a roto use a small diaphragm vac pump somewhere around 1.5cfm and an absolute vac level of 15 torr, something like this:

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thanks i do have a cold trap. il hook it up and use it. i just dont have access to dry ice all the time. i wonder if i can do something to cut the pull of the pump?

This is a continuous feed line. Crack it a hair to equalize your pull till the bumping stops

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If you put a cold trap in line then you will catch some of the ethanol vapor blow-by and keep most it out of your pump oil. It still won’t remove the fire hazard entirely, and on top of that it’ll make your pump pull even harder and won;t fix your bumping problem.

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Is it that fire hazardous?

Care to explain more on that? I’ve never had issues

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Ethanol vapor collects in the vac pump oil, lowers it’s viscosity, pump heats up and the ethanol can ignite. A dry ice cold trap will definitely remove most of the risk. As a daily practice for someone who’s inexperienced I definitely wouldn’t recommend it though. A friend at his previous job saw a coworker running a rotary vane on a 20L roto. As he approached the pump to shut it off it blew up and covered him in flaming pump oil. He healed up but I got to throw plenty of Freddy Krueger jokes his way for a while.

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Wtf thats wild

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do you need a cold trap with a diaphragm pump? if so is a single sufficient

A cold trap will help to collect vapor that’s gotten past the condenser coil, and it’ll help improve and stabilize the pump’s performance. So it’s certainly not a bad idea.

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This is why buying cheap equipment that isn’t spec’d Together properly becomes a dangerous combo.
I’ve never had this issues with rotovap work but I will help with my two cents as much as I can.

—first, try running your equipment at atmosphere. You will have to set your bath at 70-80C.
—your chiller set to 0C. If you go down to -10 or lower the equipment will Overwork and be “cycled on” more than it needs to be.
The condenser should really be able to condense the etoh at the proper rate Or the equipment should be returned or thrown in the trash.

—once you know how to work your equipment without vacuum, setup your vacuum.
Start by turning on your chiller, then vacuum. Check for leaks and turn on the heated bath and roto. Does this have a 100-200rpm range? Experiment with that when you have Done your atmosphere run. Also, if you get high evaporation of your water bath you can fill the bath with ping pong balls. This problem is exacerbated if and when you don’t have AC. 90F plus evaporating water sucks. Been there, done that.

Hopefully you have adjustable vacuum, if so, you want to target 40C temperature on your heating bath with solid flow of ethanol.

Another trick is to take your Chiller output line (cold line going to condenser) and cut the line and Install stainless steel coils submerged in dry ice/acetone or dry/ice ISO — then your flex line up to the condenser. This will not throw off your chillers temperature regulator.

If you’re pulling solvent past the condenser and into the vacuum you have too much vacuum and the cold trap will help but it’s definitely not normal and a sign this isn’t a properly working tool.
Good news is, this isn’t a huge problem and looks like youlll get this working correctly soon.
You can order cheap vacuum pumps on amazon that are used for automotive HVAC jobs that will work with your roto. Vent the exhaust gas outside, you don’t want to breathe that in your lab.

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Holy $shit
I thought that said 20L roto
Ya wow, that’s wayyyyyyyyyy tooo much vacuum pump and wrong pump.
Who sold you that setup??!!!

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Bruh, you could probably use a hand vacuum pump lol :joy:.
Get that grip strength up to level 5000

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