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 !
That pump is way overkill for a 2L roto. I would consider it my own personal hell to try to keep that from âbumpingâ (the word youâre 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 rateâŚ
You need some sort of dry ice cold trap to catch off the boiling EToH vapors. Thatâll 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
DO NOT USE A ROTARY VANE PUMP ON A ROTARY EVAPORATOR. Thatâs 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:
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?
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 wonât remove the fire hazard entirely, and on top of that itâll make your pump pull even harder and won;t fix your bumping problem.
Ethanol vapor collects in the vac pump oil, lowers itâs 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 whoâs inexperienced I definitely wouldnât 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.
A cold trap will help to collect vapor thatâs gotten past the condenser coil, and itâll help improve and stabilize the pumpâs performance. So itâs certainly not a bad idea.
This is why buying cheap equipment that isnât specâd Together properly becomes a dangerous combo.
Iâve never had this issues with rotovap work but I will help with my two cents as much as I can.
âfirst, try running your equipment at atmosphere. You will have to set your bath at 70-80C.
âyour chiller set to 0C. If you go down to -10 or lower the equipment will Overwork and be âcycled onâ 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.
âonce 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 donât 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 â then your flex line up to the condenser. This will not throw off your chillers temperature regulator.
If youâre pulling solvent past the condenser and into the vacuum you have too much vacuum and the cold trap will help but itâs definitely not normal and a sign this isnât a properly working tool.
Good news is, this isnât 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 donât want to breathe that in your lab.
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