Optimizing your RotoVap


I just figured out something that cuts a bit of time out of my roto run. I haven’t added the preheat/prechill yet, I’m setting up for it though.

I got tired of having to empty my flask every 40 minutes, breaking vac, emptying and restarting so i timed it and found out i lose 5-8 mins every time. That adds up over the day, so something had to be done. I added a 20l stainless collection pot with 2 ports on the lid and connected the bottom of the roto flask to one port on the lid and changed the vachose on the roto flask to the other port on the lid. That’s it. Now I don’t have to break vac and only feed more etho into the roto every 40 mins or so. Frees up some time to do other things.


Something to keep in mind is that the chiller has much more cooling power at a higher temp. Basically a chiller just takes heat from one area and dumps it into another. So it will be much easier to dump into the surroundings if the difference between the surroundings and exhaust air is sufficient. By turning up the heat bath you are decreasing the power required for the vacuum pump and the chiller, and if you lower the heat bath you’ll have to increase the power required to your pump and the chiller


Nice! im adding a very large recieving vessel myself.

Anyone ever put silicone thermal fluid in their Roto bath? Im curious as to the big yellow sign on my AI 20L that says: USE WATER ONLY!!!


they don’t want you using Iso :wink:


I’m trying to figure out the same thing, so i just got off the phone with ai tech support and found out that yes, you can change the max temp, but they don’t want to tell you how to do so in the advanced settings as it becomes a fire hazard when used with mineral oil due to the heating element being exposed. I asked if they’d tested that theory and he was adamant about the fire hazard. So i guess tweaking the ai vaps seems hard.


If you want to run your rotovap hot you’ll need the silicone oil, not mineral oil. Do not use any other kind of oil trust me. The stuff will gunk up and will be so difficult to remove you’ll probably throw it out. The silicone oil is specifically for open baths and will not oxidize and degrade like regular oils at high temp. I would recommend the DOW syltherm or similar. We will have a drum on the way should be here before August 1st.


I have some duratherm silicone fluid. Gonna try it out later


What’s the normal fluid, distilled or is there something better. Mine says distilled only as well


I hate oils in my rotobath, if you absolutely need the higher temp that’s one thing, the other is a oily messy flask full of product which could get contaminated by the fluid upon pouring out. Not to mention the extra effort needed for cleaning.


Bah humbug! I’ve been looking at silicone oils and they’re all too damn expensive. Anybody know of an oil that’s cheap and will do the job in an open bath? I’ll post if I find anything.


Shameless plug for the Heidolph Distimatic Automatic Module
When attached to the Heidolph 20L it can keep up with a 50L
300 Liters in a 24 hour period, Heidolph already has auto filling baths and such, you’ll never have to touch the thing except to dial in your process.

Automatic Refill
Automatic Condensate Discharge
Automatic Drainage of Residue

Wont help you with your AI, but something to look into when you’re ready to level up.


That’s the problem with open baths. You could use many different oils but they oxidize over time. The silicone oil will almost never go bad


I’ve been using the same five gallon bucket for over 2 yrs in my roto just don’t spill it on the floor you will fall down


I’ve used vegetable oil, it turns nasty in a few uses.


I’ve been talking to Arthur the tech at Duratherm and they point out that rotovaps designed to use water have less surfcae area for heat exchange and switching to silicone oils or any oil can cause degradation if the Watts per square inch exceeds ten to 12. If one knew specifically they were going to use oil when they built the rotovap they would design it with larger coils with more area. I did some estimates on my 50L and determined that I would be around 26, and I would like to be pushing it to 50 ish. So i’m at a bit of a loss. Have you or anybody else tried using oil and pushed it too hard? I really don’t want to spend 6-800$ to have the oil fail. He also pointed out that you should have a co2 fire extinguisher and not any kind of liquid or water because it would just steam away and go berserk.


Interesting. I’ll have to look into this. I’m looking at the echochyll too. For now I’m going for adding preheat to the etho and prechilling the glycol. The new lab society solvent recovery machine is looking nice aswell. New things pop up all the time, thin film is on the menu too. Time will tell.


We have a new design for the rotos that I’ve been working on for a while now. As soon as the patent is completed we will be releasing it, but I can say that it will be able to pull from and deposit into 55gal barrels and will be many times faster than traditional rotos.
For the ecochyll setup it’s really nothing special. Aside from the direct refrigerant chiller it is basically a big pot still. The labsociety machine is automated and that’s a nice benefit,but it’s also a big pot still. Rotos are going to be much better for solvent removal from viscous materials because with pot stills the weight and surface tension of the stacked material prevents more of the molecules on the bottom from escaping. In turn you’ll need much higher temps.


I like that you can empty the echochyll without having to remove the boiling flask though.


Yeah I agree. Handling the large flasks on the roto are a huge pain. I’ve seen people connect a long tube to the inlet valve and pull the concentrate out of the BP into another. There has to be some kind of good solution for an easy empty. I’ll have to think about that more.


Maybe something can stir the heating bath gently to encourage heat distribution