Sciencemadness Discussion Board

Used rotary evaporators

Mateo_swe - 16-8-2021 at 06:23

I really want a rotovap but i dont have enough money to buy a new, good quality brand one.
So i guess i have 3 options

1 - Buy a new ebay Chinese one that can be had for something like 500-700 Euros.
I doubt these have very good quality and will function for a long time.
Spare parts can be a huge issue when something breaks some time after purchase.

2 - Buy a used good brand one, like a Buchi or something similar.
Good with this option is that spare parts will be no problems.
Bad part is that these many times are more expensive used than the new Chinese rotovaps with all things included.
Also, its quite hard to find used rotovaps in Europe for a decent price.

3 - Forget a rotovap until i save up enough money to buy a new, good brand one.

Im probably going to start look for a used good brand rotovap.
But they arent easy to find with all needed items included and for a low price.
I probably will start look at ebay and similar sites, maybe a good one will pop up sooner or later.
Maybe there is some internet sites that sells used lab equipment on auction, sometimes from terminated company's.
I know one such place but they only sells bigger machines and equipment.
Anyone knows about any such action sites in northern parts of Europe and could share the info?

Also, what are important to look at when buying a used rotovap?
The seal i know is a key part that must be in good condition but are there any other parts that are important to check?
Parts that are expensive to replace.

zinc finger - 16-8-2021 at 11:35

Not long ago I was in the exact same situation. However being patient and determined eventually payed of: I now have a fully functional IKA RV-05. It is a very old but also reliable model on a stand. I got the Motor and the condenser from ebay in bad condition and some replacements like the seal, valve, spiral and union nut from other sources. The later part was far more complicated than I anticipated but in the end it only costed me ~ 200 €. It helped a lot that I am quite crafty and I was able to repair some parts in the motor. Also some lab experience was helpful to clean up the condenser which had some nasty organic stuff in it.

I also had a look at some other sites apart from ebay and German "eBay Kleinanzeigen" but was not lucky there. As I already said, patience really payed off at the end. The other sites I was visiting did not seem very accessible for private stakeholders and I have no experience ordering there. If you know someone in the industry or a company which is closing or sorting out old stuff you might be extremely lucky but those devices are rarely sorted out because they usually very durable.

Regarding the parts:
Round bottom flasks in all sizes are readily available and for most European rotovaps every NS 29/32 flask can be used as evaporation flask.

A bit more costly are ball jointed collection flasks. They can still be found on ebay for reasonable prices.

I could not find a ball joint clamp anywhere so I bought it of VWR/avator (for ~15 €) which also offers GL connectors (the screw type adaptors which you need for some condenser types to hook up cooling water or vacuum). The most usual GL connectors I came across are GL14.

The top valve was exceptionally hard to find and its valuable if you can get it together with the condenser. Mine is NS 19/38.

The seals were also difficult to find and I ended up using seals from Buchi together with Buchi vapor tube which I could not find for IKA as well. Surprisingly it all fits perfectly. Still both parts are hard to source. If you can buy the sealing rings in bulk, do so! They wear out first.

Finally the spring and the union nut. Luckily I had the nut on my motor but the spring was missing. It is in Principle a basic stainless steel spring with one narrowed end to be pushed into the other side. I finally got it somewhere else but I do believe you could get a similar spring from another more generic source much cheaper.

Of great value are the general parameters of the parts you need which were hard to find out. For example few ebay sellers write which joint size their glassware has and commercial distributers of small parts for rotovaps only give you the compatible models instead of the vapour tube outer diameter for example. That is why I added some values of my own roto above ;).

As a general note: the more specialized the equipment gets the higher its price will be at an exponential scale. That is why a rotovap is expensive. However it only keeps its high value as long as it is in the circles of those who are willing to pay and those who sell and provide guaranties. Sometimes a piece of equipment leaves these circles and ends up in the garage of someone. In that super lucky case you can make a cheap deal - so good luck!

Mateo_swe - 16-8-2021 at 13:09

Thank you for the info.

It seems to be a rather complicated task to try put together a rotovap from parts and especially to find the right parts.
I will have to try find one that has all or at least most parts included.
And i guess that means i have to save up some more money because the more complete they are, the higher price is wanted.
If one search on ebay for used rotovaps there are many but they are almost all in US, in Europe there are very few.
Maybe i get lucky if i just keep looking.
I found a good vacuum pump for a OK price before, good deals come if one is patient.
At least i hope so.
Finding a OK rotovap at a garage sale i can only dream about, that will not happen.

draculic acid69 - 16-8-2021 at 22:52

Option four: make one. There's a step by step guide on how to do it somewhere on this site. There's also a YouTube video of a very similar rotovap being made. It doesn't look that hard and all parts are easily accessible from ebay

Mateo_swe - 17-8-2021 at 03:10

I actually have thought about making a rotovap myself.
First i looked into making the rotary-stationary part from HDPE or maybe PTFE in a lathe or CNC-mill.
It might work but i doubt if will work as good as the real rotovaps and this part is important it works good under vacuum.
I also had an idea to just move the whole flask in a circular motion but not spin it.
If doing so, the liquid vill rise to the wall by gravity force and help evaporation.
Combine it with a heating mantle sleeve and vacuum and it might be quite good at evaporating solvents.

I also read about some measurements of evaporation that another person made while trying to make a DIY rotovap.
It seems that the rotation did not add very much to the evaporation rate.
The most important factor was the vacuum, and the heating was secondly important and the rotation was the parameter with the least impact on evaporation rate.
Maybe an automated distill rig (vacuum and heat) will work decently good.
It would be so much simpler to make without the rotation part.

But if trying to make a rotovap myself maybe it would be a good idea to start with some real rotovap parts, like the motor and rotary-stationary interface with the seal and maybe the condenser.
The problem is i have many projects already and so little time to spend on projects.
And building a rotovap will take a lot of time and good results are not guaranteed.
I like building stuff but want to spend some time on chemistry projects also.
Maybe its better to save up some more money and try get a used, working rotovap instead.

eyeemplus - 17-8-2021 at 09:37

I would buy a used Buchi as they seem very reliable / last forever.

One thing is that there may still be a problem with spare parts since the older, more affordable models no longer have parts availability from Buchi. Buchi shows the avaialbility of spare parts for different models on their website

So often the way to get spare parts is to buy an incomplete unit which is sold cheaply for spares or repairs. In some cases a newer model has the same part as an older model (exact same part number), so this can be helpful.

The thing to watch out for is the seals as they can be difficult to get hold of for some older models, and do need replacing at intervals.

Texium - 17-8-2021 at 20:08

The seals used on the older models are still used on the newer ones. I have a Büchi from the 70s and it uses the same seal as the new models I use at work. Vapor ducts are largely interchangeable as well. Even some of the condensers.

[Edited on 8-18-2021 by Texium]

macckone - 18-8-2021 at 12:57

The rotary to stationary seal really needs to be PTFE or similar low friction fluorocarbon.
You can also use viton seals in a homemade variety.

If you are just doing benign solvent evaporation then your choice of materials beyond the flask increases and the cost goes way down.
You can use things like hose swivels that are off the shelf, with the possible replacement of gaskets.

It may mean you need a second distillation of the solvent to reuse it but makes things much easier.

Example:
https://www.amazon.com/Mosmatic-32-864-Rotary-Unions-Swivel/...

[Edited on 18-8-2021 by macckone]

eyeemplus - 20-8-2021 at 06:28

Quote: Originally posted by Texium  
The seals used on the older models are still used on the newer ones. I have a Büchi from the 70s and it uses the same seal as the new models I use at work. Vapor ducts are largely interchangeable as well. Even some of the condensers.

[Edited on 8-18-2021 by Texium]


The R200/R205 however have a kind of rotary seal that is no longer available and different from any of the newer or older models.

Panache - 20-8-2021 at 16:28

Quote: Originally posted by macckone  
The rotary to stationary seal..

[Edited on 18-8-2021 by macckone]


Also known as the mechanical seal...