ekilsawkcalbeoj
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Looking for discontinued Buchi R-200/205 WD 34 vacuum seals or DIYing them
I recently acquired and am restoring a Buchi Rotavapor R-200. One of my concerns is that the condenser side seal that is actually quite good right
now, needs to be replaced every year or so. They also do not make this model anymore KD 34 (Buchi part #40016). I think what sets this model apart
from others was the steam duct rotates, and models before and after are stationary, and use the KD-22 or WD-26 seals (still available).
So my question is, does anyone have leads on finding new seals? If not, does anyone have leads on a place that specializes in rotary seals and could
build a new one? I imagine the hundreds of service shops that still service and refurbish/sell these models that couldn't give me any leads to find
them would be interested in throwing in on such a deal or buying the new seals at a markup to cover the cost of development.
Here is what they look like:
Evaporation Side
Condenser/Glass Assembly Side:
Here is one from above at an angle to better show the depth on the evaporation side
Here is what I know:
I tracked down the (now expired because they failed to renew) patent for the device to gain insight into the materials and construction. I'm
attaching a PDF of it below. There is an additional patent that goes into more detail with a really useful diagram that I'm also attaching.
It sounds difficult and the patent language makes them seem really cutting edge, but I've looked over some rotary seal design documents for general
purposes and these are all techniques and materials used for constructing almost all rotary seals in use today. That file is too big to attach but
can viewed at https://www.parker.com/literature/Engineered%20Polymer%20Sys...
Attachment: US5243836.pdf (302kB)
This file has been downloaded 478 times
Attachment: US6709025.pdf (540kB)
This file has been downloaded 463 times
[Edited on 6/26/2020 by ekilsawkcalbeoj]
[Edited on 6/26/2020 by ekilsawkcalbeoj]
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Dr.Bob
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The KD-22 is used on models with rotating steam ducts, and even those are getting harder to find. But I will look through my stash of Buchi parts and
see if I have any, it just may take a few days to search the boxes. I don't remember seeing one like that, but I have lots of random parts and
pieces, so I can check. But it is very hard to make one of these from scratch, they are very precise and use special polymers.
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Heptylene
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Perhaps make sure the seal stays clean to extend its life. Also the wear depends on usage I assume. Once per year seems arbitrary. Take measurements
now while it's intact, in case you want to make one from scratch in the future.
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ekilsawkcalbeoj
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Quote: Originally posted by Dr.Bob  | | The KD-22 is used on models with rotating steam ducts, and even those are getting harder to find. But I will look through my stash of Buchi parts and
see if I have any, it just may take a few days to search the boxes. I don't remember seeing one like that, but I have lots of random parts and
pieces, so I can check. But it is very hard to make one of these from scratch, they are very precise and use special polymers.
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Thanks a lot actually, hopefully, you can find something!
Interestingly I had asked a similar question with a Buchi Service Engineer, the same one I was able to get parts of the service manual from. Here's
the relevant part of the conversation:
Me: I have a question about the seals as shown in a few of the pdf’s you sent. It almost looks like if I were to switch to using the cold trap
glass assembly, I’d be able to use KD-22 Seals, or if I were to acquire the distribution head and associated assembly I could use KD-26 seals. Is
that interpretation correct?
Buchi: Unfortunately, you cannot change over to one of our other vapor ducts and use the 000636 vapor duct seal. The R200/205 systems only came with a
straight-through vapor duct and rotation drive.
What you see depicted in the picture was a special rotation drive that was used to convert the system. This rotation drive is no longer available.
I actually thought to ask him for the following reasons:
A Buchi glass assembly A (diagonal) I bought on eBay arrived with a really worn KD-22 seal still attached to the glass.
When I requested the literature and service manuals, they arrived and one contained some part diagrams I've never seen in the other literature I
was able to find on my own. The screenshot of that bit is above, and notice there are a few things highlighted, which I didn't highlight, I suspected
maybe he was trying to send a subtle hint by highlighting "Stationary-sealing system Seal KD-22 00636" but could easily have misinterpreted it.
Regardless, if you happen to have the no longer available special rotation drive used to convert the system that he mentioned, it would be pretty
amazing. I'm hoping to not have to make anything, but the wear point seems to be where the vapor duct spins against the inner lip of the PTFE part,
which being PTFE would flow and deform over time.
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