I run a few small rotary vane pumps around my shop right now on a couple rotovaps and Buchner setups. I have a couple nicer spares sitting around, any of which could replace all of the current pumps combined. I designed a 4-valve manifold, cold trap, bought some tubing, but now I’m starting to get concerned if the tubing itself is the right stuff. Its polypropylene flexible tubing from my local Grainger, rated 147 PSI (not sure how this translates to vacuum though, if at all) but if I use, say, an Alcatel 2021i on this setup then I’m wondering if it will just collapse the tubing right from the start.
Is there a way to measure a tube’s vacuum depth rating? I tried researching on here and on Google, @goldleaf_scientific had a post from a couple years ago with the necessary wall thickness of tubing based on ID, but I wasn’t sure if there was a more precise measurement that I should be researching.
If this all works out then I’ll be using a couple hundred feet of tubing total, I could just go with a $5/ft reinforced tube option but I’m hoping to keep the cost lower
Terpenes are going to partially dissolve of weaken a lot of materials. A small volume works in the matrix of the other material and off-gasses forever, so you can’t just clean it. You have to throw them away every run.
Flexible materials will permeate air. Generally the more flexible it is the more air will permeate through. The longer the hose the more it leaks. Think soaker hose.
In my experience the cheapest material to hit both of these points fairly well is natural rubber. If you find some pictures of chem labs setting up this exact manifold they always use thick rubber. The thicker the better especially with anything over 3/8" ID.
Thanks for the replies, @goldleaf_scientific that is super helpful, and makes perfect sense. I may be able to modify my pump and manifold placement to cut down on the tubing, and run the exhaust lines out further instead
@spdking I think you may be onto something with those lines. I’ll be running 1/4 inch and a 10ft line is only about $20, I’d just connect a few inches of rubber tubing off the ends to connect onto the equipment’s barbs a bit easier.
I think you’ve mixed up hose and tubing. Tubing is like pipe, but is not threaded. Tubing and pipe are solid. Hoses are flexible. Do you have any option to run tubing? Stainless tubing is much more durable than hose. And it’s pretty easy to bend and mount to Unistrut or similar brackets. Compression fittings are easy to attach to ends, and you can attach hose barb adapters, or KF25 adapters to the ends. Then you only have short lengths of hose to worry about replacing, and quality hose isn’t as costly once you only need 10 or 20 feet, instead of hundreds. No worries about .049” wall thickness tubing’s vacuum rating even with long lengths. It’s plenty strong.
From the manifold block I have I would use compression fittings directly into these lines, and when I’m within a couple feet of the equipment (Roto, Filter, etc) adapt from compression to a hose barb,and then use rubber hosing for that last bit. I would mount the supply lines along the wall and use hosing from the wall to the equipment basically
I have never tried using regular plumbing hoses, or single compression fittings for more industrial purposes. I couldn’t imagine either of those components are designed or rated for vacuum. I can’t guarantee you’d have an issue but it seems like half assing a vacuum manifold is asking for leaks. I think you’ll have much better time with compression fittings like the Swagelok double ferrule, or stainless steel braided PTFE lined hoses with JIC or tube stub/compression connections. Hose barbs with clamps like you see underhood of a car are generally to be avoided if possible.
Edit, domestically mfg’d seamless 1/2” .049” stainless tubing is available here for around $5/ft. Imported is even cheaper. It’s the connections you put on the end that cost a couple bucks.
Yeah I looked at that hosing in person and its thin PTFE tubing inside of steel braiding. I did find another hose option, propane tank hosing, that may work as well, but the more I research hosing the more I realize spending more for the right stainless lines is going to be essential.
The valves on my manifold right now are 1/4" NPT so I planned to find a hosing option with NPT fittings on each end for 95% of the tubing, but I’d have to use a hose barb+rubber hosing at the very end to connect to the Buchners/Rotovaps.
Here’s a picture of the manifold in case anyone else may be looking at this thread and thinking about setting one up. In total it cost me maybe $60 from Grianger, I spaced out the valves in the block and used plugs just so there would be room between them to tighten down and actually operate the valves. Tested it yesterday with rubber hosing and barbs and it worked fantastic, confident it will be perfect with true steel lines
Before you get to deep into this i would recommend upgrading to larger ID fittings. Especially feeding that manifold. 1/4" is quite small and will increase the time your vessels take to get to full vac pressure.
there is a reason most vacuum pumps and ovens have large fittings such as a kf25
