Has anyone converted from wet rotary vane vacuum pumps to dry scroll vacuum pumps?
Although we love to sell vacuum pump oil we know that botanical extraction is very hard on the internals of the pumps, possible contamination from oil mist and maintaining consistent vacuum levels. These are some of the reasons we are getting more inquiries for “dry” scroll pumps.
What are your thoughts on the Cost/Benefit of dry pumps versus “wet” dual stage rotary vane pumps? Which dry or wet models have worked or failed in your process?
We have actively sold Edwards, Agilent, Pfeiffer, Leybold and Anest Iwata in other industries with similar demands against particulate and moisture. They tend to work well but are much more money upfront and have a different service schedule to follow.
Going to a dry pump seems to be on many peoples short list of upgrades for the future. What are your thoughts?
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Dry scroll s are nice I run a still on a Edwards xps10 and go s well
But yes they are expensive
I also like the exhaust pressure they create making my secondary coldtrao a lot more efficient for I let it run treu a cold coil 25meter lenght
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Though the sealing elements of the various brands of “dry scroll” pumps may be dry and not actively lubricated, the bearings that the scroll faces pivot upon are packed with grease and excessive solvent coming across will cause them to fail sooner rather than later.
IMO, if your users are having complaints about diluting their vac pump oil with solvent they need to implement a better cold trap, if they are sending that much solvent across their vacuum system instead of complaints about diluted vac pump oil and varying vac levels on a wet pump, they will be complaining about failed bearings and damaged scrolls and seals on a dry scroll pump.
FWIW, ran a secondhand AI CleanVac unit to the point of failure before we got a cold trap that was capable of handling our system capacity.
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I prefer to use dry scroll pumps on my ovens for shatter. It can be used the most and almost put under the most abuse, next to the short path pumps. Plus, it doesn’t mist everywhere and it seems to be more quiet than the rotary vanes I’ve always used. But, she probably is due for some new seals and bearings.
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I was just about to say don’t dry scrolls require a cold trap to work the most effectively
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That’s great feedback about the cold trap and makes sense. Is there a particular cold trap you like more than others?
I’ve used the AI T40 mechanical trap, IMO while it gets cold enough to do the job there’s just not a lot of surface area if you’re going to be using a larger pump and multiple pieces of equipment on the same vacuum system…FWIW, we were running a vacuum still and 6x 50L rotovaps and the AI’s refrigeration system would be overwhelmed in short order, plus the small flasks fill up way too quickly.
We found putting a large (20 gal) stainless tank in a chest freezer worked pretty well for that much equipment but doubt it would pass muster with the fire marshal. Have some ideas for a continuous run cold trap that I think we could get a peer review on just haven’t had time to build it out yet.
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Yeah I have the same coldtrap 
A 120 liters of diesel fuel with 4 1/2" coils inside permanently at -86C
Working on making a revco -140C
In the same manner for butane recovery with a 200 liter tank and 4 coils
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I got to use the Welch Chemstar-Dry 2080 for a little over a year. Super dope little pump, very quiet. It does a self cleaning purge cycle upon startup as well as shutdown. They can be run without a cold trap, even marketing it can handle “heavy volatile vapor loads” though I never had the stones to test that. Awesome pump, outrageously expensive. It was super nice to know I had absolutely no chance of oil mist vapor finding its way into any of my finished product. I highly doubt you could run anything over a 5L with this guy and that may be pushing it.
Cost: $9,500-11,500
CFM: 10.6 (300L/min) @ 2 torr
Ultimate Vac: 0.05 torr
Weight: 50 lbs (22.7 Kg)
https://welchvacuum.com/products/chemstar-dry-oil-free-deep-vacuum-system
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I ran an agilent dry scroll pump with no cold trap for vacuum decarb for a long time, with no sign of damage after pulling lots and lots of terpenes through it. They are definitely robust and durable. Your vacuum level will still suffer of course so I recommend anyone attempting to use for distillation still use traps.
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Good to know and great feedback on the use of traps for distillation.
Thanks for the comment. I am looking into pricing for the Welch Chemstar Dry 2080. This pump wasn’t on my radar but looks like a sweet option if you have the money to invest.
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We have been testing a dry scroll pump by Anest Iwata for a few months and are having good success. More updates to come after we take it off line and inspect the internals for wear.
Anest Iwata ISP250C