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Author: Subject: Vacuum pump protection
charley1957
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[*] posted on 4-11-2017 at 04:52
Vacuum pump protection


Seems I've seen somewhere in the forums where someone built a scrubber of sorts for their vacuum pump. Best I remember, it was a series of, I think, Mason jars, each holding a different chemical to neutralize something or other. Seems like there were four or five of them in series before the vacuum pump. Yes, I've UTFSE now for several hours and I can't find that post, and it had pics. Does anybody else remember seeing this, and if so, where?




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[*] posted on 4-11-2017 at 05:31


As I recall it was praxichys who did this. It might be on his yt chnnel -- Doug's Lab.
(Or I may be misremembering.)
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[*] posted on 4-11-2017 at 06:01


May have been zts16, not sure, it was a long time ago
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[*] posted on 4-11-2017 at 11:17


My opinion would be that at least three of the jars contain distilled water, diluted (30-50%?) sulphuric acid, and sodium hydroxide solution - potentially an organic solvent depending on what is coming over. I've seen this sort of setup as well, where two or three jars of NaOH are sometimes used and they tend to be at the end of the chain but it may not matter regarding the order. I assume that you're wondering what is used to scrub the gases, but I haven't seen the video myself so I can't give you any pointers there.



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charley1957
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[*] posted on 12-11-2017 at 17:47


Sciencemadness Discussion Board » Fundamentals » Chemistry in General » Everyday Chemistry. I found it on page 1. It was zts16 who did it back in 2015. I knew I could find it again if I just had enough time. Thanks for all your suggestions!

[Edited on Nov11-13-2017 by charley1957]




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Texium (zts16)
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[*] posted on 12-11-2017 at 18:53


Quote: Originally posted by charley1957  
Seems I've seen somewhere in the forums where someone built a scrubber of sorts for their vacuum pump. Best I remember, it was a series of, I think, Mason jars, each holding a different chemical to neutralize something or other. Seems like there were four or five of them in series before the vacuum pump. Yes, I've UTFSE now for several hours and I can't find that post, and it had pics. Does anybody else remember seeing this, and if so, where?
Yeah, that was mine... it was terrible and broke the first time that I used it. Wouldn't recommend! Now I just stick a calcium chloride guard tube on mine, and I have a Dewar condenser that I can load with dry ice if I need to.



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[*] posted on 12-11-2017 at 19:51


If you have anything before your pump it better not boil under the vacuum your are applying (like pretty much any aqueous solution) better yet it should have pretty much nil volatility or you're going to suck it to your pump anyway. That's why people usually use KOH traps or cold traps. Nothing to suck to the pump.



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Magpie
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[*] posted on 12-11-2017 at 20:23


The first thing that struck me about this idea was that the Mason jars would be under vacuum and might implode. What broke zts16?



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[*] posted on 12-11-2017 at 21:52


The mason jars were alright (my pump is just a single stage rotary vane, so it's not the most powerful), but the way I sealed the tubing to the lids was terrible. I used hot glue because it was what I had available. It was quickly chewed up by the NaOH solution. The sulfuric acid also wreaked havoc on the lids of the jars, and I had a lot of issues with suckback. The alternating empty jars were meant to solve that issue, but it was still really annoying to empty them out all the time.

Overall, it was just an ineffective and overcomplicated design.




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[*] posted on 12-11-2017 at 22:55


just a side note;
a single stage oil sealed rotary vane vacuum pump and a dual stage create almost identical forces on evacuated vssels ...
1 Atmosphere - almost nothing.




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[*] posted on 13-11-2017 at 00:12


Yeah....basically any sort of scrubbing system will eventually allow the harmful components through and into the pump. Either due to breakage, suckback, deterioration of scrubbing media or human error. It is inevitable and not a question of "if?" but a question of "when?". Hence I see no point in trying to build a massive failureproof scrubbing system....I find it is much more reasonable to just select the right type of pump for the job. When filtrations and distillations are the main objective, then building or sourcing a closed loop aspirator system is far more sensible than trying to build a contaminant scrubber for a rotary vane pump. The aspirator system can be quite bulky, but it is robust and can handle basically any contaminants without fear of irreversible damage. Or one can use a Teflon lined pump that is designed to handle aggressive contaminants...a much more compact solution, but the pricetag can be quite rich.



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