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Author: Subject: 1/4" NPT Vacuum Regulator

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Registered: 16-6-2018
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[*] posted on 6-11-2021 at 13:20
1/4" NPT Vacuum Regulator

I have had a nice diaphragm pump just sitting around for quite some time, and want to fire it up for some vacuum distillations. I've been looking online for a good gauge/regulator to use along with the pump, but don't want to go too cheap. I would like a higher quality setup (ptfe/chemical resistant). The pump I have is an explosion proof KNF UN726 Ex series. I just can't seem to find anything that would appear to work, for a reasonable price (under $200). Any ideas or help would be greatly appreciated, thank you in advance.

[Edited on 6-11-2021 by Suessy]
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International Hazard

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[*] posted on 6-11-2021 at 13:46

Do you really need a regulator on a pump that only draws down to 46 millibar?

When would you not want max vacuum from this thing?

If I'm missing something here I'd sure like to know, as I have a similar KNF pump.

Seems like usually when I want to vacuum distill something at a specific pressure and temperature the pressure quoted is in the 10 to 25 Torr range, if not lower.
Sure, they've got those nomographs, but I'm not clear on how reliable those are for different kinds of liquids.

I really like the reliability of a PTFE pump.
No oil to contaminate, handles all sorts of corrosive with no problem, but I often wish I'd found one of those double diaphragm models that pulls down below 10 Torr.

I've even thought about hooking the exhaust of my KNF into a vacuum reservoir evacuated by a pump driven aspirator to see if that gives me a decent improvement.

[Edited on 7-11-2021 by SWIM]

[Edited on 7-11-2021 by SWIM]

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[*] posted on 7-11-2021 at 03:54

It's quite crude but I use a steel needle valve that I screwed into a 3 way pipe union/tee. The resolution of the valve is fine enough that I can vacuum distill things without getting crazy bumping/foaming.

[Edited on 11-7-2021 by monolithic]
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