LuckyWinner
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Using Compression Fittings instead of Barb for Secure Connections?
usually people stulp flexible rubber hoses over their olive barbs.
many labware comes with GL threds where you could place
a PTFE tube with a GL chem resistant compression fitting on to it.
(i know PTFE is very rigid but smaller diameters 4 to 6mm can be bent)
if you buy some high quality GL compression fittings you could get secure vacuum tight seals?
or do these compression fittings get loose over time , or do not perform as advertised?
what type of PTFE tubing diameter is recommended for vacuum and liquid transfer
purposes when working with volumes of 250-1000ml ?
transfer of
-liquid between reaction flasks
-condenser coolant
-vacuum
other reasons to use PTFE tubing , can be used to transfer most chemicals without getting brittle.
can NOT secure PTFE tube on a hose barb, since its too stiff for that.
only option is a compression fitting?
[Edited on 26-5-2021 by LuckyWinner]
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Dr.Bob
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If you use compression fittings, just link with stainless, that is what they (non-GL type) are designed for. There are entire pilot plants and
factories using SS and compression fittings. But PTFE tubing is not very strong for vacuum or pressure, so that will not do well for a flexible
connector, other than in a few places, mostly at very small scales. High pressure HPLC tubing is not PTFE, but can handle pressures. You seem
determined to build some sort of large equipment with cheap stuff, and that usually leads to fires, spills, and disasters. Having seen both good
and bad setups for scale, I can assure you that bad is not what you want.
For cooling liquids, there are silicone and fluoropolymers that are designed for cold temps, most tubes shatter at those temps, including PTFE.
For transfers between flasks, SS cannula or lines are best, but some PTFE can work, highly dependent on the materials and usage. You will get clogs
and leaks if you have not tested the system well, as that happens often in real life. PTFE is not good for vacuum at all, there are materials that
work well, but most are vacuum tubing types, and dependent on the solvents. We cannot design your pilot plant for you. If this is a work thing, get
training, if this a home or clandestine lab, hire Walter White. But your questions make it seem that you want to build a lab on a budget, which is
often a bad idea.
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LuckyWinner
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thanks thats very informative.
Im just a hobby chemist who is trying to improve tedious things.
usually I always get spills when adding liquids to a reaction or when something
asks for a slow addition over several hours its preferred to have some type of automation.
thats why I thought about using PTFE tubing for liquid transfers and
vacuum work... cause I had vacuum leaks in the past.
my flasks are mostly 100ml to 500ml.
Im trying to spend money to make everything more secure and reliable.
compression fittings are actually more expensive then just sliding a hose over the barbs.
overall you seem to agree compression fittings do work well if they are combined with the proper
tubing for their tasks.
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Dr.Bob
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Not trying to be a pain, but just want people to realize that for small scale work, you can do certain things, but when scaling up, it is critical to
be careful not to create a dangerous thing on a large scale.
The real issue is that no material is ideal for all chemicals, and in fact, many polymers that resist one thing well are terrible for others. EG,
Viton is great for chloronated solvents, but not very good for DMF, DMSO, and some other polar solvents. Some polymers are great for polar stuff,
but will swell badly in halogenated solvents. And THF can swell many polymers that handle most others fine. So if you are trying to do tubing
connections, you need to know the solvent and chemicals to pick the material. The only material I have found to work for almost everything was a
fluoropolymer made by Gore that could handle nearly every chemical I tried, but it cost more than any other material by 10 fold. I still have some
gasket material in that stuff, it will handle DCM, THF, DMSO, TFA, and many other very harsh chemicals. Never seen anything as good as that
before. It even made good septa, as it healed fro puncture very well. They sell it for as peristaltic tubing for solvents and acids. Its
amazing stuff, but costs $$$.
But for most organic cases glass and stainless steel are the best things. But not great for TFA and other acids.
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draculic acid69
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Maybe just learning some better lab techniques might be better for you. If you're having spills and leaks and problems transfering between flasks on a
500ml scale
then just using 50-100ml syringes with aquarium tubing attached is better than
trying to include PTFE tubing and ss fittings and complicating stuff even further.
At that size(500ml) I see it as very
unnecessary unless you are using air sensitive compounds or highly toxic stuff like
cyanides. Invest in some vac tubing from a car shop
and some aquarium tubing for condensers.you won't have leaks with this stuff.
[Edited on 29-5-2021 by draculic acid69]
[Edited on 29-5-2021 by draculic acid69]
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