SplendidAcylation
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Vacuum desiccator implosion risk (and how much vacuum is a Buchner funnel designed for?)
Hi,
I have a rather large, glass vacuum desiccator;
I'm not sure the exact size as it is stored away at the moment, but I'd say maybe 40cm diameter, it is surprisingly heavy and the glass is thick.
It is missing the ground-glass adapter that inserts into the top, but otherwise it seems to be in perfect condition, I have never had any need to use
it before, although I did evacuate it once (a rubber stopper inserted into the ground-glass socket is sufficient) with no problems.
Anyway, I have finally encountered a situation where I need to use it (the small vacuum-sealer jars that I normally use as vacuum-desiccators are no
longer air-tight)
I thought nothing of the implosion risk initially, as these things are so heavy and made of thick-walled glass, but then I looked them up in an old
lab equipment catalog, and they are sold with an optional "cage" made of metal mesh to surround them.
The catalog doesn't say what the mesh cage is for (although a Google search revealed that my suspicions were correct; It is supposed to protect you in
case of implosion), and it doesn't say the desiccator must be used with the cage, it is sold as an optional extra.
So this is a bit confusing, to be selling a brand-new item with an optional extra that protects you against catastrophic failure, I don't feel too
confident in using my old desiccator without some form of protection. 
It also occurred to me that perhaps the cage is there to prevent anything hitting the desiccator that may cause it to implode.
Television cathode-ray tubes have a vacuum inside, and they never implode as far as I know, so is it really a possibility that a desiccator, with
similarly thick glass, might implode?
Obviously the people selling them think the risk is significant enough to sell a cage for it!
So I guess the point of this thread is:
Why exactly do they sell cages for desiccators, and, knowing that, would it be mad to evacuate one without a cage, especially a rather large one,
would that be something you would be nervous about?
I guess I could wrap it up in blankets or something.
Oh, and another related question;
I have a porcelain Buchner funnel (~120mm) that I use for vacuum filtration, quite often if I am filtering something that takes a long time to filter,
I will pull a high vacuum and leave it, with the pump off, to filter.
It occurred to me lately that, with a high vacuum, the force pressing down upon the flat perforated porcelain surface is massive, especially since it
is a fairly big funnel.
It has withstood it so far, but would you say this is a bad idea?
Are these funnels designed to have 1 ATM between one side and the other?
Thanks in advance for reading this, rather badly constructed, post.
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Deathunter88
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You're fine and overthinking it, its not going to implode unless you drop something heavy onto it. If it makes you feel better, an effective
alternative to a cage is to wrap it with several strips of electrical tape/duct tape in a grid pattern.
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SplendidAcylation
Hazard to Self
Posts: 66
Registered: 28-10-2018
Location: Starving in some deep mystery
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Mood: More self-doubting than ever
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Quote: Originally posted by Deathunter88  | | You're fine and overthinking it, its not going to implode unless you drop something heavy onto it. If it makes you feel better, an effective
alternative to a cage is to wrap it with several strips of electrical tape/duct tape in a grid pattern. |
Thanks for the reply.
I have retrieved the desiccator, and evacuated it to a 20% vacuum, and it is air-tight, however it appears to have some suspicious chips/scratches on
the base; There are a few scratches that appear to be superficial but yet they look quite deep due to the reflection/refraction in the glass, so it is
hard to tell whether or not they are actually cracks that go right the way through.
Also, how does one tell whether a desiccator is a vacuum one, or an atmospheric pressure one?
They look similar/identical, is it that the bases of both types are identical, and only the lids are different, i.e. the vacuum one has a socket for a
vacuum line, or are the bases made differently?
I'm not sure the desiccator I'm using belongs to the lid I'm using, so I was also worried that maybe the base part might not be thick enough for
vacuum.
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