Sciencemadness Discussion Board - What shall I do with an old pressure cooker ?

What shall I do with an old pressure cooker ?

Sulaiman - 7-2-2016 at 04:36

Our pressure cooker was beginning to leak steam around the overpressure vent,
all seals can still be replaced, even though we have had it for >35 years.
(never changed seal ... old style Prestige brand)
Mainly due to it's age, I decided to replace the old aluminium cooker with a new stainless steel one.
Now available for chemistry ... a working aluminium pressure cooker.

I have used it as a steam generator to get some dH2O but I prefer glass,
I could use it as a vacuum chamber, or a very useful vacuum dessicator
any other ideas ?

This is the pressure cooker ... the condenser cooling was inadequate.

[Edited on 7-2-2016 by Sulaiman]

Herr Haber - 7-2-2016 at 09:35

I would have said a still, but you've obviously got that idea already.
Using it as a vacuum dessicator is... brilliant!
Sorry I cant give you any ideas. You on the other hand have given me a brilliant one !
Let's compare the price of a pressure cooker and a glass dessicator. Oh right ! Now where's my hand vacuum pump?
Thanks for giving me this wonderful idea, this could be a nice project. A little work on my least prefered pressure cooker and I'll have access to a few things I couldnt do so far!

Pumukli - 7-2-2016 at 10:24

Sounds interesting.
But afaik the local pressure cookers cook (boil water) at 112 C, which is 1.5 bar. They surely can whitstand this overpressure but I would be cautious evacuating them to a strong vacuum. (Which is close to -1 bar, which is almost (negative) double of the rated operating pressure (0.5 bar overpressure relative to normal air pressure at sea level). Was a bit hard to follow, wasn't it? :-)
Engineers, anyone?

Magpie - 7-2-2016 at 10:54

Quote: Originally posted by Pumukli

Sounds interesting.
But afaik the local pressure cookers cook (boil water) at 112 C, which is 1.5 bar. They surely can whitstand this overpressure but I would be cautious evacuating them to a strong vacuum. (Which is close to -1 bar, which is almost (negative) double of the rated operating pressure (0.5 bar overpressure relative to normal air pressure at sea level). Was a bit hard to follow, wasn't it? :-)
Engineers, anyone?

I pulled a full vacuum on my pressure cooker (4 qt size) as a test with no problems. I recently bought one at a garage sale specifically for use as a vacuum dryer. I haven't use it yet, however.

In the forum library is a book by Blangey & Fierz-David which gives a design for a lab vacuum dryer, FYI.

[Edited on 7-2-2016 by Magpie]

[Edited on 7-2-2016 by Magpie]

hissingnoise - 7-2-2016 at 12:25

Quote:

This is the pressure cooker ... the condenser cooling was inadequate.

You could try a PVC sleeve (sink waste pipe?) on the tubing, sealed with 2-hole stoppers for tubing and cooling water?

Sulaiman - 7-2-2016 at 23:08

a pvc water cooling jacket is a good idea
but I am planng for a few slow continuous 'processors'

. a small water still - low flow rate allowing simple air-cooling

T.B.D.
. a small Birkeland-Eyde type NO/NO2/HNO3 generator
. a modification for occasional O3 or SO3

[Edited on 8-2-2016 by Sulaiman]

careysub - 8-2-2016 at 06:50

Pressure cookers make great vacuum desiccators, I have one set aside for that purpose. Although the existing pressure release hole may be suitable for connecting tubing too, be aware that aluminum is very easy to drill and tap, and you can install any type of threaded connector to it.

If you want to seal the existing hole I suggest heating with a torch and applying solder.

Also, pvc pipe and copper tubing is a great condenser. All the hardware needed is readily available in your hardware store. A small aquarium pump and a bucket can supply cooling water of course. Use PVC cement to seal tube with caps.

Threaded taps in the PVC are the best connectors, but use silicone gasket compound from your auto store for heat proof sealing where necessary (and if not using threaded connectors). You don't actually have to use a threading tap on PVC, simply screwing the threaded attachment into an appropriately sized hole self-taps.

[Edited on 8-2-2016 by careysub]

Magpie - 8-2-2016 at 09:01

Quote: Originally posted by Sulaiman

. a small water still - low flow rate allowing simple air-cooling

Did you try blowing air past the coil with a fan? Or maybe find a discarded air conditioner radiator - ie, tubing with fins.

XeonTheMGPony - 8-2-2016 at 09:46

for all those wondering 1 atm = 14.5 psiA any thing metal will handle this with out issue if the side wall is over 2mm thick!, inside pressure geometry works against you, where as the negative pressure handling is more then sufficient.

Glass is a risk as it handles stresses poorly and when it fails it shatters Vs steel/alu, that simply bends.

pressure cookers have endless uses, I've used them as a vacuum cold trap befor too by building a coil inside of 1/4 copper and chilling to -40c.

A quality epoxy is more then good enough for repairing holes as well, solder will NOT adhere to aluminium, les it is specialized for that.

In refrigeration we used alumaweld, it is a brazing compound flux with a low MP alu solder. http://www.alumiweld.com/

Sulaiman - 8-2-2016 at 12:53

Quote: Originally posted by XeonTheMGPony

for all those wondering 1 atm = 14.5 psiA any thing metal will handle this with out issue if the side wall is over 2mm thick!, inside pressure geometry works against you, where as the negative pressure handling is more then sufficient.

Glass is a risk as it handles stresses poorly and when it fails it shatters Vs steel/alu, that simply bends.

2mm steel is not necessarily enough https://www.youtube.com/watch?v=ETdsuvi91VQ

and Geissler made his glass vacuum tubes from 1857 onwards

ok, two extremes, the tank is a little larger than my pressure cooker and I only guess >2mm steel
and Heinrich Geißler was an independent scientific glass blower
just two thoughts that popped to mind

careysub - 8-2-2016 at 14:26

Quote: Originally posted by XeonTheMGPony

A quality epoxy is more then good enough for repairing holes as well, solder will NOT adhere to aluminium, les it is specialized for that.

In refrigeration we used alumaweld, it is a brazing compound flux with a low MP alu solder. http://www.alumiweld.com/

Epoxy also has problem unless you choose the right one. Most epoxies soften at a low temperature (exceptions exist) and long-term aluminum bonding can be a problem unless the surface is etched first.

A massive glob of gasket compound might work, stuck to the bottom and extending though the hole.

Harbor Freight has the Alumiweld alloy also:
http://www.harborfreight.com/8-piece-low-temperature-aluminu...

XeonTheMGPony - 8-2-2016 at 18:44

Quote: Originally posted by Sulaiman

Quote: Originally posted by XeonTheMGPony

proper vacuum rated glas wear is fine

All so I doubt any one will try to use such a tank size as a descicator! it is a function of surface area (pie*R^2*L)*14.5 =psi force

Longer the tank the more the atmosphere has to work with, my comment was intended only for small vessels that we're talking about

So to clairify any house hold material that is both metal and around 2mm thick will most likely be of no issue.

Sulaiman - 14-2-2016 at 00:35

sorry to bump but I am going to use the pressure cooker today to get some more dH2O,
(despite my preference for glass, I feel more comfortable leaving the aluminium pot unattended than my only large glass flask)
very cold out so just two 1.2 m borosilicate tubes as a condenser,
I will use a red rubber bung in the larger 'pot' hole with 8mm glass tube through it, bent to fit the condenser tube, no fractionation.
So;
Is there any SIMPLE surface treatment of the aluminium that may improve the quality of the dH2O ?

(e.g. treatment with a strong acid/base/oxidiser/reducer possible, ptfe lining not practical)
My feed water is 'medium hard' meaning I always get some (presumed) calcium carbonate crud.
Or am I concerned over nothing ... in what form could aluminium come over in the water vapour anyway ?

One day I would like to set up a small continuous water still, along with arc/corona N2/NO/NO2/HNO3 and S/SO2/SO3/H2SO4 generators
(a little over-ambitious maybe, I tend to suffer from polyprojectitis)
but for now I just need more dH2O that will be pure enough for most uses, diluting and washing mainly.

subsecret - 14-2-2016 at 22:05

Put your electronics in it in case of an EMP strike. You never know. It'll look great on your nightstand.

Bot0nist - 15-2-2016 at 10:29

Pressure cookers are very convenient and readily available as a sort of autoclave, in a biological sterility sense. Petri dishes, and other culturing equitment, syringes and the like can be sterilized much faster in one, than in boilong water at 1 atm. They can sterile most endospores, and are also employed by the amateur mycological community for their ability to properly sterilize dense grains and other mycelium substrates. For instance, 'wild bird seed,' which is popular for its nutrient density and coarse, heterogeneous consistency. It cannot be properly sterilized by boiling or in the bag steaming methods, unlike grain flour or manure substrates.

unionised - 15-2-2016 at 12:47

Just as long as you don't take it to a marathon...

subsecret - 19-2-2016 at 20:59

@Bot0nist: I thought the purpose of an autoclave was to increase the pressure. I mean, I guess you could keep the steam in with it, but if you're only doing 1 atmosphere you may as well use a kitchen pot.

@unionised Too soon

Justin Blaise - 19-2-2016 at 21:10

@Sulaiman I wouldn't worry too much about distilling water out of glass vs. aluminum. If something in the water was to react with your aluminum vessel, the product would be non-volatile and you'd still get perfectly clean water coming over.

Bot0nist - 20-2-2016 at 08:22

Does a pressure cooker not rise to above 1 atm?
Not a crock pot.

"The standard cooking pressure of 15 psi above sea level pressure was determined by the United States Department of Agriculture in 1917. At this pressure, water boils at 121 °C (250 °F)"
https://en.m.wikipedia.org/wiki/Pressure_cooking

[Edited on 20-2-2016 by Bot0nist]

Continue to use it for cooking =)

abstfoundation - 29-2-2016 at 16:47

Build a sous vide. You will never have such perfectly cooked foods outside of the most expensive restaurants. =)

Jekyll - 1-3-2016 at 23:55

Quote: Originally posted by Bot0nist

Pressure cookers are very convenient and readily available as a sort of autoclave, in a biological sterility sense. Petri dishes, and other culturing equitment, syringes and the like can be sterilized much faster in one, than in boilong water at 1 atm. They can sterile most endospores, and are also employed by the amateur mycological community for their ability to properly sterilize dense grains and other mycelium substrates. For instance, 'wild bird seed,' which is popular for its nutrient density and coarse, heterogeneous consistency. It cannot be properly sterilized by boiling or in the bag steaming methods, unlike grain flour or manure substrates.

Word.

The big 40.5 quart All American pressure sterilizer is preferred by many amateur mycologists, nice for flasks of liquid media or jars or bags of solid media. A metal-to-metal seal and you can take the pressure up to 20 psi. Which is particularly nice when you live in the mountains like I do, one needs to add 0.5 psi to the 15 psi gauge for every 1,000 feet of elevation to obtain the 250 F. temperature.

Of course, there’s always some mad scientist mycologist who wants a double door autoclave. This one was originally used for salmon and seafood on the coast, that’s cold water piping along the top to cool down the cans after use.

[Edited on 2-3-2016 by Jekyll]

[Edited on 2-3-2016 by Jekyll]