The Home Machinist!

Stove top pressure cookers are always aluminum, why?

Being a long time livesteam fan, aluminum seems like the worst material for a pressure cooker, yet 99% of them are cast or forged aluminum.

Water, pressure, steam, salt, other corrosive spices and minerals, those all sound detrimental to a boiler, yet our grand mothers all have pressure cookers that are older than she is, they each have been through hundreds of super-fast heat pressure and cooling cycles, that would be considered excessive & abusive to any livesteamer, yet these things still look brand new.

(I know its sounds ridicules, as we are all steel and copper boiler thinkers, but just for the sake of this exercise, lets pretend like it sounds perfectly normal).

Why not 100% aluminum boilers, tubes, stays, all of it?

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Loco112

they only operate at 15 PSI. same as your car radiator. scuba tanks hole 3500 PSI but they are 1/2" thick and don't see any heat. pressure cookers will blow up if the safety valve sticks.

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Fred V
Pensacola, Fl.
home track:
http://www.waleswest.com

I'm pretty sure my mom's circa 1948 pressure cooker was stainless steel but our circa 1968 model is aluminum. I believe a big reason for aluminum vs SS is cost - and you couldn't get them in that cool avacado color that ours came in.

Okay,
A properly designed and welded aluminum boiler operated within the limits of its design, and (key part coming up),
being completely disassembled, cleaned, and dried inside and out after every run may just be fine.

As far as getting water to boil at 15 psi, haven't done the math. I do know you can get radiator water hell-hot to the point you are in serious danger if you remove the cap.

Then again, I have seen steam escaping around the pressure valve on my pressure cooker.

Lots to chew on here for the engineers in the bunch.

However, I go back to my initial statement. Scrub all of the beans out after every use and it very well may last a good while.

I would guess that they are made out of aluminum because of the weight. A cast iron or copper pressure cooker would weigh quite a bit, add to that the contents you are cooking and you have to be a pretty hefty granny to put that on the stove.


Phil

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My pressure cooker is stainless with an aluminum bottom bonded to the outside of the pressure vessel for heat distribution. Not overly heavy for it's size.

Rick

a pressure vessel raises the boiling point of water. the 15lb safety lets the water get to 250deg. before it boils. in our boilers the water is at 340deg. when it boils. in either case if the pressure is suddenly released all that water will instantly flash into steam. that is what your radiator is doing.

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Fred V
Pensacola, Fl.
home track:
http://www.waleswest.com

Leave water in your aluminum pressure cooker for a few days...it will be pitted and growing white cottage cheese. Pressure cookers last because they are washed and dried immediately after each use.

Keith

You can use cast Al for boilers:

http://www.stationroadsteam.com/archive/1995.htm

There you go...

Note: I am unsure as to the limits of the offer to deliver via Dak, and ensure you bury the parachute on recept !

James

Unlike steel, AL loses at least half it's strength as soon as you weld it. I don't think it matters what metal you make a boiler out of. With the right combination of chemicals, and time, any metal will corrode. Interesting discussion.

Eric

While true to a point, depending on the alloy, it can be restored by being given a full solution anneal, then allowed to age, or artificially aged.

Notwithstanding, aluminum wouldn't make for a very good boiler due to its inherent ability to return to the substance from which it came, aluminum oxide.

Harold

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Wise people talk because they have something to say. Fools talk because they have to say something.

You should have seen my Granny. A farm wife during the Depression, she did all the cooking and baking on a cast iron wood stove including all the canning needed for a family of eleven people, and everything else that needed to be done on a self-sufficient farm. She was stronger than some of the men. While she was the nicest granny in the world, she could have taken out a logger if needed.

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Greg Lewis
Eyeball Engineering — Home of non-interchangeable parts
Our motto: That looks about right.
Turning perfectly good metal into bits of useless scrap since 1983.