Pics! Pressure cooker arrives and something else.

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Kaido

Elite Member & Kitchen Overlord
Feb 14, 2004
48,704
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I mean, searing your face off

So, no machine is perfect. I have read several reports of EPC failures (electronic pressure cookers). This one was pretty awful:


This quote in particular:

'I had made the exact same soup before, cooking with the kids. Everybody is by the island around and Caroline wanted to come help me. The soup is done. It beeps it's done. We manually vent it and steam comes out telling you that it is un-pressurizing,' Mary said. 'The valve float drops, and we go to open it and put the kale in. We were just going to add kale. And it exploded. Completely exploded.' 'The sound was horrible. A true explosion. The lid flew somewhere — I don't even know where — and every bit, every bit of the soup came out of the pot and was in our kitchen. On the ceiling, on the floor. All the walls were covered,' she said.

Two things:

1. You never know 100% for sure how any machine will work in practice, no matter how well-designed
2. You never know if you're getting 100% of the truth in a news story

In this case:

1. She said she has used the Instant Pot before
2. And had made that particular soup before
3. She manually vented it, so that the steam came out
4. The float valve dropped, which indicates that the pressure is released
5. Then the soup exploded & the lid flew off

This is a tricky one because:

1. It sounds like the user is extremely familiar with the machine, both with the process & terminology
2. But, I don't know how the soup could have exploded if the float valve dropped, because the valve can't drop if the pressure isn't released

Maybe the machine was over-filled. Maybe a bit of food got stuck in the float valve & it only partially dropped...the tests in the article above did indicate that it was possible, sometimes, to twist off the lid while pressurized, despite all of the safety features. I've tried to wiggle mine off while pressurized before & it wouldn't budge. I just don't know how the lid would have exploded off if the pressure was vented. The float valve is literally a little hole in the lid that only drops once the pressure is released, because it's held up by pressure...so why would the machine have exploded if the valve dropped? I don't imagine you'd encounter an explosion at room pressure, even if the liquid was boiling in there.

The valve is held in place by the pressure, so if it dropped & the lid was able to be rotated, then it should have been room pressure. Possibly something got stuck in it, possibly the machine was over-filled, possibly the safety mechanism failed & allowed for lid rotation on a partially-dropped float valve. I'd really like to see an analysis on this, because there are millions of electronic pressure cookers out in the world today. This article has a bit more information on the news team test that tried to open the pots under pressure:


They didn't elaborate on their testing procedure (using foamy foods? over-filling? normal operation or purposely setting the machine up for failure?). I think common sense would be to not try to twist off the lid when it's under pressure, but in the case from the link, they said the float valve had dropped & that they had made the exact same soup before, so they apparently did everything properly. I'd like to know exactly what circumstances led to that behavior, for safety reasons! I feel really bad for the girl & her family.

1DYfMo8.jpg
 
Feb 4, 2009
35,245
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10 psi x 100 inches squared = 1000 lbs of force.

Picture looks like a 14” pot, that around 625 square inches (I think my geometry skills aren’t so good)
Per google 15 pounds per square inch is normal high pressure in a pot, that’s like 10,000 pounds of forces
 

Hayabusa Rider

Admin Emeritus & Elite Member
Jan 26, 2000
50,879
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Perhaps I should have said "safe when properly used" :D

Nothing is stupid proof.

So I wonder what to do next? No, I'm not doing something dangerous :p

Maybe I'll make some rolls and try pulled pork.
 
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Reactions: pcgeek11
Feb 4, 2009
35,245
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Perhaps I should have said "safe when properly used" :D

Nothing is stupid proof.

So I wonder what to do next? No, I'm not doing something dangerous :p

Maybe I'll make some rolls and try pulled pork.

Stew chicken or beef your choice.
Post a damn picture too when it’s complete
 

Hayabusa Rider

Admin Emeritus & Elite Member
Jan 26, 2000
50,879
4,266
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Before



before - Copy.jpg


After, which I didn't plate with food styling, etc

20191104_093414 - Copy.jpg

What I learned (or think I have TBD) is that for a similar dish I ought to subtract about 5 minutes or so from expected time to cook. There's more variation with pressure cooking than with something like sous vide, or perhaps better stated, a different learning curve which is for me part of the craft.

Next- See that container at about 2 o'clock? That's my sourdough starter and as my wife has taken a distinct liking for this formulation, I'm going to make a loaf in a bread pan which I have not done before. I've only baked this either with traditional techniques of batard etc or in a cast iron dutch oven. I'll have to think about how to adjust temp and time for a different technique and loaf shape.
 

Paperdoc

Platinum Member
Aug 17, 2006
2,359
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The way we use the term "pressure" for these things is a little deceptive and can cause confusion. What we usually mean is better lebelled "psig", meaning "pounds per square inch by gauge". And that ALSO implies that we mean "by gauge, but measured ABOVE the normal atmospheric air pressure. Since normal air pressure is 14.7 pounds per square inch above a perfect vacuum (gauge readin is zero), "15 psi" really means 29.7 psi above a perfect vacuum. Or, another phrase used would be 29.7 psia, for "pounds per square inch absolute". So a pressure cooker operating at "⅔ atmosphere" really is operating at 1⅔ atmospheres absolute pressure.

We have a very old cast aluminum pressure cooker that is very reliable and safe. It has a solid lid with about 16 wide "teeth" (small flanges) around its edge that twist-lock under matching flanges in the pot top edge, with a rubber sealing gasket at the interface. It has two simple devices to limit pressure. At top centre of the lid is a small vertical pipe about 1" tall with a centre hole maybe 1/8" diameter.It comes with a small cast round weight (with insulating Bakelite handle) that has recessed into its bottom centre a rounded cone. In operation this weight fits its cone into the top of the vent pipe, and the weight of that item is how the pressure in the pot is kept to design spec, since excess steam simply raises that weight slightly so the steam can escape through the small gap created between vent pipe and that weight's cone. Higher steam pressure merely increases that small gap to release steam faster. As additional safety, there is a small hole about 3/8" diameter bored through the top. Fitted into that is a rubber grommet and a small metal mushroom just under 1/4" diameter. If internal pressure ever gets too high, that entire mushroom and grommet will burst out of the hole, producing a 3/8" diameter pressure relief hole. Very simple and reliable decvices. The only thing that can impedde their operation is if they get dirty and are allowed to build up deposits that prevent their release, so the user needs to keep the system clean. And that is just plain normal use of a kitchen pot!