It’s interesting how science fiction oftimes misses (or ignores) the implications of its own technology.
I remember a novel pointing out that if a Starfleet vessels structural integrity field could protect a ship and crew from the forces and effects of jumping from essentially a standing start, to nearly lightspeed and then warping beyond in just a matter of a second or two, that the the ship at that moment should be more than impossibly “rigid” enough that punching the same ship right through a star should be pretty much a piece of cake…
In fact it would be the star, if anything, that came out worse for the encounter
I have a tool in my van called a bead cheater (cheetah maybe, cant remember) that is essentially a tank, filled with compressed air from my compressor with a huge lever valve on it to empty the contents of the tank instantly into a tyre to force it to seat the beads.
If i use it 4 or 5 times quickly the tank gets extremely and uncomfortably hot. It always concerns me, that if that fails or the safety valve doesnt trip and deflate it, that is going to be a bomb and shrapnel is going to explode at 120psi inside my van and me.
The problem i see with pressure cookers, is all of the above AND boiling hot water at whatever temperature it gets to in there is going to seriously ■■■■ someone up in a kitchen.
The blast.
The shrapnel
The boiling rain after
Then the added fun of cooked or cooking food entering the body through cuts and lacerations.
Its a horrendous thought. I always get the kids and the golden retriever out the blast zone
Is your bead blaster steel? If so, mild steel has a yield strength (pressure where permanent deformation occurs) of 36,000 psi. Even if it’s aluminum it’s yield strength is about~20,000 psi. It’s far more likely to have a brazed joint or a valve fail and go flying versus the whole sucker fail. If you’re worried, go get it hydro tested.
Pressure cookers unless you’re talking about some kind of purpose built IED, almost universally fail at the latching system (and its usually operator error I’d hazard). Even in the picture above the kettle is undistorted, and the lid while buried in the ceiling is also undamaged from what we can see. The odds of a pressure cooker failing in a manner that causes a primary fragmentation effect is very limited. Pressure cookers SHOULD only be getting up to about 15 psi of pressure over ambient, no where near what would be required to fragment steal or aluminum. Any modern pressure cooker has 2-3 different systems to vent pressure, and usually includes fusible plugs as a failsafe to prevent anything catastrophic from happening.
The main problem is the complacency of people becoming familiar with equipment and that’s when the big accidents happen … it’s always good to have a healthy sense of respect for any high pressure equipment
There’s one key difference to a compressed gas tank, though. When the pressure is relieved instantly (like when the lid isn’t properly secured), you have a lot of liquid that is suddenly above the boiling point and turns to steam. That is a lot of potential energy being released in a short time. You’d have to compress gas to insane pressure to get to the same energy density.
So based on some quick reading on superheated water vs super heated steam, there will be a minimal about of “flash” steam created. I’d recommend the following link Change of Water Properties with Temperature , and we’ll use the chart located here.
If my math at 0300 with 3 hours of sleep and 7 hours into my work day is correct:
4 quart pressure cooker full of water (worst case) is about 3.75 liters. At 1 bar of extra pressure in the cooker (2 bar total) the water will have 504 kj/kg of energy. For a total of 1892.6625. If that pressure cooker suddenly goes to ambient pressure, it takes 2675.43 kj/kg to convert water to steam. The heat energy stored in the water is enough to convert about .7 kg to water (about 3 cups) to steam.
EDIT: More math, if we bust out the ideal gas law we can solve for the pressure created. If we assume .7 l of water are now steam, and that the only space in the pressure cooker is space that liquid water occupied (.7 l volume), we can solve for PV=nRT. Water is ~18 grams/mol, so ~55.5 mols per kg. This works out to ~38.85 mols of water. Plug in our knows and solve and we get a pressure of ~24,974 psi.
Now for the pressure cooker to depressurize in the first place it has to crack open to the atmosphere which will result in a rapidly rising volume for the steam to vent to. So the traditional picture of the lid being buried in ceiling/wall makes sense as the initial peak pressure is going to be very high, but in milliseconds it will be ambient.
So with all that typed, I’d say a material failure resulting in fragmentation is exceedingly unlikely in any good condition pressure cooker. Not impossible with an aluminum one, and pretty much impossible in a good condition steel pressure cooker.
All the above calculations are the worst case. In actuality the pressure curve would probably have a significantly lower peak pressure.
Doing some quick googling, almost universally the injuries from pressure cooker failures seem to be from the contents being ejected on people causing burns rather than shrapnel from a materials failure.
This is why water injection on jet engines was a thing. I want to say steam expands 32:1 or 1600x normal density (I could be wrong on that, and probably am) so injecting water gave those turbojets a real boost.
