I’ve written much about pressure lately, discussing subjects such as the upper reasonable limits in hydraulics to shockingly high-pressure fuel injection systems. Regarding current or conceivable limits, I see no reason we can’t exceed 7,000 bar with commercially available machinery, such as water jet cutters. For the sake of simplicity and lower digits, I’m expressing these numbers in bar. Sure, I could use something weird like gigapascals, but come on, let’s not get ridiculous. Just remember that 1 bar equates to 14.5 PSI.
Waterjet cutting differs from hydraulics in that it’s a loss-type system that also operates dynamically. The pressure is created similarly, but we don’t just exert pressure to alleviate boredom, although some epic YouTube channels prove me wrong. Hydrostatic pressure is an etymologically precise phrase, so I’ll use examples corresponding to what occurs when we, as firmly as possible, squeeze a liquid … or a non-liquid.
You might be surprised to learn that under certain conditions, you can initiate adiabatic solidification of water not much higher than 10,000 bar. In plain terms, liquid water crystalizes and forms ice when pressure is high enough. Trying to make Ice IV cubes for your scotch won’t work since releasing pressure on the H2O immediately results in liquification again.
Going higher up the pressure scale, other weird and unpredictable changes occur with everyday matter. Even fluffy and invisible molecules such as oxygen become colourful cousins of their former selves. It’s not so challenging to create cryogenically frigid oxygen, which is a pale blue liquid. But have you ever seen red epsilon oxygen when you pressurize the element to 100,000 bar? Of course not, don’t be ridiculous. It’s even less likely that you’ve seen oxygen pressurized to a million bar where it starts to conduct electricity.
Above a million bar, matter starts to break down as we know it. The electromatic force keeping those nuclei and electrons safety miles apart (seriously, if the nucleus were a ping-pong ball, the electron would be a kilometer away) cannot cope with the external forces. Usually, solid and opaque materials may become transparent as electrons no longer assist in reflectivity.
The effects of mega-high pressure also depend on the compound you squeeze, and it would come as no surprise that diamonds and osmium need much higher pressure before physical changes compared to helium or neon. There is easily over a million bar in the Earth’s core, yet molten iron still identifies as molten iron.
If we could plug a pressure transducer into our local star, our digital display now reads over a hundred billion bar. At these incomprehensible pressures, the strong nuclear force in a hydrogen atom’s nucleus can no longer resist the pressure, and the atoms fuse to make helium. If we continue to squeeze, our understanding of matter and pressure starts to break down entirely. When matter is squeezed into a singularity, it is no longer recognizable matter and entirely undefinable regarding pressure.
None of this matters concerning hydraulics. There will never (and you can quote me) be a time when hydraulics will be measured in ridiculous gigapascals. There’s simply no reason to design a 0.01 in. bore cylinder capable of 5,000 pounds of force, as cool as that may sound.
Filed Under: Engineering Basics, News