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The Race to Seal Helium HDDs (2021)

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Re: The Race to Seal Helium HDDs (2021)

#71

Post by Enginerrrd »

kbelder wrote: post #58

What would happen if you had a rigid structure that helium could permeate, but nothing larger could, and then filled it up with helium and waited? Would most of the helium exit, until it was balanced with just the partial pressure of helium in the atmosphere? That would be nearly a vacuum, wouldn't it?

I don't think so.

Ignoring the fact that what you're describing sounds suspiciously like a Maxwell's demon, I think the equilibrium would be at a higher pressure because helium escaping against an overall pressure gradient would be doing work.

In essence, at the boundary I think the rate at which helium escapes would not simply be proportional to the gradient created by the internal pressure and the exterior partial pressure, but I think would include a term involving the whole exterior pressure.

Re: The Race to Seal Helium HDDs (2021)

#72

Post by ndiddy »

throwaway81523 wrote: post #41

Are HDD's a significant consumer of the world's helium, in the scheme of things? I had thought helium was used only in a few bleeding edge drives, and they went to normal air as the tech matured.

Helium drives are basically standard for enterprise hard drives now. The reduced drag force allows for using thinner drive platters (helium drives can hold up to 10 platters, while air-filled drives can only hold up to 6 platters) which boosts capacity. Helium drives also use less power, run cooler, and the helium gas helps to absorb vibrations that can cause wear and tear (useful in enterprise settings where you have 45 or more drives in a 4U chassis).

Re: The Race to Seal Helium HDDs (2021)

#73

Post by thereisnospork »

kbelder wrote: post #58

What would happen if you had a rigid structure that helium could permeate, but nothing larger could, and then filled it up with helium and waited? Would most of the helium exit, until it was balanced with just the partial pressure of helium in the atmosphere? That would be nearly a vacuum, wouldn't it?

Internal pressure would equilibrate to the partial pressure of helium in the atmosphere, presuming all other species can be assumed to have zero permeability. Osmotic pressure/semipermeable membranes is the analogous liquid system.

Re: The Race to Seal Helium HDDs (2021)

#74

Post by alexey-salmin »

jayd16 wrote: post #66
kbelder wrote: post #58

What would happen if you had a rigid structure that helium could permeate, but nothing larger could, and then filled it up with helium and waited? Would most of the helium exit, until it was balanced with just the partial pressure of helium in the atmosphere? That would be nearly a vacuum, wouldn't it?

Pretty sure it would simply equalize to the external pressure. Consider it another way. If you have such a device with a vacuum inside, would it not pull in the external helium over time to reduce the vacuum?

> Pretty sure it would simply equalize to the external pressure.

External partial pressure of helium which is extremely low.

> Consider it another way. If you have such a device with a vacuum inside, would it not pull in the external helium over time to reduce the vacuum?

It would, but only until the partial pressure of helium inside is equal to the partial pressure of helium outside (assuming the membrane is permeable only to helium). After that point the same amount of helium will traverse both ways, establishing the equilibrium.

Re: The Race to Seal Helium HDDs (2021)

#75

Post by huppeldepup »

kbelder wrote: post #58

What would happen if you had a rigid structure that helium could permeate, but nothing larger could, and then filled it up with helium and waited? Would most of the helium exit, until it was balanced with just the partial pressure of helium in the atmosphere? That would be nearly a vacuum, wouldn't it?

Cody’s lab on youtube did a video on this, with balloons

Re: The Race to Seal Helium HDDs (2021)

#76

Post by alexey-salmin »

Enginerrrd wrote: post #71
kbelder wrote: post #58

What would happen if you had a rigid structure that helium could permeate, but nothing larger could, and then filled it up with helium and waited? Would most of the helium exit, until it was balanced with just the partial pressure of helium in the atmosphere? That would be nearly a vacuum, wouldn't it?

I don't think so. Ignoring the fact that what you're describing sounds suspiciously like a Maxwell's demon, I think the equilibrium would be at a higher pressure because helium escaping against an overall pressure gradient would be doing work. In essence, at the boundary I think the rate at which helium escapes would not simply be proportional to the gradient created by the internal pressure and the exterior partial…

It's not a Maxwell daemon, it's just a device for which nothing but helium exists. In the ideal gas model it would indeed create almost vacuum but the second law of thermodynamics is not violated since the process is symmetrical. Pressure of helium outside is also almost zero.

Re: The Race to Seal Helium HDDs (2021)

#77

Post by buro9 »

I received a HDD only last year where the SMART status immediately reported a failure for status 22, and it led me to https://www.backblaze.com/blog/smart-22-is-a-gas-gas-gas/

It's an immediate "return the drive" scenario, as something happened between factory and the SMART test and the drive is no longer within spec.

Thankfully an easy returns and replacement process, but an eye opener too, I hadn't heard of SMART 22 prior to this.

Re: The Race to Seal Helium HDDs (2021)

#78

Post by kragen »

cainxinth wrote: post #47

The solution: - They moved all the casing openings to the top of the drive and used a thin metal foil as a second cover. - They adapted laser welding techniques from the satellite industry to seal the foil to the casing without damaging components with excess heat. - They found an aluminum alloy used in aerospace that could withstand the laser welding without cracking. - To get electricity and data in and out without…

thanks, this is great!

to add a bit more context:

- laser welding has been in use since 01967 and is used not only for satellites but also for auto body panels, pacemakers, 3-d printing (sls/slm), batteries, etc.

- glass-metal feedthroughs are used in incandescent lightbulbs, fluorescent tubes, neon tubes, and vacuum tubes (including crts and electron microscopes), because in all cases you need a vacuum-tight seal around the wires that lead into the tube. special glass formulations with custom thermal expansion coefficients have been available for this purpose since at least the 01950s. the refrigerator guys may have the cheapest ones but they didn't invent them

- nickel plating is the conventional way to make steel solderable with electronic solders since forever. it's also used, for example, to make battery tabs solderable. i think this goes back to the 19th century

that is, the design process the article depicts is considerably less daringly original than the author makes it sound. the people who made it work deserve a lot of praise, but because manufacturing is hard and they had to solve a lot of hard problems, not because they're geniuses doing totally unprecedented things with brilliant strokes of insight. the author makes it sound like that presumably because she doesn't know anything about the problem space

if you like that kind of thing, you'll probably enjoy dalibor farný's youtube channel where he documents his process of solving the problems of his nixie tube factory (including vacuum-tight glass-metal seals) in a czech castle https://www.youtube.com/@daliborfarny/videos

Re: The Race to Seal Helium HDDs (2021)

#79

Post by kragen »

yummypaint wrote: post #45
vertnerd wrote: post #19

"Helium is notoriously difficult to contain. Its atoms are some of the tiniest in the universe." It's a good article, and I learned a lot, but every so often it reads like something an 8th grader would write the night before their paper is due.

Yeah i don't get the unnecessary vagueness. They are the smallest atoms. It's like they are afraid of accidentally educating the reader.

this terror of accidentally including a fact is one of the worst of many plagues afflicting journalism today

Re: The Race to Seal Helium HDDs (2021)

#80

Post by addaon »

adrian_b wrote: post #52
bjoli wrote: post #50

Earlier quoted context omitted.

And here I was, thinking helium was the tiniest atom unless you start counting cations which has it beaten by Li+ and He+

Yes, at the same number of electrons, the heavier atoms have a smaller volume, i.e. they are tinier, because their greater nuclear charge attracts the electrons closer to the nucleus. Li+, Be++, B+++ are tinier than He, but they are ions, not neutral atoms. Neutral Li, Be, B are bigger than He, because they have an additional electron layer. Both neutral H and H- are bigger than He, because their one or two electrons…

Muonic atoms are many, many times smaller, and neutral — so small that the reduction in atomic radius by substituting a muon for an electron can catalyze fusion. Purely muon helium would be the smallest such. (Tauons can’t form atoms as their decay time is shorter by orders of magnitude than would be needed.)
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