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Imagine a vacuum flask-like container. If we filled the main compartment with helium and the vacuum compartment with high-pressure gas would helium still escape?

Let's ignore the leakage from the valve, the valve seating, o-rings, bushings, etc.

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    $\begingroup$ Are you asking if helium can diffuse through solid glass or stainless thermos bottles ? $\endgroup$ Feb 27 at 1:29
  • $\begingroup$ Please give details of your questions $\endgroup$
    – Muhammad
    Feb 27 at 7:58
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Partial answer , helium will not diffuse through steel . Long ago I did stress rupture tests of low alloy steel at 800 F . Tests were done to evaluate if hydrogen had an affect on rupture strength. The test specimens were thin tubes such as 0.012" ( about 0.3 mm) wall thickness. The stress was provided by 1800 psi gas pressure . Hydrogen in some and helium in the controls. When a tube was filled with helium , and the valve closed , pressure was held for roughly a month of test duration , so no helium passed through the steel. Hydrogen diffuses through steel easily so the tubes with hydrogen had a constant supply of 1800 psi. Hydrogen escaped through a bubbler and was vented ; within a couple seconds of the hydrogen valves being opened , hydrogen started venting . So helium does not diffuse through steel at 800 F ,it is unlikely at ambient temperature.

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  • $\begingroup$ Thank you I didn't know that helium will not diffuse through steel. Do you know if the main compartment was filled with hydrogen and the outer compartment filled with gass that has higher pressure than hydrogen compartment woud it still diffuse? Im thinking maybe the pores in steel would be sealed by the gass not allowing hydrogen to diffuse? $\endgroup$
    – Lukas
    Feb 27 at 9:10
  • $\begingroup$ The outer chamber / protection tube was hydrogen at very close to one atmosphere . There are no pores in steel , the hydrogen moves through the lattice; faster at elevated temperatures . At ambient temperature the moving hydrogen causes hydrogen embrittlement ( also known by a dozen other names). At high temperatures the hydrogen diffusion is governed by the relative partial pressure of hydrogen , any other gas does not matter. $\endgroup$ Feb 27 at 16:47

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