How do hydrogen car fuel tanks prevent hydrogen permeation through fill valves?

[chemisthypnos]

How do hydrogen powered cars prevent the permeation of hydrogen through the valve used to fill the car's tank with hydrogen? Is a regular check valve used or is the valve special in some way?

 

[russ_watters]

How do hydrogen powered cars prevent the permeation of hydrogen through the valve used to fill the car's tank with hydrogen? Is a regular check valve used or is the valve special in some way?

That's a design detail that may vary. I can tell you this though; my large neighborhood propane tanks use a type of Schrader valve using a ball bearing instead of a center post. It acts as a check valve, with the pressure and a spring popping it into place as soon as the fill hose is removed. I see no reason why this wouldn't work for H2...

...but these valves are not foolproof and a secondary manual ball valve would be a good idea...though it would also need it's own safety relief valve.

 

[chemisthypnos]

That is true for most compounds, but hydrogen is very hard to contain as it goes through the walls of most materials through permeation.

 

[Tolklein]

While I can't speak for valve manufactures, sensor manufactures plate their devices with gold or use other "super-alloys" (Elgiloy for example) to avoid the negative effects of hydrogen permeation.

https://www.yokogawa.com/us/library/resources/application-notes/hydrogen-permeation/
https://www.wika.us/upload/DS_IN0040_en_co_90765.pdf
http://blog.wika.com/applications/h...t-be-observed-when-using-the-medium-hydrogen/

 

[chemisthypnos]

Ok. Thanks everyone.