It may seem unlikely to the ignorant, but it's a sure thing to anyone who understands diffusion, you gwt this more with thin-walled containers like baloons than with thick ones like tanks.
I'm pretty sure fuel gas tanks are at lower than ignition pressure, else you'd have to purge the line before puting gas into the line, so in the absense of an ignition source there's no explosion risk.
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The surface area / volume ratio of a blimp is pretty large, and you need at least a couple of percent oxygen before you can have an explosion, iirc. That'll have an easily measurable effect on buoyancy, because air is about 15 times denser than hydrogen.
Also the H2 diffusion rate will be much higher than that of air--it's a very very small molecule and moves much faster at a given temperature.
One would probably want to circulate the hydrogen and pass it over some hot platinum to make the oxygen react safely.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
There are good explosive-gas detectors (I did one once) that could be seeded around a dirigible. Even gas analysis in the bags wouldn't be difficult.
We have a nitrogen generation system for our reflow oven, and I was concerned about a tank leaking and purging the room of oxygen. Turns out that the room volume is big enough it's not a hazard. I did find affordable O2 detectors with alarms, for this same hazard. Our new facility will probably have a smaller room for the pnp-reflow stuff, so I may include some detectors.
The surface area is the big problem with gas-lift aircraft. They are slow, hard to aim, and dangerous in wind.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
The safety problem with hydrogen filled airships isn't what happens when the flotations cells are intact, but rather what might happen after the airship's structural integrity had been compromised.
The Hindenburg was hit by lightning, and a tornado could do an even more drastic job.
An ill-place downdraft can force an airship into solid ground. If it started out full of hydrogen, you wouldn't want to be all that close to ground zero.
-- Bill Sloman, Sydney
There was never any suggestion that it was hit by lightning. It had flown through a rain storm (without thunder) shortly before arrival and the side of the ship facing the sun had dried out. The possibility is that the metallic-painted canvas panels on the dry side of the ship had become charged and flashed-over to the frame when they dropped the mooring hawser and earthed the frame.
The ship was well-built with careful arrangements of ducting to conduct any released hydrogen to vents on the top of the ship, so that it could not mix with air until it was outside and free to rise. The hull was well-ventilated so that any minor escapes of hydrogen were rapidly diluted by the airstream between the gas bags and the outer envelope.
When the ship was hovering ready to land, there would have been no air stream through the hull, so it was vulnerable to hydrogen accumulations inside the top of the envelope. The evidence from surviving crew members suggests that the fire began between two gas bags at the top of the hull near the stern, which would have been the point of highest risk.
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