Author Topic: Draught testing challenge  (Read 1432 times)

Offline yrammy

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Re: Draught testing challenge
« Reply #25 on: July 13, 2021, 08:36:51 am »
We used joss sticks in Maypole inlet (outlet)  -

Offline oldfart

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Re: Draught testing challenge
« Reply #26 on: July 13, 2021, 09:11:48 am »
You could ask one of those nice ayatollahs in Iran for some uranium hexafluoride. Detection would be easy.

Offline aardgoose

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Re: Draught testing challenge
« Reply #27 on: July 13, 2021, 10:27:34 am »
Sadly UF6 is solid at cave temperatures.

Trained bats?

For the sniffer dog scenario, you could use a dog trained for detecting corpses, and place a dead body* in the upper entrance.

*Human or otherwise.

Online alanw

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Re: Draught testing challenge
« Reply #28 on: July 13, 2021, 11:51:28 am »
uranium hexafluoride

Only in UKCaving are you likely to get two references to uranium hexafluoride in two threads within 24 hours.

See my post yesterday https://ukcaving.com/board/index.php?topic=28277.0

and four pages later in Otto Frisch's autobiography:
"[Sir James Chadwick] had asked [ICI] about the possibility of producing uranium hexafluoride, the only known gaseous compound of uranium known to be stable enough to be put in a Clusius tube"

(A "Clusius tube" is the apparatus Otto Frisch was using for separating isotopes using "heat and gravity")

Offline braveduck

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Re: Draught testing challenge
« Reply #29 on: July 13, 2021, 12:18:46 pm »
Still think Old Spice aftershave is the safest bet ,should be able to smell
it 10 miles away !  :lol:

Offline pwhole

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Re: Draught testing challenge
« Reply #30 on: July 13, 2021, 12:23:33 pm »
There's always the great smell of Brut. Then you just need a 'dolly bird' as a detector. 'Splash it all over, eh Henry?!' :)


Offline paul

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Re: Draught testing challenge
« Reply #31 on: July 13, 2021, 01:25:31 pm »
Global Moderator Comment Let's try an keep on topic please
I'm not a complete idiot: some parts are missing!

Offline crickleymal

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Re: Draught testing challenge
« Reply #32 on: July 13, 2021, 05:16:53 pm »
It's also heavier than air and will settle in any hollows...
sorry but that is incorrect.  Badino at https://caves.org/pub/journal/PDF/v71/cave-71-01-100.pdf provides a readable (not much maths) explanation of why not.  Alternatively if SF6 (molecular weight 146) did settle out, then we would all be dead because xenon (molecular weight 131) in the air would also settle out.  The key mitigating factors are drafts and thermal currents which mix the air sufficiently to stop such stratification. 

The simple explanation for CO2 apparently ponding is because it is being evolved in the zone and is not be diffused away fast enough.  The same would be true around the release point of any gas.  But release volume dependent, beyond a certain distance only dilution will occur.

But when you extract it from a waveguide into a bin bag ( as we used to do) you could see that the bin bag was heavier than air. It reacted very differently to a bin bag full of air or one full of methane. Plus the machine manufacturers issue warnings about working in pits under the machines because of the dangers of SF6 pooling in such spaces.
Malc
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all words to describe me.

 

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