Re: Helium in a tank?

Steve G8KHW / AJ4XE

You can get a good estimate of the purity of a gas by calculating the lift per unit volume. The typical "balloon helium" we get here in the UK is about 95-97% pure (the remaining 3 - 5% assumed to be air).  The lift per unit volume of balloon helium here is quite close to 1.0Kg/cu m (a rather lucky alignment).  If I have done my math right that's also almost exactly 1.0oz per cu ft.

If you know the weight of the balloon, the measured neck lift, and how much gas should have been in the tank you can calculate the lift per unit volume.


On 20/07/2020 01:56, Larry wrote:
My payload went up at a slower rate that I had forecasted last time and I know I just got kind of lazy and sloppy.  But even with me adding weight to the payload and not accounting for it the helium should have caused the milk jug to go neutrally buoyant with the amount of gas that I got from the burst calculator.  We ended up emptying the bottle into the balloon which should have been 19 cu ft more than required.  I am guessing the burst calculator was correct.  Is there any reason for me to doubt the amount of helium in the tank as long as I verify the pressure is correct?  Should I ask the welding supply shop about the purity of their helium?

I am trying to be more careful this time



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