Re: Helium in a tank?
Mark Conner N9XTN
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I think helium from virtually any industrial gas supplier, even if labeled "balloon grade", is at least 99% purity, and often balloon grade is 99.99%. Five nines is decent for most all industrial uses and six nines is towards laboratory grade. You can ask if you got balloon grade or industrial grade, might even say on the invoice. At Matheson (fka Linweld here), they put stickers on the balloon grade cylinders and the industrial grade ones aren't marked, but it's been several years since I got helium from them.
The small party balloon cylinders don't seem to have a fixed purity standard. I read once that they sometimes blend with ~20% oxygen so that people who want to make Donald Duck voices with it don't end up asphyxiating themselves. Don't bet your life on that though.
It's possible temperature effects might have affected your positive lift. Other errors in the overall system probably are larger than the effect of having two vs five nines helium purity, unless you're doing flights where you measure lift in a few grams instead of a few pounds.
73 de Mark N9XTN
On Sun, Jul 19, 2020 at 7:56 PM Larry <larry.phegley@...> wrote: