1000psi, how many balloons?

Mar 11, 2023

From: BALLOONAIR@aol.com
Date: Tue, 22 Jun 1999 03:32:08 EDT
Subject: Re: 1000psi, how many balloons?
To: balloondeco@balloonhq.com

In a message dated 6/18/99 6:07:24 PM Eastern Daylight Time, 
balloondeco-d-request@balloonhq.com writes:

<< If my tank reads a bit over 1000psi, how many 11 inch balloons can I fill 
up?  I know how many the whole tank fills up, but I don't know how to 
calculate it after some of the tank has been used.  Each balloon will hold 
about .5cu ft. >>

Very simple.  According to both my helium distributor and a PhD chemist 
friend of mine, it is a direct proportional relation between the pressure and 
the volume in the tank. In other words, when the pressure is half of what it 
started out being, the volume of gas is also half.  If your tank starts out 
at, say, 2000 psi, and that is, say, 292 cubic feet, then when it hits 1000 
psi you have half of that, or 146 cubic feet, which will do approximately 292 
Of course, in reality all the numbers are probably approximate.  Your gauge 
is probably not extremely accurate, and depending on how full they really 
filled it, and what temperature it is at, it is probably starting out at 
about 2200 to 2500 psi.  Remember, this is the pressure, not the volume of 
the tank.  A smaller tank at 2200 psi will have less gas, let's say it has 
100 cu. ft. @ 2000psi. When it is down to 1000 cu. ft. it also has half it's 
original gas, so it has about 50 cu. ft.  (In my mind I tend to use round 
numbers, so if I start with a 110 cu. ft. tank at 2200 psi, I'm thinking to 
myself that there's 100 cu.ft. @ 2000 psi, and that's 200 - 11" balloons, 
while a 292 cu.ft. tank I think of as 300 cu.ft. or 600 balloons)
Different distributors have different names for the sizes of tanks they 
carry.  I've heard of T-tanks, K-tanks.  292's, Quite frankly I haven't spent 
the time figuring out which is which.  I prefer to know how much gas is in 
the tank, in cubic feet.  This is known as "minding your P's and Cubes".
Remember to do your math, or at least think about its implications.  You 
should know that a 9" balloon holds about .29 cu.ft. while an 11" balloon 
holds about .5 cu.ft.  The implications of this are:  if you add 1" all the 
way around a 9" balloon (making it 11" in diameter) you nearly double it's 
volume.  This means that a slight variation in size when you're inflating can 
result in a tremendous difference in the number of balloons you're getting 
from your tanks.
I didn't mean to go off on tangents again, but there I go.  Anyway, assuming 
you are inflating all your balloons to the same size, and the temperature 
doesn't vary much, then your regulator gauge is a straight measure of what's 
left in the tank.

     O~     Danny Magowan
O~     : )  Balloon AffAIRs
  O~        Syracuse NY