Monday, August 26, 2013

Helium - A little bit of what you need to know as a balloon professional Part 2.

In Part 1 of this 2 part blog we looked at helium, and a little bit of what you need to know as a balloon professional, plus a brief introduction into costing.
However, for those of you who want to really understand how to calculate your helium costs for all balloon sizes then please read on, I hope that I have managed to explain this well?

Helium cylinders vary depending on it's size and the pressure (bar or PSI) that it is filled to, so knowing what you use is very important, without this information you wont be able to calculate your costs.

The world is divided by metric and imperial calculations, which has made this blog a little more complicated to write, so I have decided to show both, starting with metric, please scroll down for the imperial calculations.

METRIC Calculations:

The chart above shows us 3 cylinder sizes indicating each cylinder size codes, volume /cube metres = m3) and bar pressure, plus other information such as cylinder weight, height and diameter.
Gauge that shows bar readings only

 L size cylinder = 9 m3 (317 cu ft)
T size cylinder = 3.60 m3 (127 cu ft)
V size cylinder = 1.81 m3 (63 cu ft)

Maths was never my strong point so I am hoping that I can explain this so that you understand.

To work out how much helium your cylinder contains you need to do the following calculation.

Firstly, we need to know the capacity of our cylinder in litres, which is something that is not shown on the above chart. To find this out we take the volume which for the L Size Cylinder is 9 m3 x 1000 = 9000 now divide it by the bar pressure reading which is 200, which give us 45 litre.

Multiply the capacity in litres by the cylinder pressure (this is the bar pressure as indicated on your regulator) and then divide by 1000 to obtain the volume in cubic metres.

So lets say that we have a unused 45 litre cylinder (Size L) that reads 200 bar (full)

45 (capacity in litres) x 200 (bar pressure) = 9,000 ÷ 1000 = 9mhelium in the cylinder - which we already know.

Now, what if we have used some of the helium already and the bar reading says that we have only 50 bar pressure , the sum would look like this:

45 (capacity in litres) x 50 (bar pressure) = 2,250 ÷ 1000 = 2.25mhelium remaining in the cylinder.

So how can we use this information to tell us how many balloons we can inflate from this cylinder.

Qualatex give us all the information that we need to do this, they have produced 2 charts one for Latex and Chloroprene balloons and the other for Microfoil® balloons. There is a great downloadable helium chart just click here and keep it in an easy to find place on your computer so that you can calculate your helium costs easily.

This is a sample of the downloadable helium chart but as it's 5 pages long I have just shown you the first few lines!
As most of us use 11" balloons more than other sizes, I will use 11" balloons for my example.

So, looking at the chart under the heading Gas Capacity, it tells me that 11" latex balloons inflated to 11" takes 0.5 cu ft (cubic foot) or .015m3 cubic metres  of helium.

As we are working in metric measurements rather than imperial we need the second figure (cubic metres) that is in brackets on the chart to calculate how many 11" balloons we can inflate from our cylinder.

This was our first calculation

45 (capacity in litres) x 200 (bar pressure) = 9,000 ÷ 1000 = 9mhelium in the cylinder.

So, if we know that we have 9m3 of helium in our cylinder we can divide 9 by .015 =  600 therefore we have enough helium in our cylinder to inflate 600 11" latex balloons.

Now for our second calculation:

Now, what if we have used some of the helium already and the bar reading says that we have only 50 bar remaining, the sum would look like this:

45 (capacity in litres) x 50 (bar pressure) = 2500 ÷ 1000 = 2.25mhelium remaining in the cylinder.

So, we know that we now have 2.25mremaining in our cylinder we can divide 2.25 by .015 = 150 - therefore we have enough helium in our cylinder to inflate 150 11" latex balloons.

Let's see if you can work out how much helium is remain in these cylinders and how many 11" balloons can we inflate from the remaining gas?

Gauge 1
Gauge 1. Shows us a gauge that reads that there is 185 bar pressure remaining in the cylinder (RED numbers). The cylinder is a T Size cylinder which contain's 3.6mvolume, 3.6 x 1000 = 3600  divided by 200 = 18 which is the cylinders capacity in litres.

18 x 185 (bar) = 3330 divided by 1000 = 3.33mhelium remaining in the cylinder 3.33 divided by .015 = 222 - therefore we still have enough helium in our cylinder to inflate 222 11" latex balloons.

Gauge 2

Gauge 2. Shows us a gauge that reads that the cylinder has only 30 bar pressure remaining, once again the cylinder is a T size cylinder that when full contains 3.6m3 volume, which is equivalent to 18 litres.
18 x 30 = 540 divided by 1000 = 0.54 divided by .015 = 36 - therefore we only have enough helium in the cylinder to inflate 36 11" latex balloons.

Now let's use the same readings but this time let us see how many 16" Geo Donuts we can inflate from the remaining helium?

Firstly we need to know what the Gas capacity is for a 16" Geo Donut, and looking at the chart it tells me that it is 0.7 cu ft  or (.020m3).

So for gauge 1, we already know that there is 3.33mhelium in our cylinder. So this time we divide 3.33 by .020 = 166 - therefore we have enough helium to inflate 166 x 16" Geo Donuts.

Gauge 2, there is only 0.54mof helium in our cylinder, 0.54 divided by .020 = 27 - therefore there is only enough helium remaining in this cylinder to inflate 27 x 16" Geo Donut balloons.

Now we understand how to work out how many balloons you can expect to inflate from any cylinder...

So let's see how many of a range of balloons we can get out of a  3.6m3 cylinder.

We can calculate this ourselves using the information that we already have:

3.6 (volume) divided by the gas usage of each balloon will tell us how many balloons we can expect to get from that size cylinder.

3.6 ÷ .0141 = 255 - 11" latex
3.6 ÷ .2266 = 15 - 30" latex
3.6 ÷ .037 = 97 - 35" Crescent Moons

IMPERIAL Calculations

This time we work with the cubic footage of a cylinder rather than cubic meters.

So lets looks at the conversion between bar pressure and psi pressure.

1 bar = 14.50 pounds per square inch or psi
therefore 200 bar = 2900 psi

Gauge that shows both psi and bar readings

I have looked around the internet and see that helium cylinders come in many sizes in the US, and cannot find a cylinder chart like the one that I used in the metric example, so we will use some cylinder size examples that I found.

280 cu ft tank
242 cu ft tank
137 cu ft tank
110 cu ft tank
55 cu ft tank

I am not really sure what is the most common size used by balloon artists in the USA?

So let's start with the 280 cu ft tank that when full reads 2200 psi on the gauge, that is the outer numbers this time.

So this is quite a simple process, looking at the gas usage chart we see that an 11" balloon  requires 0.5 cu ft of gas to inflate it to 11".
280 (volume in Cu ft) divided by 0.5 = 560 - therefore we know that from this cylinder we can expect to be able to inflate 560 11" balloons.

If you were using a 137 cu ft tank the math would look like this:
137 divided by .50 = 274, therefore from this size cylinder we would expect to inflate 274 11" balloon.s

Now to work out how many balloons you can inflate from a partly used cylinder you need to know what the psi pressure was when the cylinder was delivered to you.

In the UK, cylinders are filled at 200 bar, 200 bar = 2900, however from what I understand in the US and in other countries they are not filled to such a high pressure so you will need to check, for this example we will use 2200 psi.

So the first thing we need to calculate is the psi per 11" balloon.

2200 divided by 560 = 3.93 psi per 11" balloon.

So check what your cylinder is reading, lets say 1500 psi as an example:

1500 divided by 3.93 = 381 - therefore it is telling us that we have enough helium in our cylinder to inflate 381 11" balloons.

Let's do the same again but this time with a different size balloon, let say a 16" balloons.

Firstly we need to know how much helium a 16" balloons takes, which looking at the chart tells me 1.5 cu ft (3 x more than an 11" balloon).

So if we are using a 280 cu ft tank, we divided 280 by 1.5 = 186 - therefore we can inflate 186 16" balloons from out 280 cu ft tank.

Now we need to work out the psi per 16" balloon.

2200 divided by 186 = 11.82 psi per 16" balloon

If our cylinder has 1500 psi remaining, we divide 1500 by 11.82 = 126 - we have enough helium left in our cylinder to inflate 126 16" balloons.

Here is also something else we need to consider:

PSI readings can vary when a cylinder is full, so they may not always read the same very time. Also keep in mind that temperature affects the pressure (higher temp = higher pressure , lower temp = lower pressure

As long as you have a helium usage chart (which I have created a link to in this blog, or you can find it in the Qualatex Everyday catalogues) and know how much each balloon size and type takes to inflate to it's correct size and the size of cylinder that you are working with, you should be able to work out how many balloons of each size you can inflate from your cylinder and as long as you know how much your helium costs you per cylinder then you can work out how much the helium cost is per balloon also.

Please remember if you are not using precision inflation equipment such as the Duplicator 2 or Dual Split Second Sizer which accurately measures the helium when you press the foot pedal (subject to the time v pressure setting),  these calculations can only ever be approximate as everyone's idea of an 11" balloon is slightly different, and some people let out a small amount of helium when using sizing boxes/ templates, which wastes helium and reduces the amount of balloons that you will be able to inflate from your cylinder.

I hope that this information helps some of you?

Happy Ballooning!


1 comment:

gurkirtan singh said...

I want to know can we check it in grams or in kg i just wsnt to know how much helium is in it in weigh