Rank: Guest

Posted By Graham Baldwin
Does anyone know how to calculate the maximum capacity of a air cylinder?
At present we use 9 litre cylinders pressurised to 200 bar, we are considering changing to 6 litre cylinders pressurised to 300 bar.
I'm aware of the equation used to calculate the working duration but I don't have any explaination of how the figure for the maximum capacity of the cylinder is calculated.
Thanks in anticipation
Graham




Rank: Guest

Posted By Jay Joshi
The general gas law can be used
P1V1/T1 =P2V2/T2
and as the temperature is usually constant(please check), then P1V1=P2V2, where P1 initial pressure, V1 is initial volume, P2 is final pressure and V2 is final volume. In your case, P1=300bar, V1= 6 litres, P2= 1 bar, V2 is the full gas volume at 1 bar. (I am assuming that 1 bar is 1 atmospherewhich is strictly not the caseyou will have to get the actual conversion factor).
V2=300 x 6/1=1800 litres
You may need to check the minimum operating pressure of the BA and recalculate accordingly




Rank: Guest

Posted By Stuart Nagle
Go to the cylinder manufacturers.
Cylinders are tested (See HSAW Act 1974) as are all bits of equipment supplied for use at work.
The pressure of a cylinder will be that determined by it's construction and allowing a safety margin.
The calculus explained by J Joshi is fine, but only arrives at the same answer as calculating the cylinder contents in compressed litres in relationship to the bar pressure.
This could be more easily done by saying:
300 bar X 6 (litres)(cylinder capacity) x 2 = 1800 !!
I dont really understand why you need this information if changing sets (or cylinders on the sets), as the main area of importance surely, is the duration of the set itself.
Will the new cylinder provide the longer duration you are after, if so, whats the problem. If weight is a factor (using steel cylinders) try using carbon fibre wrapped cylinders (lighter  but not a lot).
Please explain the reasons why you want this information ?
stuart nagle




Rank: Guest

Posted By Graham Baldwin
Stuart
We need the figure in order to calculate the working duration of the sets. The calcualtor we use needs this figure. From the infrmation Jay and yourself have provided the working duration of the two cylinders is identical. Our reason for changing is just a purchasing decision to do with different suppliers.
On a point of interest our calculator for working duration is a graduated slide rule with two sets of figures on for 1800 litre cylinders and one for 2250 litre cylinders. Has anyone ever come across a 2250 litre cylinder? Using the calculation it would appear to be a 9 litre cylinder charged to 250 bar did this used to be a common charging pressure I have only come across 200 or 300 bar charging.
Regards
Graham




Rank: Guest

Posted By Jay Joshi
The reason for giving the calculus was that you probably cannot consider the final pressure as 1 baralthough a simple calculation of volume x pressure will give the available volume at 1 bar.
As the BA will have resistance to flow etc, the BA supplier will give information on the minimum supply cylinder pressure below which the set will not work properly etc etc. Then, you will have to use that pressure value as the final pressure to calculte the volume




Rank: Guest

Posted By Stuart Nagle
Graham.
I have emailed you some information on the calculation of the duration of BA sets.
You will be able to use this to calculate the duration of any BA sets you have, based on the formula prescibed. Remember however, that no two persons duration will be the same and so this serves only as an indicator of duration and cannot at any time be the 'actual' duration  in use !!
Hope it helps.
best regards...
Stuart Nagle




You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.