Your chart is pretty limited. I am at work rather than home so I can't pull up the links but there are 2 or 3 sites with very extrensive tank comparision charts.
On a good tank comparision chart comparing specific models, for a given LP tank in the 80-104 cu ft capacity range, you can almost always find a 3442 psi tank that is very smiliar in external dimensions, weight and bouyancy traits. If you then look at the capacity of this very similar sized tank, you will ALWAYS find that it holds substantially more gas when both are at their rated pressures.
The tank with the larger rated gas capacity will obviously be more negative when full due to the greater weight of gas and will have a higher swing weight due to the greater volume that is used during a dive, so you have to compare the empty numbers rather than the full ones.
In Europe, it makes more sense as you rate tanks by internal volume and then can just mulitply that by the number of bars of pressure to get the tank's volume in liters at a given pressure. If you think about it, it works the same way here. The tensile stength of the steel used in a low pressure versus high pressure steel tank is different but the wall thickness is pretty similar. The extra strenght and higher rated pressure of the HP tank comes from stronger steel (or less conservative engineering safety margins, or a combinatiuon of the two, depending on who you talk to/believe) so wall thickness is therefore about the same as are overall empty weight and bouyancy when empty.
Consequently, two tanks of similar external size will have a similar internal volume. So if you fill one to 180 bar and fill the other to 232 bar, it's pretty obvious that even though they are the same exterior size, one is going to hold a lot more gas than the other.
That is exactly the case here. You have two similarly sized tanks but one is a low pressure 180 bar tank that cannot legaly be filled to exceed this pressure and the other is a higher pressure 232 bar tank that legally can be filled to the higher pressure and will legally hold a lot more gas.
On a good tank comparision chart comparing specific models, for a given LP tank in the 80-104 cu ft capacity range, you can almost always find a 3442 psi tank that is very smiliar in external dimensions, weight and bouyancy traits. If you then look at the capacity of this very similar sized tank, you will ALWAYS find that it holds substantially more gas when both are at their rated pressures.
The tank with the larger rated gas capacity will obviously be more negative when full due to the greater weight of gas and will have a higher swing weight due to the greater volume that is used during a dive, so you have to compare the empty numbers rather than the full ones.
In Europe, it makes more sense as you rate tanks by internal volume and then can just mulitply that by the number of bars of pressure to get the tank's volume in liters at a given pressure. If you think about it, it works the same way here. The tensile stength of the steel used in a low pressure versus high pressure steel tank is different but the wall thickness is pretty similar. The extra strenght and higher rated pressure of the HP tank comes from stronger steel (or less conservative engineering safety margins, or a combinatiuon of the two, depending on who you talk to/believe) so wall thickness is therefore about the same as are overall empty weight and bouyancy when empty.
Consequently, two tanks of similar external size will have a similar internal volume. So if you fill one to 180 bar and fill the other to 232 bar, it's pretty obvious that even though they are the same exterior size, one is going to hold a lot more gas than the other.
That is exactly the case here. You have two similarly sized tanks but one is a low pressure 180 bar tank that cannot legaly be filled to exceed this pressure and the other is a higher pressure 232 bar tank that legally can be filled to the higher pressure and will legally hold a lot more gas.
Do they also fill HP tanks to 4800 psi?
