markyd
Registered
I've been shopping for tanks recently, looking at the various options that are available (no, this isn't going to be another LP vs HP vs aluminum 'discussion' -- at least I hope not).
Somewhere (an on-line shop, but I don't remember where), I found a table of a significant number of tanks, their service pressure, capacity, dimensions, and buoyancy. What I find interesting is that, according to this table, many tanks of the same capacity (even different models from the same manufacturer) claim different weights for the air contained inside. In other words, if you take two 80cu-ft tanks and subtract the full buoyance from the empty buoyancy, you get the weight of the air in the tank (~6lbs in this case).
If you then divide by the capacity, you should get the density of air. In theory, that should be 0.07962lb/cu-ft, but most of the tanks on the list work out to 0.074-0.075lb/cu-ft. Some tanks go from 0.067 all the way to 0.108lb/cu-ft.
So what's the deal? Do all the tank manufacturers just over-state their capacity? Or maybe mis-state the buoyancy characteristics?
I'm just curious, because, although dry weight may change based on tank material and size, the weight of the air should be the same, whether you've got an Al80 or an HP120, so the difference in buoyancy between full and empty should be the same.
I think.
marky-d
Somewhere (an on-line shop, but I don't remember where), I found a table of a significant number of tanks, their service pressure, capacity, dimensions, and buoyancy. What I find interesting is that, according to this table, many tanks of the same capacity (even different models from the same manufacturer) claim different weights for the air contained inside. In other words, if you take two 80cu-ft tanks and subtract the full buoyance from the empty buoyancy, you get the weight of the air in the tank (~6lbs in this case).
If you then divide by the capacity, you should get the density of air. In theory, that should be 0.07962lb/cu-ft, but most of the tanks on the list work out to 0.074-0.075lb/cu-ft. Some tanks go from 0.067 all the way to 0.108lb/cu-ft.
So what's the deal? Do all the tank manufacturers just over-state their capacity? Or maybe mis-state the buoyancy characteristics?
I'm just curious, because, although dry weight may change based on tank material and size, the weight of the air should be the same, whether you've got an Al80 or an HP120, so the difference in buoyancy between full and empty should be the same.
I think.
marky-d