Cylinder Volume ( Technical Detail )

[bany39]

Its temperature dependent and not linear. The wiki page explains it well.
Compressibility factor - Wikipedia, the free encyclopedia

thank you so much , but this article get me confuse the formula is Z(compressibility factor)=pv/n.R.T , that mention that by increasing pressure the Z factor increase in the same temperature , and it got me confuse becuase in this formula ((P.V ) / z)) that show air volume in cylinder both Z factor and p=pressure increasing so what is the result the total air volume increase by pressure or decrease and how ??????

 

[JohnN]

Taking a small step back. The Ideal Gas Law: PV=nrt assumes the ideal gas is infinitely compressible. In real life the gas molecules start to interact and collide with each other as they are pushed closer together and/or become more kinetically active (temperature increases). "Z" is experimentally determined to account for this deviation from "ideal" behavior. (an ideal gas has a "Z" =1 for all temperatures and pressures)

 

[bany39]

Taking a small step back. The Ideal Gas Law: PV=nrt assumes the ideal gas is infinitely compressible. In real life the gas molecules start to interact and collide with each other as they are pushed closer together and/or become more kinetically active (temperature increases). "Z" is experimentally determined to account for this deviation from "ideal" behavior. (an ideal gas has a "Z" =1 for all temperatures and pressures)

thank you JohnN
but maybe the question is wrong because every body just say read this article read that article and ..... but my question is simple and i say it again ....if the 10 liter tank with 200 working pressure 200 bar has the volume of 2000 liter air what is the volume of air for this tank in 300 and 400 bar ????? ( T and all others Items are constant ) is that too hard ???at the end of question say please give your answer with formula that you use it to solve it .
thanks again

 

[Diver0001]

1. I've never had a problem getting my HP tanks filled
2. Nope, HP (3442 PSI) tanks are sold with yoke valves
3. Hydro intervals are set by DOT (in USA), TC (in Canada). 5 years irregardless of HP or LP designation

So why LP cylinders? If you live in a place where you can get them over-filled them, they would be wonderful (good luck getting a 'cave' fill in the PNW), otherwise they are bigger and heavier for the same volume of gas.

I think we need a definition of HP tanks. Outside the USA a 3442psi (232bar) tank is not generally thought of as an HP tank. In Europe, and most of the rest of the world, an HP tank are the 4350psi (300bar) ones.

I suspect this is also the definition the OP is using. In that case, his comment that an HP tank (the 300bar ones) DO need a DIN connection.

I do not, however, see that as a disadvantage. The fact that anyone is still using international valves in this day and age is what surprises me.

It is also true that depending on your location, getting a 300bar fill could be problematic. Not all compressors/buffers are set up for this. However, this problem is becoming less and less an issue as time goes by.

Finally, I am not aware of a different hydro requirement for 300 bar tanks. In some places, local laws may require it but in the EU, the norm, if I am not mistaken is 5 years, just like all other tanks.

Hope that helps.

R..

 

[KevinNM]

thank you JohnN
but maybe the question is wrong because every body just say read this article read that article and ..... but my question is simple and i say it again ....if the 10 liter tank with 200 working pressure 200 bar has the volume of 2000 liter air what is the volume of air for this tank in 300 and 400 bar ????? ( T and all others Items are constant ) is that too hard ???at the end of question say please give your answer with formula that you use it to solve it .
thanks again

It's not that simple, as it depends on just what gas or gas mix you are compressing, as there are variables that need to be looked up for each gas. I'm not sure this is the right gas law for your purpose, but it's the first one that popped up, so here's an online equation solver for Van der Waals equation: Van der Waals law calculator - Chemistry Online Education

 

[Agility]

at 20°C you will have about 2700l of air @ 300bar and about 3100 @ 400bar

 

[rjack321]

thank you JohnN
but maybe the question is wrong because every body just say read this article read that article and ..... but my question is simple and i say it again ....if the 10 liter tank with 200 working pressure 200 bar has the volume of 2000 liter air what is the volume of air for this tank in 300 and 400 bar ????? ( T and all others Items are constant ) is that too hard ???at the end of question say please give your answer with formula that you use it to solve it .
thanks again

OK look at this figure, notice its a curve and its temperature dependent.
Compressibility factor - Wikipedia, the free encyclopedia

You can see that on a warm day (~300K) the compressability of air is about 1.1 at 200bar, so go from 199 liters to 200 liters requires just under one free liter at 1 ATA. (1/1.1= 0.91L) Yet notice that from 0 to 80 bar the compressability is slightly greater at 0.99. These differences effectively cancel each other out and your 1L cylinder at 200bar holds very close to 200L of air.

To go from 200 bar to 300 bar (at 300K) the compressability of air changes from 1.1 to 1.32. Assuming the average of those values is 1.2. This means that instead of 100 more liters to go from 200 to 300 bar in your 1L cylinder its really only holding 83 more liters. (1/1.2=83)

So functionally your 200 bar cylinder holds 200L and your 300bar cylinder holds 283L. By 400bar you don't hold anywhere near 400L as the compressability is about a factor of 1.26. So instead of taking 100L to go from 300 bar to 400 bar it only takes about more 79 liters. (100/1.26=79)

Hence for a 1L cylinder:
200bar = 200L
300bar = 283L
400bar = 362L

This all changes if you go ice diving or anywhere else the ambient temperature isn't about 300K = 80F = 26C.

 

[JohnN]

thank you JohnN
but maybe the question is wrong because every body just say read this article read that article and ..... but my question is simple and i say it again ....if the 10 liter tank with 200 working pressure 200 bar has the volume of 2000 liter air what is the volume of air for this tank in 300 and 400 bar ????? ( T and all others Items are constant ) is that too hard ???at the end of question say please give your answer with formula that you use it to solve it .
thanks again

Here is a easy reference: Air Compressibility Factor Table – Enggcyclopedia

So assuming 25 oC which is ~300 oK,

The "Z" factor:
200 1.0326
300 1.0669
400 1.1089

With 10 liters of water volume:
200 2000/1.0326 = 1937 l
300 2000/1.0669 = 1875 l
400 2000/1.1089 = 1804 l

 

[bany39]

Here is a easy reference: Air Compressibility Factor Table – Enggcyclopedia

So assuming 25 oC which is ~300 oK,

The "Z" factor:
200 1.0326
300 1.0669
400 1.1089

With 10 liters of water volume:
200 2000/1.0326 = 1937 l
300 2000/1.0669 = 1875 l
400 2000/1.1089 = 1804 l

this is nice answer but at the all the volume equal to 2000 and it`s should be 2000 , 3000, 4000 if wrong correct me .thank yo johnN

 

[bany39]

OK look at this figure, notice its a curve and its temperature dependent.
Compressibility factor - Wikipedia, the free encyclopedia

You can see that on a warm day (~300K) the compressability of air is about 1.1 at 200bar, so go from 199 liters to 200 liters requires just under one free liter at 1 ATA. (1/1.1= 0.91L) Yet notice that from 0 to 80 bar the compressability is slightly greater at 0.99. These differences effectively cancel each other out and your 1L cylinder at 200bar holds very close to 200L of air.

To go from 200 bar to 300 bar (at 300K) the compressability of air changes from 1.1 to 1.32. Assuming the average of those values is 1.2. This means that instead of 100 more liters to go from 200 to 300 bar in your 1L cylinder its really only holding 83 more liters. (1/1.2=83)

So functionally your 200 bar cylinder holds 200L and your 300bar cylinder holds 283L. By 400bar you don't hold anywhere near 400L as the compressability is about a factor of 1.26. So instead of taking 100L to go from 300 bar to 400 bar it only takes about more 79 liters. (100/1.26=79)

Hence for a 1L cylinder:
200bar = 200L
300bar = 283L
400bar = 362L

This all changes if you go ice diving or anywhere else the ambient temperature isn't about 300K = 80F = 26C.

thank you so much for correspondence .