Help with white Faber cylinder size

[SoCalDiver07]

So based on everything I have found plus the helpful info above as well as the info gained at the Hydro shop today it is in fact a MP80 with a volume of 77 cu ft (rounded to the nearest whole number) at working pressure of 2730psi. It has a + allowing it to be filled to 3003 PSI again lets round to 3000. This would give the tank a volume of not 80cu ft as I have read so many places but actually 85 cu ft. I confirmed that figure with a few different tank air volume calculators to ensure I was correct since everywhere I have read about the MP80s said they are 77cu ft and 80 when filled to 3000 which didnt make sense to me.

I appreciate everyones help. Now to determine if I will be keeping both of these tanks for myself and the wife and getting rid of my Faber LP95 (which was my go to boat cylinder) or what?

 

[Tracy]

So based on everything I have found plus the helpful info above as well as the info gained at the Hydro shop today it is in fact a MP80 with a volume of 77 cu ft (rounded to the nearest whole number) at working pressure of 2730psi. It has a + allowing it to be filled to 3003 PSI again lets round to 3000. This would give the tank a volume of not 80cu ft as I have read so many places but actually 85 cu ft. I confirmed that figure with a few different tank air volume calculators to ensure I was correct since everywhere I have read about the MP80s said they are 77cu ft and 80 when filled to 3000 which didnt make sense to me.

I appreciate everyones help. Now to determine if I will be keeping both of these tanks for myself and the wife and getting rid of my Faber LP95 (which was my go to boat cylinder) or what?

It is 77cf at 3000psi.
The volume is listed at the fill pressure, not the tank pressure.

 

[Scared Silly]

As noted above by @Tracy but to be pedantic. Any cylinder with a plus rating is only at capacity when at the working pressure plus the 10%.

As such, the cylinder is at capacity, 77 cu ft when filled to 2730 psi plus 10% or 3003 psi.

Similarly an LP85 is full when filled to 2400 psi plus 10% or 2640 psi.

For the OP, many cylinder capacities are rounded. For instance, an AL80 is not a true 80 cuft. That rounding is marketing.

 

[Tanks A Lot]

Not trying to beat a dead horse and I understand next to nothing how the US cylinder classification comes about - It seems nothing but marketing jargon to me...

The exact numbers are as follows:

Compressibility factor of air (21% O₂ - 79% N) at 20°C at 188 bar (2730psi) = 1.0210
Compressibility factor of air (21% O₂ - 79% N) at 20°C at 207 bar (3000psi) = 1.0325

Gas Volume at 188 bar (2730 psi) at 20°C:
(11.1L x 188 bar) / (1.01325 bar x 1.0210)
= 2017.15L or 71.24 f³

Gas Volume at 207 bar (3000 psi) at 20°C:
(11.1L x 207 bar) / (1.01325 bar x 1.0325)
= 2196.27L or 77.56 f³

I have no idea at what temperature Faber would classify their free gas volumes (In fact they themselves do not do that at all) or which model they would use. The above compressessiblity factors come from miniREFPROP.

If that would be called MP, LP, HP or whatnot is beyond me.

 

[SoCalDiver07]

It is 77cf at 3000psi.
The volume is listed at the fill pressure, not the tank pressure.

This is not correct. It’s 77 at working pressure.

 

[Tracy]

This is not correct. It’s 77 at working pressure.

I'm not incorrect, but you are free to believe what you wish.

 

[rjack321]

Not trying to beat a dead horse and I understand next to nothing how the US cylinder classification comes about - It seems nothing but marketing jargon to me...

The exact numbers are as follows:

Compressibility factor of air (21% O₂ - 79% N) at 20°C at 188 bar (2730psi) = 1.0210
Compressibility factor of air (21% O₂ - 79% N) at 20°C at 207 bar (3000psi) = 1.0325

Gas Volume at 188 bar (2730 psi) at 20°C:
(11.1L x 188 bar) / (1.01325 bar x 1.0210)
= 2017.15L or 71.24 f³

Gas Volume at 207 bar (3000 psi) at 20°C:
(11.1L x 207 bar) / (1.01325 bar x 1.0325)
= 2196.27L or 77.56 f³

I have no idea at what temperature Faber would classify their free gas volumes (In fact they themselves do not do that at all) or which model they would use. The above compressessiblity factors come from miniREFPROP.

If that would be called MP, LP, HP or whatnot is beyond me.

In theory it would be at 70F (which is 21C to the rest of the world) That's the "room temperature" used in the regulations here. At the time this cylinder was made it was marketed as "mid pressure" cause 170ish bar cylinders existed ("LP") and 240 bar cylinders existed "HP". And 188 bar was between those. Those LP, MP, and HP labels were 90% marketing and 10% based on the actual range of pressures being described in words. Apparently cause numbers are hard to American's lol

This is not correct. It’s 77 at working pressure.

If you even glance at the math already posted you'll see your assumptions are incorrect.

 

[MrVegas]

I can't add anything technical to this conversation, other than I own two of these, and I was always told they were only 80 cubic feet (or 77.4) at the 10% overfill (3000 psi).

 

[Still Kicking]

This is not correct. It’s 77 at working pressure.

Sorry but wishing don't make it so.