How much air does an LP85 hold at 2400 PSI?

[kelemvor]

Error ID 10 T. Failure.

 

[Marie13]

AL80 have a capacity of 77 something (think that’s correct-going off memory) when filled to rated pressure.

Do you feel ripped off when diving an AL80?

 

[tbone1004]

Now to throw another monkey in the fire... According to Faber/Blue Steel. The LP85 actually has only a capacity of 81.1 Cuft of gas when filled to the rated pressure. SO when it is filled to only 2400psi it has only 73.72 cuft in them. kind of makes me question the whole ordeal on FALSE advertisement and misrepresentation.

where did you see that?
On the Blue Steel spec page it claims 85cf.
They claim water capacity of 13L and since other tanks are in tenths of liters we can assume that to be pretty close. 2640psi=182bar, 182*13=2366 Liters which is 83.55 cf/1.0173 for Z factor is roughly 82.1cf ish at 2640. Now that's only to tenths of liters, and is also assuming it's filled at 70F which they don't state, so it may be quoted at a different temperature. Either way they are very clear that all cubic foot capacities are nominal which is something we're used to in this industry...

 

[Sidemount_Ben]

where did you see that?
On the Blue Steel spec page it claims 85cf.
They claim water capacity of 13L and since other tanks are in tenths of liters we can assume that to be pretty close. 2640psi=182bar, 182*13=2366 Liters which is 83.55 cf/1.0173 for Z factor is roughly 82.1cf ish at 2640. Now that's only to tenths of liters, and is also assuming it's filled at 70F which they don't state, so it may be quoted at a different temperature. Either way they are very clear that all cubic foot capacities are nominal which is something we're used to in this industry...

So, I got my information from this table, we even talked about it on the phone.. and I got the Z factor from what you was telling me on the phone the other day. I personally hate whole false pretense on scuba cylinder capacity. regardless how long it has been going on. I don't care for it. that being said, when I run gas numbers, I run at true capacity, not a nominal, ,maybe, and now since I learned about Z factor and that an Lp108 and a HP133 has the same CUFT in them at 3442, I will buy HP133 next time, not the LP.


Calculating SCUBA Cylinder Capacity | Dive Gear Express®

 

[tbone1004]

@Sidemount_Ben fair enough, not going to do the math on it and will assume that @DiveGearExpress did the math properly when they backed into the true gas capacity vs the actual gas capacity, but they do use the term nominal, so you can't get too pissy at them. I wish we used direct tank measurement in the US instead of indirect measurement, but lord knows that won't ever happen.

 

[Eric Sedletzky]

Deleted/Duplicate

 

[mderrick]

So, I got my information from this table, we even talked about it on the phone.. and I got the Z factor from what you was telling me on the phone the other day. I personally hate whole false pretense on scuba cylinder capacity. regardless how long it has been going on. I don't care for it. that being said, when I run gas numbers, I run at true capacity, not a nominal, ,maybe, and now since I learned about Z factor and that an Lp108 and a HP133 has the same CUFT in them at 3442, I will buy HP133 next time, not the LP.


Calculating SCUBA Cylinder Capacity | Dive Gear Express®

The 2640 psi LP cylinder true capacities have always been overstated. The source of the misrepresentation in Faber LP cylinders is their original importer for the US market. Many years ago the first US importer of Faber low pressure 2400+10% = 2640 psi steel cylinders did some extremely specious math for the marketing descriptions of their capacities. The 13 ×(2640÷14.5) ÷28 =? 85 ft3 description has followed the 13 liter water capacity cylinder through the years and it is still referred to in the US as the "LP85" because the name has become synonymous with it's excellent buoyancy characteristics and in-water trim, even though 85 ft3 is no where near it's true capacity of 81 ft3.

However, all the 3442 psi HP steel cylinders (although equivalent in size to the LP versions) are actually marketed at true capacity... the HP100 has a true capacity of 101 cf for example.

I have battled the misunderstanding of true capacity in LP vs HP for years, with little success. Even today DGX is asked about availability of LP cylinders even though it is almost pointless to sell them if an HP version is available. I can't recall ever successfully changing anybody's 'opinion' regarding LP cylinders.

 

[Storker]

*Donning flameproof suit*

Another reason for using water volume/service pressure for tank capacity. Forget the surface volume and manufacturers' wishful thinking, just do the frikkin' math and remember that compressibility reduces your actual surface liters by some 10% when you go from 232 bar to 300 bar.

My old 15L 200bar tank held 15x200=3000 surface liters.
My current 10L 300bar tanks hold 10x300-10%=2700 surface liters.
My buddy's 12L 232 bar tank holds 12x232=close to 2800 surface liters.

And if I remember correctly, an Al80 is 11L 207 bar. -ish.

 

[TravelGas]

Can someone save me the reading of an 18 page thread and just tell a layman if I should be buying LP or HP, if I want as much air as possible in the tank for deep diving ? Thanks.

 

[lexvil]

Can someone save me the reading of an 18 page thread and just tell a layman if I should be buying LP or HP, if I want as much air as possible in the tank for deep diving ? Thanks.

Where and what type of diving do you do? The gist here is do the math but I think more along the line of “just tell me how much the F’n tank holds” everyone knows it’s supposed to hold “X” at “Y”, we’re it only so easy.

if you do boat dives where they refill your tanks and you‘re dealing with hot fills, pant the lp tank white and make sure it’s surrounded by aluminum tanks, you’ll likely get a hot 3200 which is a pretty good fill.

if you shore dive and find a good shop HP tanks are a great option.