Converting liters to cubic feet

[Bento.Box]

The responding posters are not understanding my issue.

This isn't about "exact volumes" or finding a conversion table.

It's about why conversion tables, including the one posted by @scubadada show a 12L tank equals 0.4237760007 cubic feet when obviously a 12L tank holds close to 77 cubic feet.

a foot is little over 3dm. A liter is an alias for dm^3.
So a 12l tank has an internal volume of 0.423776 cubic feet. Or 405.7695 US fluid ounces.

This is correct.

 

[34109411]

I find it convenient to think of a tank in terms of the volume of sea-level-pressure gas it can hold, so I can think of a tank in terms of how many at-the-surface minutes I'll get from it at my Imperial RMV. I can't do that if you tell me my tank is a 12 liter (by he way, the metric abbreviation for liter is l not L) tank, I also have to know what its pressure rating is, or I can't work out how many minutes I'll get from it if I fill it to max pressure. It's just a bit more algebra, however, so no big deal.

On the other hand, if you tell me my tank is 100 cuft, I'm good...I know immediately how many minutes I can get from it. That, to me, is the advantage of the "imperial system" but has nothing to do with the units, it ahs to do with how the szie of the tank is expressed.

So instead of telling me I have a 12 liter tank, just tell me I have a 2500 liter tank (or whatever), then I can divide by my metric RMV.

The issue is NOT just Imperial vs Metric units, it is also how tank size is expressed and used. The units thing is just a little calculation, of no consequence.

(amount of psi in tank/ working pressure) * tank size in CF = total gas available in CF

So it give this (2000/3000) * 80 CF = 53 CF of gas available.

If this could help out with your rmv calculation somehow

 

[therookie]

Calculations will become easier, just stop thinking imperial.

The OP may find this as difficult to do as I do

Taking it out of scuba math for a moment, I instinctively "know" my height in feet and inches and my weight in pounds. I have now spent the last couple of decades living in a country where those units of measurement are useless in the medical realm, and even though my height has never changed and my weight has fluctuated only slightly, every time I am asked I have to pull out my phone and do the conversion to metric. And every time I say to myself "OK I'm going to memorize this for the next time" and it seems I never can. As soon as I'm asked the question my brain goes right to the Imperial numbers and I have to do the calc all over again.

For scuba math I do indeed find the metric calculations much simpler. But I am new at it, so I do not have to overcome years (or perhaps decades) of my brain working with Imperial numbers. From the posts that I read it seems that an experienced diver from the United States is able to do their scuba calculations using their system every bit as quickly and easily as a European one does with theirs - and neither one can make the slightest sense out of what the other is doing if they start talking about it.

The OP will probably be translating and calculating for some time, unless they are living in Europe long enough (and hopefully do enough diving!!!) that it starts to become to them as "instinctive" as the US system is.

 

[LI-er]

The issue is NOT just Imperial vs Metric units, it is also how tank size is expressed and used. The units thing is just a little calculation, of no consequence.

This is what I was having a problem with. It's not about conversion at all, it's the confusing nomenclature regarding how tank sizes are expressed in the EU vs USA.

 

[tursiops]

(amount of psi in tank/ working pressure) * tank size in CF = total gas available in CF

So it give this (2000/3000) * 80 CF = 53 CF of gas available.

If this could help out with your rmv calculation somehow

Thanks, but I'm not having any problems. I'm good at math, fairly fluent in both Imperial and Metric, and understand the issues and methodologies with scuba tanks.
I also like proper nomenclature and units, so dislike CF and prefer cuft for clarity. CF = ClusterF***.

 

[Belzelbub]

This is what I was having a problem with. It's not about conversion at all, it's the confusing nomenclature regarding how tank sizes are expressed in the EU vs USA.

EU standard is in water volume. US standard is in air volume at working pressure. Since water is largely incompressible, the volume is equivalent to the air volume at one ATM.

As I recall, some EU tanks are rated for much higher pressure than US tanks, so the conversion is not quite as straight forward, but you should be able to convert the volume in liters to cu ft, then multiply that by the rated pressure in Bar.

 

[34109411]

Thanks, but I'm not having any problems. I'm good at math, fairly fluent in both Imperial and Metric, and understand the issues and methodologies with scuba tanks.
I also like proper nomenclature and units, so dislike CF and prefer cuft for clarity. CF = ClusterF***.

 

[Sascha314]

I am very well educated in mathematics, but I can only calculate with variables not numbers in my head

So I actually prefer the metrical system, as it has lower numbers. I had my owd in the imperial system.

 

[NothingClever]

 

[JuLe]

NothingClever:
I like this, gives a easy reference with just one glance. I've been doing feet to meters for ages in my head, but volume and pressure I can't do as easy..
Only thing to gripe about, we use quite a bit of 300 bar tanks (10l, 12l and even some 15l ones) here, so I'll add those to my version of the table if you don't mind me using your work.