Converting liters to cubic feet

[NothingClever]

15l tank with 300 bar and a fully charged tech-class DPV - dream dive for me!

 

[BoltSnap]

An usual steel tank filling is 190 to 200 bar, rarely you get 220-230 bar.

Why so? We fill to 230 and even more.

 

[Bento.Box]

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..

But the math is the same.

Let's say you fill you 0.423776 ft^3 tank with 300 bar.
Which is 4351.131 PSI
so you have:
0.423776 ft^3 * (4351.131 PSI /14.50377 PSI) = 127.1328 ft^3 of "usable" air (surface pressure)
or 1.2173086*10^5 fluid ounces. Or 951.022344 US Gallons. Or 791.8892897 Imperial Gallons.

Thus if the filling is specified, then the pressure must also be specified for you to know how big the tank is.

People just use metric because then the numbers are not so odd. But it really doesn't matter.

 

[scubadada]

View attachment 863119

Nice tables, how about temperature?

 

[NothingClever]

 

[JuLe]

But the math is the same.

Let's say you fill you 0.423776 ft^3 tank with 300 bar.
Which is 4351.131 PSI
so you have:
0.423776 ft^3 * (4351.131 PSI /14.50377 PSI) = 127.1328 ft^3 of "usable" air (surface pressure)
or 1.2173086*10^5 fluid ounces. Or 951.022344 US Gallons. Or 791.8892897 Imperial Gallons.

Thus if the filling is specified, then the pressure must also be specified for you to know how big the tank is.

People just use metric because then the numbers are not so odd. But it really doesn't matter.

Yes, the math is the same. A table like the one posted is just nice as a quick reference when someone uses imperial measurements.

My biggest problem with inches, feet, yards, miles, ounces, pounds, gallons and what have you, is that the numbers are odd, they don't scale up or down in standard increments like the metric system. With 1/10 increments the math is REALLY easy.
I have been using (nautical) miles and feet quite a bit in the past and still do. Same with pounds and even inches. No problems there. Using them enough makes them sort of second nature. But having to compute odd numbers like 0.4237... and 14.503... for gas volume just seems a bit complicated.

 

[tursiops]

But the math is the same.

Let's say you fill you 0.423776 ft^3 tank with 300 bar.
Which is 4351.131 PSI
so you have:
0.423776 ft^3 * (4351.131 PSI /14.50377 PSI) = 127.1328 ft^3 of "usable" air (surface pressure)
or 1.2173086*10^5 fluid ounces. Or 951.022344 US Gallons. Or 791.8892897 Imperial Gallons.

Thus if the filling is specified, then the pressure must also be specified for you to know how big the tank is.

People just use metric because then the numbers are not so odd. But it really doesn't matter.

Why all those decimal places? Your measurements and sizes are hardly that accurate!

 

[Bento.Box]

But having to compute odd numbers like 0.4237... and 14.503... for gas volume just seems a bit complicated.

But that's just normal in freedom units, even if you don't convert to/from metric

E.g. it's funny that the diving community uses psi for pressure, while the aviation community uses mmhg.
1 psi is 51.71508 mmHg.

Personally, I'm skeptical at tables in safety-related applications. As I see only the results of somebody elses' math who I may or may not trust to do it properly. I don't see the calculation / their formula.

Why all those decimal places? Your measurements and sizes are hardly that accurate!

you can round at the end, but I would not do it mid-calculation because the rounding errors accumulate.
e.g. I would round it down to 125 or 120 ft^3

 

[tursiops]

having to compute odd numbers like 0.4237... and 14.503... for gas volume just seems a bit complicated.

Yeah, it is especially hard when you use all those unnecessary decimal places.

 

[tursiops]

the rounding errors accumulate.

Only if you always round up or down. Otherwise, they tend to cancel each other out. Look, you are only needing maybe one decimal place, if that....so why fuss with whether the fourth or fift palce is wrong?