When does the world go metric...

[grazie42]

Thats why our system is "easier"...a 12l tank will always be larger than a 10-liter tank...If someone in the US asked me to get that "100cft-tank" from a bundle of bottles I´d just stand there looking confused because the 100cft-tank could just as easily be a small as a big one...

Multiplying by hundreds is easy...a 12l 200 bar tank = 2400 liters of gas. A sac of 20 (free)liters/min means it lasts 120mins at the surface or 30mins @ 30 meters...All that can be done in your head...I´m not saying that the same can´t be done in imperial, everything/anything can be learned by rote if you do it often enough but the formulas for EAD/SAC/depth etc are fare less complicated in metric than in imperial...

 

[diebeste]

or can some one please explain the differance between cft.and liters.
so how does a 80cft tank compares to a xx lt.tank.
as I understand it Lt. is the water content of a tank,and cft is the compresed air content.

Plaese make a list,
70 cft
72 cft
80 cft
100 cft
and so on.

thanx

The most popular metric tanks in SA are 10l, 12.2l and 15l. At a pressure of 200 bar, that should be 2000l, 2440l and 3000l respectively. 200bar is a standard air fill over here. However, the tanks are generally rated to a 232 bar fill, which some shops will give you. This then gives 2320l, 2830l and 3480l respectively. Of course, this assumes that air compresses like an ideal gas, which it doesn't. So the bar x l conversion is not always accurate.
But, the standard size over here is the 12.2l tank, and at 232 bar contains 95cu ft of air. The AL 80 generally contains 77cu ft of air, so that would be very close to the 10l cylinder filled to 232 bar. Of course, all these cylinders are steel cylinders, except the AL 80 I mentioned.

 

[Rick Murchison]

I remember when I was in grade school, they had us learn the metric system since we would eventually convert to it. That was almost fifty years ago and we still haven't. Maybe if we really want to reach international markets, we could follow the standards most of them use.

In Alabama about twenty years ago, kilometer markers went up (at great expense) on all the major highways, to be at the front of the dictated switch just around the corner. There was such a hue and cry from the public that the kilo markers came back down (at great expense).
We really are reaching international markets, with more and more goods every day, so that one's a red herring.

'The world' has already gone metric. It's the pesky USA that refuses to fall in line.

Last time I was in England ('88) the markers were still in miles and the posted speed limits were in mph - has that changed?
The entire international aviation world uses feet for altitude and knots for speed. The entire nautical world uses knots for speed, fathoms (feetX6) for depth.
"The World" has quite a few holdouts other than the pesky USA.
Me, I just carry two sets of wrenches
With the happy accident that 10 meters is one atmosphere, there is no doubt that "diving math" is far easier in metric than in imperial.
On the other hand, computers are more accurate using base 2, so we really ought to junk both metric and imperial and go to a hex system, eh? (There are 10 kinds of people - those who understand binary, and those who don't )
Rick

 

[Benthic]

Last time I was in England ('88) the markers were still in miles and the posted speed limits were in mph - has that changed?

Heather and I were there about six weeks ago and it was still that way then. Guess you're right Rick--I hadn't thought of some of the other hold outs.

Brian

 

[String]

The UK still has a mix of units. While mainly metric speeds and distances are still in miles per hour/miles/feet/yards on the roads.

Pretty much everything else is metric though.


Im a horrible mix like most my generation, i think of distances in miles, altitudes in feet but depth in meters (as thats what ive been trained on).

I'll readily admit that metric maths for diving makes things a LOT easier especially when calculating things in your head or underwater.

 

[victor]

Yes the UK is a complete mismash of units.

Seen recently on a container, pity I did not have my camera, width 4.2 metres, Warning height 12 ft.

We can buy 12 metres of carpet 36 inches wide.
You can be arrested for selling 2 lbs of bananas, and yes the prosecution was succsesful.
We buy 1.136 or 2.273 or 4.546 litres of milk (2, 4, or 8 pints).

We buy petrol in litres but everyone thinks of miles per gallon.

However Metric is much better for diving.

 

[Diver0001]

or can some one please explain the differance between cft.and liters.
so how does a 80cft tank compares to a xx lt.tank.
as I understand it Lt. is the water content of a tank,and cft is the compresed air content.

Plaese make a list,
70 cft
72 cft
80 cft
100 cft
and so on.

thanx

In Holland the size of the tanks are measured in the internal water volume. That's to say, the amount of water that would fit into the tank if you took off the valve and filled it up with water. So a 10 litre tank would hold 10 litres of water, a 15 holds 15 litres and so on. This water volume is *independent* of the service pressure so to know how much air (or whatever) will go into the tank you also have to mention the service pressure. For example, you might have 10litre/232bar tanks or 10litre/300 bar tanks which are physically about the same size but hold different amounts of air

In parts of the world they use another way of measuring tank volume. Instead of mentioning size and pressure they just mention the amount of air (or whatever) that will go into a tank when it's full. So your full 232 bar 10 litre tank would hold 2320 litres of air. To make matters worse, the places where they do this are generally backward enough that they don't use metric either so you end up saying 80 cubic feet instead of 2320 litres.

And to make the confusion even more complete, some tanks are called by a name that does not actually correspond to their full volume. In fact, most 80cf tanks, for example, don't hold a full 80cf when they're full...just like a 10 litre tank is never really pumped up to 232bar. However, for all practical purposes they're the same size.

And to make the confusion utterly complete, the AL80's are made from aluminium and a typical 10 litre tank in Holland is made from steel so while they hold about the same amount of air (or whatever) the 10 litre tank is actually quite a bit smaller, physically, than the aluminium tank.

Still following?

You can google the conversion but to save you some time, here it is.

To convert a number of litres to a number of cubic feet just mulitiply by 0,0353154
To convert a number of cubic feet to litres divide by the same number.

Make any sense?

R..

 

[Diver0001]

Allow me to rephrase the question in a way that will answer the question I would ask.... if an al80 is the standard tank throughout the US, Canada, and the Caribbean, what would the equivilent tank be in Europe?

Rachel

a 10 litre / 232 bar tank.

R..

 

[Blackwood]

You can be arrested for selling 2 lbs of bananas

In metric, do you guys generally use N or kN for weights?

Or do you just run with mass (e.g. is that 2lbm of bananas)?

If memory serves, I've heard people say so-and-so is 10 stones, but I've never been quite sure what a stone is.

 

[String]

One stone is 14lbs

(old imperial measurement)

Its how i still understand weight