Imperial units for gas density?

[Akimbo]

I was talking to a European friend who asked what Imperial units are used for gas density? It occurred to me that we rarely had a requirement to express gas density in military or commercial saturation diving. As I recall, physiologists at NEDU used Metric and converted depth in ATA to FSW.

Our only option was HeO2 and knew to switch to Hydrox deeper than around 1,600'/500M. All I remember using Grams/Liter on the few projects that we were concerned with gas density, which was mostly in welding habitats.

Back to the question: What do tech divers in the US use for gas density calculations?

 

[wetb4igetinthewater]

Metric (darn you Reagan)

 

[grantctobin]

I was talking to a European friend who asked what Imperial units are used for gas density? It occurred to me that we rarely had a requirement to express gas density in military or commercial saturation diving. As I recall, physiologists at NEDU used Metric and converted depth in ATA to FSW.

Our only option was HeO2 and knew to switch to Hydrox deeper than around 1,600'/500M. All I remember using Grams/Liter on the few projects that we were concerned with gas density, which was mostly in welding habitats.

Back to the question: What do tech divers in the US use for gas density calculations?

g/L. I don't think I've ever seen it expressed otherwise.

 

[Wibble]

Metric (darn you Reagan)

Didn't the US loose a satellite because it interpreted a 2km high mountain as 2000 miles, so turned the satellite over?

I cannot understand why US-based tech divers cling to that arcane cubits per unicorn measurements and pressurised gas volumes rather than the far simpler MKS (metres, kilo, seconds) system. I'm a Brit who'd never give up a pint! But life's not worth it for technical measurements; even UK buildings have gone metric (although some very odd standards which were mapped over from imperial measurements). The metric system's so much easier: 1 atm = 10m/33' So a 50m dive is 6 atm; gas consumption would be SAC x depth so 15 litres/min x 6 = 90 litres per min of gas.

Good to see the commie divers still keep to international units.

 

[wetb4igetinthewater]

Didn't the US loose a satellite because it interpreted a 2km high mountain as 2000 miles, so turned the satellite over?

I cannot understand why US-based tech divers cling to that arcane cubits per unicorn measurements and pressurised gas volumes rather than the far simpler MKS (metres, kilo, seconds) system. I'm a Brit who'd never give up a pint! But life's not worth it for technical measurements; even UK buildings have gone metric (although some very odd standards which were mapped over from imperial measurements). The metric system's so much easier: 1 atm = 10m/33' So a 50m dive is 6 atm; gas consumption would be SAC x depth so 15 litres/min x 6 = 90 litres per min of gas.

Good to see the commie divers still keep to international units.

Yes, that was an incident between JPL and NASA. I don't remember which, but what was using Imperial and the other metric. There was an assumption that some numbers were one or the other.

It is just asinine to stay with Imperial. The worst part is, and I think @cerich posted somewhere, was a mix of metric and imperial bolts on a Jeep (do I remember that right Chris?). I think Chris had some colorful commentary for that unpleasant experience.

 

[Wibble]

Having said that, the DIN valves on my rebreather are actually 5/8 BSP... Could go for the Metric O2 one which is called M26 (but why when you'd need a pair of adapters to fill the cylinder).

Just looked at Flight Radar; good to see the airline industry still uses feet for height!

 

[Akimbo]

I cannot understand why US-based tech divers cling to that arcane cubits per unicorn measurements and pressurised gas volumes rather than the far simpler MKS (metres, kilo, seconds) system. I'm a Brit who'd never give up a pint!

The irony is the US is still suffering from the units that you Brits stuck us with! Just joking. It was just bad timing and the distance between markets.

In hindsight, the Meter, or Metre, was really a mistake. They should have used a decimal fraction of a Nautical Mile instead of one ten-millionth of the distance between the North Pole and the Equator along the meridian through Paris. It ended up being inaccurate and had to be redefined a few times anyway. The worse part was the lame attempt to survey that meridian delayed the definition of the Meter by years. That delay significantly hurt the promoters in the early US government that were pushing the metric system. It is more complex than that and an interesting story but that was the net effect.

The Nautical mile was also based on natural or earth units and was no less precise than they were capable of measuring the length of a meridian in those days. The Nautical mile is probably the only pre-Metric unit that will survive, at least as long as anyone remembers how to navigate beyond looking at a GPS.

Time itself is another victim of bad timing. It is too bad that the availability of time pieces was so widespread in the 1700s. Otherwise, we would have 10 hours/day, 100 minutes/hour, and 100 seconds/minute.

Edit: And what is with 360 degrees instead of 100? Of course that would have changed the Nautical mile.

 

[kelemvor]

Yes, that was an incident between JPL and NASA. I don't remember which, but what was using Imperial and the other metric. There was an assumption that some numbers were one or the other.

A great example of why the metric system is a problem, 'eh?

Just kidding. I'm all for using the metric system. It'll never happen here though.

As an aside, the "others" who are using the metric system are still managing to do screwy stuff with it. For example measuring tank volumes by how much water a tank holds instead of how much compressed gas it holds. Only the hydro guy needs to know how much water my tank holds.

The tank monkey and I are concerned with how much gas goes in there. I'd be fine with a cubic meters and guages that read in pascals. Fill my LP108 to 3 cubic meters and I'll head up when my gauge hits 3.4MPa.

I mean, if you're going to go - go all out.

 

[wetb4igetinthewater]

A great example of why the metric system is a problem, 'eh?

Just kidding. I'm all for using the metric system. It'll never happen here though.

As an aside, the "others" who are using the metric system are still managing to do screwy stuff with it. For example measuring tank volumes by how much water a tank holds instead of how much compressed gas it holds. Only the hydro guy needs to know how much water my tank holds.

The tank monkey and I are concerned with how much gas goes in there. I'd be fine with a cubic meters and guages that read in pascals. Fill my LP108 to 3 cubic meters and I'll head up when my gauge hits 3.4MPa.

I mean, if you're going to go - go all out.

Not sure if I follow. What is the issue with the amount of compressed gas in a cylinder being the volume of the cylinder x pressure in bars?

 

[kelemvor]

Not sure if I follow. What is the issue with the amount of compressed gas in a cylinder being the volume of the cylinder x pressure in bars?

Having to do the math, although easy, is an extra and un-necessary step. SI units for pressure are pascals, not BAR.


Although I'd rather see megapascals instead of kilopascals on there.