Metric measurements?

[laikabear]

Very familiar with kg. I work in international shipping and I’m converting between lbs and kgs all day long by hand. I use an online conversion tool for cm and m.

@Marie13 can you PM me? I can't send you a PM and I have a question for you regarding a customs thing. I would really appreciate it. (I'm trying to order a UK drysuit.)

To not do a total threadjack (sorry!), I'll say that I'm trying to convert to metric for diving. I use kg and L at work, but I am so attached to the foot (like @drrich2). A lot of my local buddies use metric and so I'm going to keep trying to make myself convert. I just don't think it will ever feel natural to me. I'll always be thinking "what's that in feet?" in my head.

 

[Dan]

Yes but calculating consumption is easier

For a 12l tank, 1 bar=12l on a 15l tank, 1 bar=15l, So if you know you're breathing 15l/m at the surface you can easily figure that to be 4bar/m at 30min

I may have missed the detail somewhere. How do you get 30 min from 15l/m and 4bar/m, assuming a full tank containing 200 bars?

 

[JackD342]

I may have missed the detail somewhere. How do you get 30 min from 15l/m and 4bar/m, assuming a full tank containing 200 bars?

Typo? I think @Diving Dubai meant to write 30 meters, not 30 minutes.

 

[Marie13]

What irks me about metric is when I get dimensions for shipments that are in mm rather than cm. Really?

 

[taimen]

mm is usually used in engineering and construction. Including bigger stuff like buildings.
Never seen any serious drawings in cm. That would look strange.

 

[Storker]

mm is usually used in engineering and construction. Including bigger stuff like buildings.
Never seen any serious drawings in cm.

Yep. Technical drawings are in mm. Since you have worry about units smaller than 1mm only for precision machining, no risk of missing or misplacing a decimal point.

If you want cm, just mentally move the decimal point one place to the left. If you want meters, move it three places.

 

[Marie13]

Yep. Technical drawings are in mm. Since you have worry about units smaller than 1mm only for precision machining, no risk of missing or misplacing a decimal point.

If you want cm, just mentally move the decimal point one place to the left. If you want meters, move it three places.

Yep, already move the decimal point. It’s just one agent in Europe that always gives measurements in mm, regardless of the customer.

 

[Dan]

Typo? I think @Diving Dubai meant to write 30 meters, not 30 minutes.

Make sense.

So if I breathe 12 l/min at the surface (1 bar), at 30 m depth (4 bars) I’d consume 200 bar 15 liter tank in 62 minutes (200 x 15 / 12 / 4)?

 

[Neilwood]

Have to say that, to me anyway, it irks me when I see sizes in cm as they are often not accurate enough. Example being kitchen appliances such as washing machines etc where the size is normally shown online or in catalogues as 59cm whereas the actual size is nearer 595mm and can make fitting it very tight.

I work in construction and all sizes are in millimetres.

 

[Storker]

Make sense.

So if I breathe 12 l/min at the surface (1 bar), at 30 m depth (4 bars) I’d consume 200 bar 15 liter tank in 62 minutes (200 x 15 / 12 / 4)?

Seems right, even if I'd do the math a little different and in steps:

• 12 L/min @ surface = 12/15=0.8 bar/min @ surface
• @ 30M (4 barA), that's 0.8*4=3.2 bar/min (a really nice number to have, because you can use it to monitor if your gas consumption is what you planned for. "10 minutes bottom time should be about 30 bar")
• 200 bar / 3.2 bar/min = 62.5 min

I'd recommend ascending a little before that, though No matter whether you use metric or Imperial...


Now let me do a quick min gas calculation using those numbers:

Time at depth to sort out the issues: 1 min @ 30M, 4 barA
12 lpm @ surface = 48 lpm @ 4 barA. Round to 50. Times one minute is 50L.

Ascent: 10 m/min, average dept: 15m, average pressure: 2.5 barA
12 lpm @ surface = 30 lpm @ 2.5 barA. Times 3 minutes ascent time is 90L.

Safety stop: 3 min @5m, 1.5 barA.
12 lpm @ surface = 18 lpm @ 1.5 barA. Round to 20. Times 3 minutes is 60L.

90+60+50=200L. Plus buddy is 400L. Times two for stress is 800L. Divide by 15L/bar is 53 bar, round to 60. Add 10 bar to ensure a working 1st, and your min gas tank pressure @ 30M is 70 bar. A little less if you're willing to skip the SS if SHTF.

So considering min gas your available bottom time goes from 62.5 min to (200-70)/3.2 = 41 min. Still a bit excessive to me, even on EAN32 Which is probably the reason I've only seen 12L 200 bar tanks when I'm vacation diving.