That's a Blue Steel marking, not a Faber marking.
How much air does an LP85 hold at 2400 PSI?
- Thread starter CaveSloth
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CaveSloth
Contributor
Where should I look for the stamp? Did you see the pics I took of the tanks?
Dropbox - tank pics - Simplify your life
BrackaFish
Contributor
Tursiops is correct. Those would be Blue Steel markings for tank size. If your tanks were not sold by Blue Steel, those markings would be absent. My bad.
runsongas
Contributor
narrower tank, hence lower water volume and capacity. lp85 is wider
It's relevant because it's just as pointless as using cuft as a basis of measurement. A cuft rating means nothing without pressure, so you have to do math anyway to actually figure out how much breathable volume you have so you might as well do it the easy way, and the one that translates across the board for all of your diving calculations.
runsongas
Contributor
cubic feet is a direct representation of stored gas volume whereas water capacity is not
if you are calculating reserves, you still have to deal with pressure calculations either way
if you are calculating reserves, you still have to deal with pressure calculations either way
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No, it' isn't. It's surface gas volume.
BTW, how do you calculate min gas pressure with an imperial sized tank? Here's how I do it with a metric sized tank:
My gas consumption (call it whatever you want, but let's avoid yet another RMV vs SAC debacle) is between 15 and 20 liters per minute. Actual liters at ambient pressure. I'll use 20 as my number, both because it's conservative and because it makes for easy math.
An ascent from 30m (4 bara) at 10 m/min takes 3 minutes, average depth is 15m (2.5 bara). That's 20 times 3 times 2.5, or 90 surface liters.
Add one minute at depth to sort things out, that's 20 times 1 times 4, 80 surface liters.
Since I've been rather deep I prefer to make a safety stop. 3 minutes at 5m/1.5 bara is another 90 surface liters. So at my normal breathing rate I need 260 surface liters for my ascent.
But I'm calculating for an incident, so my buddy will also need gas. That takes me to 520. And we'll probably be a mite stressed, so I'm going to assume a doubled gas consumption rate. That's 1040 surface liters.
With my 10L tank, 1040 surface liters is 104 bar, add 10 bar to have a working 1st stage and my min gas pressure at 30m is 115 bar.
With a 12, 1040 surface liters is about 85 bar, add those 10 bar reserve and call it an even 100.
With a 15, 1040 surface liters is 70 bar, add those 10 bar reserve and I should leave the bottom with at least 80 bar left in my tank.
Perhaps with the exception of that last division by 12 or 15, I can do those calcs in my head.
runsongas
Contributor
when you do the calculation in liters, you are using surface gas volume also. only difference is doing the calculation in liters or cf. doing the calculation for 0.5 cf/min is not that much harder than your 15 liters.
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I've showed you mine, what about you showing me yours?
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