Imperial vs Metric specifications for AL tanks

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JohnN

JohnN

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So. . if I look up the Imperial specifications of an AL80 tank (lets say Luxfer) I get an volume of 77.4 cuft @ 3000 PSI.

If I look up the same tank, the metric specifications give an "internal volume" of 11.1 l @ 207 bar.

(11.1 * 207) * 0.035315 = 81.1 cu ft

However if I use the "true capacity" (2192 l) I get the 77.4 I've come to know and love.

WTF?
 
true capacity is lower due to the z value (for compressibility) of air deviating from that of an ideal gas at high pressure.
 
runsongas:
true capacity is lower due to the z value (for compressibility) of air deviating from that of an ideal gas at high pressure.
Click to expand...

That's not how I read the data:

[TABLE="class: wikitable"]
[TR]
[TD] [/TD]
[TD="colspan: 14"]Pressure, bar (absolute)[/TD]
[/TR]
[TR]
[TD]Temp, K[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]5[/TD]
[TD="align: right"]10[/TD]
[TD="align: right"]20[/TD]
[TD="align: right"]40[/TD]
[TD="align: right"]60[/TD]
[TD="align: right"]80[/TD]
[TD="align: right"]100[/TD]
[TD="align: right"]150[/TD]
[TD="align: right"]200[/TD]
[TD="align: right"]250[/TD]
[TD="align: right"]300[/TD]
[TD="align: right"]400[/TD]
[TD="align: right"]500[/TD]
[/TR]
[TR]
[TD]75[/TD]
[TD]0.0052[/TD]
[TD]0.0260[/TD]
[TD]0.0519[/TD]
[TD]0.1036[/TD]
[TD]0.2063[/TD]
[TD]0.3082[/TD]
[TD]0.4094[/TD]
[TD]0.5099[/TD]
[TD]0.7581[/TD]
[TD]1.0125[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]80[/TD]
[TD][/TD]
[TD]0.0250[/TD]
[TD]0.0499[/TD]
[TD]0.0995[/TD]
[TD]0.1981[/TD]
[TD]0.2958[/TD]
[TD]0.3927[/TD]
[TD]0.4887[/TD]
[TD]0.7258[/TD]
[TD]0.9588[/TD]
[TD]1.1931[/TD]
[TD]1.4139[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]90[/TD]
[TD]0.9764[/TD]
[TD]0.0236[/TD]
[TD]0.0453[/TD]
[TD]0.0940[/TD]
[TD]0.1866[/TD]
[TD]0.2781[/TD]
[TD]0.3686[/TD]
[TD]0.4681[/TD]
[TD]0.6779[/TD]
[TD]0.8929[/TD]
[TD]1.1098[/TD]
[TD]1.3110[/TD]
[TD]1.7161[/TD]
[TD]2.1105[/TD]
[/TR]
[TR]
[TD]100[/TD]
[TD]0.9797[/TD]
[TD]0.8872[/TD]
[TD]0.0453[/TD]
[TD]0.0900[/TD]
[TD]0.1782[/TD]
[TD]0.2635[/TD]
[TD]0.3498[/TD]
[TD]0.4337[/TD]
[TD]0.6386[/TD]
[TD]0.8377[/TD]
[TD]1.0395[/TD]
[TD]1.2227[/TD]
[TD]1.5937[/TD]
[TD]1.9536[/TD]
[/TR]
[TR]
[TD]120[/TD]
[TD]0.9880[/TD]
[TD]0.9373[/TD]
[TD]0.8860[/TD]
[TD]0.6730[/TD]
[TD]0.1778[/TD]
[TD]0.2557[/TD]
[TD]0.3371[/TD]
[TD]0.4132[/TD]
[TD]0.5964[/TD]
[TD]0.7720[/TD]
[TD]0.9530[/TD]
[TD]1.1076[/TD]
[TD]1.5091[/TD]
[TD]1.7366[/TD]
[/TR]
[TR]
[TD]140[/TD]
[TD]0.9927[/TD]
[TD]0.9614[/TD]
[TD]0.9205[/TD]
[TD]0.8297[/TD]
[TD]0.5856[/TD]
[TD]0.3313[/TD]
[TD]0.3737[/TD]
[TD]0.4340[/TD]
[TD]0.5909[/TD]
[TD]0.7699[/TD]
[TD]0.9114[/TD]
[TD]1.0393[/TD]
[TD]1.3202[/TD]
[TD]1.5903[/TD]
[/TR]
[TR]
[TD]160[/TD]
[TD]0.9951[/TD]
[TD]0.9748[/TD]
[TD]0.9489[/TD]
[TD]0.8954[/TD]
[TD]0.7803[/TD]
[TD]0.6603[/TD]
[TD]0.5696[/TD]
[TD]0.5489[/TD]
[TD]0.6340[/TD]
[TD]0.7564[/TD]
[TD]0.8840[/TD]
[TD]1.0105[/TD]
[TD]1.2585[/TD]
[TD]1.4970[/TD]
[/TR]
[TR]
[TD]180[/TD]
[TD]0.9967[/TD]
[TD]0.9832[/TD]
[TD]0.9660[/TD]
[TD]0.9314[/TD]
[TD]0.8625[/TD]
[TD]0.7977[/TD]
[TD]0.7432[/TD]
[TD]0.7084[/TD]
[TD]0.7180[/TD]
[TD]0.7986[/TD]
[TD]0.9000[/TD]
[TD]1.0068[/TD]
[TD]1.2232[/TD]
[TD]1.4361[/TD]
[/TR]
[TR]
[TD]200[/TD]
[TD]0.9978[/TD]
[TD]0.9886[/TD]
[TD]0.9767[/TD]
[TD]0.9539[/TD]
[TD]0.9100[/TD]
[TD]0.8701[/TD]
[TD]0.8374[/TD]
[TD]0.8142[/TD]
[TD]0.8061[/TD]
[TD]0.8549[/TD]
[TD]0.9311[/TD]
[TD]1.0185[/TD]
[TD]1.2054[/TD]
[TD]1.3944[/TD]
[/TR]
[TR]
[TD]250[/TD]
[TD]0.9992[/TD]
[TD]0.9957[/TD]
[TD]0.9911[/TD]
[TD]0.9822[/TD]
[TD]0.9671[/TD]
[TD]0.9549[/TD]
[TD]0.9463[/TD]
[TD]0.9411[/TD]
[TD]0.9450[/TD]
[TD]0.9713[/TD]
[TD]1.0152[/TD]
[TD]1.0702[/TD]
[TD]1.1990[/TD]
[TD]1.3392[/TD]
[/TR]
[TR]
[TD]300[/TD]
[TD]0.9999[/TD]
[TD]0.9987[/TD]
[TD]0.9974[/TD]
[TD]0.9950[/TD]
[TD]0.9917[/TD]
[TD]0.9901[/TD]
[TD]0.9903[/TD]
[TD]0.9930[/TD]
[TD]1.0074[/TD]
[TD]1.0326[/TD]
[TD]1.0669[/TD]
[TD]1.1089[/TD]
[TD]1.2073[/TD]
[TD]1.3163[/TD]
[/TR]
[/TABLE]
Figure 300 oK approximates the temperature, @ ~200 Bar, Air doesn't deviate that much from an ideal gas
 
If using Luxfer AL80, SAC rate in cubic feet is computed using tank capacity of 77.4 cf. vs 80. This will lower your sac rate :).
 
I cannot believe how often these algebra/physics tank capacity fights start.
But please carry on.
It is always a good knowledge review.
And sometimes very funny.

Chug
Does not accept the word low, on low pressure tanks.
 
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