Missing Default tank on DC import

Steve Butler kg7je at comcast.net
Sun Nov 23 19:46:03 PST 2014


On 11/23/2014 07:34 PM, Steve Butler wrote:
>
> On 11/23/2014 07:34 AM, Dirk Hohndel wrote:
>> On Sat, Nov 22, 2014 at 11:30:33PM -0800, Steve Butler wrote:
>>> Deleted last dive so I could import from DC.  It came in without the 
>>> default
>>> tank from my preferences (HP119).
>>>
>>> In addition, when I selected HP119, the cu ft is not 123 (the 
>>> manufacturer
>>> of my XL-119 tanks claims they have 123 cu ft at 3442 #).  I have 
>>> verified
>>> that all occurrences of HP119 in my dives have been modified to show 
>>> 123.
>>> Is there some other place I should change?
>> What's the wet volume of that tank? It's possible that the manufacturer
>> gives the gas volume based on the ideal gas law (i.e., wet volume
>> multiplied with the pressure in bar). But air doesn't behave like an 
>> ideal
>> gas at higher pressures. We try to calculate an approximation of the 
>> real
>> behavior of air (look at surface_volume_multiplier() in dive.c) which
>> gives a lower gas volume at higher pressures as you would assume by 
>> simply
>> using the ideal gas laws.
>>
>> /D
>>
> The specs are:  http://www.xsscuba.com/tank_steel_specs.html
> The Nominal Capacity at 
> http://www.xsscuba.com/tank_steel_specs_metric.html is what we need.
> 15.3 liters should be 0.54 cuft.  @230 Bar the ideal gas is 124.34.
>
> The Z-factor for air at 250 bar and 300 K (little warm for room temp) 
> is 1.0669.
> The Z-factor at 200 bar/300K is 1.0326.  I'd estimate the Z-factor 
> around 1.05 for 230 bar.  Just an eyeball would put the "real" around 
> 119.
>
> <<sigh>> and here I wanted to believe the manufacturer especially 
> since their 120 tank is listed as having 120 cu ft and costs $25 more 
> at my LDS.
> --Steve
>
>
> So I'm guessing the True Volume from the first web page is the ideal 
> gas calculation.  However that implies to me that the actual capacity 
> is 116 cu ft  (124.34/1.0669=116.55).
>
> However, we are not at 250 bar so looking down at 200 bar with a Z 
> factor of
>
>
>
>
Been a long day.  Obviously that lower part was supposed to have been 
removed.


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