This was in response to the particular example that Dave Sutton posted,
about a 190 foot open ocean dive with medium surface conditions (10'
swell?).  I get oxygen from my supplier at 2200 and have no booster
pump, so use the 40's.  If I had the option of filling to 3000, I would
step down to a 30 cu. ft. cylinder, since to require more oxygen than
that means that I did too long a bottom time for those particular
conditions.  I am not a big fan of incurring huge decompression
obligations in the open ocean where conditions are subject to change at
a moments notice.

-Sean


On Mon, 25 Oct 1999 10:07:32 -0400, Joel Silverstein wrote:

>Sean,  you wrote 
>>
>>Fourth, a 40 of oxygen filled to supply pressure (2015-2200 psi)
>>contains more than enough gas to deco out on for that dive, unless you
>>are doing ridiculous bottom times, in which case you should ask
>>yourself if you can do two shorter dives instead of one long one, or
>>you are doing a ridiculous deco for a given dive, or if your RMV is
>>poor and you need to hit the gym.
>>
>
>This has come up a few times before, recently I was speaking with some
>folks in Florida about this same issue. 
>
>It seems that you folks are filling your 40 cuft 3000 psi oxygen cylinders
>to only 2/3rds their rated volume resulting in approximately 26 cuft of
>gas. One operation told me they will only fill to the supply pressure of
>the oxygen for "legal reasons" another very large operation tells me they
>only fill to supply pressure because they don't have an oxygen booster. 
>
>Now we know this is where the stroke mix (80%) came from by topping up
>these tanks to rate pressure, but that's not an issue since 80% is just.
>well its just stroke mix. 
>
>Up this way all of the reputable fill stations have gas boosters and are
>very happy to fill oxygen to 3000 psi so one has a proper fill.
>
>Is the reason for the acceptance of a partial fill purely the fact that
>there are no gas boosters out there or is there another reason ? 
>
>I have also seen some oxygen suppliers able to deliver O2 in supply
>pressures of 4500 psi but that's not too common, 2400 and 3000 supplies are. 
>
>Just looking to find out why ? 
>
>Thanks 
>
>Joel Silverstein
>http://www.nitroxdiver.com
>
>


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