Posted by northcoast diver on January 11, 2005 at 14:06:27:
Here is a procedure I set up for cross-filling my double tanks, when you have multiple sets of doubles, together with a cross-filling DIN hose. I got this out of one of Gary Gentile's tech manuals.
You need multiple sets of twin tanks of the same size, and also a cross-fill hose which can be ordered from any technical dive store.
For this example the depth is 180 ft and the bottom time is 20 mins. At a 0.75 cu ft per min surface consumption rate, you would consume 104.9 cu ft of bottom mix (according to V-Planner). The tanks are twin E8 130s.
PAIR #1 ..... PAIR #2
260 cu ft ... 260 cu ft
<104.9> cu ft used during Dive #1
155.1 cu ft ... 260 cu ft
207.6 cu ft ... 207.6 cu ft after the cross-fill
<104.9> cu ft used during Dive #2
102.7 cu ft ... 207.6 cu ft
155.1 cu ft ... 155.1 cu ft after the cross-fill
<104.9> cu ft ... <104.9> cu ft used during Dive #3 and Dive #4
50.2 cu ft ... 50.2 cu ft minimum Rule of Thirds remainder
If you live far away from a technical dive store (like I do), this makes it very convenient for you to replenish your own tanks between dives. This also saves money (half off, in this case) rather than getting new fills every dive.
The concept was designed by Gary Gentile for excursions to locations without Helium or Oxygen fills available. He sometimes even fills his 2nd and 3rd sets of doubles with richer He and O2 mixes so that when he dilutes them with air after the cross-filling process, he then gets the same mix as the original one he was using.
My cross-filling hose has also been O2 cleaned so that I can use it with my deco bottles as well.