waterpirate
Contributor
Title says it all. Did two dives yesterday with long bottom times, on the same set of my double 72's????
Those of us that mix our own gas are quick to forget what the IQ of a average tank jockey really is. We tend to come to believe that they are equal to us, they are not. Mid season I was forced to move my fill station out of the garage it was in. The new location for it needs some renovation, so it went into storage. A local shop just started continuos blending nitrox, so no biggeie. I showed up there a month ago with 4 sets of doubles. 2 sets hp 100's and 2 sets lp 72's. I had filled them with HE prior to going and all should have been well. I told the tank jockey I wanted 32 in my 100's and 36 in my 72's. He obliged and cause I was in a hurry, told themI would annylise at home.
I use my 72's for 100' or less dives and the 100's for deep stuff. I dove a lot of deep stuff at first and noticed the 100's had cooled to a psi of around 32 or 3300 psi, a little lighter than what I would have filled but still diveable. I since went back to get the 100's re filled and everything was fine. Fast forward to Friday night. I am scheduled to go 90fsw on Saturday, so out come the 72's. I anylised them and came up with 29.5 for 02. The target was for 32/20 when filled. A little lite on 02 but still diveable, no biggie.
I asymbled my kit on the boat and all became clear. When I turned on the gas the pressure gauge went to 3700. OMG! Rather than fill the 72's with 36%, tank jockey filled with 32% to a final pressure of I am guessing somewhere in the neihborhood of 4k to yeild a cool pressure of 3700.
So I got a cave fill. Longstory short was I did 2 dives with 205 cubic feet of gas in 1 set of 72's. If you go outside your own fill station pay attention, it is scarry out there.
Eric
Those of us that mix our own gas are quick to forget what the IQ of a average tank jockey really is. We tend to come to believe that they are equal to us, they are not. Mid season I was forced to move my fill station out of the garage it was in. The new location for it needs some renovation, so it went into storage. A local shop just started continuos blending nitrox, so no biggeie. I showed up there a month ago with 4 sets of doubles. 2 sets hp 100's and 2 sets lp 72's. I had filled them with HE prior to going and all should have been well. I told the tank jockey I wanted 32 in my 100's and 36 in my 72's. He obliged and cause I was in a hurry, told themI would annylise at home.
I use my 72's for 100' or less dives and the 100's for deep stuff. I dove a lot of deep stuff at first and noticed the 100's had cooled to a psi of around 32 or 3300 psi, a little lighter than what I would have filled but still diveable. I since went back to get the 100's re filled and everything was fine. Fast forward to Friday night. I am scheduled to go 90fsw on Saturday, so out come the 72's. I anylised them and came up with 29.5 for 02. The target was for 32/20 when filled. A little lite on 02 but still diveable, no biggie.
I asymbled my kit on the boat and all became clear. When I turned on the gas the pressure gauge went to 3700. OMG! Rather than fill the 72's with 36%, tank jockey filled with 32% to a final pressure of I am guessing somewhere in the neihborhood of 4k to yeild a cool pressure of 3700.
So I got a cave fill. Longstory short was I did 2 dives with 205 cubic feet of gas in 1 set of 72's. If you go outside your own fill station pay attention, it is scarry out there.
Eric
