Sorry about the formatting... I copy and pasted this from a post I made on another board...
Some friends and I drove up to Rutland, Vt. to go diving. There's an old
abandoned quarry/mine up there with depths as deep as 180 feet, or so I'm told.
The bottom is littered by all sorts of junk, old cars, propane tanks, you name
it. Despite all the litter, the water clarity is superb. Because of all of the
debris and the depth, it makes a good training site for wreck and deep diving
classes. We were there for the mine, though.
So we all drove up there an unloaded tons of gear. It was so hot
out and here we are each with about 150 lbs of gear. It pretty much sucked. So
did putting all that gear on. The air temperature is in the high 80's but the
water temperature is in the low 50's. So we need all sorts of thermal
protection on, but we've got to put it on in some of the hottest weather.
Anyway, we got all geared up, hopped into the water and began our dive.
Now, to understand what happened on the dive, I have to give a quick equipment
lecture. Basically, we each are wearing two steel tanks. The tanks are banded
together and there's a isolation manifold connecting the two. The way this
works is that, for all intents and purposes, we have one big tank on our backs.
The sets have two valves, and each valve has a regulator attached to it. Each
regulator feeds one second stage (the part you put in your mouth) and each
provides inflation to either your wing or your suit. The idea being that if any
one piece of equipment failed, you'd have complete redundancy. If a regulator
fails we can just shut the valve off that's feeding it and we still have all of
our air supply available to us. Then we just switch to the backup second stage
if we need to. There is a valve in between the two tanks so that if a tank
valve actually fails, we can isolate the two tanks from each other, so we only
lose half of our air supply. Better half than all of it. Anyway, there is only
one pressure guage, and that's fed from the left regulator.
So anyway, I'm on this dive and I'm monitoring my air pressure. I started the
dive with ~2000 psi. At one point I noticed I was still in the high 1800's. So
I'm feeling pretty good about my breathing rate. A few minutes later I check
again and it's at 1865 psi. Hmmm.... not bad. But then I started thinking about
that. It seems like my air supply has been in the high 1800's for quite a while
now. I wonder.... I check again and sure enough, the pressure guage hasn't
budged. So there are 2 possibilities here. Either my pressure guage has gone to
nuts or... I reached back behind my head and cranked the isolation valve. There
was a loud-ass noise of two tanks equalizing pressure between the two. It's the
same sound you get when you fill a tank really quickly. Underwater, in a cave
and right behind my head, that was a really loud sound. Sure enough, the darn
thing had been close, and so had isolated the tank I was actually breathing
from from the tank that had the pressure guage attached to it. The tank with
the guage was the same one that was also feeding my drysuit inflation, so
that's why it appeared to be ok for a while, because I had added air to my suit
in the beginning of the dive.
I checked the pressure again and it had dropped to 1500 psi. Which means there
was a 600 psi difference between the two tanks. Wonderful. Now all I have to do
is determine if the air I've got left is enough to get me back out of the
cave...
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Topic: My dive this weekend... (Read 1927 times)