Cautionary Tale on a LP hose rupture
Saturday, just before the social, I did a dive in Cow with Forrest, TJ, and Richard. The exit plan was for TJ to take out the mainline reel and Forrest to lead out the SM exit with me following to take out the reel there. I had just waved Forrest and TJ ahead of me at about the end of the ski rope and I thought I had a free flow from my other reg (right tank). I looked down and it was fine. I heard a loud roar and realized I had a serious issue with the first stage on my left tank. I signaled Forrest who was ahead of me and started isolating that reg. I stopped and switched to my right reg and continued isolating my left tank. It was a pretty impressive leak, especially in a small area/ceiling like Cow. I swam to Forrest and TJ giving each the big thumb as I pointed to my left tank and finished the exit hastily.
It turned out that I had two fine cuts on my second stage hose on the left tank a few inches from the first stage.
I checked the remaining pressure in the tank after the dive and found it to be about 600-650 psi by my regulator gages!!!
We had turned before thirds and I had breathed my right tank down to 2400 and switched to my left tank, which had about 2900 in it. My guess is I was above 2000, probably closer to 2400 psi in that tank as I had planned on switching again before I made the exit.
I lost at least 1400 psi, maybe 1700 psi!!!!
I was not exactly counting off the time when I was isolating, but it was probably 10 seconds or a little more.
I first thought it was a free flow as it started at about that volume. Then it turned into a roar and I knew it was something more serious.
On reflection, I should have isolated much quicker. I was close to the exit, my buddies were close, I was diving side mount, so I had a completely separate air source with plenty of gas, all those things went through my mind as I switched regs and turned off the left tank pretty nonchalantly (after the WTF and I can’t believe this is happening passed. :) )
Now that I know my Apeks will push that much gas through a damaged LP hose I will isolate immediately, then switch regs. That extra few seconds may have cost me 3-400 psi of gas.
I enclosed a picture of the hose. I apologize for the fuzziness, but I guess my Iphone does not macro well.
http://www.cavediver.net/forum/galle...8/lp_hose2.jpg
http://www.cavediver.net/forum/galle...8/lp_hose1.jpg
I don’t recall contacting anything in Cow in the area of my hose, but Cow does have lots of sharp rocks. It may have been damaged when I set the tanks in the water, but there was no leakage up to that point in the dive. I use the swivel top apecks regs for SM and that hose has just gradual bends as it comes straight up over my left shoulder and around my neck on a necklace.
Below I attached a post from The Deco Stop on an experiment Curt Bowen did in Eagle’s Nest about 5 years ago. He tested different failure mechanisms at different depths. Good info for those who have not read it. I believe he may have written an ADM article on it also.
Divers
Here is a little test I did at Eagles Nest cave on Feb 12th for a small article to be placed in issue 17 of Advanced Diver Magazine.
The question I wanted to answer was:
How much time would it take to empty a full aluminum 80 cuft cylinder from 3000 psi to 0 for the following situations and would depth affect the times.
1. Failed Burst Disk
2. Failed HP Hose
3. Failed LP Hose
4. Free Flow high performance regulator 2nd stage.
I completed the test on the surface (0 feet) with 4 aluminum 80’s and a Zeagle D50 regulator.
Here are the results
1. Failed Burst Disk = 72 seconds
2. Failed HP Hose = 22 minutes
3. Failed LP Hose = 83 seconds
4. Free Flow High Performance Regulator = 255 seconds
I then repeated the test at 4 atm’s / 99ft
1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = Same within a minute
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 155 seconds
I then repeated the test at 8 atm’s / 231ft
1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = did not complete due to time restraints but would assume it would be with a minute difference
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 91 seconds
The results show the small amounts of time a diver would have to solve a major equipment failure while at deeper depths.
The question I post for you is
What would be the best procedure to follow if such an equipment failure occurred to you and why?
1. Isolate manifold
2. Turn off affected post
3. Dive independents
4. Other answer
Next time you’re in your rig, conduct a test on yourself and your buddy by doing a shut down drill. Not cheating estimate in seconds how long it takes you to shut down you manifold.
By the numbers given above, estimate how much gas you would have lost, would you have enough left even if you where following the rule of thirds or half + 200.
The answers will affect the finished article.
Thanks for your responses
Curt Bowen
