Blown Burst Disk right after thirds

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Divesherpa

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Scuba Instructor
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Girdwood, Ak
Blew burst disk today for the first time in the water. I was under the misconception that a blown burst disk underwater would be classified as a catastrophic failure. I isolated that tank, then breathed off that bottle until there was only about 700 PSI left in the bottle, then switched to the other. I'm breaking the tanks down now and giving them a simple green dip. I haven't popped out the disks, but there are two in there.

Any ideas why this could happen?

Cheers
 
I've never heard of a burst disk blowing once a dive has started and the pressure has started down in a tank.. that's really wierd!
Out of curiosity, how much gas did you have in the tank when you isolated it, and how long were you able to continue to breathe off it before it was depleted? How much gas do you think you lost before you isolated?
And did you test your "P" valve??
I probably would have... :)
Rick
 
Originally posted by Rick Murchison
that's really wierd!
Blowing a doubled disk!!
That's that's really really weird weird!!

Maaaybeeee somebody's messin' with ya Sherp...
Made any new enemies lately?
 
Not away from this forum! Ha Ha
I isolated with about 2600 PSI, continued to breathe off the side with the ruptured disk (c?) for probably 10 minutes (guage read 700 PSI), then switched.
I heard the constant bubbling start then I isolated and signalled for my buddy to see where the problem was. I shut down the post and purged, but the problem persisted. It felt like the disk and he confirmed that in fact it was a disk problem. Due to the confined space that we were in, we covered the next thousand feet in a hurry. After picking up the stage, we exited and completed deco (including deep stops).
I have decided not to break down the bottles and am not touching it anymore. Since I have never had this happen, I am consulting someone tomorrow who has a lot more experience in these matters.
I did loan out this set a few days ago, but the chick that borrowed them swore that she didn't touch a thing.

I am completely baffled by this whole event.

Any assistance would be greatly appreciated.
 
I had one bubbling in the fill tank the other day and I stopped the fill and set the tank aside to drain. Once the pressure was off I was able to retighten the bolt holding the disk in... it was loose by a quarter turn but impossible to tighten with pressure on... I have no idea how it got that way... this was a single disk and it looked good so I left it in... it was a HP tank and I took it to 3500 with no further bubbling.

Are you sure the disk is blown and not just loose?
 
Pug, I'm not sure. I'm not going to mess with it tonight. I'll have it looked at tomorrow. That theory makes more sense than the disk blowing.
 
I wasn't alone. If I were alone, it may have been of more concern. Looking into two 112's with over twice the gas needed to get to the stages (2/3's full) and having enough gas in the other bottle to make it with plenty to spare was very comforting. We rehearse for stuff like this, so it was cool to be tested so far back in a low area. You can't substitute a drill for the real thing.

You never truly know what you will do until it's over.

I spent too much time trying to figure out why my disk blew to be worried about anything.
Cave protocol is good at managing situations like this. I assumed the gas would flee much faster, which is why I dive independents so often. I could have taken a ten minute nap, then woke up and been fine.

Gotta love this stuff.
jdr
 
JDR,

Way to stay cool. Good to here you got back without spending all the available adrenalin. Just makes me keep doing my shutdown drills.

Larry
 
Sounds to me like 2 things could have occurred either your hollow bolt got loosened somehow( I sheared a bolt off on a wreck dive) or the copper disk corroded and put a pinhole in them. The leak was not as though the disk went completely. I have had them go and the tank drains in less than 2 minutes. Just my $.02
Ken
 
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