O-ring/low pressure hose failure

[g1138]

Your hose is most likely to "explode" unexpectedly when you first turn your tank on.
I will take an educated guess and say rarely will it explode and sever completely so you're left with a hose whipping you in the face. Most likely there would a loud bang and a gash would form leaking air from the outer bend of your hose, if it happened after you donned your kit.

Keep your hose kinked at a very tight angle near the hose connection when you pressurize and you increase your chances of blowing a hose. So ie. keep your hoses relatively straight or have a long easy curve to it before you turn the tank on. Turn your tank on very slowly until the hoses fully pressurize, then you can spin the knob quicker if you're in a rush.

For HP hoses you might see a bubble form under the rubber after you turn the tank on, then it might blow; sometimes it won't. At that point you should replace it though and not dive it. You can usually tell when an HP hose might blow after you turn on your tank. No bubbling rubber then you're pretty safe.
For LP hoses, if it doesn't blow when you pressurize, you can assume 99.99999% of the time it will not blow unless you inflict trauma on it during your dive.

 

[g1138]

For reference:
HP hose VS LP hose cross section.

HP has an thick inner core covered by rubber, which is why you can get a bubble forming underneath.
LP hose has a core imbedded in the rubber. So often it an LP leaks, it leaks through tiny pin holes along the hose.

You're not going to get any of these to Michael Bay explode on you unless you're plugging something much higher than what's in your tank or first stage IP.

 

[fire_diver]

I have a question that relates to the minimum of air one should have in order to resurface safelly with his buddy. Most "scholl of thought" would indicate that you need to calculate the amount of air that you need to safely surface ( including deco/safety stops ) for both YOU AND YOUR BUDDY. plus a certain reserve. Lets say 50 bars (700 PSI?).


My questions has to do with the frequency of low pressure line failure during ascent wich is, in my opinion, the only real reason why you want to have air for your buddy ( appart from LOA which has nothing to do in this case). Correct me if I am wrong, my questions relates to tropical water so I guess that the elimination of uncontrolable free flow is reasonable . EXPERTS PLEASE CORRECT ME IF YOU THINK I AM CRAZY

You indicate yourself as a divemaster and having 500+ dives but you think a hose "explosion" is the only reason to have air for your buddy?

 

[Doc]

For reference:

View attachment 192821

What explodes in Vegas stays in Vegas. Check out the all you can eat pre-Thanksgiving Turkey Buffet.

.... Back to topic....

 

[mathauck0814]

Hoses don't suddenly and mysteriously fail in the middle of a dive. I've never seen it happen. Hoses fatigue and start to bubble and you change them out. Take care of your equipment, rinse it well and inspect it prior to use and you won't have problems.

Insofar as gas planning to accommodate your buddy, I'd expect that a divemaster would have a grasp on that. If you're doing gas planning in a manner to accommodate low pressure hose failure, dive redundant first stages or redundant gas supplies. Low pressure failure will empty a tank in a hurry.

 

[KeithG]

during the first third of the dive... http://www.scubaboard.com/forums/near-misses-lessons-learned/444928-split-reg-hose.html

It did not "explode". It also did not "bubble" during prior dives.

 

[mathauck0814]

during the first third of the dive... http://www.scubaboard.com/forums/near-misses-lessons-learned/444928-split-reg-hose.html

It did not "explode". It also did not "bubble" during prior dives.

The hose was 22 years old, only 750 dives. The regs are serviced yearly and have always passed "inspection". The hose had no external signs of wear and appeared to be in pristine shape. The split was small enough that the repair tech could not visually locate the split - it was up under the steel sleeve... But maybe 22 years is a little too long.....

Sounds like you arrived at the same conclusion that ran through my head as I read your thread. I'm willing to allow room for an exception in my argument that hoses don't just fail suddenly and mysteriously to caveat that "20+ year old dive gear may suddenly and mysteriously fail"

Honestly I'm more impressed that you have a 22 year old hose than anything! Mine get swapped every couple of years.

I would suggest that the small hole and resulting 400psi of gas lost over 5 minutes would indicate what I intended to convey when I said "bubbling"

 

[nimoh]

during the first third of the dive... http://www.scubaboard.com/forums/near-misses-lessons-learned/444928-split-reg-hose.html

It did not "explode". It also did not "bubble" during prior dives.

the story indicates going through 400psi in 5 minutes at 10 feet. This sort of suggests the fatigue and bubble scenario that Mathauck0814 was talking about.

 

[fbk]

I've seen 2 LP hoses rupture mid-dive, both on the same dive trip. One was rental gear, the other was a DM's. I can only assume poor maintenance, but it does happen.

 

[Freewillow]

Thanks for your answer. To be honnest with you I do believe that hose failure at the end of a dive is close to IMPOSSIBLE. I just want to have a little proof of that. The reason for the question is as follows.In order to do your gas management , should one take the gas consumtion in order to go to the surface + an amount of safety ( let's say 700 PSI ), OR calculate the gas needed in order to get you AND your buddy to the surface on a SINGLE tank + A very very small reserve.