HP hose failure at max penetrartion

[Nitrogenius]

This is something Curt Bowen wrote up years ago -

Worth taking a look at the different times it takes to drain a tank (LP vs. HP)

Thanks Walter, when I first read this report I was thinking about exactly that test and article, just could not remember the source anymore. Also a German dive magazine had done a similar test with same conclusions.


So knowing that I thought, this really should be a non issue, but as this thread is showing to a lot of folks a lot can be learned..

The main reason I wrote it up was because I was shocked I couldn't hear it. I can always hear free flows or my wife's reg honk occasionally. I was shocked I didn't hear it.

Due to the above it actually is not surprising at all. Even a full rupture of a HP hose is not a very "heavy" leak as in not much gas is actually flowing. This is way different than a "traditional" free flow. It is due to the diameter of the boring in the 1st stage . As you can see disassembling a HP hose vs an LP hose from a reg the hole on the HP side is extremely small, whereas the LP side uses the whole diameter available. The actual mass flow is heavily depending on such diameter, surely pressure differential has its role, but the diameter is key.
The hole diameter at the regs is purpose driven as well. on The HP side the hole is there to simply allow the reading of a pressure it is not designed that a lot of flow is supposed to pass, just enough to provide a reliable reading to an SPG. The LP sides function is to provide gas for heavy breathing at high depths while still maintaining a comfortable work of breath..
The noise created again is a function of the mass flow.


So given that a HP leak is really not something that is extremely time sensitive.. 22 min for a full tank to empty.. no biggie..

I have only lost 2 like that, but still scary.

Given the above a HP side failure should never be scary at all..If that gets you in trouble one is doing several things terribly wrong in other areas of safe cave diving..

I would've thought one could easily hear big air leaks, even scootering, but my prior experience has been thankfully limited to just the occasional free flows, I guess those are pretty easy to notice. I'm surprised you lost 300psi in 30 seconds or less, so your tank would've been empty in less than 5 minutes?! Wow, many times I scooter for way longer than that on a stage without checking any pressures, maybe time to reassess that habit.
And why not pointing the spgs forward? Easier to see and no more bending.

here we are at the big lesson learned from this!
As explained not being able to hear it is quite reasonable as in fact it is NOT a big air leak, but the opposite..
For draining times Curts article is a great reference. So the reverse math seems a bit off but likely due to the relatively short period of time.. 30 sec or 1 minute and 300 psi makes a huge of a difference..
But still it is enough to remember: Always know your gas, so also main tanks need to be checked frequently.. So if i.e. checked every 5 minutes or so.. an HP leak is no biggie, one lost a little gas, should not have any effect turning the dive at that point when the leak is detected.
But even when going undetected at all, that's what conservative gas rules are for.
Hence I said for this to get scary one needs to do a couple of things wrongly..


Talking about scary.. That blown elbow on the LP side.. that is the stuff scary is made of
Again also no biggie given conservative gas rules etc. but even with noticing immediately, and this will not go unnoticed by the time one has closed that tank likely a lot more gas will have been lost than with an HP leak..
Real scary DIR doubles with open manifold diving solo.. hence why one on such configuration should at least have a "buddy stage"..
While one will be able to reserve some gas.. will it be fast enough to really save half a gas supply.. this at max penetration will certainly effect ones SAC

[rddvet]

Good article on blown hoses. I've always been told an hpwas no big deal, just as this one wasnt. It was a great learning experience as you never know if what you've been told is accurate. On top of that it showed how good my wife and my team skills are. We both were in perfect sync and didnt miss a beat and didnt have any change in depth while we discussed and corrected the issue. I cant say that it would have been the same if I had an instabuddy. We've always had great respect for the gue team diving mentality and wish we'd known more about it when we went down the technical road. Though it wouldnt have led to a catastrophe, trying to handle the same situation with someone not trained the same as we were together would not have been as smooth.
We practice emergency scenarios regularly but having a minor unexpected one was actually a nice skill solidifier. Though I sure as hell dont want a lp failure.


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[gschaut]

Sorry to join the thread late, been on the road.

I've always carried LP and HP blind plug and wrench in my man-purse. Would removing blown hose and plugging HP outlet have been an option?

Thanks, Gary

[rddvet]

Sorry to join the thread late, been on the road.

I've always carried LP and HP blind plug and wrench in my man-purse. Would removing blown hose and plugging HP outlet have been an option?

Thanks, Gary

Sure but it also would have slown down the exit tremebdously which when in wide open passage in ginnie and a scooter to get you out why waste unnecessary time. Maybe if I was going to be pushing gas to get out but when would that happen anyway unless you had another emergency issue as well. It took 30 seconds for my buddy to get to me, shut down my valve while shoving her long hose in my face, me to assess what happened, confirm all was good and head out. Since my spg showed 500 psi (which I knew couldnt be accurate), it wouldnt be smart to waste extra time doing a reg repair just in case that 500 psi was accurate. Probably wpuld waste half of it doing a reg repair. Whereas if it was accurate at least I had the option of feathering that valve if something happened to my left tank.

I try to justify every tool I bring in with me, and I could never justify a situation to carry spare plug ports except for fixig a surface problem. Any other problem that would require ports would likely require immediate exit regardless.


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[Nitrogenius]

Sorry to join the thread late, been on the road.

I've always carried LP and HP blind plug and wrench in my man-purse. Would removing blown hose and plugging HP outlet have been an option?

Thanks, Gary

HP i think repair is not worth it. once you notice you shut off that tank. if you really need to acces that gas for some reason you can still feather.. i did the latter in a dive before when i had a spg oring blow just when i have been in the water in a shallow ow dive with a lengthy walk from car to water.. i had an almost regular dive feathering..
for lp plug i have a hard time coming up with a scenario where it is helpful. the only would be a rupture of an inflator hose.. then it will spare you additional gas due to the repair. repair likely better to handle than feathering such lp failure..
but still question is if time for repair is worth it..
all other lp failures a plug would not help you anything..

[Red Hat Jef]

I prefer to have my SPGs forward, but angled into my chest for a number of reasons. However, maybe there is not a practical way to configure some first stages for this?

The way you rig your forward facing SPGs is pretty good. I always cringe when I see people with them sticking straight out like antennas. I've seen a few low places where there are sidemount SPG trenches and wonder if folks are self-aware of that situation.

[Webmaster]

I started out with the spg's on 6" hoses pointed up, they always seemed to be catching on rocks, limbs, etc... but switched to 9" hoses laid along the tanks. That works pretty well, and because you have a bit more length don't have to bend it nearly as tight as you would with a shorter hose.

I only use rubber hoses, and I've only had two real issues. The sheath was cut through, I think moving the tank out of the water after a dive. And also the glass on a spg got smashed, also I think while moving the tank. Hose never leaked though.