Catastrophic Failure At 50 Feet Revisited

[@mikesbigadventures194]

This is brilliant. I love not only the demo, but science and math. This is going to save lives. Also, Gus and Woody wanted to do this so now they have their answer.

[@LakeHickoryScuba]

We enjoyed making this video. Hopefully this will help other stay calm during emergency situations.

[@Chogogo717]

Watching the LP failure makes carrying redundant air seem like a no brainer. I like the one you did a few years ago in the pool, so at depth was really cool.

[@LakeHickoryScuba]

Thanks Caleb Mcelhaney, glad you liked the video.

[@jeffconley6366]

This actually happened to me back in 1982. I was doing a triangle navigation pattern over deep water as part of an instructor course. I was using a pilot valve second stage regulator. The pilot valve blew out. I was able to breath normally, the excess air just went out the exhaust valve. I don't recall what depth we were at or how long into the dive. I would guess around thirty feet. And we were half way through the pattern. But, when I looked at my pressure gauge I could see the pressure going down rather quickly. By the time my buddy and I reached the surface and he turned my tank valve off. My tank was almost empty (if memory serves approximately 200-400 psi). I blew my BC up by mouth. And we headed to shore. Pilot valves were going through a short phase as the best breathing second stage regulators. I never had mine repaired and never dove a pilot valve second stage again. They fell out of popularity rather quickly. I did notice that my perception of time slowed down. It seemed like it took forever for my buddy to recognize that I had a major equipment malfunction and needed to head to the surface. However, I'm sure it was only a few seconds. I had enough air to get to the surface. However, I was not deep. Had, I been at 100 feet. Would I have needed to get air from my buddy? I would say very likely. I was using an aluminum 80 cuft cylinder (tank). I am not saying this is how it would happen to someone else this was just what happened to me with that particular regulator and tank.

[@LakeHickoryScuba]

Hello Jeffrey Conley, thank you for sharing your story with us. First, I would like to say I am glad to hear you made it back to the surface safely, I'm sure it was a scary situation. Hopefully others reading this can learn from it as well, and they can rest assure that if they stay calm, they will have a better chance at making it back to the surface safely as well. Second, this is another great example of why we should always dive with a buddy and the basic rescue skills we are taught in Open Water should be practiced regularly.

[@lkndiver8186]

Nice job Bryan… been a while since we did that first video…. Thanks for taking the time to show us divers how to be informed and better prepared divers. Knowledge, understanding and practice help us divers surface safely from our alien environment adventures… 2 minutes of air for a free flow at 50 feet on a full cylinder. Your science proved that….I had less time… I was already 20 mins into that dive. That’s why I ran out of air so quickly . Case closed…. Knowledge, understanding and practice allowed me to remain calm while I tried to fix the problem. Preparedness allowed me to switch to bailout and safely surface. Thanks for taking the time help make us all better divers!! I look forward to our next dive!!

[@LakeHickoryScuba]

You're welcome LKN Diver. Hopefully, this never happens again, but you handled it perfectly last time. Like you said, being prepared and remaining calm is the key.

[@utubeflyer]

My daughter and I are both DiveMasters and anytime we are in low Vis, strong current, or below 60ft we sling ponies. No reason not to - you forget they are even there if your trimmed right. She has a crazy low SAC and carries a 13 cf which lets her do a normal ascent with safety stop from 120 ft. I carry a 19 cf. If we are in a group in any of those conditions I sling a 40 (rescue diver in me). Love what you said - gear is man made - failures can happen.

[@LakeHickoryScuba]

Sounds like you have a great system there Marty B. 60 feet is the threshhold for me as well, on when I decide to take a redundant air source. Most of the time I am in sidemount, thus, my system itself is redundant.

[@utubeflyer]

@@LakeHickoryScuba awesome, after 35 years of diving I'm finally doing doubles and advanced nitrox with my guy Manny here in Orlando next week, then definitely going sidemount. My 50 year old back doesn't even like thinking about toting those doubles. lol. Keep up the great vids!!!

[@sammoyers905]

Excellent, Excellent video Bryan. It is always great when the math works out like it is supposed to. As a Radiation Protection Technician, math is our business also. As for the tests themselves, WOW. Quite the eye opener. Thanks again for the excellent video.

[@LakeHickoryScuba]

Hello Sam Moyers, glad you liked the video. We thoroughly enjoy making videos like these.

[@maxtorque2277]

The HP hose failure should not really be affected by depth! The cylinder starts at say 3000 psi above sea level ambient air pressure, so average pressure is 1,500 psi. At 50 feet, ambient water pressure is about 20 psi. More likely to be a bigger difference is simply small differences in the HP hose inlet orrifice, which is tiny (< 1mm) and which is effectively going to "choke" (supersonic gas flow) when the hose is cut (the hose has a bigger internal diameter than the inlet orrifice so will not be the flow limiter

[@LakeHickoryScuba]

Hello Max Torgue, there are a lot of unanswered questions that has arised from this test.

[@jasonharris4349]

As others have said I love this. I will never forget the first time I was introduced to the concept that an HP failure is actually less serious than an LP failure!! This is something I want to share with all future students!! =)

[@LakeHickoryScuba]

Hello Jason Harris, I'm glad you liked our video. Feel free to share it with your students.

[@tobiashartung856]

Bryan, I'm happy to see you did the test and that you are trying to answer some of the theoretical questions that came up on the other video, but I would very much appreciate if you could address the criticism in the theoretical argument because as I see it, your argument in the last video was flawed. So let's recap the argument in your last video. There is a total volume of gas V in the cylinder. You measured the time T for it to bleed out. This gives you a loss rate of r = V/T. You now compute the loss rate R at depth by converting r into RMV (division by pressure at 10ft) and multiplying by pressure at 50ft. My criticism of this approach: this is a valid approach if we were looking at a free-flowing second stage that still modulates the gas pressure to ambient pressure. However, this is not the case here. For simplicity, the pressure at the hose end of the cut HP hose is still cylinder pressure. You are bleeding the air at cylinder pressure, not at ambient pressure. As such, I would consider the isothermal pipe-flow to be more accurate here. v^2 = A^2 V / (fL/D + 2 ln (p_1/p_2)) * (p_1^2-p_2^2)/p_1 where v is the volume flow rate, p_1 is the beginning pressure (in cylinder), p_2 is the ambient pressure, A the pipe cross-section area, V the specific volume, f a friction parameter, L the length of the pipe, and D the pipe diameter. Now the problem is that p_1 is time dependent and dp_1/dt = v, i.e., dp_1/dt = sqrt( A^2 V / (fL/D + 2 ln (p_1/p_2)) * (p_1^2-p_2^2)/p_1 ) This needs to be solved and is A LOT more complicated than a quick comparison to a free flowing regulator. Now, I understand that your 29 minute HP result was pretty nice but your LP result was off by 33% of your prediction. Your open valve results are off by 12%. That is quite a lot and even though your HP result looks nice, I am not sure you can justify your claim that the math worked out nicely with errors that large. In that sense and given that you have not controlled for things like hose length after cut and hose diameter, I think your computation in the last video is too simplistic and makes assumptions which in my opinion are not justified. I'd therefore highly appreciate if you could explain in detail why the cut hose should provide a constant volume flow at ambient pressure just like a free-flowing regulator would as this is the underlying assumption of your computation that I would dispute. Furthermore, if the assumption should be satisfied, then why are two of your three tests off by such immense margins?

[@LakeHickoryScuba]

Hello Tobis Hartung and thank you for the very detailed response. I will preface my response with a disclaimer. My understanding of physics is minimal as a Scuba Instructor. It would appear that there are even more unanswered questions that has arised from this video. Some that we are trying to address with another KZbinr who works with physics ever single day. Hopefully, he will have the time to collaborate with us to answer some of these questions. Stay tuned. Oh and as far as the 33% and 12% discrepancies, one of the main purposes of this video was to help new divers understand what happens at depth and to remind them to remain calm during emergencies. Whether it was 5 seconds off from our prediction or 30 seconds off our prediction, this gives our viewers a better understanding of just how quickly a diver can lose air at depth, and the reason they should remain calm during the emergency. For the purpose of this video, we are satisfied with the results. Hopefully, if the collaboration we are trying to get goes through, we can get a more scientific result to answer your question.

[@tobiashartung856]

@@LakeHickoryScuba "the main purposes of this video was to help new divers understand what happens at depth and to remind them to remain calm during emergencies" That's fine and I appreciate that you are showing this as it certainly is a good video to show people but if this is the point you want to bring across then you should have said "Let's give this a try and see what happens." There is nothing wrong with saying "I don't know what is going to happen, so I'll give it a try and show you my results." However, that is not the main statements I took from your expose here. I heard that you made predictions based on some scientific argument and that this prediction held true. I might have a go at the computation myself but I can't promise I can get a reasonable prediction given that there are too many unknowns and many of the material quantities were changed between your two tests, so it's not even possible to try and estimate them from the data. Yet, if your focus is to show students what happens at depth, is it really a good idea to use assumptions that aren't justified to make a point that is outside the applicability of the theory you use? In that case, what stops us from using air tables for decompression theory with trimix or oxygen stop times for air decompression? They are all decompression theories just like you used a theory of gas flow at depth without checking whether this is a reasonable description of the problem. Then, of course, what are we telling our students about the reliability of dive theory if we are talking about 33% error rates and considering them "good results"? I'm pretty sure if you were to ask a contractor to build an extension to your shop and ask him what he estimates the price is going to be, his answer being "$150k" and then he charges you $200k (a 33% error in the initial estimate), you are not going to go home and be like "man, this contractor was spot on with his price estimate!" Or using a more diving related example, let's plan a dive. Rule of thirds, I turn exactly at my turn pressure and oh my god I had a catastrophic 33% error. I surface with an empty tank. Not even time for a safety stop. Is this the message you want to send to students and new divers?

[@LakeHickoryScuba]

Seems like you are extemely passionate in the subject. That is awesome. Not real sure I will have an answer that you will find satisfactory. Happy diving.

[@DivingDeveloper]

*This was a fabulous video.* Very, very interesting. And you've busted some myths too. Thank you for sharing!

[@LakeHickoryScuba]

Thanks DivingDeveloper, glad you liked the video.

[@jhkleinberg2]

These are great videos. I really appreciate you doing these kinds of test. It really brings things to light. Definitely helpful to know if you ever have a failure like this at depth. This also reinforces why I dive with a redundant gas supply at all times.

[@ronbeatty516]

A Pony bottle is worth the money and peace of mind. 😀

[@LakeHickoryScuba]

Glad you liked the video Joe kle. These are definitely fun to make, just time consuming.

[@ahugenerd.]

The thing that confuses me is that the LP hose failure uses up the cylinder three times faster than a full open cylinder with no reg on it. Conceptually that makes no sense. It's not like the regulator first stage has the ability to make the cylinder valve flow faster or make the valve orifice larger. So what gives? Is it the expansion of air bubbles from the full open valve that is impeding airflow vs having a more efficient path through the LP hose? The physics here is very interesting. I fully trust the experimental data, I just don't think we have fully examined the differences between the LP and no-reg drain times.

[@mrstihl16]

I'm a bit confused by that too. My only theory is that some sort of venturi or laminar flow or other similar effect is happening in the first stage. These things can impact flow rates. I don't know enough about scuba regulators to say for sure what the exact mechanism that is occuring is. Something you can do to see the different types of flow are to empty a bottle by turning it upside down and then doing it tilted just right where it doesn't glug. You are working with the same opening, and the same.amoint of air enters, but the 2nd one empties faster. I can only assume the first stage allows for some similar event.

[@LakeHickoryScuba]

Hello Rene Enguehard, we are attempting to work with another KZbinr who is 1000 times smarter than us, so hopefully a collaboration will be able to answer this very question in the near future.

[@ahugenerd.]

@@LakeHickoryScuba If it's Destin from SmarterEveryDay I will be very excited! I believe he is a diver as well.

[@jpearce08055]

Yeah - this was very incongruous to me. I doubt that laminar or turbulent flow would affect the air coming out of the tank valve since there's no pipe through which a laminar or turbulent flow would occur. The 1st reg stage would restrict the airflow going into the low pressure hose so it should empty much slower. I didn't pay attention to the tanks and pressures used but perhaps the three tanks weren't identical in capacity and pressure, which would make the results not comparable. Also - these results are only applicable to the tanks used at the pressures used - it would be interesting to extrapolate them to (for example) an 80 cu ft tank at 3000 psi, which is what I'm used to renting in the Caribbean. Also - it might be useful to extend the explanation, especially for the LP loss which gives the least time, to what the diver should do in that circumstance. Since that type of incident is probably going to be caused by a stuck reg, how long should you try to clear it before heading to your buddy for air or immediately trying to surface? I'd be concerned that someone with a stuck reg would concentrate on clearing it, not be watching their SPG and not realize that they were rapidly running out of air. Also - note that you were starting with FULL tanks - if the incident occurred midway through a dive the remaining air time would be significantly reduced; consequently the actions of the diver might be different (i.e., don't try to clear the reg - instead head immediately to the buddy). What do you guys think?

[@ronbeatty516]

What great scientific experiments! Proving the scientific math formulas match reality is a beautiful thing...and it’s so fun!

[@LakeHickoryScuba]

Glad you like the video Ron Beatty.

[@gjjb6662]

Nicely done. Really appreciate the work you do for these. Where the vid for the tank moisture analysis?

[@LakeHickoryScuba]

Hello GJJB 66, we are still working on that one. Editing takes time when you run a business.

[@maxtorque2277]

I just carried out a "dry" test with my Apeks MTX-R reg set (1st and 2nd) when on a 10l cylinder with just 50 bar (700 psi) in it, and with a Miflex "carbon" HP hose, the small diameter braided type 1) setup as std: IP sat at 9.7 bar with no breathing demand, and dropped to a pretty stable 9.4 bar when breathed with a normal steady continuous breathing rate 2) Removed the SPG and swivel pin connector from the far end of the HP hose, effectively leaving that HP hose open to ambient pressure. IP sat at 9.7 / 9.4 unchanged. The Air leak was relatively small as the HP hose has two small orifii in it, what looks to be about 0.3mm at the 1st stage end, and around 0.8mm at the SPG end where the swivel pin sits. As the SPG orifice is much bigger than the 1st stage end (2.7 x the dia, 7 x the area) this test is most certainly very similar to actually cutting the HP hose, as the very small orrifice at the 1st stage end is going to totally dominate the discharge co-efficient. 3) Unscrewed the HP hose from the 1st stage completely, leaving the raw HP port open to ambient. The hole in the bottom of the HP port part, through to the HP zone inside the 1st stage, is about 1.6mm diameter (2.0 mm squared area, a huge hole at 50 bar!). Now, well, the air leak is best described as substantial, even at "just" 50 bar behind it, but the 1st stage did an amazing job, with an IP of 9.5 bar with no air demand from 2nd stage, and dropping to 9.1 bar with the same steady breathing demand as used in test1. This "hole" is roughly 28 times larger in terms of area than the 0.3mm hole that is in the end of the HP hose itself, but you would have to have the HP hose completely unscrew in order to experience a loss of air this great normally. If the O ring failed on the HP hose to 1st stage mating bore, then the air leak would be substanitally less because of the tortuous and long leak path up along the thread form, which has a tight clearance and so very poor flow characteristic. In terms of WOB, i could feel no difference in inhalation effort, as you would expect with such a small IP change on a pnuematically balanced 2nd stage Now at 15m/ 50 feet, the same breathing consumption as my nice smooth even breaths at sea level would of course require 2.5 times the flow through the pressure control system of the 1st stage, but i experimented with the cylinder valve position, and once the valve was more than about half a turn open, it no longer was a restriction, so with the cylinder valve fully open i would expect this performance to be repeated at a 50 foot depth. In fact, if we consider the spring rate of the 1st stage pressure control spring to be broadly linear, then we had a 25% increase in IP sag at the HP air leak tested in case 3) so assuming pressure loss is broadly linear to kinematic viscousity (and hence density) i'd expect the IP sag to be 2.5 times greater at 50 feet. Which is still well above an IP of 8.5 bar and would not lead to any change in inhalation effort. I also have no doubt that my classic SP MK25 1st stage, which has flow paths big enough to breath through easily at zero bar (I've tried, you can breath a cylinder down to zero bar incredibly easily with this piston 1st stage because the default position is fully open) would perform even better at maintaining the IP under such duress. If you repeat the test, it would be fascinating to do it with cylinder pressure and IP being logged during the test!

[@LakeHickoryScuba]

We would love to repeat this test, and hopefully a future collaboration with another KZbinr, we will have the opportunity to do so. Unfortunately, at this time, walking over to the sales floor to pull product off the shelf for testing is not really an option. Its interesting to hear about the results you got during your dry test. We have had others respond with many different theories, theories we wished we could answer. Adding the IP at the beginning of the test is a great idea, one that we didn't even think about. Over the last 33 years that I have been in the scuba industry, I have come to realize, the more I know, the more I have to learn. Here at the shop, one of the biggest discussions our staff has had, is why does air travel through the valve, first stage, and low pressure hose faster than just through the tank valve. The orfice of the tank valve does not change. My personal theory is, the first stage simply moves the orfice to the end of the hose, which is larger in diameter, allowing a larger volume of gas to come through in a shorter period of time. But this is just my theory. We are hoping a future collaboration will answer a lot of these unaswered questions.

[@maxtorque2277]

@@LakeHickoryScuba The answer is the weird world of gas discharge co-efficients, that we can sum up for the lay person as "turbulent vs laminar" Imagine water flowing down a pipe, all flowing together, linearly as a "chunk" of water. It clearly exits the pipe at the diameter of that pipe. Therefore the flow rate is simply the velocity of the flow, multipled by the exit area. Simple, easy to visualise But with compressable gases, things get weird real quick! At very high pressure differences, the effective exit area is "choked" because of the speed of sound not allowing pressure waves to flow "upstream" These problems are the same problems that resulted in the mythical "sound barrier" in the late 1940's. The effective throat area becomes smaller, sometimes much smaller, as the air arriving has no time to get in a nice ordely que, and simply tumbles around the place in all sorts of directions. That "turbulence" takes away energy from the stream (and makes a lot of noise!), and as the free stream velocity is no longer straight down the tube but at a angle to the tube (radially) the effective velocity falls. Both those characteristics mean that counter intuitively, less air can flow out of a bigger hole if the discharge co-efficient is worse than for a smaller hole. So with a cylinder valve and the 1st stage attached, the pressure drop across the 1st stage happens at effectively "Better" conditions than for the raw valve, which perhaps isn't that suprising if you look at a valve internals, which is all sharp edges etc. Hope that sort of explains why :-)

[@LakeHickoryScuba]

You make perfect sence, and most of our staff have been discussing this all morning.

[@ivoryjohnson4662]

Thank you for doing this test and educating us.

[@LakeHickoryScuba]

You're welcome Ivory Johnson, glad you liked the video.

[@pacediver2594]

That was very interesting and informative thanks

[@LakeHickoryScuba]

Glad you liked it Pacediver.

[@ericburgess4995]

Great job, very informative and somewhat scary. Thanks for making the video. The lesson is clear, second stage failure has very little margin for making it out. Maybe another argument for sidemount. Certainly a big consideration for solo divers.

[@LakeHickoryScuba]

Glad you liked the video Eric burgess.

[@johndavid7783]

Nice video great info.. would be a great video to show in open water course . And let them see that even if it was a controlled failure that while you were breathing you stayed calm. In my personal opinion it would take a bit of fear away and maybe stop someone from just a full out panic and bolting to the surface..

[@LakeHickoryScuba]

Hello John David, we show our first video all the time to our Rescue Students. We plan on showing this one as well.

[@morganames8142]

WELL DONE, Bryan!

[@LakeHickoryScuba]

Thanks Morgan Ames.

[@zachdenney]

in terms of zip tying... if you had an industrial zip tie could you not close the valve, zip tie, and then reopen the valve? yes, you are cutting off your air source, but in theory, would this work?

[@LakeHickoryScuba]

Hello @zachdenney, it might be something worth trying in a controlled environment.

[@brazeagle]

Great, thanks a lot. Valuable information

[@LakeHickoryScuba]

Glad you liked the video Luiz Carlos Laba.

[@maxtorque2277]

Just tested the effect of removing an LP hose! cylinder at about 40 bar, completely removed the LP hose from the turret of my MTR-X 1st stage. Basically leaving a wopping great hole in the side of the turret f about 10mm diameter (75mm square!!) Astonishingly the 1st stage managed to get the turret up to just under 3 bar with that hole, and i could breath from the 1st stage attached to the turret, although the inhalation effort was increased above normal, but not catastrophically so. With a 700 cm miflex LP hose without anything on the end screwed into the turret, having holes of min diameter of about 7mm (38mm square) on each end, the 1st stage managed to get the IP up to a pretty impressive 8 bar, and the 1st stage on the other hose breathed normally. I think the take away from all this is that there will be SIGNIFICANT differences in breathing performance and cylinder total blow down time depending the exact format and location of the pressure containment system failure, and the architecture and type of 1st stage being used. Counter intuitively, a very "high performance" 1st stage, ie one that can supply a lot of gas, will both drain the cylinder faster because it's internal flow paths are less "lossy" but actually be able to supply a diver with more gas and a lower inhalation effort whilst it does so!! So, choose you fate really? You can have a system you can't breath from but that takes longer to blow the cylinder down, or a system you can breath from that takes less time to blow it down........ To me, this means that redundancy, via a buddly, dual supply system (doubles, pony/stage etc) is still the best option in all cases, but that in the event of a large loss of gas, it is probably worth at least trying to breath from the failed system as this could buy you a vital few extra minutes.

[@LakeHickoryScuba]

Thanks for your results. We second always having a back up system.

[@beaverstaterich881]

Excellent!! Thank you.

[@LakeHickoryScuba]

You are welcome Beaver State Rich, glad you liked the video.

[@KB-gd6fc]

What was the SAC rate you used for the various failures? I'd like to do the math down to technical depths. If one has a failure on a single tank the best course of action is to share gas with a buddy, shut the valve off, and safely ascend to the surface. There's no need for rapid ascents or feathering valves if you and your buddy act as a team and plan gas accordingly.

[@LakeHickoryScuba]

K B, the SAC rate formula is simple. Air used / Depth in ata / time at depth. Then you can convert that to an RMV rate by Cylinder Volume / working pressure. Then simply multiply the two together. SAC (Air Used / Depth in ata / Time at Depth) x (Cylinder Volume / working Pressure) = Respitory Minute Volume. Hope this helps.

[@KB-gd6fc]

@@LakeHickoryScuba I understand that part. I'm wondering what was the actual SAC rate you used for the calculation.

[@LakeHickoryScuba]

In our previous test we used the numbers from that test. So with the low pressure failure it was Air Used (3000psi) / Depth in ata (1.3 ata) / Time at Depth (3 minutes) = SAC RATE of 769.23 psi/min. While still at the surface, we took the working pressure of 3000 psi, and divided it by 769.23 psi/min. This gives us a run time of 3.9 minutes at the surface. Then to take it back down to 50 ft (2.51 ata), we simply divide 3.9 minutes by 2.51 ata, and our theoretical run time is 1.55 minutes. Here is the origional video which may help in your calculation. kzbin.info/www/bejne/qH3VYmpvpcqdarM

[@tiagor3272]

Great video and follow up. Do you agree that there will be a depth after which the time to deplete the cylinder due to the low pressure failure will be constant, i.e., at the depth at which the regulator maximum flow is reached.

[@LakeHickoryScuba]

This is a great question. If the cylinder is pressurized to 3000 psi and a diver was physically able to make it to a depth of 6701 feet, which is where ambient pressure is 3000 psi, then physics would tell us if we opened the cylinder valve, no air would come out. This would definitely be a great test, just no safe way for me to do it.

[@tiagor3272]

@@LakeHickoryScuba I think that you missed my point. For example a Scubapro MK2 has a maximum flow rate of 3000l/m as per its datasheet. In your video a 80cuft (11.1l @ 200bar) took 2min to deplete @ 15.24m, which gives a flow rate of 1110l/min@15.24m (11.1lx200bar/2min), thus the maximum regulator flow rate would be reached at 6.8bar=58m (P=3000l/min/1110l/min x 2.524bar), meaning that if you are at 58m or deeper your cylinder will deplete in 0.74min=44s. Would this mean that if we have a better regulator, say a Scubapro MK25 with max flow rate of 8500l/min that we would have less air time in the event of a low pressure hose failure? Or do you think that the indicated times would be independent of the regulator type?

[@LakeHickoryScuba]

Hey Tiago r, yes, we most definitely misread and misunderstood your comment. Sorry, we have got so many comments in the last few hours its hard to read and respond to all of them. As another subscriber has commented, in his dry testing, he got many different results from producing the same failures in different ways. An example was to remove his second stage, then cut his second stage hose, then remove the hose completely from the first stage. All 3 gave him different results. He also stated that his theory was the first stage and its design would also play a huge role in how quickly you lost air. So it may very well be a depth where time to deplete your cylinder is constant.

[@Etimos1]

very informative!! thank you

[@LakeHickoryScuba]

You are very welcome Etimosman.

[@pearls4avant]

LP vs HP hose makes sense, but the slower time with tank valve failure and no regulator at all is odd. If there's no resistance from a reg, this seems like it should have been faster than 2018 with a cracked reg seal. And faster than the LP failure. How can the air escape faster with the reg and punctured LP hose vs. no reg at all? The reg is lowering pressure to the IP (~150psi) - directly from the cylinder with nothing connected has to be the highest flow or else you're saying the regulator is increasing the flow?

[@LakeHickoryScuba]

Hello Andrew Chang, this has been the talk for days now with our staff and others. Our first theory is its a more controlled flow, which means the air is not circulating back on itself. You can see this by opening a valve on the surface and by placing a golf ball in front of the valve, it will suck to the valve. Thus, creating resistance. This of course is just a theory. Hopefully, in the near future, someone a lot smarter than us will be able to explain what is happening and we will all become smarter.

[@pearls4avant]

@@LakeHickoryScuba where's a fluid dynamics PhD when you need one?!? LOL!

[@ihti20]

Probably, blasting air creates a void, that collapses and causes shockwave, which plugs a hole. Seems like HP hose is plugged more effectively. The air goes out one bubble at a time. With valve and hoses in place, when cutting the LP hose we have a quite constant flow in HP circuit, which can be miles faster, and the air exits at low pressure without supersonic flow, so nothing plugs the hole, resistance is much lower. I think, similar thing happens when you pour the water out of the bottle: being flipped upside down it discharges slower, while air bubbles struggle to get in, rather than when tilted slightly and air passes through a bottleneck in a constant flow.

[@bikeon143]

I wish I could find the video of a diver that lost his connection to the Wisdom 3, his tank wasn't full at the time and he didn't have much time at all.

[@LakeHickoryScuba]

Let's us know Hojo in SC if you find it. We would be interested in seeing it and studying it.

[@maxtorque2277]

I suspect the "o ring failure" which was a cyl with an open valve and no 1st stage was significantly worse than a real o ring failure. This is because the orifice in a cylinder valve is pretty big where as an O ring sits in a groove that fits up to the sealing face only leaving a small gap (other wise the O ring would clearly just extrude straight away given the gas load that it experiences (3000 pounds per square inch!). if a O ring fails, it would, even on a yoke style attachment system be unlikely to either be completely extruded, or if it were, to leave behind such a large flow path. The unexpected thing for me is that you seemed to experience a poor breathing capability (using the 2ns stage) during the HP hose failure test? This doesn't make a lot of sense. We know the cylinder valve can supply enough air to empty the tank very quickly (a couple of minutes as your test proved) so the small amount of air leaking via the HP hose orrifice (taking 29 min to empty cyl), which is tiny as mentioned, should make no difference at all in the feed pressure to the 1st stage regulator and hence virtually no difference to the IP and the performance of the 2nd? Given the stream of leaking bubbles from the 1st, and the apparent difficulty in opening the cyl valve, i wonder if something had phycially gone wrong / failed in that 1st stage prior to the test?

[@LakeHickoryScuba]

Hello Max Torgue, you pose a great question, and one at this time, I do not have a good answer for. I can confirm that the first stage used was out of service for use, but did hold an intermediate pressure of 10 bar / 150 psi, even with the leak. It shocked me as well at depth on just how hard it was to breathe from it.

[@Kroggnagch]

I think they meant “kink and then zip tie”, maybe even several kinks and several ties. But maybe they did mean just straight up zip tie the hose... but even I can see how that wouldn’t work.

[@LakeHickoryScuba]

Hello @dudiusmcthude9559, we had another commenter ask if the pressure was turned off then zipped tied, would it be able to hold the pressure once the cylinder was once again turned on. It would definitely be worth testing.

[@dh5645]

Fun experiment and I am a fan BUT basically meaningless since during a dive and prior to failure you will only have a full tank for a fraction of a second… So if your failure happens halfway through the dive or towards the end of your dive… The only real safe solution is redundant gas

[@LakeHickoryScuba]

We are big supporters of redundant air as well. Even more so, proper gear maintenance is the most important thing a diver can do to prevent this from happening.

[@asdf154]

How come the low pressure hose failure was so much faster than the valve failure? I would have thought the valve supplies all the air, so would be faster

[@LakeHickoryScuba]

Hello asdf154, in the video we did back in 2018, we showed the orfices of each hose and how air flowed through it. It explains why air travels faster through a low pressure hose. I will link the video here for you. kzbin.info/www/bejne/qH3VYmpvpcqdarM

[@josesolis5803]

Thank for you compromise with the scuba dive community is so good have this Cain the info thanks

[@LakeHickoryScuba]

Glad you liked the video Jose solis.

[@richlaw5136]

So, you would have 2 minutes of air in the regulator.. but after you take that last breath you still have a few minutes before you black out. So what if you're at half a tank at 50 feet and you get a catostrophic failure?

[@LakeHickoryScuba]

Hello Rich Law, this is why we encourage to always stay near your buddy. If a divers is trained in Solo Diving Techniques, carrying redundant air is always required / recommended / suggested.

[@MrMustangMan]

Ocean Gate CEO should have watched this video.!!!!!!!!!

[@LakeHickoryScuba]

Hello @mrmustangman, our thoughts and prayers go out to the victims and their families.

[@Kroggnagch]

Can you show us how fast a vessel is crushed at, say, 4k meters? Are there any clear cases or containers where crush depth pressure can be reached and show us how fast something implodes? Does sonoluminescence occur when submersibles are crushed? I’m gonna subscribe, and hope to heck you see this comment and will be able to show us something (a hollow something, similar to a sub) being crushed under massive pressure, and underwater.

[@LakeHickoryScuba]

Hello dudiusmcthude9559, with the recent tragedy of the OceanGate fatalities, our thoughts and prayers go out to the victims and their families. There have been several videos released by others explaining how much pressure is exerted on an object at that depth, and how fast a vessel (sealed vessel) would implode. The theory of Sonoluminescence is a very interested one. Currently, we have videos produced and uploaded (scheduled until late October, 2023). It may be a while before we can schedule and produce content related to Sonoluminescence.

[@MegaFPVFlyer]

You would need some very serious equipment to perform testing at those depths, even simulated on the surface in a pressure chamber. But yes, it would be incredibly interesting to see a deep sea implosion in real time. The easiest way, I think, would be to run a very long line straight down with a camera and simulated hull on a sled.

[@landgin3781]

Seems you got an air leak.

[@LakeHickoryScuba]

Oh it will be fine. A little duct tape should fix it right up. LOL. Hope you are doing well Calvin.

[@jonathangodfrey6474]

Loved this video thank you. Love slinging a 19cu ft under my left arm

[@LakeHickoryScuba]

Glad you liked the video Jonathan Godfrey.

[@KB-gd6fc]

New tat? Looks nice. What's I say? Looks like Hebrew.

[@LakeHickoryScuba]

Hello K B. Its an optical illusion. If you read between the line it says Jesus. Do a Google search for Jesus Optical Illusion and you will see a picture of it.