Low Pressure vs High Pressure Air Loss Test
HTML-код
- Опубликовано: 4 сен 2024
- Low Pressure vs High Pressure Air Loss Test
After receiving an email from one of our subscribers, telling us of an incident that occurred to him while diving at one of our local quarries, we invited him to join us at the pool to simulate his catastrophic failure. We then compared our results to his incident and looked at the equipment itself to determined why a diver loses so much air at depth during a catastrophic failure. We want to give a big shout out to Steve Nash, for sharing his story with us, and for coming out to help us do this experiment.
If you are interested to learn more about the SSI Equipment Techniques Course, click this link here.
info.divessi.c...
/ lakehickoryscuba
Lake Hickory Scuba Center & Marina
/ lakehickoryscuba
www.lakehickor...
/ lakehickoryscuba
/ lhscuba
/ lhscubamarina
Instagram - Lake Hickory Scuba
lakehickoryscuba@gmail.com
420 Taylorsville Beach Ct. Taylorsville, NC 28681
828-632-7649
One of the most informative scuba videos I've ever seen! THANKS
You're welcome Bill, glad you liked it.
@@LakeHickoryScuba yup
Just found this even though it’s old - thanks for showing exactly what we needed to know. I had seen similar tests (Alex Pierce did one) but hadn’t seen it done so dramatically. Initially I thought as others did that you also needed to factor in the diver’s air consumption but that would be minimal (about 1/1000 from your numbers) when compared to the leak. And you did this with a full tank - the remaining air time would less (although probably not linearly less - a 1500 psi tank would probably last more than 90 seconds) with a half-full tank. But the short time suggests to me that a diver experiencing a low-pressure freeflow should spend NO time trying to fix it and should instead immediately abort to his buddy’s air supply, or surface immediately if no buddy was nearby. Even if the freeflow could be fixed (while breathing the buddy’s air) the loss of tank pressure would mean the dive would need to end anyway. Do you agree? Is this what’s taught in these cases? Thanks.
Hello Jon, we use this video in all of our Stress and Rescue Courses. You would be correct in choosing to abort the dive instead of wasting time trying to fix the problem. With this being said, you can still try to fix the problem, however, there would be no need to continue the dive as you have already had a catastrophic failure. I would definitely want to get my regulator serviced before I continued to dive with it.
Thanks for including the data also in Metric
You're welcome
Metric master race
You don't need me to tell you you're contents outstanding ... but I like to "talk". Good shit man. Made me decide to swap out all orings.
Hello Kevin Gumfory, glad you liked the video. A little repair on land can definite prevent a major catastophe underwater.
another excellent video, keep 'em coming. also it pays to consider the failure may come 1/2 way or greater thru the dive giving you seconds of usable air.
Thank you sparky.
I'm a new driver and was shopping for a tank.
HP it is!
This was EYE OPENING!
Thanks!
Hello Juror63, glad you liked the video.
That's not how it works. Both HP and LP cylinders with have HP and LP hoses coming off of the 1st stage of the regulator. This video shows what happens when HP and LP hoses fail, or the O ring does. LP hoses are used for the power inflation, regulator second stage, drysuit hoses and the like. The HP hoses are for the pressure gauge.
I had the high pressure o ring go on me on my tank pod this weekend when doing my Rescue Diver course.it was found very quickly whilst doing my pre dive check.o ring replaced and safe dive made.needless to day I passed my course.loving your vids keep em coming.all if them are very informative
Hello sayittrue, glad you like our videos, and even more glad you prevented a problem before going underwater. Great job.
This is an old video, but great one. Let me throw this in through. This is a BEST case scenario of a WORST case scenario. at 3000psi, you probably just began your dive. if you're mid dive, so you're anywhere between 1000-2000 psi, those times will be significantly less. so your valve failure might give you 2-3 minutes. a regular descent with a 3 min safety stop at about 60-80 feet, ,you're not going to have enough time. at that point, an emergency ascent from the depth you've run out of air might be due.
You make a great point @sofloemir. This is a controlled version of a catastrophic failure. All the more reason for a diver to maintain their equipment and to check it often.
Great video, thanks for the table breaking down the calculations!
Hello Paden Clayton, glad you liked the video.
Remember high performance flow through piston first stages like mk25 will drain your tank faster than diaphragm/basic unbalanced pistons in the event of a burst hose. Not all tank valves flow the same either, the old one with pinched dip tubes flow much less. Lots of variables that make this test data unique to your valve/first stage and not that relevant
Hello Michelle Lousise, thanks for commenting.
Thanks for posting, surprised at the results in this experiment..... good job done....
Thank You.
I have always wondered why manufacturers don't put a smaller orifice on the low pressure ports. Large enough to supply the heaviest breathing at depth, and good bcd inflation rate, but smaller to limit extreme free flow like that.
That would be a great questing for an engineer.
First i want to say great video and valuable examples.
One add i would like to make is that the divers air consumption is not taken into account on remaining time to surface. So a diver would have less time than that on the chart.
Still very interestingand useful though. I would have never guessed that kind of difference in the high-pressure and low-pressure line
Thank you Don, glad you liked the video.
Should repeat the HP test using DIN, then you might think differently about your yoke preference (PADI DM for 15 years :-) ) Been there done that
Congratulations on reaching the Divemaster level, that is an awesome achievement.
I know this is an old video but just wanted to point out doubling depth doesn’t always double flow rate. There’s a couple other videos on RUclips where they tested LP and HP ruptures at surface,30ft and 60ft and there was only a slight increase with depth. Not a service tech but I think the bottle neck has to do with orifice sizes and so much the ambient pressure. Like always, still a great demonstration and video!
Hello KlixTrio, the physics is still the same. But with this being said, it is still all theoretical.
Physics are the same, ideed. However SAC rate doesn’t apply in this case, as the free flowing hoses didn’t need to fill a cavity, i.e. lungs, to a certain pressure, increasing delivered volume. Hence the ambient pressure is affecting airflow just slightly.
Brian,
Long time follower and a big fan of your work.
I truly appreciate your work in teaching us to be better and smarter divers.
I’d love to get your feedback on best practices/techniques to deal with these situations especially - and this happens a lot unfortunately - when your buddy is too far away to notice what’s going on. Gear set up is single cylinder without a bailout.
A ruptured LP line at 50ft leaves less than 2 minutes of air. It’d require surfacing without a safety stop while ascending as slow as possible and simultaneously checking SPG drop progression is probably recommended.
But what if this happens at 100ft?
I recently discovered an o-ring problem on my cylinder valve and was prone to leaks. Good thing I caught it while on the boat and brought a spare cylinder.
Thanks in advance!
Hiro (pronounced like “hero”)
Thanks again for your continued work!
Hello H, thanks for being a subscriber and viewer. We are planning on revisiting this video very soon, and we are going to demostrate this same failure at the 100 foot mark. Stay tuned, because we are going to demostrate how to ascend during one of these incidents.
On the spg line blow first instincts might be to grab the hose and try and slow the leak Is the pressure great enough to cause air penetrate the skin ? And on the tank valve test, is the pressure coming out goin to be enough to push you deeper if your trying to surface ? And how would you deal with that situation ?
Great questions. Thankfully the water creates enough drag, so the risk of skin penetration is limited. Not saying it couldn't happen, but saying it didn't happen during the test. In regards to the tank valve test, I believe a diver could still easily swim to the surface. In the video with the tank started to float, this was due to the weight of the tank changing because of the depletion of air, and it didn't take much force for me to hold it in place. Now if the tank valve was suddenly severed, then that may be enough force to create propulsion on the diver, thus shooting him deeper. Not sure how I would handle that situation. In that case, I would assume the shock wave would possible be enough to cause a concussion to the diver, and may even be enough force that it would knock him unconscious.
Common intermediate pressures (low pressure line) are around 125 - 150 psi above ambient pressure.
A 1/4 inch hose end has an area of .049 inches, and has 7.35 pounds of force from the end. With a gloved hand you could easily hold your thumb over the end to stop the freeflow. I wouldn't try it bare handed, as medical websites online say 100 psi air has penetrated skin of mechanics dusting themselves off with their shop air compressors.
Don't even think about plugging the high pressure hose.
@@deerlakediver5554 what about kinking the hose like a garden hose?
Great video thanks for this info.
You’re welcome, glad you liked it
Thanks for your vids!
If you test again, could you try kinking the LP hose to see if the leak slows or even stops? And to see if it is at al possible to kink it, depending on hose type? Its common practice in workshops (and in cartoons) to block leaking compressorhoses that way.
Thanks for the suggestion, we may try it again in the future.
@@LakeHickoryScuba Hi, I had a low pressure quick connector fall apart and my first instinct was to kink the hose. It didn't really kink and didn't slow down the flow appreciably. So I tried to tie a knot in it also no good. Best I could do was to stick my thumb over the end and try and bend the hose. Also not very effective. This was about half way through the dive so I returned to the boat where the quick connector was rapidly re-assembled as luckily I had managed to hold the end in my hand and not drop it. I'll just mention this was a new BCD and I was very surprised to see the connector had unscrewed with no help from me. Once screwed back together the BCD is fine and no re-occurrence.
Also, I have several times had the O-rings on the spg leak and I can confirm it takes a long while to make a big difference due, as you say, to the pin hole that admits the air to the hose and spg. Don't know if any of that helps your future experiment?
@@patggreen77 Thanks for sharing your experience. And good to read it worked out ok for you. Was this a regular rubber hose or a flexhose? Did you orally inflate the BCD to get up?
Joyzy & Mechanikos the hose was normal rubber and I swam up and kicked until the boat captain released the ladder then we turned off the tank and he had a spanner and screwed the connector back together and I jumped back in and finished the dive. I always dive with as low weight as I can. So I can always swim up and stay on the surface with bcd deflated.
Thanks for great video
You're Welcome
Loving your content. Going to learn scuba. Love it.
Glad you like our videos. Thank You for watching and good luck on your Scuba Diving Journey
Thanks sir. Throwing on the fins today and hitting swimming pool.
Great video
Thank You
The valve leak time seems misleading. As far as breathability from your lines. If you are having that much volume loss at the source of intake to your first stage. How much is actually making it to your second stage would be my question. Furthermore would it be sufficient enough to actually get a breath off it. Granted some is better than none but depending on the answer buddy breathing seems to be the safer option. Love your videos man! very educational and presented in an approachable supportive manner
Great question Earl, and one that we can definitely revisit and test out. I can say from personal experience, I have had a tank O-ring (the O-ring that seals the first stage to the tank valve) rupture while underwater, which did cause a catastrophic failure. At the depth I was at (20ftsw), I had no difficulty making a slow and safe ascent to the surface. You can imagine my surprise when I heard the loud pop directly behind my head. But as you stated, having your buddy there to provide air is a much safer and practical solution.
Thanks for the reply back to answer my question! Good info to know if it ever happens to me in the future. And yeah I would probably need a new wet suit if I heard that right behind my head as well.
Keep up the good work buddy! Look forward to seeing more videos from you.
You're welcome. And thank you for being a subscriber. If you ever have video suggestion for us, let us know, and we will try to get it produced for you.
Very informative
Thank You. Glad you liked it.
I know this is an older video, but we recently had a discussion about this topic in our diveclub with different opinions. I personally think your calculations are wrong (Not 100% sure though :D). And here is my explanation: When you dive you use more air at depth, because the gas inside of your lungs get compressed and you need to inhale more gas to fill them up. BUT when a hose breaks there is no dead airspace that needs to be filled up, the flow rate determines how much air escapes, not the volume that needs to be filled and that shouldn't change no matter of how deep you are. So it should take the same exact time to drain a cylinder at 3m and 30m.
Hello Fabian Buckreus, we are planning a dive in the near future to 100 feet as a retest to see if our numbers are correct. Stay tuned.
@@LakeHickoryScuba Awesome, I can't wait. I place my bet on: the only difference you will see from 10 and 100 feet is the different flow rate, if you use an overbalanced first stage.
I realize this is an old video just happen to come across my feed just so happens last time when we went to bonaire I was given a tank with a bad turn wheel sealjust noticed that something you didn't cover in this video ironically enough I did a full hour long and came back with about 1450
These tend to get looked over by a lot of technicians during a visual inspection.
Steve, not all HP hoses have the pinhole constriction you showed in your video. The miflex HP SPG hoses on my sidemount and BPW setup have large diameter openings (and look a lot like the LP hose you show at the bottom at approximately 11:15 in this video). I suspect an HP hose failure without the pinhole constriction would drain even faster than the 3 minutes in your example.
question was meant for Bryan (not Steve)... B^)
You would be correct Jonathan TLG, miflex hoses are different. However, if you were to break down the coupling that connects the hose itself, the back side of it is restricted.
Brilliant exercise and demonstration. Glad im setting up a pony bottle . Dont care if others laugh at me.
Its always good to have redundancy, no matter what type of diving you do.
I always do as im a solo diver mostly.
The diver would actually have less time than the calculations indicate, as the diver also needs to breath off the tanks, assuming Breathing from an octopus. The problem with the O-ring failure is that it could impact the performance of the regulator too. If so, that would hamper regulator performance, and unless the diver had another first stage to breath from, or a pony bottle/independent doubles, (s)he may not be able to use the main regulator.
This is very possible. And you are correct, the catastrophic failure could cause regulator performance issues.
And this is why I don't dive in pools anymore! Hoses be gett'en cuts all the time......
It's definitely dangerous out there. What is even worse is when a swimmer comes by and doesn't realize you are below him, and he starts peeing in the pool. No respect from kids these days.
I had a diver jump in right on top of me from the dive boat in Bonaire in 2014. The bottom of his/her tank just missed my head and smacked the top of my regulator (Scubapro Mk 5). The high pressure hose snapped off flush with the first stage reg body (the threaded part of the fitting was retained). Once I gathered my senses, it took me a minute or so to realize I had a big freeflow coming from the first stage. The second stage never freeflowed. I never got deeper than 15-20 feet. I made a slow ascent back to the boat, never had a breathing restriction. As I was climbing up the ladder, the last of my gas was hissing out. Looking on my computer, the entire episode took about 3 minutes from getting hit to climbing up the ladder. The reg has a small HP orifice, and the HP hose fitting has a small orifice as well (and it remained in the reg). It should have taken a longer time to lose that gas. The best I can figure is that the blow broke the o-ring seal between the reg and the tank, so I sort of had two high pressure failures at once. My wife actually got a couple of pictures of the freeflow. Its pretty impressive. The reg was never the same--wouldn't hold stable IP even once everything was replaced and overhauled. I figured the body of the reg was damaged, so I retired it. It's now a paperweight with a good story attached to it. I never got a visual ID on the diver who smacked me (more concerned with the state of my head). Whoever it was swam away, never fessed up and never even mentioned it.
That is an amazing story. Glad to hear that you only had damage to your regulator and not to your head. Sounds like you definitely had a failure at the connection of the valve and first stage, and not just the high pressure line. In regards to the first stage not holding intermediate pressure, a scratched internal surface or a warped housing is usually the reason. Sounds like the impact and the sudden release of air warped the housing itself.
10:50 10 feet equals 1.3 atmosphere?
I'm a newbie to diving so please forgive me for a stupid question. I've read that 1 atmosphere equals 33 feet of ocean depth. By your statement that 10 feet equals 1.3 atmospheres, you are adding the weight of the air above the water on top of the water pressure. So you are using absolute pressure. That makes sense to me since the body is experiencing the sum of the two. . So 33 feet down is really 2 atmospheres of pressure not 1.
So when a diver says I went down to 2 atmospheres, he means 33 feet not 66 feet. Correct?
Hello TheNYgolfer, there is no such thing as a stupid question. You have it correct. The constant pressure of the surface is always calculated back into the formula for absolute pressure. The easiest way to determine absolute pressure is with the formula, (DEPTH / 33) + 1. This of course being for Saltwater. For freshwater, change 33 to 34. (DEPTH / 34) + 1. Hope this clears it up for you.
I'm surprised the valve leaked slower than the LP hose. I would think gas could escape faster out of the valve (from 200 bar down to 1.3 bar) than out of the LP hose (from ~10 bar down to 1.3 bar). But it looks like you had the first stage attached with all the ports open, so maybe it's the same intermediate pressure? I'm still missing something here...
This video was very fun to make. We learned a lot about the orifices in a regulator and how they directly relate to air loss. We were also shocked at the results ourselves.
thanks
You're welcome
I don't understand the final line of your calculations, surely a leaking hose will take the same time to empty (or less, because of slightly lower pressure differential) at depth as it does near the surface?
And do the calculations take into account the air used by the diver as he ascends? Or just the air lost by the leak?
We added the bottom line as more of a frame of reference to just how serious a catastrophic failure can be to a diver. The easiest way to think of it is to compare it to a divers SAC or RMV rate, the deeper we are, the more air we use up. Try not to over think it. We want to prevent all catastrophic failures. In the event one occurs, we do not want to panic, however, we do want to make a direct ascent to the surface, slowly as possible not to exceed a 30 feet per minute ascent rate, but at the same time, we need to understand that we will not have control of how quickly our air supply is depleted.
Al Locke "...surely a leaking hose will take the same time to empty...at depth as it does near the surface?"
The leak rate will be the same, but the amount of air the diver is using changes. So if you have a leak at depth you'll have less total time to depletion than at the surface, because it's leak rate PLUS consumption rate.
I know nothing, and am nor certified, but air pressure at sea level is 14.7 absolute pressure (ISA), so doesn't the regulator diaphragm maintain a minimum of 14.7 differential pressure at any depth? Meaning all depths dove to will require a low pressure line to be equal to ambient pressure + 14.7psid to = regulated pressure. Meaning much higher leak rate would exist at greater depths on account of higher regulated air pressure? And thus further reducing recovery time following a failure at deeper and deeper depths?
@@innerverse1809 You are right about the regulator (1st stage on the bottle) adjusting for ambient pressure, but air supplied by the hose to the 2nd stage (the thing in the divers mouth) of the regulator is usually about 10 bar/150psi above ambient pressure.
@@mechanikos84 so 1st stage = pressure at depth + 14.7 psi? And 2nd stage = ?
I'm rewatching this video, and noticed something I missed the first time around: the SPG is leaking before the HP line is cut. Is that why you sacrificed this one?
Yes, that is exactly why we used it. Good eye.
Yeah it was obvious. Why to destroy a good one?
This is in a pool, if this happened at depth it would drain much quicker. I don’t think that was stated in the video, so hopefully it doesn’t give people false confidence that they have a lot of time to get to the surface.
Hello alphahxr, if you watch the entire video, you will see that we did mention the times change at depth.
Do you have to worry about getting water in the tanks doing testing like this?
All of the equipment shown aside from the SPG can be disassembled, cleaned, and returned to service if necessary.
Yes this is a concern, and the biggest reason we chose these 3 tanks is simple. They were due for a visual inspection anyways, so any water that gets in them can be dried out during inspection. The regulators we chose, can no longer be serviced because there are no parts available for them.
He mentioned he went to his "bailout"... can you tell me what he had? And do you recommend any backup air supplies? (Spare Air"?)
He was using a 40 cf pony system. Redundant Air Sources are always a great idea, depending on the need.
I have to ask... Do you always dive with an SMB in a pool? 😁😁
Depends on which BCD I grab off the shelf. Some have them, some don't.
Did he ever find out why he had free flow.?
LA5150 Yes, his cracking pressure was set too low, and it was uncontrollable once the free flow began.
Helllo.... What is a "cracking pressure" and where do you set that?
The Cracking Pressure, is the amount of force it takes to open and close the demand valve / lever, inside the second stage. In short, how hard it is to breathe from the second stage. The is a small nut that has to be turned either from the inside of the second stage, or on the internal portion of the hose adapter, to adjust it. When you see regulators with an adjustable knob on the side, this is its purpose, to change the cracking pressure.
Wouldn't a high cracking pressure make the 2nd stage harder to breath off of and also reduce the chance of free flow? Did you mean the cracking pressure was set to low making the 2nd stage more sensitive and likely to free flow?
You are correct, thank you for pointing that out, I have edited my response. Sometimes my fingers and my brain don't get alone very well.
Could I still breathe if the hose or valve is broken?
Possibly, just not sure I would try without proper training. Its always best to signal to your buddy for help, secure an alternate air source from them, and then ascend slowly.
I think there is an error to your calculations.
Namely - airtime.
Shouldn't you take into account divers air consumption?
I believe that would cut the hp hose failure air time by half
We have had others comment the same thing. We have discussed doing the test again, but this time, have a diver breathing from the cylinder as well, to see if the results change.
Interesting idea.
I thought it was a simple math, but why not to experiment if you can afford that?
I imagine you are not going to test a resting and relaxed diver.
Testing is the easy part, and our purpose would be to create a base line number of how long a cylinder would last. Regardless of a diver's SAC or RMV rate, in the event any of the scenarios were to occur, the dive would be immediately aborted. The video's purpose was to show just how quickly a cylinder could be depleted. Considering Boyle's Law into the mix, I'm not to certain it would make that much difference if a diver was breathing from the system. He or She would still make a direct ascent, thus he or she would be using less air on the way up. I feel confident the numbers would still be close to the results we discovered during our test in the video.
Ok. So what I have understood you are saying here:
1) those results are not that important (dive aborted);
2) your purpose was different that to show exact numbers;
3) there are factors which can render the testing not so relevant.
I have two questions in that case:
a) When exactly are you planning to perform those tests;
b) what was the initial reason to speculate on the airtime on 15m anyway if you consider the above points?
1) We believe the results are important, and Yes, in the event you have a catastrophic failure, you should abort the dive, no questions asked.
2) The purpose of showing the math (or in respect to a diver's SAC or RMV rate), was to give the viewers a realistic time frame to how long their air would last during the ascent phase of the dive, compared to a normal breathing rate of a diver. Also, showing the math was the only option we had, considering the pool is only 10 feet deep. We were unable to conduct the test at the depth the diver stated during the opening. The visibility would not have been good enough to shoot a video, here in out geographical location.
3) We believe the testing is very relevant, regardless of the factors, as each problem shown can and has happen to divers over the years.
a) Hopefully soon we will be able to shoot a new video (so stay tuned), with a diver breathing from each cylinder, to see if the numbers change.
b) 15 meters (50 feet) was used, simply because that is where the diver said he had the catastrophic failure.
Hopefully these answered your questions.
LP results will be much worse at depth, the first stage is letting more air through, so at depth LP failures could be instantly catastrophic, should do this LP test at 100 ft, the HP test will not be much different
I wished we had a 100ft pool to do the test in.
The A clamp fan boys will kill me, but if you worry about tank valve failures, go DIN.
Thanks for the comment Leopold Bloom, hopefully the Yoke Fans will take it easy on you. LOL.