Report from Fatality at Devil’s Ear

Sutty · 20th May 2008, 21:51

Its an interesting idea that on OPV that is "burping" excess gas/pressure could also allow entry of water, but it wouldn't surprise me if its possible.
One problem with Mike's mathematical model is that it assumes that the pressures/seal all occur at a single point, whereas real OPVs are of finite size, and have natural variations in their sealing action in differing parts of the sealing area.
Imagine an OPV an inch or so across lying on its side in the water column, with a gas feed into the rebreather from the solenoid. Internal pressure will rise until it overcomes the external pressure plus whatever is applied by the OPV's spring and the OPV opens, gas burps out of uppermost point of the valve until the pressure in the unit drops enough to let the valve close. Unlike when in use normally the pressure in the unit is not cycling with breathing, so the valve only just closes - perhaps it doesn't seal properly as there is no real pressure gradient to push it shut, and it carries on bleeding small amounts of gas out of the uppermost point of the nearly-sealing valve, whilst leaking water in through the lowest point of the nearly-sealing valve. This would continue to flood the unit.

Neil

Jerry · 20th May 2008, 22:11

[quote=Drmike;187836]...........But thats not happening is it - just show of needless anger.

No anger; frustration with someone that does not have ANY facts. I haven't even begun to approach anger yet.

Laws of physics?? I am also somewhat versed in this. Like the fact that some means of flow actually create venturies at some points causing reverse flow where substance might be "pulled in" by the outflow.

How does water enter my perfectly good drysuit valve? It is the same as my rebreather valve; I leave it at its' lowest setting and let it burp as it wills. Exactly like described in the article. My undergarment does not block it open; it has a grate to prevent this and yet my arm still gets wets.

You keep going back to your law of physics; there is always an exception. If I recall you quoted a very simplistic formula to describe a very complex occurrence. As for staging units outside of habitats etc; I believe orientation has every thing to do with the success. The OPV(unattended) only opens because of internal pressure exceeding the spring tension. If i is low the gas inside will rise away from it and the pressure on the spring will be low; if it is at the high point all of the internal gas pressure will force it open. The greater the pressure the farther it will open and the longer it will stay open.

After inspection of the scrubber it is believed that it would not have taken much water at all to render his scrubber useless. The balance of the flood had nearly 24 hrs to occur.

As I said, I am not a Meg expert, so I asked a Meg Instructor who I respect (so does Leon): "How easy is the actuation of a Meg DSV?" "It is a very deliberate action." This lead to the question: "How likely is it to get accidentally knocked open?" "Impossible; the very best cared for is difficult enough and one that hasn't been cared for is only worse." Therefore, it is highly unlikely it was knocked open.

If he left it open; why would he have bothered to donn the unit? It would have been incredibly heavy; it was during the extraction, that is why we removed it from him.

Someone asked if the OPV was inspected for debris; only after extraction. It had a 4,000 ft scooter ride. I can say that it was opening and closing as it should when we approached the deceased. This same person pointed out that the article stated that this is one possibility and I agree that there could be other options. I also know that some very knowledgeable people put this in a legal report to the Gilchrist County Sheriff as their best guess as to how this occurred.

This scenario was based on direct knowledge of the deceased, direct inspection of the unit, and direct observation.

I find it irresponsible for someone with absolutely NO direct knowledge of any specific details to say anyone else is wrong.

Jerry

Drmike · 21st May 2008, 03:15

Quote: (Originally Posted by Sutty)

Its an interesting idea that on OPV that is "burping" excess gas/pressure could also allow entry of water, but it wouldn't surprise me if its possible.
One problem with Mike's mathematical model is that it assumes that the pressures/seal all occur at a single point, whereas real OPVs are of finite size, and have natural variations in their sealing action in differing parts of the sealing area.

Hi Neil,

Where the seal occurs or size or design of opv doesnt change the fact that the pressure in the CL still has to be same or below ambient for water to enter.

Quote:

perhaps it doesn't seal properly as there is no real pressure gradient to push it shut, and it carries on bleeding small amounts of gas out of the uppermost point of the nearly-sealing valve, whilst leaking water in through the lowest point of the nearly-sealing valve. This would continue to flood the unit.

Yes this could happen and there is no despute about that (it was discussed earlier, http://www.rebreatherworld.com/rebre...tml#post186987) but again in order for water to leak into the bottom of the opv the pressure inside the CL must still be at ambient or below - ergo the only way this could happen would be if gas is leaking out faster than the o2 solenoid can inject, or once the o2 supply runs out and enough gas has leaked out the opv sp pressures balance.

This fits with the findings and is what I assumed too until Jerry mentioned that 24hrs later the cls were still full of gas and opv still venting (suggesting +ve pressure in the lungs. I would have thought a opv leak that could vent a whole tank of o2 and allow a flood in under 1 hour would not still have full lungs and still be venting 24hrs later. It was this that led me to look at alternative possibilities (and as has been mentioned already its all guess work and we will never know for sure)

Perhaps the lungs werent really 'full' 24hrs later and the opv not actually venting - just a small occasional bubble - that would fit better. Remember even if whatever gas is still in the lungs is at ambient that gas will still be bouyant in water so the 'floating up' may not infer full of gas

If the recovered opv was inspected for crud and ability to seal that should give more confidence as to that theory.

Im am still unclear why Jerry is so angry. I wasnt brought up to believe blindly everything Im told and I believe one should keep and open mind and question. It seams like some think we should just believe what we are told and never question anything. Some apear to relate keeping an open mind and quetioning to insulting unreasonable behavior .....ho hum

Drmike · 21st May 2008, 03:51

Quote: (Originally Posted by Jerry)

No anger; frustration with someone that does not have ANY facts. I haven't even begun to approach anger yet.

then I suggest your time would be much better spent informing of any relevant facts and correcting any mistakes (as I have invited many times) in my physics instead of getting into a meaningless defensive pissing contest. But consider that I am not debating facts i am debating physics. the facts wont change physics! which is why a practical discussion about physics is not necesarily reliant on having addition situational facts that you closet

Quote:

Laws of physics?? I am also somewhat versed in this. Like the fact that some means of flow actually create venturies at some points causing reverse flow where substance might be "pulled in" by the outflow.

No, a Venturi works by flow resulting in localised pressure drop (due to increase in velocity) that draws in material INTO the low pressure zone/flow. (high to low pressure flow see links below)

This is not what we have here. escaping gas from the opv is the flow through the 'venturi' the surounding water could be drawn into that flow of escaping gas - but it will go with the flow away from the opv not backwards (uphill from a pressure gradient perspective) into the higher pressure lungs.

Jerry in physics theres a thing called the 'Pressure Gradient Force'
Basically what this says is things always flow from high to low pressure and not visa versa. See:

http://en.wikipedia.org/wiki/Pressure_gradient_force

and simple illustration:

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/pgf.rxml

Egro, given a normally functioning opv or a leaking one, or even a gaping hole ,water cannot enter no mater what orientation unless the pressure in lung is same or below ambient. If its venting gas out of solenoid induced over inflated lungs its clearly not. Im sorry but thats physics and no lack of facts I may have about the incident, the fact I wasnt there or the fact Moses himself inspected the kit will change that. Blame Newton not me

Quote:

How does water enter my perfectly good drysuit valve?

it cant - if its perfectly good - see above. It can if its not seating correctly or got crud in it as mentioned here: http://www.rebreatherworld.com/rebre...tml#post186987
remember a drysuit spends a lot of its time -ve so any small leak in the opv at those times could allow water in (see above) a Rebreather lung doesnt spend any real time -ve underwater to nowhere near the same degree of differential.

if opvs in normal operation leaked we would see a lot of flooded rbs you could never stage and Rebreather and every bob would flood. my opv on my bob faces upwards it cant flood unless its leaking and at same time lung pressure is same or below as ambient.

Quote:

It is the same as my rebreather valve; I leave it at its' lowest setting and let it burp as it wills. Exactly like described in the article. My undergarment does not block it open; it has a grate to prevent this and yet my arm still gets wets.

You keep going back to your law of physics; there is always an exception.

by defininition if its a physical law there cant be. There is no exception to pressure gradient law.

Quote:

If I recall you quoted a very simplistic formula to describe a very complex occurrence.

what complex? its a very simple occurance.
Its a basic law of dynamics that things dont flow up gradients. see http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/pgf.rxml

Quote:

As for staging units outside of habitats etc; I believe orientation has every thing to do with the success. The OPV(unattended) only opens because of internal pressure exceeding the spring tension. If i is low the gas inside will rise away from it and the pressure on the spring will be low; if it is at the high point all of the internal gas pressure will force it open. The greater the pressure the farther it will open and the longer it will stay open.

Yes but it will close as soon as pressure in lung drops enough. unless its really crudded up and doesnt close the pressure will always be +ve

Quote:

After inspection of the scrubber it is believed that it would not have taken much water at all to render his scrubber useless. The balance of the flood had nearly 24 hrs to occur.

As I said, I am not a Meg expert, so I asked a Meg Instructor who I respect (so does Leon): "How easy is the actuation of a Meg DSV?" "It is a very deliberate action." This lead to the question: "How likely is it to get accidentally knocked open?" "Impossible; the very best cared for is difficult enough and one that hasn't been cared for is only worse." Therefore, it is highly unlikely it was knocked open.

well my m15.5 dsv (used on my bob) is almost same design as the meg and Ive knocked it open crawling through tight caves - hence the mod. In zero vis struggling to get back into a unit I can sure see how its more than possible in a stressful situation. You only need for example to get the handle caught on a d-ring and be too vigarous in pulling the loop trying to get it on (in zero vis)

Quote:

If he left it open; why would he have bothered to donn the unit? It would have been incredibly heavy; it was during the extraction, that is why we removed it from him.

This is pure speculation but as you asked, he could have easily knocked it open whilst donning it and therefore not have known until it was flooded until it was on and he tried it.

Quote:

Someone asked if the OPV was inspected for debris; only after extraction. It had a 4,000 ft scooter ride. I can say that it was opening and closing as it should when we approached the deceased.

That would be me that asked. so no crud or leak? how does that fit? if the leak was so bad that it vented a whole tank of o2 and allowed a flood in under 1 hour how come theres still gas in the rig after 24hrs?

Quote:

This same person pointed out that the article stated that this is one possibility and I agree that there could be other options. I also know that some very knowledgeable people put this in a legal report to the Gilchrist County Sheriff as their best guess as to how this occurred.

This scenario was based on direct knowledge of the deceased, direct inspection of the unit, and direct observation.

I find it irresponsible for someone with absolutely NO direct knowledge of any specific details to say anyone else is wrong.

Jerry

I find it somewhat surprising that you are unable or unwillling to see that I am debating PHYSICS OF AN OPV OPERATION and the Pressure gardient law and that therefore not being there and having other non relevant (to opv operation and PG law) info is irelevant

I would argue that it would be more irresponsible to say nothing if one sees something that sounds unlikely just because Jerry doesnt want anyone to do so

On one hand you say you appreciate other theories can exist and yet at the same time when i try to investigate the likely hood of one FROM A PHYSICS perspective in order to gain some more insight - you get all offended

who appointed you as Rebreather World censor? who are you to tell people what they can or cant debate or think about? Jerry has decided he doesnt want anyone to look into the physics so thats it folks discussion ends. Jerry thinks the people who did the inspection are cool so thats it folks no other discussion is allowed

uhuh

Im sure the people you clearly look up to are capable intelligent people and its clear in the way they worded the report that they are (unlike you) open to the fact its all speculation and there will neve be any certainties- but I think Newton was also a capable and inteligent guy too so his opinion ought to be at least considered without a need for you to get defensive

ho hum

Mark Chase · 21st May 2008, 05:20

Quote: (Originally Posted by Jerry)

Defensive No. Sick to death of people that were not at the site, haven't seen the rig, and don't have all the facts telling us we are wrong; yes.

I spoke with Lamar about why reports weren't published anymore because I also was curious. Besides pending lawsuits; it is this very thing. You post a report for peoples edification and then every expert in the world comes out to tell you how you are wrong.

In every report there are many details that are left out even though they may have contributed to the problem because the public just doesn't need to know. You disagree, so what. You are arguing a point that doesn't matter. Mark made so many little errors whether or not he left the DSV open is immaterial; besides that we will never know.

You say you tested your valve and you have your equations. I have worked in the field as a geologist enough to know that mathmatical calculations and real world values are quite frequently divergent. Did you test Mark's OP? Did you test the same type OP valve as Mark's? If not your testing is meaningless.

Jerry

I would have thaught the whole point of analasis would be to provoke discussion.

I think your being overly defensive. Even the most well thaught out and reserched investigation should be open to review. Discussion and debait about the incident can only make for better understanding of this incidant or simila events that we as divers can then try to avoid in the future.

ATB

Mark

graham_hk · 21st May 2008, 05:44

All,

I am pretty sure that water does get into OPV when they dump (especially facing up - I suspect gravity is enough to overcome the pressure but thats a wild ass guess). Instead of pondering over the theory (science used to say and may still say bees couldn't fly and sharks and dolphins couldn't eat enough to swim at the speeds they do) might I suggest a simple experiment to put this to bed - fill your bath up with water and inflate a device containing an OPV (an SMB would be easiest) and try it.

Let us know what you find out and we'll have either validated all the theory or need to do some more research to find out the right theory

Graham

Drmike · 21st May 2008, 05:50

Quote: (Originally Posted by graham_hk)

All,

I am pretty sure that water does get into OPV when they dump (especially facing up - I suspect gravity is enough to overcome the pressure but thats a wild ass guess). Instead of pondering over the theory (science used to say and may still say bees couldn't fly and sharks and dolphins couldn't eat enough to swim at the speeds they do) might I suggest a simple experiment to put this to bed - fill your bath up with water and inflate a device containing an OPV (an SMB would be easiest) and try it.

Let us know what you find out and we'll have either validated all the theory or need to do some more research to find out the right theory

Graham

hey Graham, did that

http://www.rebreatherworld.com/rebre...tml#post187798

the only way to 'force' water in was if the opv closing is artificially slowed down enough for the gas in the lung to equalise with water pressure (or if an obstruction is placed to prevent a seal, in which case water comes in after the opv closes after equalisation not during venting. In normal operation no water comes in as spring force ensures pressure in lung is always higher than ambient.

In case of adding a foreign body to prevent good seal: findings were no water comes in until enough gas has leaked out to equalise with water pressure and then a very small leak. Im not sure its likely that the leak out a closed opv would be fast enough that the injected o2 would go from over pressure to equalised with ambient water pressure and then time for any significant water to trickle in as gas bubbles out, in the short time between the constant injections (in the given scenario) and i would expect such a leak size would ensure that 24hrs later the lungs would not still be venting gas.

but who knows - we never will Im sure.

remember as the lung is not a rigid body the water pressure acts on both sides of opv, gas is bouyant and the bouyant force will overcome gravity everytime. Only by exchange (bouyant air bubbles out and water trickes in to take up space left behind) can that happen (at ambient pressure)

ps any news about the suit?

graham_hk · 21st May 2008, 06:10

Quote: (Originally Posted by Drmike)

hey Graham, did that

http://www.rebreatherworld.com/rebre...tml#post187798

the only way to 'force' water in was if the opv closing is artificially slowed down enough for the gas in the lung to equalise with water pressure (or if an obstruction is placed to prevent a seal, in which case water comes in after the opv closes after equalisation not during venting. In normal operation no water comes in as spring force ensures pressure in lung is always higher than ambient.

In case of adding a foreign body to prevent good seal: findings were no water comes in until enough gas has leaked out to equalise with water pressure and then a very small leak. Im not sure its likely that the leak out a closed opv would be fast enough that the injected o2 would go from over pressure to equalised with ambient water pressure in the short time between the constant injections (in the given scenario) and i would expect such a leak size would ensure that 24hrs later the lungs would not still be venting gas.

but who knows - we never will Im sure.

remember as the lung is not a rigid body the water pressure acts on both sides of opv, gas is bouyant and the bouyant force will overcome gravity everytime. Only by exchange (bouyant air bubbles out and water trickes in to take up space left behind) can that happen (at ambient pressure)

ps any news about the suit?

Just copied you on a followup about the suit. Regarding OPV I should've read the whole thread more carefully ...

Graham

farmerted · 24th May 2008, 02:44

Hey all,
First off, everyone should thank Jerry for the gruesome task of recovering Marks body. My hats off to you brother. There is only one person who will ever truly know what happened and he cannot tell us.
Now, as for the water trickling in as the lung burps, I tried this last night and got water in my lung. It wasn't much for the short time that i did it, but water did get in. The theory we came up with 2 days after the recovery was this. He stowed the rebreather on it's back and the lungs floated upwards or it rolled into this position during the time it was left unattended. At this time the water began trickling in the opv and ran down into the stack. Not such a big deal, many water traps. His body was found with the primary in the mud. He probably never put it on his wrist. The setpoint was on .7. From either a low p02 upon ditching the unit or moisture from cooling gathering on the cells caused the solenoid to fire time and again. The lungs are now floating above the unit and o2 is not passing over the cells, so the solenoid keeps firing. The left side o2 tank drains soon and allows more places for water to enter the unit. We also agreed that at some point he could have accidentally opened the dsv. Either way, we all agreed that he had pushed his thirds or had a serious problem before getting back to his rebreather and wasted valuable time trying to put it back on and ran short. The distance where he ditched his rig and where there was a full bailout was less than 100 feet. I'm sure he was in zero vis returning and possibly got lost after twisting around putting the rig on. The line in this room was slack and laying in the silt when I went in there 3 days later, so there had definitely been a problem at this point in his dive. The recovery team disscussed many variables as to what happened. We all agreed no one will ever know. The theory we came up with is sound.I'm not saying it is what happened. there are a lot of little details which led to our proccess of elimination which have not been mentioned. This is not deliberate of course, just that we all have regular jobs and little time to address every point. I appologize up front for not posting replies right away. I am a farmer and it is planting season, so a day or 2 in between cyber visits is normal. Ted

mempilot · 24th May 2008, 10:44

Mike,

There is a concept called turbulent flow. In allowing for the transfer from high pressure to low pressure stabilization, there is the possibility of disrupted flow which can cause eddies in the transfer and actually cause reverse flow around the area causing the turbulence. This happens in rivers at break waters, on wings, and in other instances. A non-perfect oprv, which they all are, will cause turbulence at the outlet and therefore allow for some backflow.

The physics you quote are correct, but only in an perfect world where there is no turbulence. Sorry to burst your bubble on this one, but it is very possible to get wet on the backside of an OPRV.

Mem, da pilot

20th May 2008, 21:51	#51 (permalink)
Sutty Classic Kiss diver Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Jun 2005 Location: Glossop, Derbyshire, UK Posts: 789	Re: Report from Fatality at Devil’s Ear Its an interesting idea that on OPV that is "burping" excess gas/pressure could also allow entry of water, but it wouldn't surprise me if its possible. One problem with Mike's mathematical model is that it assumes that the pressures/seal all occur at a single point, whereas real OPVs are of finite size, and have natural variations in their sealing action in differing parts of the sealing area. Imagine an OPV an inch or so across lying on its side in the water column, with a gas feed into the rebreather from the solenoid. Internal pressure will rise until it overcomes the external pressure plus whatever is applied by the OPV's spring and the OPV opens, gas burps out of uppermost point of the valve until the pressure in the unit drops enough to let the valve close. Unlike when in use normally the pressure in the unit is not cycling with breathing, so the valve only just closes - perhaps it doesn't seal properly as there is no real pressure gradient to push it shut, and it carries on bleeding small amounts of gas out of the uppermost point of the nearly-sealing valve, whilst leaking water in through the lowest point of the nearly-sealing valve. This would continue to flood the unit. Neil __________________ Never forget that life is a finite resource.
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20th May 2008, 22:11	#52 (permalink)
Jerry New Member Current Rebreather/s: Optima Other Rebreather/s: Join Date: Jul 2005 Location: USA Posts: 23	Re: Report from Fatality at Devil’s Ear [quote=Drmike;187836]...........But thats not happening is it - just show of needless anger. No anger; frustration with someone that does not have ANY facts. I haven't even begun to approach anger yet. Laws of physics?? I am also somewhat versed in this. Like the fact that some means of flow actually create venturies at some points causing reverse flow where substance might be "pulled in" by the outflow. How does water enter my perfectly good drysuit valve? It is the same as my rebreather valve; I leave it at its' lowest setting and let it burp as it wills. Exactly like described in the article. My undergarment does not block it open; it has a grate to prevent this and yet my arm still gets wets. You keep going back to your law of physics; there is always an exception. If I recall you quoted a very simplistic formula to describe a very complex occurrence. As for staging units outside of habitats etc; I believe orientation has every thing to do with the success. The OPV(unattended) only opens because of internal pressure exceeding the spring tension. If i is low the gas inside will rise away from it and the pressure on the spring will be low; if it is at the high point all of the internal gas pressure will force it open. The greater the pressure the farther it will open and the longer it will stay open. After inspection of the scrubber it is believed that it would not have taken much water at all to render his scrubber useless. The balance of the flood had nearly 24 hrs to occur. As I said, I am not a Meg expert, so I asked a Meg Instructor who I respect (so does Leon): "How easy is the actuation of a Meg DSV?" "It is a very deliberate action." This lead to the question: "How likely is it to get accidentally knocked open?" "Impossible; the very best cared for is difficult enough and one that hasn't been cared for is only worse." Therefore, it is highly unlikely it was knocked open. If he left it open; why would he have bothered to donn the unit? It would have been incredibly heavy; it was during the extraction, that is why we removed it from him. Someone asked if the OPV was inspected for debris; only after extraction. It had a 4,000 ft scooter ride. I can say that it was opening and closing as it should when we approached the deceased. This same person pointed out that the article stated that this is one possibility and I agree that there could be other options. I also know that some very knowledgeable people put this in a legal report to the Gilchrist County Sheriff as their best guess as to how this occurred. This scenario was based on direct knowledge of the deceased, direct inspection of the unit, and direct observation. I find it irresponsible for someone with absolutely NO direct knowledge of any specific details to say anyone else is wrong. Jerry
(Offline)

21st May 2008, 03:15	#53 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,165	Re: Report from Fatality at Devil’s Ear Quote: (Originally Posted by Sutty) Its an interesting idea that on OPV that is "burping" excess gas/pressure could also allow entry of water, but it wouldn't surprise me if its possible. One problem with Mike's mathematical model is that it assumes that the pressures/seal all occur at a single point, whereas real OPVs are of finite size, and have natural variations in their sealing action in differing parts of the sealing area. Hi Neil, Where the seal occurs or size or design of opv doesnt change the fact that the pressure in the CL still has to be same or below ambient for water to enter. Quote: perhaps it doesn't seal properly as there is no real pressure gradient to push it shut, and it carries on bleeding small amounts of gas out of the uppermost point of the nearly-sealing valve, whilst leaking water in through the lowest point of the nearly-sealing valve. This would continue to flood the unit. Yes this could happen and there is no despute about that (it was discussed earlier, http://www.rebreatherworld.com/rebre...tml#post186987) but again in order for water to leak into the bottom of the opv the pressure inside the CL must still be at ambient or below - ergo the only way this could happen would be if gas is leaking out faster than the o2 solenoid can inject, or once the o2 supply runs out and enough gas has leaked out the opv sp pressures balance. This fits with the findings and is what I assumed too until Jerry mentioned that 24hrs later the cls were still full of gas and opv still venting (suggesting +ve pressure in the lungs. I would have thought a opv leak that could vent a whole tank of o2 and allow a flood in under 1 hour would not still have full lungs and still be venting 24hrs later. It was this that led me to look at alternative possibilities (and as has been mentioned already its all guess work and we will never know for sure) Perhaps the lungs werent really 'full' 24hrs later and the opv not actually venting - just a small occasional bubble - that would fit better. Remember even if whatever gas is still in the lungs is at ambient that gas will still be bouyant in water so the 'floating up' may not infer full of gas If the recovered opv was inspected for crud and ability to seal that should give more confidence as to that theory. Im am still unclear why Jerry is so angry. I wasnt brought up to believe blindly everything Im told and I believe one should keep and open mind and question. It seams like some think we should just believe what we are told and never question anything. Some apear to relate keeping an open mind and quetioning to insulting unreasonable behavior .....ho hum __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 21st May 2008 at 03:19.
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21st May 2008, 03:51	#54 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,165	Re: Report from Fatality at Devil’s Ear Quote: (Originally Posted by Jerry) No anger; frustration with someone that does not have ANY facts. I haven't even begun to approach anger yet. then I suggest your time would be much better spent informing of any relevant facts and correcting any mistakes (as I have invited many times) in my physics instead of getting into a meaningless defensive pissing contest. But consider that I am not debating facts i am debating physics. the facts wont change physics! which is why a practical discussion about physics is not necesarily reliant on having addition situational facts that you closet Quote: Laws of physics?? I am also somewhat versed in this. Like the fact that some means of flow actually create venturies at some points causing reverse flow where substance might be "pulled in" by the outflow. No, a Venturi works by flow resulting in localised pressure drop (due to increase in velocity) that draws in material INTO the low pressure zone/flow. (high to low pressure flow see links below) This is not what we have here. escaping gas from the opv is the flow through the 'venturi' the surounding water could be drawn into that flow of escaping gas - but it will go with the flow away from the opv not backwards (uphill from a pressure gradient perspective) into the higher pressure lungs. Jerry in physics theres a thing called the 'Pressure Gradient Force' Basically what this says is things always flow from high to low pressure and not visa versa. See: http://en.wikipedia.org/wiki/Pressure_gradient_force and simple illustration: http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/pgf.rxml Egro, given a normally functioning opv or a leaking one, or even a gaping hole ,water cannot enter no mater what orientation unless the pressure in lung is same or below ambient. If its venting gas out of solenoid induced over inflated lungs its clearly not. Im sorry but thats physics and no lack of facts I may have about the incident, the fact I wasnt there or the fact Moses himself inspected the kit will change that. Blame Newton not me Quote: How does water enter my perfectly good drysuit valve? it cant - if its perfectly good - see above. It can if its not seating correctly or got crud in it as mentioned here: http://www.rebreatherworld.com/rebre...tml#post186987 remember a drysuit spends a lot of its time -ve so any small leak in the opv at those times could allow water in (see above) a Rebreather lung doesnt spend any real time -ve underwater to nowhere near the same degree of differential. if opvs in normal operation leaked we would see a lot of flooded rbs you could never stage and Rebreather and every bob would flood. my opv on my bob faces upwards it cant flood unless its leaking and at same time lung pressure is same or below as ambient. Quote: It is the same as my rebreather valve; I leave it at its' lowest setting and let it burp as it wills. Exactly like described in the article. My undergarment does not block it open; it has a grate to prevent this and yet my arm still gets wets. You keep going back to your law of physics; there is always an exception. by defininition if its a physical law there cant be. There is no exception to pressure gradient law. Quote: If I recall you quoted a very simplistic formula to describe a very complex occurrence. what complex? its a very simple occurance. Its a basic law of dynamics that things dont flow up gradients. see http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/pgf.rxml Quote: As for staging units outside of habitats etc; I believe orientation has every thing to do with the success. The OPV(unattended) only opens because of internal pressure exceeding the spring tension. If i is low the gas inside will rise away from it and the pressure on the spring will be low; if it is at the high point all of the internal gas pressure will force it open. The greater the pressure the farther it will open and the longer it will stay open. Yes but it will close as soon as pressure in lung drops enough. unless its really crudded up and doesnt close the pressure will always be +ve Quote: After inspection of the scrubber it is believed that it would not have taken much water at all to render his scrubber useless. The balance of the flood had nearly 24 hrs to occur. As I said, I am not a Meg expert, so I asked a Meg Instructor who I respect (so does Leon): "How easy is the actuation of a Meg DSV?" "It is a very deliberate action." This lead to the question: "How likely is it to get accidentally knocked open?" "Impossible; the very best cared for is difficult enough and one that hasn't been cared for is only worse." Therefore, it is highly unlikely it was knocked open. well my m15.5 dsv (used on my bob) is almost same design as the meg and Ive knocked it open crawling through tight caves - hence the mod. In zero vis struggling to get back into a unit I can sure see how its more than possible in a stressful situation. You only need for example to get the handle caught on a d-ring and be too vigarous in pulling the loop trying to get it on (in zero vis) Quote: If he left it open; why would he have bothered to donn the unit? It would have been incredibly heavy; it was during the extraction, that is why we removed it from him. This is pure speculation but as you asked, he could have easily knocked it open whilst donning it and therefore not have known until it was flooded until it was on and he tried it. Quote: Someone asked if the OPV was inspected for debris; only after extraction. It had a 4,000 ft scooter ride. I can say that it was opening and closing as it should when we approached the deceased. That would be me that asked. so no crud or leak? how does that fit? if the leak was so bad that it vented a whole tank of o2 and allowed a flood in under 1 hour how come theres still gas in the rig after 24hrs? Quote: This same person pointed out that the article stated that this is one possibility and I agree that there could be other options. I also know that some very knowledgeable people put this in a legal report to the Gilchrist County Sheriff as their best guess as to how this occurred. This scenario was based on direct knowledge of the deceased, direct inspection of the unit, and direct observation. I find it irresponsible for someone with absolutely NO direct knowledge of any specific details to say anyone else is wrong. Jerry I find it somewhat surprising that you are unable or unwillling to see that I am debating PHYSICS OF AN OPV OPERATION and the Pressure gardient law and that therefore not being there and having other non relevant (to opv operation and PG law) info is irelevant I would argue that it would be more irresponsible to say nothing if one sees something that sounds unlikely just because Jerry doesnt want anyone to do so On one hand you say you appreciate other theories can exist and yet at the same time when i try to investigate the likely hood of one FROM A PHYSICS perspective in order to gain some more insight - you get all offended who appointed you as Rebreather World censor? who are you to tell people what they can or cant debate or think about? Jerry has decided he doesnt want anyone to look into the physics so thats it folks discussion ends. Jerry thinks the people who did the inspection are cool so thats it folks no other discussion is allowed uhuh Im sure the people you clearly look up to are capable intelligent people and its clear in the way they worded the report that they are (unlike you) open to the fact its all speculation and there will neve be any certainties- but I think Newton was also a capable and inteligent guy too so his opinion ought to be at least considered without a need for you to get defensive ho hum __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 21st May 2008 at 05:41.
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21st May 2008, 05:20	#55 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,564	Re: Report from Fatality at Devil’s Ear Quote: (Originally Posted by Jerry) Defensive No. Sick to death of people that were not at the site, haven't seen the rig, and don't have all the facts telling us we are wrong; yes. I spoke with Lamar about why reports weren't published anymore because I also was curious. Besides pending lawsuits; it is this very thing. You post a report for peoples edification and then every expert in the world comes out to tell you how you are wrong. In every report there are many details that are left out even though they may have contributed to the problem because the public just doesn't need to know. You disagree, so what. You are arguing a point that doesn't matter. Mark made so many little errors whether or not he left the DSV open is immaterial; besides that we will never know. You say you tested your valve and you have your equations. I have worked in the field as a geologist enough to know that mathmatical calculations and real world values are quite frequently divergent. Did you test Mark's OP? Did you test the same type OP valve as Mark's? If not your testing is meaningless. Jerry I would have thaught the whole point of analasis would be to provoke discussion. I think your being overly defensive. Even the most well thaught out and reserched investigation should be open to review. Discussion and debait about the incident can only make for better understanding of this incidant or simila events that we as divers can then try to avoid in the future. ATB Mark __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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21st May 2008, 05:44	#56 (permalink)
graham_hk New Member Current Rebreather/s: RB80 / Clone Other Rebreather/s: Inspiration Classic Classic Kiss MK 15.X RB80 / Clone Join Date: Nov 2005 Location: Philippines Posts: 90	Re: Report from Fatality at Devil’s Ear All, I am pretty sure that water does get into OPV when they dump (especially facing up - I suspect gravity is enough to overcome the pressure but thats a wild ass guess). Instead of pondering over the theory (science used to say and may still say bees couldn't fly and sharks and dolphins couldn't eat enough to swim at the speeds they do) might I suggest a simple experiment to put this to bed - fill your bath up with water and inflate a device containing an OPV (an SMB would be easiest) and try it. Let us know what you find out and we'll have either validated all the theory or need to do some more research to find out the right theory Graham
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21st May 2008, 05:50	#57 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,165	Re: Report from Fatality at Devil’s Ear Quote: (Originally Posted by graham_hk) All, I am pretty sure that water does get into OPV when they dump (especially facing up - I suspect gravity is enough to overcome the pressure but thats a wild ass guess). Instead of pondering over the theory (science used to say and may still say bees couldn't fly and sharks and dolphins couldn't eat enough to swim at the speeds they do) might I suggest a simple experiment to put this to bed - fill your bath up with water and inflate a device containing an OPV (an SMB would be easiest) and try it. Let us know what you find out and we'll have either validated all the theory or need to do some more research to find out the right theory Graham hey Graham, did that http://www.rebreatherworld.com/rebre...tml#post187798 the only way to 'force' water in was if the opv closing is artificially slowed down enough for the gas in the lung to equalise with water pressure (or if an obstruction is placed to prevent a seal, in which case water comes in after the opv closes after equalisation not during venting. In normal operation no water comes in as spring force ensures pressure in lung is always higher than ambient. In case of adding a foreign body to prevent good seal: findings were no water comes in until enough gas has leaked out to equalise with water pressure and then a very small leak. Im not sure its likely that the leak out a closed opv would be fast enough that the injected o2 would go from over pressure to equalised with ambient water pressure and then time for any significant water to trickle in as gas bubbles out, in the short time between the constant injections (in the given scenario) and i would expect such a leak size would ensure that 24hrs later the lungs would not still be venting gas. but who knows - we never will Im sure. remember as the lung is not a rigid body the water pressure acts on both sides of opv, gas is bouyant and the bouyant force will overcome gravity everytime. Only by exchange (bouyant air bubbles out and water trickes in to take up space left behind) can that happen (at ambient pressure) ps any news about the suit? __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 21st May 2008 at 06:20.
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21st May 2008, 06:10	#58 (permalink)
graham_hk New Member Current Rebreather/s: RB80 / Clone Other Rebreather/s: Inspiration Classic Classic Kiss MK 15.X RB80 / Clone Join Date: Nov 2005 Location: Philippines Posts: 90	Re: Report from Fatality at Devil’s Ear Quote: (Originally Posted by Drmike) hey Graham, did that http://www.rebreatherworld.com/rebre...tml#post187798 the only way to 'force' water in was if the opv closing is artificially slowed down enough for the gas in the lung to equalise with water pressure (or if an obstruction is placed to prevent a seal, in which case water comes in after the opv closes after equalisation not during venting. In normal operation no water comes in as spring force ensures pressure in lung is always higher than ambient. In case of adding a foreign body to prevent good seal: findings were no water comes in until enough gas has leaked out to equalise with water pressure and then a very small leak. Im not sure its likely that the leak out a closed opv would be fast enough that the injected o2 would go from over pressure to equalised with ambient water pressure in the short time between the constant injections (in the given scenario) and i would expect such a leak size would ensure that 24hrs later the lungs would not still be venting gas. but who knows - we never will Im sure. remember as the lung is not a rigid body the water pressure acts on both sides of opv, gas is bouyant and the bouyant force will overcome gravity everytime. Only by exchange (bouyant air bubbles out and water trickes in to take up space left behind) can that happen (at ambient pressure) ps any news about the suit? Just copied you on a followup about the suit. Regarding OPV I should've read the whole thread more carefully ... Graham
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24th May 2008, 02:44	#59 (permalink)
farmerted New Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jul 2005 Location: Long Island/Wakulla Posts: 13	Re: Report from Fatality at Devil’s Ear Hey all, First off, everyone should thank Jerry for the gruesome task of recovering Marks body. My hats off to you brother. There is only one person who will ever truly know what happened and he cannot tell us. Now, as for the water trickling in as the lung burps, I tried this last night and got water in my lung. It wasn't much for the short time that i did it, but water did get in. The theory we came up with 2 days after the recovery was this. He stowed the rebreather on it's back and the lungs floated upwards or it rolled into this position during the time it was left unattended. At this time the water began trickling in the opv and ran down into the stack. Not such a big deal, many water traps. His body was found with the primary in the mud. He probably never put it on his wrist. The setpoint was on .7. From either a low p02 upon ditching the unit or moisture from cooling gathering on the cells caused the solenoid to fire time and again. The lungs are now floating above the unit and o2 is not passing over the cells, so the solenoid keeps firing. The left side o2 tank drains soon and allows more places for water to enter the unit. We also agreed that at some point he could have accidentally opened the dsv. Either way, we all agreed that he had pushed his thirds or had a serious problem before getting back to his rebreather and wasted valuable time trying to put it back on and ran short. The distance where he ditched his rig and where there was a full bailout was less than 100 feet. I'm sure he was in zero vis returning and possibly got lost after twisting around putting the rig on. The line in this room was slack and laying in the silt when I went in there 3 days later, so there had definitely been a problem at this point in his dive. The recovery team disscussed many variables as to what happened. We all agreed no one will ever know. The theory we came up with is sound.I'm not saying it is what happened. there are a lot of little details which led to our proccess of elimination which have not been mentioned. This is not deliberate of course, just that we all have regular jobs and little time to address every point. I appologize up front for not posting replies right away. I am a farmer and it is planting season, so a day or 2 in between cyber visits is normal. Ted
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24th May 2008, 10:44	#60 (permalink)
mempilot What is this..terrafirma? Current Rebreather/s: Megalodon Other Rebreather/s: Megalodon Join Date: Aug 2006 Location: Ft. Lauderdale Posts: 1,269	Re: Report from Fatality at Devil’s Ear Mike, There is a concept called turbulent flow. In allowing for the transfer from high pressure to low pressure stabilization, there is the possibility of disrupted flow which can cause eddies in the transfer and actually cause reverse flow around the area causing the turbulence. This happens in rivers at break waters, on wings, and in other instances. A non-perfect oprv, which they all are, will cause turbulence at the outlet and therefore allow for some backflow. The physics you quote are correct, but only in an perfect world where there is no turbulence. Sorry to burst your bubble on this one, but it is very possible to get wet on the backside of an OPRV. Mem, da pilot __________________ MEM "Da Pilot" Black holes are where God divided by zero. "If at first you don't succeed, don't dive silent." "Would you mind not shooting at the thermo-nuclear weapons." ~ Vic Deakins "Donkey's kill more people annually than plane crashes."
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