Wheatondiver
Contributor
The training indicates to stop diving if the computer fails. What if you dive the computer, but also back up with the tables?
Computer Failure question
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Damselfish
Contributor
sure you can back up with tables, provided you them and still have your depth and time. One problem you may run into though, is that if you are doing a multilevel dive (where a computer is a real advantage) if you look up your max depth and current time you may be off the table.
(I dive with 2 computers, works for me.)
(I dive with 2 computers, works for me.)
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As Phil Sharkey observed (page 101) at the American Academy of Underwater Sciences Dive Computer Workshop, (Rubicon Link) September 26 -28,1988:
LOST RESIDUAL NITROGEN DATA PROCEDURES
When the data in the computer is lost, regardless of the cause, there are two considerations. The primary consideration (assuming the data is lost while in the water) is effecting a safe return to the surface and the secondary consideration is how to safely begin diving again. Getting back to the surface is easy if the diver is never in a decompression status, which is one of the reasons that U.R.I. requires that the diver always keep 5 minutes of no-decompression time available. The failure of a dive computer while a physiological ceiling is in effect could be a very serious problem (I suggest carrying a backup computer for all planned decompression dives).
Getting a diver back in the water after the failure of a computer is the second problem. The best way is to follow the manufacturer's recommendation on how long to wait to clear out the residual nitrogen and begin diving again with a restarted computer.
This is not always possible. On occasion, a diver would prefer to get back into the water without waiting twenty-four to forty-eight hours. There are several techniques in use, all of which depend on keeping good dive records, especially records of the scrolling no-decompression limits that are displayed by most all computers in their surface mode. None of the currently available computers are set up to permit user access to set levels of tissue saturations. Thus it is impossible to "get back on the computer" without waiting for residual nitrogen to clear. So the first question is, "How long must I really wait?"
There is no complete answer to this question. Clearly, a diver who made a few, short (even deep) dives will clear out excess nitrogen before a diver who made many, long (even shallow) dives. If all the divers in the group have similar past profiles, it becomes a judgment call to permit a diver to reenter the water with a computer when other computers in the group are clear. This has been done successfully and usually involved waits of 12 to 18 hours, but the ultimate safety of this procedures is clearly problematical.
More to the point is the question, "How can I immediately get onto a set of written tables?" A technique that was independently developed by Mike Emmerman of LifeGuard Systems and myself has been used. It requires that the diver record the time of day and scrolling no-decompression limits after every dive. Refer to M. Emmerman - "Dive computer log for the EDGE or Skinny Dipper" (page 189) in these AAUS Dive Computer Workshop Proceedings for the complete procedure and warnings.
If a computer fails the diver must then:
This technique seems to yield reasonable results using the Huggins Tables with the EDGE or SKINNY DIPPER or the Swiss Tables with dive computer programmed with the Buhlmann Model. This technique has not been proven, so use it at your own risk.
LOST RESIDUAL NITROGEN DATA PROCEDURES
When the data in the computer is lost, regardless of the cause, there are two considerations. The primary consideration (assuming the data is lost while in the water) is effecting a safe return to the surface and the secondary consideration is how to safely begin diving again. Getting back to the surface is easy if the diver is never in a decompression status, which is one of the reasons that U.R.I. requires that the diver always keep 5 minutes of no-decompression time available. The failure of a dive computer while a physiological ceiling is in effect could be a very serious problem (I suggest carrying a backup computer for all planned decompression dives).
Getting a diver back in the water after the failure of a computer is the second problem. The best way is to follow the manufacturer's recommendation on how long to wait to clear out the residual nitrogen and begin diving again with a restarted computer.
This is not always possible. On occasion, a diver would prefer to get back into the water without waiting twenty-four to forty-eight hours. There are several techniques in use, all of which depend on keeping good dive records, especially records of the scrolling no-decompression limits that are displayed by most all computers in their surface mode. None of the currently available computers are set up to permit user access to set levels of tissue saturations. Thus it is impossible to "get back on the computer" without waiting for residual nitrogen to clear. So the first question is, "How long must I really wait?"
There is no complete answer to this question. Clearly, a diver who made a few, short (even deep) dives will clear out excess nitrogen before a diver who made many, long (even shallow) dives. If all the divers in the group have similar past profiles, it becomes a judgment call to permit a diver to reenter the water with a computer when other computers in the group are clear. This has been done successfully and usually involved waits of 12 to 18 hours, but the ultimate safety of this procedures is clearly problematical.
More to the point is the question, "How can I immediately get onto a set of written tables?" A technique that was independently developed by Mike Emmerman of LifeGuard Systems and myself has been used. It requires that the diver record the time of day and scrolling no-decompression limits after every dive. Refer to M. Emmerman - "Dive computer log for the EDGE or Skinny Dipper" (page 189) in these AAUS Dive Computer Workshop Proceedings for the complete procedure and warnings.
If a computer fails the diver must then:
- look back at the scrolling no decompression limits and subtract the available time for each depth to come up with a series of time/depth pairs describing dives that would have resulted in equivalent nitrogen uptake.
- determine the repetitive dive designator for each of the time/depth pairs determined.
- use the designator that represents the greatest amount of nitrogen to enters the tables and continue on.
This technique seems to yield reasonable results using the Huggins Tables with the EDGE or SKINNY DIPPER or the Swiss Tables with dive computer programmed with the Buhlmann Model. This technique has not been proven, so use it at your own risk.
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I always have a set of tables in my dive bag. The night before my dives, I run my tables and just write my info on my slate. I have had a computer suddenly die on me at depth, and I just pulled my slate and knew roughly what I needed to do. I always wear a watch so I was covered there for my time. My tables are usually much more conservative than my computer. When I had my failure, I gathered the dive profile from my dive buddy during the SI and then reran my tables for the next dive. It always helps to have some redundancy in one form or another.
It is also conducive to the type of diving you are doing.
Carolyn:shark2:
PS: I dive a wrist mounted computer.
It is also conducive to the type of diving you are doing.
Carolyn:shark2:
PS: I dive a wrist mounted computer.
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Air On
Guest
If you have a complete computer falure and its air integrated... You have a compund problem.
You have lost your tank pressure and depth gauges too.
The reality is though that complete failures are pretty rair with the modern computers that are serviced with any regularity.
You could continue to dive... if you've been using your tables as a backup... but replacing the air gauge and depth gauge could be the real deal breaker.
Even if you were just diving with old school analogue gauges and lost one of them without replacment you'd be in the same boat and a computer falure basicaly.
If you didn't maintain and service the analouge gauges they will fail on you too.
You have lost your tank pressure and depth gauges too.
The reality is though that complete failures are pretty rair with the modern computers that are serviced with any regularity.
You could continue to dive... if you've been using your tables as a backup... but replacing the air gauge and depth gauge could be the real deal breaker.
Even if you were just diving with old school analogue gauges and lost one of them without replacment you'd be in the same boat and a computer falure basicaly.
If you didn't maintain and service the analouge gauges they will fail on you too.
I dive with an integrated computer, the Galileo Sol, but I also have an analogue pressure and depth gauges. To top it off, I dive with a spare computer (Suunto Gheko). If the big boy computer fails, this enables me to continue diving with little or no effect on the dives themselves. The reason I do this, is because most of my dives are on a liveaboard in another country, I'd hate to waste 2 days out of 6 or 7 when the cost of the redundancy is so (relatively) cheap.
At the end of the day, it is a case of how much risk you are prepared to endure, risk of the loss of dives, risk of making a bad judgement call by getting back in the water and so on. Discussions like this make us think of these variables and then either reduce the risks or at least mitigate them.
Oh well, that's my 2c, they are about to call our flight, I am flying to Hurghada in order to start a one week liveaboard tomorrow.
Very Best of Regards, and keep those computers wet!
Richard
At the end of the day, it is a case of how much risk you are prepared to endure, risk of the loss of dives, risk of making a bad judgement call by getting back in the water and so on. Discussions like this make us think of these variables and then either reduce the risks or at least mitigate them.
Oh well, that's my 2c, they are about to call our flight, I am flying to Hurghada in order to start a one week liveaboard tomorrow.
Very Best of Regards, and keep those computers wet!
Richard
I had a computer take a dump a few months ago. We were diving a wreck and were down to 120 feet. I checked my watch and we were 10 minutes into the bottom time. I figured that I would be alright for another 15 minutes or that one of the newbies would be hogging air and need to go up so I used this as an indicator to ascend so just needed to keep an eye on my air supply. Worked out OK. Next dive was a shallow reef where I really didn't need any type of indicator since time would run out long before I would.
BabyDuck
Contributor
if your computer dies, will you still know your time and max depth? if they're on your computer, too, aborting that dive safely might be the best option. then perhaps you can run the tables and plan your next one with the site's max depth and a watch. but if you don't have a backup timer & don't know the site's depth, you need to stop that dive.
i dive with two computers, and tables in my pocket.
i dive with two computers, and tables in my pocket.
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