Incident due to battery change on dive computer

[MMM]

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A ScubaBoard Staff Message...

a number of off topic posts have been removed. Marg, SB Senior Moderator

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[Hatul]

Great thread. I'm pretty sure that the OP now knows what the SB crowd thinks about this incident, his decision making, and his lack of situational awareness. Thanks for posting, I hope you learned something (and I hope that this has been useful for other, less experienced divers).

I didn't see this mentioned in the thread (sorry if I missed it), but I just want to comment on one thing that is often a point of confusion for new divers. The importance of slow ascents are stressed early in training, and some people think that means the slower the better. This is not always the case, especially for the deeper portions of the dive.

The OP ascended from 80 to 15 feet in 19 minutes, which means a bit over 3 feet per minute. If the OP meant that the 19 minutes included the five minute stop, it would be just over 4 fpm. Either way, this is much slower than the commonly accepted 30 FPM (for the shallower portion of the dive). By doing this - I'm guessing in an attempt to make the ascent "safer" - the divers probably made their DCS risk greater by increasing their nitrogen loading, ongassing during much of the ascent.

So while ascents that are too rapid can accelerate bubble formation and add to decompression stress (in addition to making barotrauma more likely), ascents that are too slow can also be dangerous. Different agencies have different recommendations, but 30 fpm above 60 feet and 60 fpm below that point are good rules of thumb.

Once you realize that you are inadvertently in deco, the most important thing is to get shallow and to stop ongassing. That's why the DM's computer just showed "UP" - the computer was not designed for technical diving, and it was trying to get these guys to start offgassing as quickly as possible.

Agree. This sounds like a Suunto computer which shows the up arrow when in deco and below the "floor". In Suunto lingo the floor is where there is no more net ongassing, so the computer was telling him to get above this but to stay below the ceiling (the deco stop depth). If you violate the Suunto deco it locks out as a computer for 48 hrs. It did that to me once too.

---------- Post added April 21st, 2015 at 09:28 AM ----------

I dive an Oceanic VT3 primary, almost 5 years, more than 500 dives, absolutely perfect. Just started on battery #3. I dive a Geo2/SPG backup, have never needed it but, I could. This would save me from aborted dive and/or series.

Yes, when I go on a dive trip I take and wear a backup computer. They're so cheap now that it's a good idea, so if one fails you don't need to abort your dives.

 

[dberry]

It has been long acceptable to use the timed average depth as bottom depth. the rule of thumb for new divers was to use max depth for bottom depth.

I haven't looked at this thread for a week or so - been diving, go figure - and in catching up this caught me by surprise. Yup, I'm a new diver and I trust the NDL time given by my PDC, and I was taught to use tables with a square dive profile (max depth x time) to give a very conservative sanity check of the PDC. But do experienced divers really use "timed average depth" for multi-level dives? I'm not planning to try it, but I hadn't realized tables could be used that way (safely). Is this something "everyone knows"? No implied criticism, I'm just curious...

 

[boulderjohn]

I haven't looked at this thread for a week or so - been diving, go figure - and in catching up this caught me by surprise. Yup, I'm a new diver and I trust the NDL time given by my PDC, and I was taught to use tables with a square dive profile (max depth x time) to give a very conservative sanity check of the PDC. But do experienced divers really use "timed average depth" for multi-level dives? I'm not planning to try it, but I hadn't realized tables could be used that way (safely). Is this something "everyone knows"? No implied criticism, I'm just curious...

It is done by some divers and some agencies that are in the minority, but it is by no means a universally accepted procedure. If it were, you would be able to find direct quotes from standard dive instructions.

 

[dumpsterDiver]

I haven't looked at this thread for a week or so - been diving, go figure - and in catching up this caught me by surprise. Yup, I'm a new diver and I trust the NDL time given by my PDC, and I was taught to use tables with a square dive profile (max depth x time) to give a very conservative sanity check of the PDC. But do experienced divers really use "timed average depth" for multi-level dives? I'm not planning to try it, but I hadn't realized tables could be used that way (safely). Is this something "everyone knows"? No implied criticism, I'm just curious...

NO, Follow the computer, do your sanity checks and after dozens of similar dives, you will begin to get a good feel for what you can do and can't do with respect to no deco limits. Eventually your sanity check will be a gut feeling on what is reasonable and this will actually incorporate variable depth profiles, if that is the type of dives you normally do.

I follow a recreational dive computer, push it to the limits, do a little extra hang time here and there and pretty much never violate it.

You should continue to use the tables to do the sanity check. You should also be a little conservative. Some divers can get away with pushing the limits and others can't. Until you have done a lot of dives, you won't know which type of diver you are, so be conservative!

 

[RJP]

Some divers can get away with pushing the limits and others can't. Until you have done a [-]lot of dives[/-] chamber ride you won't know which type of diver you are, so be conservative!

Fixed it for [-]you[/-] everyone.