Gas Pressure Indication Redundancy

[DevonDiver]

The advantage is not having to ascend if you have a dysfunction. It may not be a big deal at Dutch Springs, but it is if you are on the beginning of a trip on a live aboard.

There's two issues there: prematurely aborting a single dive or losing a series of dives.

The difference between those two issues is whether you have the option to change SPG between dives. I'd expect a liveaboard to have spare SPGs/Regs stocked to cater for such instances. If in doubt, I'd take an SPG/HP hose as part of my spares kit. Hey presto - worst case scenario, without redundancy is a premature end to a single dive..

Give the rare chance of AI failure - the cost of a single lost dive is going to be off-set by the cost of buying a reserve SPG anyway.

Aborting a dive is a bummer.... fair enough..... but those with experience will appreciate that there's plenty of reasons why a prudent diver will choose to abort a dive. SPG/AI failure is one of the most rare reasons for that. IMHO, extreme reluctance to abort a dive, tends to place a diver firmly in the 'potential victim' demographic... as too much persistence in "getting your buck's worth", when other factors point towards surfacing, is often the first step onto an accident spiral. That's a mindset issue.

 

[diverdoug1]

When diving with a single tank, I use a 1st stage with 2 high pressure ports. One port goes to a wireless transmitter for a Gallileo SOL wrist computer, and the other port is connected to an analog SPG in a console with a Suunto Vyper2. I like the ease of monitoring my remaining gas on the wrist computer when I am doing underwater photography, but repeated strobe flashes can interfere with the wireless signal, so I like the redundancy provided by the SPG. Otherwise I would have to start to abort my dive every time I fired a number of shots close together (a frequent occurance). The wireless signal re-establishes itself after about 45 seconds, but I would not feel comfortable "flying blind" while waiting for it to come back.

 

[RonFrank]

I look at my pressure a couple times during a dive. Some of you folks talk like you spend so much time monitoring gauges that you miss the dive!

If my SPG stops functioning I may not realize it for 20 minutes. I would not likely abort the dive, that's what a buddy or pony tank is for! Loosing the SPG does not mean anything has changed. So why am I changing my dive plan? Now if I lost the ability to monitor my time, but thats very unlikely and a different situation.

I often exit with 1500lbs so why am I worried that my pressure is low? I rarely come up with less than 750psi. I do carry a backup SPG but have never used that. If my AI SPG fails then I add my backup between dives, and continue on. This is also depth dependent. If at 120' than its very different than a 30' dive off Key Largo. I'm guessing the OP had a lazy DM who loved the idea of exiting early and spending the remainder of the evening relaxing! Group night dive? Seriously?

I think some people have too much time on their hands leading to threads like this!

 

[diverdoug1]

If my SPG stops functioning I may not realize it for 20 minutes. I would not likely abort the dive, that's what a buddy or pony tank is for!
I think some people have too much time on their hands leading to threads like this!

I am shocked that a diver with such a cavalier attitude about gas management and OOA emergencies would be made a moderator on a SCUBA diving website.

 

[scubadada]

I have 163 dives on an Oceanic VT3 since July 2010 with no more than a transient loss of signal. I dive a backup Oceanic Geo 2 but have not had to use it. I do carry a SPG in my backup kit but have never had to use it either. At worse I would have to end a single dive somewhat prematurely but know my gas consumption within 100-200 psi on all dives. I would not lose multiple dives on an extended trip by switching to the SPG. I don't think this is a big problem and will not be diving with a redundant SPG on every dive. To each their own.

Good diving, Craig

 

[flots am]

I am shocked that a diver with such a cavalier attitude about gas management and OOA emergencies would be made a moderator on a SCUBA diving website.

That's pretty much the whole issue right there (bold mine).

A real "OOA" should definitely be embarrassing, and in fact, I beleive that boat captains should be allowed to punch "I was a dumbass" holes in c-cards each time it happens and revoke them after 4 punches. However if OOA is an actual emergency, the diver needs more training and practice and better buddy skills.

I "run out of air" a half dozen times each week. If you follow your training, it should be nothing more than an interesting exercise.

flots.

 

[diverdoug1]

That's pretty much the whole issue right there (bold mine).

A real "OOA" should definitely be embarrassing, and in fact, I beleive that boat captains should be allowed to punch "I was a dumbass" holes in c-cards each time it happens and revoke them after 4 punches. However if OOA is an actual emergency, the diver needs more training and practice and better buddy skills.

I "run out of air" a half dozen times each week. If you follow your training, it should be nothing more than an interesting exercise.

flots.

So your c-card would be punched in 4 days?

Unless you have gills, OOA is an emergency. Relying on buddy breathing is great, unless your buddy has his head as far up his alimentary canal as anyone relying on "buddy skils" as a crutch for poor gas management. Running out of air is a sentinel event for poor vigilance and poor discipline, saying it is no big deal is just plain stupid! Pay attention to your gas reserves and you will greatly decrease your risk. You may not be able to reach your buddy when you suck your tank , or he might not have adequate gas reserves necessary for you to make a safe ascent. Also, you put your buddy at unnecessary risk by having to buddy breathe with you. Sure, I train my students to buddy breathe 1000 feet out of a cave, but they do it with adequate gas on their back so that the can go back to "real world' gas management if things do not go as planned. Saying that running out of air for real is no big deal because you can use you buddies air is a reckless attitude.

 

[JamesK]

So your c-card would be punched in 4 days?

I think when he said he "I "run out of air" a half a dozen times a week," he meant that he practices a half a dozen times a week.

 

[KD8NPB]

"A man with one watch knows what time it is; a man with two watches is never quite sure."

 

[doctormike]

"A man with one watch knows what time it is; a man with two watches is never quite sure."

That's a good point!

I use a Suunto vyper air with a transmitter on my right post, and an analog SPG on my left post. I mainly keep the transmitter because I am - like others in this thread - a data junkie and I like having my SAC, etc... incorporated into my electronic logs. However, I must admit, the transmitter isn't really so reliable. I have had frequent de-links while using strobes at night (a well known bug, apparently), and I have had to reset the code on other occasions as well.

But in regards to this quote, I find the digital reading to be 300-400 lower than the analog reading at the start of the dive, and they slowly converge as the tank runs down.