Ran out of air today...

[lamont]

I would respectfully offer the observation that hospitals don't expect their electronics to work while immersed in salt water . . .

Hospitals will also buy consumer-grade electronics when it doesn't matter as much, but can afford to buy over-engineered closer-to-bulletproof electronics when it matters.

If it costs $1,000 to make a digital SPG with zero-testing, self-monitoring and voting logic, i'll skip it and buy an analog SPG.

self-monitoring and voting logic, i'll skip it and buy an analog SPG.

Oh, and I also work in IT, and I have a healthy skepticism of increased complexity and the law of unintended consequences. For example, you'd think that adding redundant drops to a server to increase its bandwidth and redundancy would always be better -- but you have to load the bonding driver into the kernel in that case which increases the complexity of a single-point-of-failure (the O/S kernel) which can lead to lower availability if you don't spend some time on maintaining that additional complexity (patching, debugging, etc). Going for complexity is often expensive -- and you are either paying via your own time, or else paying for someone else's time to do all the testing and debugging for you....

 

[alibi 2]

Wow, I havent seen a gauge like that in a looooong time

 

[DC53]

A couple of months ago on a boat in Roatan, I heard a diver across the boat tell his buddy and those around him that his gauge was showing a drop of 100 psi. He was very concerned because his air consumption is very high and he was checking for a leak or reason. He was fiddling with his gear for a while. Well, shortly after, I had backrolled in on the other side of the boat and then heard thrashing and yelling on his side of the boat. I found out later that he had jumped in with the air off, thinking that it was on because it still showed a pressure of 2900 or so. His buddy turned it on for him. Everyone on the boat (including me) had assumed that with all his concern and checking his gear, that he had checked to make sure the air was on. He had not purged the air, however, between setting up the tank and arriving at the dive site, so it still showed a nearly full tank. That had confused him into thinking his air was on. Purging it after setting it up would have avoided that confusion. Inhaling while watching the pressure reading would also have signalled that the air was off, since it would have fluctuated with a closed valve and a pressurized reg.

Hey you got that right.... I was in Cozumel, My FIRST boat dive.... The Mexican boat crew literally runs around slapping bc's and regulators on as the boat takes over and I jump back to not get run over. After I go look at everything and it all looks good and the SPG says 3000 psi. At the dive site the DM comes for his quick chat and I point out that my SPG says 2800, 200 less (I was worried there was a leak.) He looks at me and says "Ees OFF" then continues. It all hit me in a flash, including that I (might) have jumped in with no air. No one teaches you these little things, however.

 

[caseybird]

I've never liked the set up tank-open valve- pressure check- observe needle- close valve thing. I don't like losing a few pounds of pressure, but I HATE jumping into the water with the valve closed. My rule of thumb is: once the rig is built, and the pressure checked, I leave the valve open. No chance of forgetting to open it in the last minute rush to get off the boat.
As for accidental purges, helpful DM's closing the valves and other screw up's, I keep my eye on my gear. The boat isn't that big.

 

[caseybird]

Oh yeah, I don't mind using up the last few hundred useable psi on the safety stop. I love the look of the wide open blue on a drift dive, in Fiji the safety stop is a few feet over the top of coral pillars. There was a fantastic amount of life on the top of these "bommies", and it's a study of marine ecology on a small scale. If the surface is rough and I'm expecting more of a challenge getting on the boat, I'll use that 500 psi reserve to get on the boat.

 

[Ayisha]

I've never liked the set up tank-open valve- pressure check- observe needle- close valve thing. I don't like losing a few pounds of pressure, but I HATE jumping into the water with the valve closed. My rule of thumb is: once the rig is built, and the pressure checked, I leave the valve open. No chance of forgetting to open it in the last minute rush to get off the boat.

The issue is that if it's a long time between turning on the valve and diving with it, the o-ring could blow due to the pressure. If you don't turn the valve off right away, have extra o-rings or have extra tanks, it's dive over. That is why you should turn off the valve if it will be a long time until you use it.

Rushing at the last minute makes it more likely that things get forgotten or missed, and you jump in not fully prepared. Most people set up their gear as soon as they board the boat or return from their first dive, so they can relax until they do their dive and not rush or encounter issues at the last minute before diving. You set your rig up, go chat, have your surface interval or whatever. If you make it your routine to turn the valve on as soon as you return to your rig, then continue with gearing up, it is really very easy to remember.

 

[caseybird]

The issue is that if it's a long time between turning on the valve and diving with it, the o-ring could blow due to the pressure. If you don't turn the valve off right away, have extra o-rings or have extra tanks, it's dive over. That is why you should turn off the valve if it will be a long time until you use it.

Sure, to define a long time, I wouldn't leave the valve open overnight. ! hour surface interval? I leave it open. As far as the o-ring blowing, I think the vast majority blow when the system is pressurized. Therefore I can repace it with plenty of time to spare doing it my way. I did have one o-ring extrude from a DIN valve :shocked2: about fifteen minutes after I pressurized the system once. Believe me, I inspect that little sucker everytime now.
Of course, using good procedure when getting ready to dive is a good idea. But once the system is checked, I like leaving it alone.

 

[Ayisha]

I have seen tank o-rings blow in less than an hour. I have seen them blow on the ride to a dive site, probably half an hour or less. And yes, during surface intervals. Not often, of course, but it's happened. Some people I know who once didn't bother to turn off their valve now always turn off their valve because they lost their dive once. By the time someone gets to the correct tank and turns it off, depending on where everyone is, too much air could have escaped to make the dive safely. DM's often turn off tanks during those times, so you need to check your valve before you splash anyway. Might as well just turn it off and get in the habit of checking before you jump in. It could save a dive or more.

 

[josh]

Inhaling while watching the pressure reading would also have signalled that the air was off, since it would have fluctuated with a closed valve and a pressurized reg.

Exactly. And, even more so, if you breath it right down, you also get to see the "zero" (as well as checking the integrity of the regulator).

A very useful extra step.

 

[caseybird]

Another diver's experience:

http://www.scubaboard.com/forums/4241009-post27.html

see the follow up in post 29.

http://www.scubaboard.com/forums/4243452-post29.html