Ran out of air today...

[Thalassamania]

No one seems to be the least concerned that he came up with les than 500PSI to start with.!!

Not concerned in the least.

Where I come from, that last 500 PSI is for last ditch emergencies, not for another ten mins under water.

Air that is left in my tank when I get to ten or fifteen feet is best consumed there down to a few hundred PSI. That assures the best nitrogen status before your final ascent. Gas left in the tank does you no good.

Maybe I am just conservative, but then again, I am still alive, after 30 plus years diving.

I'm very risk adverse, after 53 years of diving having never suffered from any sort of DCS, I prefer my approach.

Most dive ops require you come up with at least 500 psi

Screw em'. It's not their spine, not their bowel function, not their bladder function, not their sexual function. Their lunch schedule can wait.

 

[fppf]

In the Marine Tech group At the Oceanographic Institution I used to work at,

We were interested in seeing exactly what the errors were and following them over time, and the gear was sitting there.

What we found was that there were individual SPGs that were good to go and pretty much stayed that way, there were others that were not very good stayed that way, but zero error was very rare in new gauges and did not appear within the seven years that we did the testing. Error elsewhere in the scale was common and gauges changed from one year to the next.

This was how we developed the standards that were used in "SCIENTIFIC DIVING: A GENERAL CODE OF PRACTICE" N.C. Flemming and M.D. Max (eds)

Ahhhhh, thanks for the added details.
Kinda struck me very odd, most people don't even know a dead weight exists, LOL
I verify the calibration of all my gauges every year, its tough being a system engineer

 

[therealtreehugger]

In the Marine Tech group At the Oceanographic Institution I used to work at,

We were interested in seeing exactly what the errors were and following them over time, and the gear was sitting there.

What we found was that there were individual SPGs that were good to go and pretty much stayed that way, there were others that were not very good stayed that way, but zero error was very rare in new gauges and did not appear within the seven years that we did the testing. Error elsewhere in the scale was common and gauges changed from one year to the next.

This was how we developed the standards that were used in "SCIENTIFIC DIVING: A GENERAL CODE OF PRACTICE" N.C. Flemming and M.D. Max (eds)

Thalass - and where can I get ahold of this publication? Sounds interesting, and I'ld like to read it. Is it related in any way to AAUS?
Thanks

 

[diverrick]

To each thier own. glad to see you survived.

 

[DA Aquamaster]

I noticed that the starting pressure was higher (180 bar / 2610 psi) than I remembered it to be (150 bar / 2175 psi) but I attributed that to the tank having spent some time standing in the bright sun.

30 bar / 435 psi is a lot of increase for a tank sitting in the sun - 200 to 300 psi/13 to 20 bar is more normal. Obvious at ths point, but shutting off the tank valve and depressurizing the reg would have confirmed the gauge was not resetting to zero.

I'm a bit old school, but I was taught to look at the gauge to confirm it reads zero and then turn it away from you (no longer neccesary as new SPG's don't decontruct the way the old ones did if they fail), pressurize it and then look and confirm that the tank reads full as expected. In this case you probably would have noted the gauge at 30 bar with the reg depressurized and that would have been a much more obvious indicator of the gauge failure than the excessively full tank reading.

-----

Most mechanical SPG's are more accurate toward the middle of the range. Gauges are in my experience most often prone to reading low at the low end of the scale, just because gauges that read high never make it out of the factory in that condition as if the gauge reads anything higher than zero when it is unpressurized, it is obviously poorly calibrated at the low end of the scale. Guages that read 100-300 psi low at the low end of the scale are common as the error is not as obvious and the error is on the safe side as it adds to the safety margin at the low end of the scale.

When a gauge goes that bad that fast it is probably due to an impact jarring the needle loose on the stem or otherwise causing it to jump in relationship to the mechanism.

 

[LeadTurn_SD]

No one seems to be the least concerned that he came up with les than 500PSI to start with.!!
Where I come from, that last 500 PSI is for last ditch emergencies, not for another ten mins under water. Maybe I am just conservative, but then again, I am still alive, after 30 plus years diving. Most dive ops require you come up with at least 500 psi The only exeption if your diving so shallow you could come up no problem in one breath. Not a common occurance

Also not concerned.

I understand what you are saying in principle, but disagree in practice.

Once I arrive in the shallows, especially after a deep or even long shallowish dive, I try to "off gas" as much as I can. I've never gone OOA (in 33 years ), but I would have no problem sucking a tank bone dry at 15 feet if I thought I needed to for added "DCS-proofing".

And sometimes, depending on the dive profile, I don't do a safety stop at all...

Best wishes.

 

[D_B]

Little clues that are easilly overlooked, and don't mean anything to you untill looked at in a different light
Glad that it worked out well Laurens

(I also think Thal is correct)

... now, what I want to know is ...
............ did you put your mask on your forehead when you surfaced ??

 

[openmindOW]

I was taught to look at the gauge to confirm it reads zero and then turn it away from you (no longer neccesary as new SPG's don't decontruct the way the old ones did if they fail), pressurize it and then look and confirm that the tank reads full as expected.

I was not taught to do this, but I wonder if this is the procedure that I should be teaching to my students. Based on reading this thread, this sounds like a good idea.

Yes, I was taught to turn the gauge glass away from you. (Does that happen these days?) But checking that the gauge is zero before pressurization -this is the first I heard of it. And it sounds like it might be a good idea.

 

[Divingdispatcher]

Glad everything turned out ok. I hope your next dive turns out better.

 

[diverrick]

Sorry .. but if you feel the need to suck a tank dry at 15 feet to prevent DCS, your diving WAY too close to the edge. That also goes for anyone who needs to buddy breath from 15 feet as well.. because their gauge was off for what ever reason.
Just not a good way to dive..IMHO. You could ascend just as easy from 15 FSW by simply breathing out.
What is abundantly clear is I am not going to change your opnions, no matter what, so like I said before "To each thier own".