Equipment My first out of air situation

[CG43]

In the tank pressure graph, there are two noticeable points. At minute 38-40, there is a peak of about 60 bar. Can you remember if you noticed this peak while breathing? After minute 50, there is a rise to at least 25 bar. You must have noticed that while breathing if it occurred, and this is not the time when you switched to the octo of the DM. At 25 bar, almost all modern first stages provide enough air for this shallow depth. Was the breathing from your regs equally heavy the whole time despite these different displayed pressures, it is likely an AI error.

By the way, from my point of view, there is nothing to criticize about your actions and those of the DM.
If you can do it this way do it .

 

[grantmac]

This looks like blockage via either debris or moisture in the tank. Probably no dip tube and happened when the diver trimmed head down to follow the octo.
I'd be questioning any equipment from that operator.

 

[kdlv]

Здрасти,

How did you have the AI on rental regs? Is it your own AI and if yes, on what device, I don't recognize the graph.
Happy to have a dm chat, I am also curious which dive ops in Greece it was (no fingerpointing intended, just curious).
These seizures in pressure are strange. Either blockage as mentioned earlier, or faulty 1st stage... however 1st stages tend to leak, not to block.
What were the regs? Brand / model? No conclusions to draw, just curious.
Did the dive center remove the spg to install the AI (if your device was installed) or did they just use the 2nd HP port?
You have most the gear, now on to the regs

 

[Alurpal]

I’ve seen a novice diver have an ooa emergency exactly like this on a boat once. I always check my own valve right before splashing. I always wondered if a deck hand did a quarter turn from closed by mistake.

 

[scubadada]

If you look at a typical dive profile, like the one below, despite variation in the gas consumption rate (purple line), the tank pressure curve is relatively smooth with no acute changes (pink line). The line always slopes downward with ongoing gas consumption.

View attachment 914127

The tank pressure curve supplied by @ispasov looks very different. There are 2 smaller blips at about 6 and 11 minutes with a decrease in pressure that recovered back to baseline. The 3rd decrease at about 35 min is quite dramatic. At about 40 min the pressure recovers to baseline, or nearly so, but falls again to zero. There is one more increase in pressure at around 50 min. It easily seems most likely that this represents mechanical obstruction of the dip tube and/or first stage filter. Perhaps the OP can inquire with the operator to find out what inspection of the tank, valve, and regulator revealed.

View attachment 914129

Even in a dive like this, with a very significant increase in gas consumption due to exertion mid-dive (purple line), the tank pressure line shows no abrupt change, just a steeper slope during the exertion (pink line). And, just to be clear, the tank pressure curve is never going to increase during the dive (except for Avelo )

 

[JMarc]

Even in a dive like this, with a very significant increase in gas consumption due to exertion mid-dive (purple line), the tank pressure line shows no abrupt change, just a steeper slope during the exertion (pink line). And, just to be clear, the tank pressure curve is never going to increase during the dive (except for Avelo )

I've got a very steep slope on the pressure line the first time I used a DPV: the orientation of my octopus was such that I've left a lot of bubbles behind me.

 

[wdeutsch]

I would expect a transmitter failure to be all or nothing, whether because of a dead battery, loss of synch, or whatever. It continuing to work while providing a plausible but incorrect reading sounds more like the behavior of a mechanical device, such as an SPG. It would certainly be worthwhile for the OP to check it against another gauge, electronic or mechanical, before his next trip.

I'd kinda expect the same thing, except I own a transmitter that reads several hundred PSI high, consistently. I only use it to watch for leaks/freeflows on my pony tank, so don't need accurate readings. But, if something like that developed in OP's transmitter, it could lead to thinking everything was OK until the transmitter was reporting gas left when there really wasn't.

 

[tursiops]

I'd kinda expect the same thing, except I own a transmitter that reads several hundred PSI high, consistently. I only use it to watch for leaks/freeflows on my pony tank, so don't need accurate readings. But, if something like that developed in OP's transmitter, it could lead to thinking everything was OK until the transmitter was reporting gas left when there really wasn't.

What brand transmitter do you have? I've never heard of this on the PPS MH8A type transmitters.

 

[wdeutsch]

What brand transmitter do you have? I've never heard of this on the PPS MH8A type transmitters.

Aqualung MH8A. I even took it apart to see if there were any calibration screws I could reset, but no such luck.

 

[tursiops]

Aqualung MH8A. I even took it apart to see if there were any calibration screws I could reset, but no such luck.

Interesting. And how did you determine it reads high by a "few hundred PSI" ?