My first screw up on Boris

Drmike

I like to talk about my screw ups. I think there's good lessons to learn from peoples screw ups so don't mind sharing them. If people want to think Im an ass it doesn't bother me. I hope the following is useful.

This is my first ever real screw up on the Ouroboros. As is often the case this screw up was not just one mistake but a combination of mistakes and situations that came together.

The mistakes that led to this incident actually started a week ago after my last trip. I noticed my neck seal on my dedicated off board O2 tank was leaking a bit so when I got home I replaced the seal. Not wanting to fill the tank back with 'expensive' O2 only to find it still leaking I decided to test the seal using air. I put some air into the tank checked for leaks and found none.

Fast forward a week to the morning I left for the trip. I got together all my offboard and onboard tanks and took them to my workshop for filling. I filled the on-board O2 to 120 bar and the off-board O2 to the same from the same source. This is where the first mistake came in. As I have dedicated offboard O2 tank that only ever has O2 in it over the years Ive got into the very bad habit of not analysing it. I analyse my on-board O2 so I can calibrate my unit by as that tank is filled from the same source as my off-board O2 tank (which only ever has O2 in it, *normally, see above) I have got into the bad habit of thinking there is no need to analyse both tanks. As you have probably guessed by now my 1st mistake was I didnt bleed the air out of the offboard O2 tank.

Ok two days ago we found this really great new wreck. A big cargo ship with intact superstructure sat almost upright in 60m of water. I had a great time inside the cavernous superstructure. The engine room was particularly nice as it was not silty and the visibility was really the best Ive seen in South China Seas in a long time. As is my habit I dived with my off-board O2 plugged in and turned on. This is because I only get 120bar fills so the little onboard 2L is not enough. During the dive I was not surprised when the unit alerted me to low HP O2 but wasnt concerned as I knew it would be drawing O2 from the larger offboard tank as well so I had plenty of O2 for the dive.

The dive over I began my ascent. The currents were totally screaming now and the upline was bouncing up and down several meters. I was being thrown around like a rag doll. It took quite some time for me to get my Jon line out and secure it, my arms burning with the effort. Finally with the Jon line clipped to me I could relax a little more but still the swell was throwing me all over the place.

I think it was towards the end of my 9m stop that I saw my ppo2 was dropping (green light on hud not working so noticed on my secondary) I pressed the manual O2 injector and realised immediately that no gas was going through it. I scrolled to the SUM screen and saw the on-board O2 was zero bar. I was a little surprised at this (and a bit concerned) seeing as my offboard was plumbed in and turned on, it should be drawing gas from both. I checked the swagelock was fully in, it was. I checked the offboard O2 tank valve was open, it was. But it was not fully open. These valves have to be right open they stick a bit and sometimes can catch you out when you think its open but its not. This was the second mistake - the valve was not open enough. It hadnt been feeding off board O2 and basically the solenoid had sucked the onboard tank dry without taking anything from the off-board.

No problem I thought as I opened the valve fully and flushed some O2 in.
Then I saw the ppo2 drop even faster! Now I was confused. I flushed some more of the offboard O2 in and still the ppo2 was dropping.
I unclipped my offboard tanks and verified I had them the right way around. I even flushed in some of the bottom bail gas to make sure I had the tanks the right way around and to verify the cells were reading correct. I moved up to my 6m stop and did a full flush. It showed I had 40% in my offboard O2 tank. Ok no problem I figured. Ill just do longer deco. I set the unit setpoint to 0.5 then changed my VR3 setpoint to the same. I saw the TTS jump to 86 mins! Oh well.

I wondered if I had enough off board 40% to do 86 mins of deco? Soon find out I guess.

With my scooter tailing behind me in the strong current I tucked my head down and rode it out. The line bucked and flapped me around like a rag doll. It was not fun.

Finally it was time to ascend. I knew I would face problems on the surface with the setpoint controller seeing as the lowest setpoint the unit will run is 0.4 which is what I had in my offboard. I figured it would just keep injecting - which I figured was Ok as I would be on the surface anyway and based on how much the line was bucking I knew it would be a rough ride and checking handsets (green light on hud not working) can be impossible at times with bad surface conditions. Anyway I reached the surface and couldnt believe what I saw. Every divers worse nightmare. We were in the middle of a tropical storm.

Waves at least 6 feet in height raging currents screaming wind and visibility down to a few meters with the driving rain and sea spray. The dive boat was crashing up and down with the huge swells. With the CL filling up with 40% I made a grab for the trail line and hung on. The crew pulled the line in closer to the boat but it was too dangerous for me to get to close for fear of it coming down on me in the swells. My scooter was dead drag behind me. Hanging on with one arm I dragged it forward and somehow managed to pass it up to a crew member at a moment when the rear of the boat was within reach. As is my habit when in this kind of condition and especially when hanging on with the left arm and unclipping gear with the right on the surface I manually inject O2 rather than worry about checking the displays so whenever I could I did the same thing here.

I was taking a real pounding. The waves and swell were dragging me up and down. At one stage they took me under the dive boat as it raised on a swell and it almost took me out as it crashed back down again. It was quite an ordeal. I was puffing, I was exhausted, my arms were killing me from hanging on. I unclipped my bottom bail gas and managed to pass that up during the slightest pause in the swell. Then a few moments later I managed to pass up the off board O2. As I did so I lost my grip as the swell yanked the trail line out of my hand. I managed to grab it again with my now cut and bleeding hand but had drifted some ways back. I pulled and pulled struggling along the line back to the boat. Puffing and panting arms and legs burning from the effort I had to wait for the right moment to get the center ladder that was the Christmas tree design that you could climb wearing fins. There was no way I was going to be able to take my fins off in the water.

Still hanging on for dear life and now needing both hands to hold on I checked to see the blue light came on ever few moments (the blue and white lights are the only ones that are working). That reassured me the unit was firing in 40% and the loop would be breathable. I would have fired the adv to flush with breathable gas but my dil was 10/50 so that wasnt an option.
I got to the ladder but the swell pulled me off it. I tried again and again. I was growing exhausted. Finally I saw my chance at a pause in the swell and made a rush for it. I pulled myself up the ladder exhausted and fighting to get enough air in my lungs. As soon as I was out of the water and there was no risk of me falling back in, I ripped out my mouthpiece and gulped back lung fulls of sweet fresh air.

I walked across to the bench and sat down. Before I even took my facemask off I glanced down at my secondary display to see, for curiosities sake just what my loop ppo2 was. I knew it wouldnt be high but figured it would be around 0.2-0.3

It was 0.09

Yes 9%.

I was stunned. Then of course I realised my third mistake.
Normally when I pass up my off board O2 tank there is still O2 in my on board for the solenoid to fire into the loop. In this case I had emptied my onboard O2 (due to the fact the offboard tank had been closed) so from the moment I passed up my offboard O2 tank to the moment I got onto the boat I had just been breathing down the loop. Even though I could see the blue hud light come on no fresh gas was being added because the onboard was empty and the offboard passed up. That might not have been so bad had I been starting with a loop ppo2 of 1.0, but because of mistake no.1 my starting loop ppo2 was 0.4

There were a lot of lessons learnt on this dive.

In future I will certainly analyse both my O2 tanks and not just one and assume the other is the same just because its a dedicated O2 tank that normally never has anything but O2 out in it.

I will open my off-board O2 tank valve fully all the way.

If for some reason I end up with an empty onboard o2 tank in the future I will not pass up the offboard o2 tank but will carry it up the ladder instead

I will get that hud fixed.

I was surprised that I didnt pass out breathing only 9%. If I had done whilst climbing the ladder with those sea conditions I hate to think what would have happened.

My booster arrives next week so no more low pressure O2 fills

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

onetime

Thanks for sharing Mike. I'm glad everything worked out.

RZEP17

I second that! Sharing that kind of the stories can save somebody's life.
THX, pal!
T

Phil Ennis

Bloody hell! That wore me out just reading it.

Glad it was a happy ending and thanks for sharing.

__________________
Phil Ennis.



My Website

diverklondike

Mike,

Thanks for sharing... Glad you are ok... This sure once again proves out it's not the first mistake that gets you... It's the potential tail spin that the first one can start...

Dive Safe....

Mark

Skipbreather

Mike-

Many thanks for an outstanding write up of what should be a memorable lesson to all. It is an excellent example of a “chain of events” situation that almost ended in a tragedy. Thank God it did not.

Admission by a diver as accomplished as you that he can dig himself into a hole THAT deep is highly commendable and should be truly sobering for all who read it regardless of skill level. Hopefully folks will see some errors they themselves have made under more benign conditions and resolve to not make those oversights/ assumptions in the future.

Dive safe,
Ken

Alan Crichton

Phew ! Glad it worked out Mike - It always amazes me how some action or lack therof which deemed insignificant at the time can turn around and bite you later on. Really appreciate you sharing it with us all ! Just a thought what about your buddy's oxygen ?

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Al from the Bay

The best dive is the next dive !

Sutty

Thanks for sharing that Mike! Glad you didn't pass out on the surface in a tropical storm - quite a "near miss"!!
Incidentally breathing from my loop sitting on the sofa with no O2 supply to it (and competent supervision) I was still conscious with PO2 0.05!! - not sure how long I would have stayed conscious at that PO2 though.
If you have you off-board O2 plugged in would it be a good idea to turn off your on-board so that you always have a full on-board O2 supply with the rebreather in its most minimal configuration? Also means you will spot during the dive if the off-board is not switched on
It has been well demonstrated in aviation accident anaysis that it is nearly always a chain of errors/problems that cause accidents rather than a single problem.

Very glad you made it OK

Neil

__________________
Never forget that life is a finite resource.

Silent

Mike,

As always a great post.
As has already been said a good reminder to us all not to get complacent about our setup routines.

Thanks for sharing.

Neil

__________________
On the dark side everyone can hear you scream......

Toren

Military pilots refer to this as "falling into the incident pit."
Thanks for the reminder that there is no such thing as a minor problem when diving an Rebreather.

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"Sh*t does happen, it is our job to keep it a minor annoyance by training, proper gear configuration, emergency skills practice and a survival mindset."
--Ron Micjan