The 'Jascon 4' rescue video - 3 days at 30m and lived!

[kwinter]

Not a sat diver, but have many mates who are. They most definitely breathe helium in the chamber, if they did not they would all be narked all the time.

I thought that might be the case under deeper circumstances. But this was only 30m/100ft. I'm not that surprised that the rescue diver was using heliox, but to put the guy they rescued on it for a very brief ascent into the bell seemed odd.

 

[Andyoak]

This article explains some of it
http://www.nxtbook.com/naylor/ADCS/ADCS0513/index.php#/14

On my phone so can't type an essay but the article should give you a good idea. Remember you don't have to be deep to need a SAT team, but you do of you want people to spend a long time underwater, such as combing wreckage for bodies.

---------- Post added December 7th, 2013 at 11:44 PM ----------

Addressing your point; surprised they put him on helium to get him out?
Well being that
A) you would want him thinking clearly while you got him out
B) he was going to be on helium for 2 days to get desaturated
Seems to me the earlier he got on the helium the better.

 

[Akimbo]

Can one of you sat divers out there explain to me why the cook was put on heliox for his removal? Is it because they can only pump down one gas through both umbilicals? Or was it because getting some He into him was necessary before the long decompression in the chamber? Seems to me they wouldn't be breathing helium in the chamber.

According to this article in Subsea World the sat team aboard the Lewek Toucan was at 70 Meters/230' when they got the call. It took 17 hours to transit to the site, which they used to decompress to about 30 Meters/100' (which would normally take more than 25 hours). Naturally they would be on HeO2. I have never seen a bell that could supply different mixes on separate umbilicals, nor can I imagine a reason why you would want to, even in this case. Also, air sats are extraordinarily unusual.

Virtually all jobs above 50 M/165' are done with surface supplied air and may employ Sur-D-O2 (Surface Decompression using Oxygen) in the deeper range. Saturation operations are fantastically expensive, require larger support vessels, support personnel that outnumber the sat team 3-5x (depending on who gets counted). Everyone on an air diving team except the supervisor cycles between support and diving.

Open circuit masks are rarely used in saturation diving anymore, except for the standby diver in the bell. I imagine they chose to use a mask for the rescue instead of a hat fitted with surface-based closed-circuit recycling gear for simplicity during the short swim (walk really) back to the bell.

It would be more expensive to switch from HeO2 to air on decompression since all the Helium from the chambers is reclaimed/recycled these days. Except for Oxygen, gas is rarely added to the chamber after reaching depth. Switching gas would mean ventilating the atmosphere so a lot of the gas being bled off would be heavily contaminated with Nitrogen and Oxygen, making Helium reclamation more difficult.

You would also have the problem of reducing the PPO2 back down to the 0.3 ATA range in the chambers if you ventilated with air on ascent. Chambers and bells are totally closed circuit with CO2 scrubbers, O2 analyzers, and O2 injection systems unlike typical DCS treatment chambers which are simply ventilated with air.

Does all this make sense?

---------- Post added December 7th, 2013 at 10:31 AM ----------

This article explains some of it Underwater Magazine -September/October 2013....

Thanks, the ADCI (Association of Diving Contractors International) article is the only interview of divers and supervisors I have seen.

I can’t tell from the article if they brought an air umbilical from the surface or a mixed gas umbilical from the bell. It sounds like it took them a couple of hours to figure out that they had to bring him back to the bell instead of using Sur-D-O2 on deck. I imagine there is a lot more to the story since any sat super would know that sat decompression was the only practical option.

I doubt that there was any concern of narcosis, especially after that amount of time. I can see that air would be less likely to freak-out a non-diver on the way back to the bell though.

 

[TinmanJones]

Regarding the hand coming out of the muck, read the stories regarding the divers doing the recovery of

American Airlines flight 587 that crash in Nov. 2011. They were working in similar conditions and had hands come out of the muck. ​

Where can I find and read these stories?

 

[BlueTrin]

Sorry to resurrect but someone made a cool video