Quote: (Originally Posted by
Abbo)
One thing I'd like to know is how surface-supplied divers have managed to overcome HPNS to dive beyond 330m?
Slow compression. When we did the 1030 foot dive, we stowed the sat system at about 800 feet (need to go look at the logs) and then did excursions to working depth. Our time to 800 from zero was measured in hours, not minutes. Sat Super would stop compression as soon as anyone had a HPNS symptom and we would just sit and acclimate until it was gone and then start descent again. When we hit stow depth we rested for 12 hours before we got the first team ready for excursion. Deco was fixed obligation, so no need to hurry.
Just for interest, sort of on the same topic: we set PP02 by pressurizing the deck system to about 7 meters with air, and then blew down to stow depth with pure helium. Think of this like a rebreather with pure He diluent. There were electrically fan-driven scrubbers inside the deck chamber, about 25 CM diameter and perhaps 50 CM long, and these were changed every 12 hours or so by locking them out for scrubber change. Scrubber agent was Baralyme. C02 was not monitored. PP02 was monitored, but the means of maintaining PP02 was not based 'mainly' on PP02, but depth. As long as ambient temperature was not fluctuating too much, the sat techs just watched the stow depth, and as depth decreased (due to divers metabolizing the 02), pure 02 was added to mantain constant depth. Crosscheck was done to the 02 analizer. Interesting enough, they only had ONE 02 analizer cell on the system, and analized a one atmosphere sample gas that was released from the system with a needle valve and flowed over ONE sensor. Analizers were analog needle Beckman units. Sensors were changed "now and then".
Went into the scrapbook and found these, might be of interest. The first one is Mike Stubbs, one of our LST's (Life Support Technicians) at the sat console. Sort of center-right on the panel you can see the two Dwyer flowmeters to meter the sample gas to the 02 analizer. Second one is the logo for the sat system, the "Cachalot 1000", "Cachalot" being French for a deep diving whale, and "1000" for the design working depth. The "Cachalot 1" was the first experimental sat diving system manufactured by Westinghouse. Santa Fe bought the Westinghouse diving department and AFAIK was the first ever commercial operator of saturation diving systems anywhere (Smith Mountain dam project in 1965 was the first working sat job, the Newport Rhode Island Bridge was the first salt-water sat done, for the pile cutoffs).
I had posted the other two photos elsewhere here years ago, cannot remember where though, so forgive the re-post. The 3rd shot is a modified CCR-1000 used for sat bell-excursion work (this one by Harbor Branch for lockout from the JSL Submersible), circa 1979, and the helmet was the one used with the same system. Deep diving with this stuff is just an industrial process.
Dave (glad not to be offshore... memories of 5 Christmas's in a row at sea.....)
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