[rollei_list] Re: Hard-Hat Diving
- From: Don Williams <dwilli10@xxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Fri, 07 Jul 2006 14:43:37 -0700
At 03:58 PM 7/7/2006 -0400, Marc wrote, in part:
(The record today is
classified, as it is held by the US Navy team out of the Norfolk Navy Base
in Virginia, but it is in excess of 3,000 feet (about 980m). These guys go
down to about 600 feet (190m) on Heliox, then convert to Hydrogen-Oxygen.
But these guys are not in hard hats: they use the deep-water equivalent of
SCUBA gear. I have spoken with a couple of these deep divers and they
assure me that such descents are a grand adventure but admit that it gets
really lonely down there in the dark. They have to wear electric warming
gear as both Helium and Hydrogen cause the body to lose heat more rapidly
than does the standard Nitrogen basis.)
That's called saturation diving and they descend and ascend in a
pressure chamber and de-compress on deck over a period of hours or
days after they finish a mission.
The advantage is that they can get several working days from one
dive/one decompression series since they stay in the high-pressure
environment during their tour.
I don't know about electric warming gear. The guys I know about wear
hot water suits to keep warm, but it's true that the gas mixtures,
generally running about 1-3% oxygen, have very high heat transfers,
making them get colder faster, even through their lungs.
It would be a grand adventure, but not one for me.
I have pictures of me diving in home-made equipment as early as 1948
or 1949, believe it or not! We used pure oxygen because compressed
air was not readily available. My friend's dad owned a machine shop
and we had ready access to Oxygen. Only later did we learn that
below about 35' pure oxygen could be lethal.
DAW
Don Williams
La Jolla, CA
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