There  is no "design flaw" in the RB 80 -  the thing vents itself when you
ascend , and with any rebreather, you need to expect the ppo2 to drop as
you ascend unless you replace the gas in a mechanical  RB or oxygen is
added in the case of the CCRs. The idea of flushing the loop on ascending
deco at each new step is to take advantage of the ppo2 inherent in that
step. The shape of the ppo2 at any given step with any venting or not
venting is predictable bases on the behavior of offgassing and the nature
of the equipment.

Conversely, what I actually do in practice is NOT immediately flush the
loop when I switch gases so as to not spike the ppo2, but let it rise more
slowly for a while, and then I start flushing  it out periodically to
overcome the drop in effective oxygen content caused by the offgassing of
inerts, the water vapor, etc, which diminishes as the step progresses,  and
I flush it out when I change depths.

I will remind all of you who incurs the most massive decompression
obligations in technical diving and who executes them most effectively - me
- and I do them without incident of any kind on the Halcyon rebreather as
well as open circuit. What other people do who refuse to recognize or
believe that we have this worked out is none of my concern, but I will not
sit here while people speculate about things that are clearly not well
understood by them and hold no significance in and of themselves.

As far as the question that somebody asked ( directed at me) about constant
ppo2 deco, see the WKPP.org website regarding deco procedures. In a
nutshell, you need to "toggle" on and off the high ppo2s.  Constant ppo2
only works for dives where no real deco is required in the first place - in
other words, it is not the correct way to decompress.

I am still waiting for somebody to try to live through one of my
decompressions on a constant ppo2 - any takers?




-----Original Message-----
From: Esbjörn [mailto:esbjorn@no*.co*]
Sent: Thursday, September 12, 2002 4:20 PM
To: techdiver@aquanaut.com
Subject: Re: Halcyon RB 80 Accident


Having read  a translation of the report, (which accuracy i can in no way
check) the following grabs me.

"> Both divers said they forgot to flush the RB80' Loop before ascenting
till arrive at the first stop (change mix) at 66m. They also said they do
not remember what happened during this part of the dive and that sometimes
breathing became ¨heavy¨. Arriving at 40m , Luiz Toledo said he was having
difficulties to coordinate movements of his bellow members. "

Basically the only achilles heel of the RB80/DC55 design is the need to
flush the loop continuesly when ascending. Not suprising breathing became
"heavy" or that they do not remember that part of the dive when hypoxic.

Would this have been the starting point of the chain of unfortunate events
or I am completely out on the wrong limb here ?

regards /e


--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]