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Hi John

I tried to send this via private email but I couldn't connect.  Since
it is probably of interest to the list I posted it here.

>Electronically controlled mixed gas units such as the CCR1000 do not have
>cmfv's.  A solenoid opens periodically on command from the oxygen sensors to
>add
>oxygen to the breathing loop.  A bypass valve is provided in the event of
>electronic failure.  

I should have called it a "flow restriction orifice" and not cmfv.  Because
the flow restriction orifice is not connected to a constant absolute preasure 
,in the ccr-1000, the flow will vary with depth and not be cmf.  I would, 
however, guess that the flow restriction orifice is identical to a cmfv 
orifice and hence subject to similar failures.

>In my experience the most often cause of death with these
>units was battery failure.  Low voltage prevents the oxygen solenoid from
>firing, and the diver is not watching his back up displays to note that the
>circuits oxygen is low.

Do you have documented cases of this?  I would love to read some actual 
incident reports.  Most of the techdivers I have talked to are afraid of
the solenoid failing open and getting a huge O2 hit.  Bill and I are looking
at closing the loop on our breather and hence are interested in the history
of this area.

Barrie Kovish
Vancouver, Canada

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