Mike,
  If you read my posts you will see that I have not advocated any of the
options for how to operate your valves.  I have stated only that it is not
"common sense" that the valve should be fully open.  I have stated that a
valve not fully shut is open (this in response to the statement that a valve
not fully open is shut).  I think if you think of the "system response" to
the 2 scenarios (partially shut = open or partially shut = shut) you would
have to agree with my version.  In any case, I think these "arguments" have
little to do with the real discussion of whether or not a valve should be
fully open or not.  I haven't even really gotten into that.  I am simply
commenting on the "absolutist" posts that make statements of common sense or
fact because it suits someone's argument.  To this end, what is your source
on the design basis of scuba valves being several turns to shut as an
"intrinsic safety factor".  Also, I think you would have to admit, (without
coming to a conclusion on how you should operate your valves) their is a
difference in the likelihood of rolling shut an isolator vice an orifice
valve. If this argument were made to me, I would counter with.."There is
still the likelihood..."  But then, that is why we have good technique and
don't contact our manifolds.  And when in spite of that technique, we
do...we check.  (Not to start another thread, but my isolator knob is
inverted and CAN'T contact the overhead!)
  In any case, it may amuse you to discover that I keep my isolator fully
open.  I didn't used to.  And I arrived at this decision based very little
on any of the arguments posed so far.  I just take issue with the fact that
some have arrived at conclusions/statements of FACT, without any proof or
"authority".

So as I go on and on....Let me state one more time what I CONSIDER to be
fact...whether it is relevant to the main issue or not.

A partially open valve will act like an open valve.
A partially open valve will be more easily shut (whether intentionally or
not).
I should notice an inadvertently shut isolator by monitoring my SPG.
If I am too stupid to open my isolator before mixing/filling, then that is
Darwin at work.

Now, there are many more, more relevant facts.  These are just the ones
presented (or contradicted) in order to arrive at the decision that the
isolator MUST remain fully open.  (Lest you be a farm animal or something.
<g>)  So I plead, argue/discuss/whatever the merits...That is why we are all
here (I presume).  Let us not dispute fact with opinion and state it as a
fact.

Happy Diving!
Dave Smith

dsmith218@ho*.co*
ICQ# 25409809

Moderation is for the poor, and the healthy...of which I am neither. -
Polver




-----Original Message-----
From: Mike Rodriguez [mailto:mikey@ma*.co*]
Sent: Sunday, April 15, 2001 5:43 PM
To: David E. Smith
Cc: Joel Silverstein; RDecker388@ao*.co*; rikard.lundgren@sw*.se*;
techdiver@aquanaut.com
Subject: RE: Isolating Manifold Question


At 11:11 AM 4/15/2001 -0400, David E. Smith wrote:

Hello David,

>If it is not shut, it is open.

A bump on a fully open valve results in a non-event.  The same bump
on a mostly closed valve can result in an accident, maybe a fatal one,
as analysis of several diving deaths over the years related to
inadvertently closed isolators suggests.  If it can happen to other
divers, it can happen to any of us, including you.

-Mike Rodriguez
<mikey@mi*.ne*>
http://www.mikey.net/scuba
Pn(x) = (1/(2^n)n!)[d/dx]^n(x^2 - 1)^n

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