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I agree with you...except I would go a little further. (Refer to my post
to Joel for my excuse for my "short" statement about open or shut.)
I would just add to your statement that FULLY open is not the only
case of the valve being open. Here is why:
Once the valve is open a certain amount the path is no longer effectively
restricted.
For a given size opening (i.e. isolator valve opening), there is a critical
differential
pressure. Once that critical differential pressure is reached, flow rate
will not increase
even if the differential pressure increases. Working this backwards (kind
of), if the
opening of your isolator keeps the flow rate across the isolator for the
maximum
your regulator would deliver during normal breathing (in other words not a
free flow
malfunction)... And the differential pressure across the isolator is minimal
(as it would
be in normal cases)...The only time a partially open manifold would be TOO
restricted,
was when the flow rate out of a orifice caused a differential pressure large
enough to
exceed the critical differential pressure AND the flow rate for that opening
did not keep up with
the flow rate out of the orifice. That flow rate would correspond to a
failed regulator and you
would not want the tanks to equalize anyway!
Now....Having said ALL that...Have I or would I do this calculation...NO
WAY. Although with a
little experimenting one could determine that it did not take much for the
flow rate across the
isolator to keep up with breathing. This experiment could be performed on a
single tank and
regulator (just watch the SPG to see if it dips or not). In any case...The
point of this verbose
post is only to say that partially open does not mean shut. Partially open
does not necessarily
mean restricted.
So dive the way you determine to be safe...smart...whatever...
Just make the arguments make sense.
Cheers!
dsmith218@ho*.co*
ICQ# 25409809
Moderation is for the poor, and the healthy...of which I am neither. -
Polver
-----Original Message-----
From: David Sweetin [mailto:dsweetin@ea*.ne*]
Sent: Tuesday, April 17, 2001 11:08 AM
To: David E. Smith
Cc: techdiver@aquanaut.com
Subject: Re: Isolating Manifold Question
Just a clarification,
If it is not shut, it is either RESTRICTED, or open.
The restricted orifice concept is part of basic open water training.
Now dust off those basic scuba books and tell us what it says about that.
Dave
----- Original Message -----
From: David E. Smith
Subject: RE: Isolating Manifold Question
I say again, louder...
If it is not shut, it is open.
(This is a good argument, don't you think?)
dsmith218@ho*.co*
ICQ# 25409809
Moderation is for the poor, and the healthy...of which I am neither. -
Polver
-----Original Message-----
From: Joel Silverstein [mailto:JoelSilverstein@sn*.ne*]
Sent: Sunday, April 15, 2001 12:48 AM
To: David E. Smith; RDecker388@ao*.co*; rikard.lundgren@sw*.se*
Cc: techdiver@aquanaut.com
Subject: RE: Isolating Manifold Question
If it's not open it's closed.
At 10:18 PM 4/14/2001 -0400, David E. Smith wrote:
I don't think it is "common sense" that a valve be fully open or
fully shut. That is a matter of opinion. Clearly there are
arguments/opinions
for either method (fully open or partially shut).
dsmith218@ho*.co*
ICQ# 25409809
Moderation is for the poor, and the healthy...of which I am neither. -
Polver
-----Original Message-----
From: RDecker388@ao*.co* [mailto:RDecker388@ao*.co*]
Sent: Saturday, April 14, 2001 7:55 PM
To: rikard.lundgren@sw*.se*
Cc: techdiver@aquanaut.com
Subject: Re: Isolating Manifold Question
In a message dated 4/14/01 9:55:22 AM Eastern Daylight Time,
rikard.lundgren@sw*.se* writes:
> >As for the 3/4 of European divers using this method, divers taking
there
> first steps into tech training , do so with IANTD or TDI,
> >, as shut downs are apart of syllabus, my instructor & people i
have
> listened to use this method, and as far as i a aware As the said
> organisations are wide spread >around Europe , i can only conclude
that
they
> are also shown this method.
>
I suspect this is more a matter of the individual instructor than what's
actually in the standards. I've read both of these agency's standards
at
one
time or another and do not recall a single line about requiring
paritially
open ISOs.
Common sense dictates that all valves need to be either all the way on
or
all
the way off. In a stressful situation requiring a valve shut-down it
would
be way too easy to turn the valve the wrong way if it's only partly
open.
With a strict on/off approach, the valve is only going to turn one
way......
THE RIGHT ONE! Bare handed, gloves or mitts, shutting down a valve is
not a
difficult matter with a little practice.
Bob D.
www.SportDiverHQ.com
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<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>I agree with=20
you...except I would go a little further. (Refer to my=20
post</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>to Joel for=20
my excuse for my "short" statement about open or =
shut.)</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>I would just=20
add to your statement that FULLY open is not the =
only</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>case of the=20
valve being open. Here is why:</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>Once the=20
valve is open a certain amount </SPAN></FONT><FONT color=3D#0000ff=20
face=3DTahoma><SPAN class=3D030363400-18042001>the path is no longer =
effectively=20
restricted. </SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001></SPAN></FONT><FONT color=3D#0000ff =
face=3DTahoma><SPAN=20
class=3D030363400-18042001>For a given size opening (i.e. isolator =
valve=20
opening), </SPAN></FONT><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>there</SPAN></FONT><FONT color=3D#0000ff=20
face=3DTahoma><SPAN class=3D030363400-18042001> is a critical =
differential=20
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>pressure. Once that
</SPAN></FONT><FONT =
color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>critical</SPAN></FONT><FONT
color=3D#0000ff=20
face=3DTahoma><SPAN class=3D030363400-18042001> differential =
pressure=20
is</SPAN></FONT><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001> reached, flow rate will not increase=20
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>even</SPAN></FONT><FONT color=3D#0000ff =
face=3DTahoma><SPAN=20
class=3D030363400-18042001> if the differential </SPAN></FONT><FONT =
color=3D#0000ff=20
face=3DTahoma><SPAN class=3D030363400-18042001>pressure increases.=20
</SPAN></FONT><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>Working this backwards (kind of), if the=20
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>opening of=20
your isolator keeps the flow</SPAN></FONT><FONT color=3D#0000ff =
face=3DTahoma><SPAN=20
class=3D030363400-18042001> rate </SPAN></FONT><FONT size=3D4><FONT
=
color=3D#0000ff=20
face=3DTahoma size=3D3><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>across the isolator for the maximum=20
</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT size=3D4><FONT color=3D#0000ff face=3DTahoma
size=3D3><FONT =
color=3D#0000ff=20
face=3DTahoma><SPAN class=3D030363400-18042001>your regulator would=20
deliver</SPAN></FONT><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001> during normal breathing (in other words not =
a free=20
flow </SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT size=3D4><FONT color=3D#0000ff face=3DTahoma
size=3D3><FONT =
color=3D#0000ff=20
face=3DTahoma><SPAN =
class=3D030363400-18042001>malfunction)...</SPAN></FONT><FONT=20
color=3D#0000ff face=3DTahoma><SPAN class=3D030363400-18042001> And the =
differential=20
pressure across the isolator is minimal (as it would =
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>be in normal=20
cases)...The only time a partially open manifold would =
</SPAN></FONT><FONT=20
color=3D#0000ff face=3DTahoma><SPAN class=3D030363400-18042001>be TOO =
restricted,=20
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>was when the=20
flow rate out of a orifice caused a </SPAN></FONT><FONT =
color=3D#0000ff=20
face=3DTahoma><SPAN class=3D030363400-18042001>differential pressure =
large enough to=20
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>exceed the=20
critical differential</SPAN></FONT><FONT color=3D#0000ff =
face=3DTahoma><SPAN=20
class=3D030363400-18042001> pressure AND the flow rate for that opening =
did not=20
keep up with</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>the flow=20
rate out of the orifice. That flow rate would correspond to=20
</SPAN></FONT><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>a=20
failed regulator and you </SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>would not=20
want the tanks to equalize</SPAN></FONT><FONT color=3D#0000ff =
face=3DTahoma><SPAN=20
class=3D030363400-18042001> anyway!</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001></SPAN></FONT> </DIV></FONT></FON
T>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>Now....Having said ALL that...Have I or =
would I do=20
this calculation...NO WAY. Although with a </SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>little=20
experimenting one could determine that it did not take much for the flow =
rate=20
across the </SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>isolator to=20
keep up with breathing. This experiment could be performed on a =
single=20
tank and </SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>regulator (just watch the SPG to see if =
it dips or=20
not).</SPAN></FONT><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001> In any case...The point of this =
verbose=20
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>post is only=20
to say that partially open does not mean shut. </SPAN></FONT><FONT =
color=3D#0000ff=20
face=3DTahoma><SPAN class=3D030363400-18042001>Partially open does not =
necessarily=20
</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>mean=20
restricted.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>So dive the=20
way you determine to be safe...smart...whatever...</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030363400-18042001>Just make=20
the arguments make sense.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030363400-18042001>Cheers!</SPAN></FONT></DIV>
<P><FONT size=3D4><FONT color=3D#808000=20
face=3D"Lucida Handwriting">dsmith218@ho*.co*<BR></FONT><FONT =
color=3D#000080=20
face=3DTahoma>ICQ# 25409809</FONT></FONT></P>
<P><FONT color=3D#ff0000 face=3D"Monotype Corsiva" size=3D4>Moderation =
is for the=20
poor, and the healthy...of which I am neither. - Polver<BR> =
</FONT></P>
<DIV align=3Dleft class=3DOutlookMessageHeader dir=3Dltr><FONT =
face=3DTahoma=20
size=3D2>-----Original Message-----<BR><B>From:</B> David Sweetin=20
[mailto:dsweetin@ea*.ne*]<BR><B>Sent:</B> Tuesday, April 17, 2001 =
11:08=20
AM<BR><B>To:</B> David E. Smith<BR><B>Cc:</B>=20
techdiver@aquanaut.com<BR><B>Subject:</B> Re: Isolating Manifold=20
Question<BR><BR></FONT></DIV>
<DIV><FONT size=3D2>Just a clarification,</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>If it is not shut, it is either </FONT><FONT=20
size=3D3>RESTRICTED, </FONT><FONT size=3D2>or open.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>The restricted orifice concept is part of basic open =
water=20
training.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Now dust off those basic scuba books and tell us =
what it says=20
about that.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Dave</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A href=3D"mailto:dsmith218@ho*.co*" title=3Ddsmith218@ho*.co*>David =
E.=20
Smith</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> RE: Isolating
Manifold =
Question</DIV>
<DIV><BR></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030290700-17042001>I say=20
again, louder...</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030290700-17042001></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030290700-17042001>If it is=20
not shut, it is open.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN=20
class=3D030290700-17042001></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DTahoma><SPAN =
class=3D030290700-17042001>(This is a=20
good argument, don't you think?)</SPAN></FONT></DIV>
<DIV> </DIV>
<P><FONT size=3D4><FONT color=3D#808000 face=3D"Lucida
Handwriting"><A =
=
href=3D"mailto:dsmith218@ho*.co*">dsmith218@home.com</A><BR></FONT><
FONT=
=20
color=3D#000080 face=3DTahoma>ICQ# 25409809</FONT></FONT></P>
<P><FONT color=3D#ff0000 face=3D"Monotype Corsiva" size=3D4>Moderation =
is for the=20
poor, and the healthy...of which I am neither. - Polver<BR> =
</FONT></P>
<DIV align=3Dleft class=3DOutlookMessageHeader dir=3Dltr><FONT =
face=3DTahoma=20
size=3D2>-----Original Message-----<BR><B>From:</B> Joel Silverstein
=
[<A=20
=
href=3D"mailto:JoelSilverstein@sn*.ne*">mailto:JoelSilverstein@snet.net<=
/A>]<BR><B>Sent:</B>=20
Sunday, April 15, 2001 12:48 AM<BR><B>To:</B> David E. Smith;
<A=20
href=3D"mailto:RDecker388@ao*.co*">RDecker388@aol.com</A>; <A=20
=
href=3D"mailto:rikard.lundgren@sw*.se*">rikard.lundgren@swipnet.se</A>=
<BR><B>Cc:</B>=20
<A=20
=
href=3D"mailto:techdiver@aquanaut.com">techdiver@aquanaut.com</A><BR><B
>S=
ubject:</B>=20
RE: Isolating Manifold Question<BR><BR></FONT></DIV><FONT
size=3D3>If =
it's not=20
open it's closed. <BR><BR><BR><BR><BR>At 10:18 PM 4/14/2001
-0400, =
David E.=20
Smith wrote:<BR>
<BLOCKQUOTE class=3Dcite cite type=3D"cite">I don't think it is =
"common sense"=20
that a valve be fully open or<BR>fully shut. That is a matter =
of=20
opinion. Clearly there are<BR>arguments/opinions<BR>for either =
method=20
(fully open or partially shut).<BR><BR>dsmith218@ho*.co*<BR>ICQ#=20
25409809<BR><BR>Moderation is for the poor, and the healthy...of =
which I am=20
neither. -<BR>Polver<BR><BR><BR><BR><BR>-----Original =
Message-----<BR>From:=20
RDecker388@ao*.co* [<A href=3D"mailto:RDecker388@ao*.co*"=20
eudora=3D"autourl">mailto:RDecker388@ao*.co*</A>]<BR>Sent: Saturday, =
April 14,=20
2001 7:55 PM<BR>To: rikard.lundgren@sw*.se*<BR>Cc:=20
techdiver@aquanaut.com<BR>Subject: Re: Isolating Manifold=20
Question<BR><BR><BR>In a message dated 4/14/01 9:55:22 AM Eastern =
Daylight=20
Time,<BR>rikard.lundgren@sw*.se* writes:<BR><BR>> >As for =
the 3/4=20
of European divers using this method, divers taking there<BR>> =
first=20
steps into tech training , do so with IANTD or=20
TDI,<BR>> >, as shut downs are apart of =
syllabus, my=20
instructor & people i have<BR>> listened to use this =
method,=20
and as far as i a aware As the said<BR>> organisations are wide =
spread=20
>around Europe , i can only conclude that<BR>they<BR>> are =
also shown=20
this method.<BR>><BR><BR><BR>I suspect this is more a matter
of =
the=20
individual instructor than what's<BR>actually in the =
standards. I've=20
read both of these agency's standards at<BR>one<BR>time or another =
and do=20
not recall a single line about requiring paritially<BR>open=20
ISOs.<BR><BR>Common sense dictates that all valves need to be either =
all the=20
way on or<BR>all<BR>the way off. In a stressful situation =
requiring a=20
valve shut-down it would<BR>be way too easy to turn the valve the =
wrong way=20
if it's only partly open.<BR>With a strict on/off approach, the =
valve is=20
only going to turn one way......<BR>THE RIGHT ONE! Bare =
handed, gloves=20
or mitts, shutting down a valve is not a<BR>difficult matter with a =
little=20
practice.<BR><BR>Bob D.<BR><A
href=3D"http://www.sportdiverhq.com/"=20
eudora=3D"autourl">www.SportDiverHQ.com</A><BR>--<BR>Send mail for
=
the=20
`techdiver' mailing list to `techdiver@aquanaut.com'.<BR>Send=20
subscribe/unsubscribe requests to=20
`techdiver-request@aquanaut.com'.<BR><BR>--<BR>Send mail for the =
`techdiver'=20
mailing list to `techdiver@aquanaut.com'.<BR>Send =
subscribe/unsubscribe=20
requests to=20
`techdiver-request@aquanaut.com'.</FONT></BLOCKQUOTE></BLOCKQUOTE></
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