Re: [APD] Ooch

["S. Hieber" <shieber at yahoo_com>]

Nope, Mrs. Ooch is unaffected. That would be me with the
upside down tanks.

One of the CGA's concerns about compressed gas tanks not
being stored upright is that the valve is more likely than
otherwise to be unprotected and knocked about. 

sh
--- Vaughn Hopkins <hoppy1 at surewest_net> wrote:

> Now I understand "Mr. Wood's problem"!
> Thank  you for a very good explanation of the use of a
> needle valve to 
> control an almost zero gas flow.  I spent the first part
> of my 
> engineering career working with lots of valves and
> various pressure 
> gases, mostly air, plus using sonic flow nozzles on a
> daily basis.   I 
> agree with your explanation.  But, the "ooch", like the
> hertz, came on 
> the scene after I left it.  Alas, poor Mrs. Ooch.  At
> least  she didn't 
> meet her doom by using CO2 cylinders upside down.
> 
> On Monday, February 21, 2005, at 09:47 AM, Tom Wood
> wrote:
> 
> > "What the hell is Mr. Wood's problem?"
> >
> > I just don't like seeing misinformation constantly
> repeated.
> >
> >
> > Regarding the sonic nonsense. We don't use needle
> valves in a way that 
> > any of that applies. Sonic flow, Cv and all that
> applies when the 
> > valve is under relatively high pressure on the inlet
> side and is 
> > moving a lot of gas at a relatively high rate of flow
> measured in lots 
> > of cubic feet per minute (CFM) against a given head
> pressure. At best 
> > we are moving a fraction of a cubic foot per -hour-
> with relatively 
> > low pressures on both sides of the valve.
> >
> >
> >
> > We use the valves in an 'almost closed' position. We
> use needle valves 
> > because they have tiny parts with tiny threads that can
> create what is 
> > best described as a tiny leak. A small thread pitch
> coupled with a 
> > finely tapered needle and seat provide a higher degree
> of control over 
> > the leak through the valve. The bubble of CO2 gas
> ooches* around the 
> > needle and into the outlet hole on the other side of
> the chamber. It 
> > doesn't matter how fast it does that because it is
> laminar flow anyway 
> > at the tiny rate of flow we are using.
> >
> >
> >
> > It doesn't even have to be a 'needle' valve. We could
> use any type of 
> > valve, including any clunky hardware store valve, if
> they had fine 
> > enough threads and seats to create small movements and
> pathways. But 
> > they don't so we use needle valves to get that small
> movement with our 
> > big clumsy fingers.
> >
> >
> >
> > When used in the 'almost closed' position the way we
> use them, needle 
> > valves have the additional benefit of creating
> back-pressure on the 
> > regulator. Which keeps the regulator from over-reacting
> to the effects 
> > of a CO2 cylinder that is running empty. Without that
> back-pressure, 
> > the mechanism in a single stage regulator interprets
> the dropping 
> > pressure on its inlet side as a higher demand on its
> outlet side, and 
> > it opens up, thus creating the fabled end of tank dump.
> Add an 'almost 
> > closed' valve to create some back-pressure, and there
> is no dump. > Ever.
> >
> >
> >
> > TW
> >
> >
> >
> > * The Ooch is a unit of measure named after Beatrice
> Ophelia Ooch, who 
> > with her husband Horatio Octavius Ooch, died tragically
> while 
> > performing an experiment involving seven chickens and a
> garden hose. 
> > They were buried side by side with only their initials
> on the 
> > headstones:  B.O.O.   H.O.O.
> >
> >
> > _______________________________________________
> > Aquatic-Plants mailing list
> > Aquatic-Plants at actwin_com
> > http://www.actwin.com/mailman/listinfo/aquatic-plants
> >
> 
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