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Re: My last word on needle valves

> From: Dave Gomberg <gomberg at wcf_com> 
> Date: Sat, 20 Jan 2001 07:30:56 -0800 
> In-Reply-To: <200101192048.PAA02943 at actwin_com> 
> At 03:48 PM 1/19/01 -0500, Chuck Gadd asks:
> >Or was Dave running the
> >regulator output at a higher pressure with the needle-valve?
> Yes, I was running my regulator flat out into the needle valve.  Unless 
> there is quite a pressure drop across the valve, the flow will not go sonic 
> and the valve will not restrict the flow as desired.

Umm, with all due respect, what are you talking about?

Are you still using a check-valve that has a high cracking pressure?
What does "flat out" mean? 20 psi? 40 psi? 60?  My regulator goes up to
You are too hung up on "pressure" rather than "flow rates".

Unless you are using an extraordinarily small (and expensive) valve, you
are operating the valve almost closed, where it is kind of difficult to
make fine adjustments.  That's OK.  You want to set your regulator for
as low a pressure as it is stable.  My old decrepit Victor 2-stage O2
regulator is stable at *any* delivery pressure, but that's unusual.  A
beer regulator, I'm guessing, should be stable at 5 or 10 psig.  Then
close your metering valve until you get the flow rate you want.  It is
easier IMHO to make fine adjustments by tweaking your regulator output
pressure rather than tweaking the metering valve.

You shouldn't need a check valve with this arrangement because your
valve is closed down so much that it will not pass water at low
pressure.  The proper place then for the metering valve is to *replace*
the check valve (with a proper hose clamp on the upstream connection),
or screwed into the regulator output fitting and then lose the check

Best regards,

"Donuts...  Is there anything they can't do??"
--Homer Simpson