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Pressure Regulator

Hello David,

I don't know whether it is TRUE or not that "When the input
pressure to the regulator decreases, the output pressure
*increases*", but I think your explanation about the principle
of operation of a Pressure Reducing Regulator is wrong. Any increase
in Outlet Pressure will only generate more force by the diaphragm
to push more against the set spring force towards the direction of
closing the valve NOT opening.

When the inlet pressure decreases substantially, the pressure acting on
the diaphragm which is connected to the outlet side will also decreases,
therefore the force generated will not be enough to overcome / counter
the spring force to shut the valve (similar to complete diaphragm failure
- fail open).

For more explanation, please go to:


 (just because it has good explanation and drawings)

You can see the detailed explanation (SECTION III, PRINCIPLE OF OPERATION)
and the internal design of a typical Pressure Reducing Regulator.

"Dumping" is an uncontrolled flow of gas at LOWER than SET pressure. If you
have a flow control valve (needle valve) downstream, it should not cause
an increase in CO2 dosage in your tank (lower pressure, same orifice = less
gas passing through). 

Casey Huang

>Date: Wed, 27 Sep 2000 13:54:27 -0700
>From: "David Ozenne" <dozenne at 10fold_com>
>Subject: Re: CO2 discussion
>Good post.  But I think you have made a serious mistake.  When the input
pressure to the regulator decreases, the output pressure *increases*, at
least until the output pressure equals the input pressure.  (At that point
the regulator essentially becomes an open valve.)  That is what causes the
"dumping" when your tank runs low.
>David Ozenne
>whose CO2 tank reached ~400 psi before he noticed the fish acting funny...
>(my apologies for this corporate sig)