Re: [APD] Re: Hagen CO2 natural plant system -- or - Gas & KeepingRegular

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

That's basically it, although 2-stage regulators aren't
immune to  dumps, they just hold a steadier outlet pressure
as the CO2 tank pressure varies.

"Tank" is used to mean a pressurized gas container *and* an
aquarium.  It can be confusing.  End of CO2 tank dumping is
a rapid release of the contents when only a relatively
small amount is still in CO2 tank. Although relatively
small, the amount , if injected into your Aquarium all at
once, can raise the CO2 level up to lethal levels for the
fish.

The regulators use the pressure inside the tank and a
spring to open/close a diaphragm.  The CO2 tank pressure
holds the diaphragm closed while tightening down the spring
pushes the diaphragm open.  Thus, adjusting the knob, which
adjusts the spring compression allows you to achieve
different output pressures.  

When the gas pressure gets too low, it can't hold against
the spring anymore and the diaphragm opens and stays open,
thus "dumping" or quickly releasing the remaining CO2 in
the CO2 tank.  The gas pressure in a compressed CO2 tank is
relatively constant and most of the gas is pressurized into
liquid form.  As some gas is let out, more liquid reverts
to gas form and the pressure inside the CO2 tank remains
relatively constant.  But once the liquid is all gone, the
pressure slowly decreases until it's too low to hold the
against the regulator spring.  

Regulators usually have, and should have, a gauge on each
side of hte diaphragm, one measuring the high side pressure
and one the low side pressure.  When the High side pressure
starts to drop significantly, you know the liquid CO2 is
gone and it's about time to refill.  Don't wait for all the
remaining gas to escape because somewhere towards the end,
it can just dump.  And the remaining gas is only worth a
few cents anyway -- too few cents to make the price of a
2-stage regulator practical.  Once the high side pressure
starts dropping, how long until the dump will occur?  It
depends on a few things --like ambient temperature, whether
there is a metering valve and how low it's set, and the
particular characteristics of your regulator.  But from a
stable 750-1000 psi when there is liquid CO2 in the CO2
tank, the pressure will drop down once the liquid is gone. 
It will drop to 600, 500, 400  and lower slowly over the
course of several days or several weeks.  As the high side
pressure drops, the regulator might need to be adjust to
maintain your CO2 flow rate (your bubble rate).  The bubble
rate actually increases as the CO2 tank high side pressure
decreases -- less CO2 tank pressure pushing against the
spring. If you notice the need to keep turning down the
outlet pressure or the metering valve, look and see if the
high side pressure is dropping, it might be time for a
refill.

Scott H.
--- Douglas Guynn <d_guynn at sbcglobal.net> wrote:
> Joanne wrote
> 	"Just a couple more questions What exactly is the
> end-of-cycle
> dump?"
> 
> I have only recently heard of the "end of CYCLE dump". I
> have heard of the
> "end of TANK dump", although I have never experienced it
> myself. This is a
> phenomenon that apparently occurs when using a
> pressurized CO2 cylinder and
> a single stage regulator. The regulator is unable to
> maintain the desired
> outlet pressure when the inlet pressure approaches the
> output pressure
> setting.
> 
> "The power to do things for you is the power to do things
> to you."
>  - Dorothy Parker
> 
> Douglas Guynn
> 	432.368.5411
> 	d_guynn at sbcglobal.net
> 
> > _______________________________________________
> Aquatic-Plants mailing list
> Aquatic-Plants at actwin_com
> http://www.actwin.com/mailman/listinfo.cgi/aquatic-plants
> 


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