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Re:Nupro Needle Valves


>From: "Spencer, James R." <spenceja at osi_SYLVANIA.com>

[James gives flow coefficients of the M series as .03 open
and the S series as .004 open.]

I take it then that the S series is about 10 times more sensitive than
the M series giving much finer control of the flow. This is exactly
what a metering valve is designed for.

In practice, I find that the S series has 10 or more full turns from
full open to fully closed. In the space of the first few turns I can
go from fully off to a bubble every now and then. I have a very wide
latitude for fine control - a quarter turn one way or the other gives
only a very slight change in bubble rate. I would imagine you can do
the same with the M series, but would have only a small fraction of a
turn of area where you would end up leaving it set. With the S series,
I can give it a turn or two to hasten the bubbles if I wanted to
add a little more CO2 to hasten some growth, such as when adding a new
plant.

The valve I use is stainless steel or perhaps an alloy, since it is
greyish white. It's definitely not brass. It has the feel of a fine
swiss watch - very solid, smooth valve control with no slack or
sluggishness. It turns just like a fine volume control on an expensive
stereo.

It's expensive, but a real joy.

I remember when I bought it that I needed a special version for CO2,
I think the elastic bushing is made of a different substance in this
case, probably because other rubber compounds might embrittle in
exposure to CO2.

I remember hearing reports of CO2 airline tubes becoming brittle with
time. I use a Vichem tube and it hasn't changed in 7 years as far as I
can tell. It's very flexible and transparent.

>George Booth writes

>Note that with a controller, you still need to check the calibration
>every so often so that probe drift doesn't get you.  The controller
>will control the CO2 to produce what it *thinks* is the right pH based
>on what the probe returns. If the probe has gotten dirty or is at
>the end of its lifetime, the pH reading may not be the actual pH.  We
>manually check pH with a good test kit every two weeks at water
>changes to make sure the controller is still calibrated.    

I've found the pH probe doesn't change very much over it's lifetime.
I've used 2 Hannah 1910 pH probes since 1992. The first one lasted
until 1996. During those four years I checked the calibration fairly
often when I started, then less frequently. When it reaches the end of
it's lifespan it seemed that the internal electrolyte had been
displaced with water (internally it is mostly KCl) and the probe put
out 0 volts. This is interpreted as approximately a pH of 7 and the pH
will never register a change no matter how much CO2 you inject.

I used to clean it occasionally, but I neglected that for the last
few years.

I guess I'm lazy, but I do inspect the tank visually every day and I
think I can tell rather quickly when something is wrong. Things seem
to work best for me when I tinker the least. I used to be quite a
fanatic about changing things, but not so any more. I don't even
change my web page very much;-) I guess it's no longer under
construction.

-- 
    Jim Hurley         mailto:hurleyj at arachnaut_org
 Arachnaut's Lair    <URL: http://www.arachnaut.org/ >