Re: [APD] Needle valves

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

I've tried lots of valves. I don't sell them and am not
affiliated with anyone that does. I have liked some valves
and not others. Gave away quite a few to make room for new
ones -- it's embarrassing to have more meetering valves
than aquaria, even harder to explain than substrate heating
cables ;-) .

A needle valve is one that controls flow by having a
tapered needle protrude through an orifice. As the needle
is lowered or raised the passageway through the orifice is
more or less blcoked respectively. The control precision of
a needle valve is a function of two things, the taper of
the needle and the pitch of the thread on the adjustment
knob. The narrower the angle of the taper, other things
being equal, the less effect on flow when the needle is
raised or lowered in the orifice by a given amount. The
steeper the pitch of the threads on the knob, other things
being equal, the more the needle is moved up or down by,
and the greater the effect on flow of, a given number of
turns of the knob.

My personal favorite is the Swagelok part number B-SS4
Brass Very Fine Metering valve with 1/4 in. Tube Fittings.
With that I use the pat number B-405-3 Brass Insert for
Tubing, 1/4 in. OD - 3/16 in. ID.  If you want to go whole
hog, get the vernier scale dial, part number NY-5K-SS
Series Metering Valve Nylon Vernier Handle Kit. Once you
know your setting you can redial it by number. These valves
not only work well, but the design and construction is
excellent.

All *very pricey* but you'll never complain that minor knob
adjustments overshoot. Your wallet might complain.

If you don't mind less precision, and most folks won't, the
B-2MG models have the same excellent construction, a wider
angle of taper and steeper threads so, each turn of the
knob has a bigger impact on the rate of flow. But they are
cheaper. 

It might surprise some folks without internet access but
you can get Swagelok (aka Nupro) items with revisiting
Highway 61. It can be easily done by going to this place:

http://www.swagelok.com

If you want something more economical, check out Bob's list
and pick your poison:

http://members.cox.net/tulsaalstons/Documents/Aquarium%20Needle-Metering%20Valve%20Recommendations.htm

The clippard's, which are listed as choice 5 out of 5 on
Bob's list, are inexpensive and definitely suitable for
aquatic gardening purposes.

I have heard of folks using the Aro F0 models successfully
-- people I respect -- but I found them useless for aquatic
gardening -- simply not enough control to make it useful as
a valve. Imo, if you dissasemble one, you can see why one
should not expect too much from these valves. 

Gomberg swears by what he sells and he sells the Fabco
NV-55 with "airline tubing" adaptors. Others have used them
and like them. The precision is almost as high as the
B-SS4, using the same 3 degree taper on the needle but with
a slightly steeper thread pitch. They can be used as shut
off valves if manual on-off is your thing. They cost
substantially less than the Swagelok B-SS4 -- currently
about $28 vs $50, with adapters.


sh
--- urville <urville at peoplepc_com> wrote:

> well what do you suggest mr Hieber? i'd like to get the
> palette of ideas
> 


* * * * * * * * * * *
Coming Soon in November, the winners and all the other beautiful entries in the 6th Annual International Aquascaping Contest. Every continent is represented -- except Antarctica. Maybe next year Antarctica, too ;-)

http://showcase.aquatic-gardeners.org
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