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Re: Shut-off Valves

On Wed, 13 Sep 2000 James Purchase wrote:
> During the discussion on CO2 hardware, it was noted that the Nupro M and S
> series valves are not "shut-off" valves (i.e. they aren't designed to close
> off the flow of gas completely). A "work-around" was suggested in the
> archives (there is a small adjusting screw that you can play with to allow
> the valve to close more completely) but someone noted that this voids the
> valve's warranty.

I respond:

I'm using the Nupro M valve and the adjusting screw you are referring to
is a set screw in the knob.  It seems that the knob is located on the
needle shaft in a position that allows the knob to bottom out on the
packing nut before the needle itself bottoms out in the taper.  I assume
this is to prevent the needle from becoming wedged in the taper (because
of the very small angle, 3 degrees I believe) and twisting off.  When I
first set mine up,  the valve wouldn't close far enough to get 1 b/s.  I
adjusted the knob to allow a slower flow rate.  I wouldn't suggest using
these valves as shut off devices, but, why would you want to?  You could
just turn off the bottle.  My beer regulator has a ball valve shut off
built into it.

James again:

> In looking at the Swagelok catalogue, I see that they DO make shut-off
> valves. If you want to be able to totally shut down the flow of CO2, is
> there any reason why one of these shut-off valves could not just be placed
> in the line (after the regulator and before the needle valve) in series with
> the needle valve? Would shutting off the flow in this way cause any damage
> to the regulator up-line (back pressure)???

Me again:

This is exactly how the ball valve I mentioned above is plumbed...
without any damage to anything.

Bob Ashcraft
Pittsburgh, PA