RE: [APD] Re: Clippard valves and such -- Closing a rumor aboutclosing

["Eric Wahlig" <ewahlig at earthlink_net>]

Chuck writes:

"Most folks probably don't need a needle valve that shuts off. But I 
run multiple tanks off of a single regulator. Sometimes I may break 
a tank down for extended periods (lately to store it until I have 
more free time), and it is far easier for me to just shut the gas off 
at the needle valve than rebuild the manifold, plug the port, or add 
a second valve to close off the line."

If I remember right, Chuck is using the Clippard MNV-4K valve. I looked up
the specs on this and it said "0-5 scfm at 100 psig" which implies that it is
capable of stopping the flow of up to100 pounds of line pressure. This is,
of course, way more than any of us run. I think most people set the
regulator anywhere from 5 to 40 PSI line pressure. So, I guess these valves
are capable of shut-off  without damaging the needle. If you want to take
one out of service or move it to another application then its just as easy
to unscrew them as they are only finger tight (avoid ruining the very small
O-ring seal and causing a leak by over tightening them). You then just
screw a 10-32 plug (part number 11755) into the hole. Very simple.

If you are using a Nupro/Swagelok "S" series or "M" series valve then
before you put it into service, adjust it so that the knob bottoms out just
as the needle is starting to seat. This is an adjustment which is most
carefully done but you only do it once. I buy these valves used so this is
just part of the "clean, inspect, and repair if necessary" procedure. They
may be adjusted this way from the factory if you bought a new one. While
these valves can not really stop the flow (they are not intended to), if
the adjustment is made correctly the bubble rate is zero even before you
reach the stop point on the knob. You might get one bubble per hour or
something. I can accept a slow leak like that from a valve that is on the
manifold but not in service.

---Eric



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