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Re: nupro metering valve fittings
> For those Nupro valve users out there: I just decided to try out an "S" series
> nupro metering valve...I got an adapter to take it from the "Swagelok" style
> fitting to the 1/4 NPT on my regulator, as well as a hose barb. My question is
> this: how does one attach the fittings to the valve? The Swagelok side looks
> like a mostly smooth shaft with one tapered groove around the circumference
> about 1/3 way down. The fitting themselves seem to move freely into and out of
> the valve intake and output; I have not as yet figured a way to secure them in
> place. Thanks for the help.
The swageloks are just high-tech compression fittings. Inside the female
fitting is a ferrule (cone-shaped ring) which fits over the tube connector.
When you tighten the nut, the ferrule is wedged into the cone-shaped opening
in the fitting and compresses around the tube very tight. Depending on what
size Swagelok fitting you have, the amount you tighten the nut varies.
The following comes from Swagelok's installation instructions:
Step 1: Simply insert the tubing into the Swagelok tube fitting. Make sure
that the tubing rests firmly on the shoulder of the fitting and that the nut
Step 2: Before tightening the Swagelok nut, scribe the nut at the 6 o¹clock
Step 3: Hold the fitting body steady with a backup wrench and tighten the
nut 1 1/4 turns. Watch the scribe mark, make one complete revolution and
continue to the 9 o¹clock position. By scribing the nut at the 6 o¹clock
position as it appears to you, there will be no doubt as to the starting
position. When the nut is tightened 1 1/4 turns to the 9 o¹clock position,
you can easily see that the fitting has been properly tightened.
Due to variations in tubing diameters, a common starting point is desirable.
Using a wrench, tighten the nut to SNUG position. Snug is determined by
tightening the nut until the tubing will not rotate freely (by hand) in the
fitting. (If tube rotation is not possible, tighten the nut approximately
1/8 turn from the finger-tight position.) At this point, scribe the nut at
the 6 o'clock position and tighten the nut 1 1/4 turns. The fitting will now
hold pressures well above the rated working pressure of the tubing.
For 1/16, 1/8, 3/16 in., 2, 3, and 4 mm size tube fittings, only 3/4 turn
from finger-tight is necessary.
If you want a PDF file of the above instructions, which includes pictures,
email me offlist and I'll send it to you.