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topic 17712

Control Valve Stem with PTFE Coating


2002

Control Valve Stem, Looking in to Reducing Fugitive Emissions from Control Valves. One problem is high friction between stem and packing. The Packing can be made from PFTE or Graphite. The friction wares out the packing and increase the leakage from the valve beyond acceptable limits.

What I would like to know is:

1.would a PTFE coating on a stem reduce the friction and increase the life of the packing?
2.how does PTFE against PTFE react?
3. does the stem need any special surface finishes to help the coating?

Steve Brunning
- Huddersfield, England


2002

I am not a valve expert, but teflon on teflon is probably not a good bearing surface. Usually a hard material against a soft material is a better idea. If the stem is highly polished, and then plated with electroless nickel, it would probably run well against teflon packing.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


2002

Steve,

Believe it or not, but it would have been helpful to know the size of the valves, chemistry going through them ... and temperature.

Why? Because instead of labyrinth seals and a conventional stem, you can buy diaphragm valves which DON'T LEAK (as much?)and last much longer. These are mainly made in different plastics.

Try Plast-0-matics .

Food for thought, anyhow.

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).




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