Re: Needle valve

[Wright Huntley <jwwiii at pacbell_net>]

> Date: Sun, 6 Oct 2002 06:16:24 -0700 (PDT)
> From: john wheeler <jcwheel76 at yahoo_com>
> Subject: Needle valve
> 
> Hey gang,
> 
> Either Tom Barr, or Wright Huntley in a recent post
> warned against using teflon tape on a needle
> valve....Or was it after a needle valve? Why?
> 
> I may have done that.

Guilty! I warned about Teflon, but Tom suggested the wet stuff, so he has 
to share the guilt in some small way.

Teflon tape is a great *water* sealer, as it won't wet, so still blocks 
leaks in moderately imperfect pipe-joint connections. Not so for gasses. 
It also is a pretty good lubricant for those metal-to-metal connections.

Unfortunately, it can shred and in a system from a high-pressure tank to a 
tiny orifice that could be dangerous. If applied perfectly, by experienced 
plumbers, it probably is OK. [The problem was so serious that 
Hewlett-Packard banned teflon tape, company wide, at one time, while I was 
a Dept. Manager, there. We had some really bad accidents.]

The wet pipe goop works as well or better on gases, and doesn't run the 
danger of an accidental needle-valve blockage piling up a huge back 
pressure until something blows up. Hopefully, the regulator stops that, 
but at near zero flow, the regulator might gradually allow a greater 
pressure to build. They can need *some* minimal flow to work right. They 
may only sense the pressure difference from inlet to outlet, but do not 
always measure absolute pressure.

Simple way to avoid potential problems is to just use the tube of wet pipe 
stuff. My "beer" regulators came with teflon on the gauges, so I left well 
enough alone and did not try to replace it. Shreds from the gauges are not 
very likely to go toward the needle valve, anyway. OTOH, I did not add to 
the problem by using any on *my* connections.

Wright

-- 
Wright Huntley -- 209 521-0557 -- 731 Loletta Ave, Modesto CA 95351

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