Re: DIY silicone hoses?

[Larry Mittell <lmittel@ibm.net>]

Odd that they'd call them silicone, actually. If they're meant for an
automobile and are marketed by a responsible firm, they're *not* silicone. More
than likely they're fluorosilicone. If I learned nothing else in years of
designing fuel system equipment, it's which elastomers get along with
hydrocarbons and which don't. If you're so inclined, drop a silicone 'o'-ring
into a jar of gasoline and see what happens to it in a few hours. If you're
interested, I'll be happy to fax a page or two from the media compatibility
section of an 'o'-ring catalog to you to prove the point.

I suspect hose manufacturers mislabel their products because the "fluoro"
prefix has gotten such bad press from folks who style themselves
environmentalists. Chlorofluorocarbons, ozone "holes" and all that. For that
very reason, the Fluorocarbon Company changed its name to Furon, even though it
makes nothing even remotely offensive to environmentalists. 

This mislabeling certainly clouds the issue of what you're buying. Because of
the incompatibility problem, the aerospace industry color-codes the two
compounds. Silicone is a reddish color, while fluorosilicone is blue.They might
be so coded in the automotive industry as well, but I don't know that. 

Cheers,
Larry Mittell

At 01:58 AM 7/24/99 , JShadzi@aol.com wrote:
>In a message dated 7/24/99 12:52:10 AM Eastern Daylight Time, lmittel@ibm.net 
>writes:
>
><< Yikes! Do not under any circumstances use silicone hoses! Silicone turns to
> mush when exposed to hydrocarbons. Fluorosilicone is what you want. Either 
>that
> or nitrile (a.k.a. Buna-N). The latter is better than fluorosilicone
> mechanically but doesn't like temperatures much higher than 160 deg F.
> Fluorosilicone is good for at least 350 deg F.
> 
> HTH,
> Larry Mittell >>
>
> Hmm, thats odd.  Why are the best hoses offered on the market all 
>claiming to be made from silicone if it is so bad?
>Javad Shadzi
>