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Re: fuel lines revisited (and flaring tools)

To: Peter Zaborski <>
Subject: Re: fuel lines revisited (and flaring tools)
From: Michael Marr <>
Date: Mon, 10 Nov 1997 16:14:12 -0600
Cc: Triumph Mailing List <>
Organization: Evantage Division of Virginia Power Company
References: <>
Peter Zaborski wrote:
> > -----Original Message-----
> > From: Michael Marr []
> > Sent: Monday, November 10, 1997 2:26 PM
> > To:   Triumph Mailing List
> > Subject:      Re: fuel lines revisited (and flaring tools)
> >
>         <bunchastufdeleted>
> > At the risk of repeating something that has already been said (I have
> > not been following this thread religiously), compression fittings
> > should
> > never be used on brake lines - they are not designed for the pressures
> > developed in a hydraulic system.
> >
>         What is the definition of a compression fitting? To me it seems
> that all the seals involving flares use some form of compression of two
> metals against each other. I assumed that compression fitting meant
> using a rubber hose and clamp. This seems to be a mistake on my part. So
> can someone enlighten me as to the correct meaning of "compression
> fittings" (at least in this context).
>         BTW, I have no intention of changing the fittings on my brake
> system, I am only working on fuel lines. My car has the dual carbs so
> high pressures are not an issue there IMO.
>         Thanks!
> Peter Zaborski
> 76 TR6 (CF58310 UO)
> Calgary AB Canada

Here goes!  The generally accepted definition of a compression fitting,
in my experience, is one that relies on the frictional force between the
compression sleeve, or olive, and the tubing, to hold the joint
together.  Flare fittings are not compression fittings in this sense
because they are held together by the mechanical interaction of the
flare nut, the flared portion of the tube, and the flare fitting. 
Certainly, friction is involved, but in order for a flare fitting to
separate under load the tube will have to deform, whereas a compression
fitting will fail when the internal pressure is enough to overcome the
frictional force between the components.  

Also, I believe the correct term for the "olive" is compression sleeve.
A ferrule is the small metal tube that fits inside a compression fitting
used on poly tubing to stop the tubing from collapsing when the fitting
is tightened.  Thus, the ferrule fits inside the tube and the sleeve and
nut fit outside the tube.

Having said all this, I now wait for different opinions.  Isn't this

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