>I have used a stainless ferrule on the Kel--F tubes.  I felt that teflon on
>Kel-F would not make for a very good seal.  It the seal slippled the Kel-F
>tube could slip out of hte fitting.  The stainless ferrule seem to bite into
>the kel-f and hold it well
>
>Andrew Campbell

Hi Steve,
We've used a SS back ferrule and a teflon front ferrule for many years.
Our logic was based on a concern that loss of the seal might occur with
corrosion between a SS union-T fitting and a SS front ferrule.

The kel-F finger would not slip out of the fitting.  We do have a SS
bracket around the finger that also holds the finger in place.  This is a
precaution against someone breaking the Kel F finger when it is brittle
while submerged in liquid nitrogen.

It seems you can use either system in perfect safety.


Joe Cali