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Posted for Earl Schroeder <earleschroeder@yahoo.com>:
Colyn,
I used the standard 37 deg flare for all metal tubing connections.
The failure mode is tubing breakage in the area of the ferrules in swagelok
type fittings - caused usually by over tightening - either in the initial
installation or after maintenance and re tightening. The ferrules actually
cut the tubing into and any vibration causes the failure sooner. The torque
required to properly tighten a swagelok is so low that it is very easy to give
it another 'hitch'. Six flats is the absolute max. On a re tighten, finger
tight and then just a bit more. Eventually, the fitting needs to be replaced
depending on the number of re makes and a visual inspection of the tubing
deformation. [this causes the tubing to be a bit short and probably the entire
run has to be replaced]
IMHO, a proper flare is much superior in our aircraft applications. Earl
colyncase on earthlink wrote:
/I do not have any metal 'compression' fittings in my Lancair. I did use
some nylon types in the static system but the plastic tubing withstands
vibration much better IMHO./
// Earl,
what DID you use instead of compression fittings?
...and exactly what is the failure mode? breakage or loosening?
Colyn
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