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Date: Wed, 14 Feb 2007 17:25:03 -0500
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From: Earl Schroeder <earleschroeder@yahoo.com>
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Subject: Re: [LML] DH Lines
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Angier [and others interested]
In the interest of safety [mine and others] I have as much passion about 
not using Swagelok in Lancair brake lines as Brent has about not using 
plastic.  In my job at GE Plastics [before retirement - 31 yrs] I 
installed thousands of compression tube fittings from various 
manufactures.  Swagelok is the MOST likely to fail from improper 
installation of all the others.  [tylok, nupro, gyrolok, etc]  Note the 
small ferrule in the picture where it joins the larger one.  If 
overtightened initially or in subsequent  remakes, it will cut into the 
tubing and eventually the tubing will fail.  Any vibration will make it 
fail quicker.  Swagelok is great for lab gas systems etc but NOT for 
aircraft. You can  make certain that YOU installed it according to the 
directions [six flats - no more] but will the next person know the rules 
or will you forget and just give it a bit more to make sure it doesn't 
leak?  There is NO discernible increase in torque when it is 'tight' 
enough.  Tylok can be tightened until it 'squeaks' and it will not cut 
the tubing.  The others are less likely to cut but will if severely 
overtightened.  Unfortunately, tylok is the most likely to leak.  Hmmm, 
what to do?  I would use flared and support the line close to the fitting.

Remember, as Brent says, I may not know anything... use at your own 
risk.  Earl


Greenbacks, UnLtd. wrote:
> Here are several pics of 24" DH line. The two fittings on the right 
> were swaged at the factory. Those on the other end are designed to 
> accept compression fittings, in this case from Swagelok.
> ------------------------------------------------------------------------
>
> Typical Swagelok compression fitting...
>
> ------------------------------------------------------------------------
>
>
>  Not the cheapest way to go, but just think of that tinker-toy 
> nylaflow line, installed in the last century, turning yellow and 
> getting more brittle by the hour...
>  Getting ready to burst at the worst possible time...
>
> Angier Ames
>