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  #11  
Old 10-14-2013, 07:38 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Threads on NPT are not always made with single point threading tools. Often they are made a tool that cuts all the threads at once. Since the feed rate can be high, when it stops rotating, it can leave what looks like a parting line along the length of the threads. I always inspect NPT threads for this defect. I found it on an air system installation. I began checking about 10 joints in and they all leaked. I ended up chasing internal and external threads on about 140 joints, but none leaked, and still don't 23 years later.

I have not found parts for my 7 like that yet, but still check.

Good luck.
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  #12  
Old 10-15-2013, 07:45 PM
tfarrell839 tfarrell839 is offline
 
Join Date: Oct 2009
Location: Canby, OR
Posts: 53
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We see this A LOT. Our first step is to try tightening and applying a generous amount of Teflon thread sealer ( the liquid stuff, not the tape) and get a good strong torque on it. If it still leaks, try new fittings. They are ever so slightly different and it is often necessary to swap fittings to get them torqued down and get the proper orientation. We haven't tried steel recently.
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  #13  
Old 10-21-2013, 03:02 AM
SuperCubDriver SuperCubDriver is offline
 
Join Date: Feb 2011
Location: Germany
Posts: 443
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I too had leaking pipe connections on the cylinders. My mechanic told me to use teflon tape which I did and that helped. He said there is no fluid movement so tape is acceptable here. Now I also use Loctite 567 with success.
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Last edited by SuperCubDriver : 10-21-2013 at 03:05 AM.
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  #14  
Old 10-21-2013, 06:57 AM
gossend gossend is offline
 
Join Date: Dec 2011
Location: Georgetown, Texas
Posts: 184
Default What about brass compression fittings?

So, i take it the main problem is the npt threads, not the compression fittings. Can the compression fittings be removed and then re-tightened like flare fittings can, or do they have to be cut off and replaced?
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