|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

10-22-2015, 08:30 AM
|
 |
|
|
Join Date: Jul 2009
Location: Mojave
Posts: 4,652
|
|
Quote:
Originally Posted by DanH
Re teflon tape, RTV, fuel lube, etc.....fact is, you CAN seal successfully with almost anything, if you start with new, clean fittings, and apply the sealant carefully...
|
We are in agreement. You can easily plug up a fluid system with the correct sealant if the application is incorrect.
The point to be made here is that there is more to aircraft maintenance than just knowing what materials to use or the torque values of a fastener, etc. Just like flying skills, learning maintenance by rote vs. a real comprehension is only a partial solution.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
|

10-22-2015, 08:43 AM
|
 |
|
|
Join Date: Oct 2008
Location: Lake Country, B.C. Canada
Posts: 2,416
|
|
best practices - in real life
What jumps out for me is the 'clean thoroughly before reassembly'.
If there's one thing I've noticed working on mechanical things, and especially aircraft, is the fitting you'd like to inspect most closely, and clean, and thread, and torque, are the ones that are almost impossible to access and accomplish any or all of the preceding tasks!
Could cleaning include vacuuming out the old sealant? sounds like the time-honoured blowing out with compressed air would be a very bad idea, for obvious reasons!....(and yet another shop process that might not be so obvious for inexperienced builders)
__________________
Perry Y.
RV-9a - SOLD!....
Lake Country, BC
|

10-22-2015, 08:43 AM
|
 |
|
|
Join Date: Dec 2014
Location: Just Minutes from KBVI!
Posts: 1,039
|
|
Quote:
Originally Posted by mburch
I will admit that I use a tiny amount of EZ-Turn (fuel lube) on the threaded portion of aluminum flare fittings, just to prevent galling. Never anything on the sealing surfaces of course. I forget who showed me this practice, years ago, but this thread has got me thinking critically about what I've been doing. Hmm.
|
Flare fittings are not designed to have additional lubrication applied to the nut threads, especially when the fittings are tightened to a torque specification. The mechanical properties of the joint, including the metal to metal seal in the flare, depend on a certain load being developed in the threads. Some flare fittings come prelubricated with a dry compound (often silver based) but generally they should not be lubricated. The should be tightened either to a torque specification or to a clearance between the nut and the fitting, as specified by the fitting manufacturer. Often the manufacturer will provide a special wrench that allows the installer to meet and check the clearance specification easily.
|

10-22-2015, 09:20 AM
|
|
|
|
Join Date: Jul 2005
Location: Denver, CO
Posts: 295
|
|
Quote:
Originally Posted by mburch
I will admit that I use a tiny amount of EZ-Turn (fuel lube) on the threaded portion of aluminum flare fittings, just to prevent galling. Never anything on the sealing surfaces of course. I forget who showed me this practice, years ago, but this thread has got me thinking critically about what I've been doing. Hmm.
|
I've been doing this as well, just a bit on the threads and ensuring that no Fuel Lube is on the sealing surfaces. (Which is why I asked the question about the AN fittings earlier). The fact that this would impact the torque brings up an excellent point.
__________________
// corey crawford
// rv-7a (sold)
// denver, co @ KBJC
|

10-22-2015, 09:39 AM
|
 |
|
|
Join Date: Jul 2009
Location: Mojave
Posts: 4,652
|
|
Quote:
Originally Posted by 1001001
Flare fittings are not designed to have additional lubrication applied to the nut threads, especially when the fittings are tightened to a torque specification...
|
This also is not an absolute. It is very common to apply lubricant to the threads and friction surfaces of the ferrule of AN fittings in military aviation. That's why there are multiple columns in the torque charts for "dry" or "lubricated" threads. This is very similar to the multiple columns used for torque values of threaded fasteners. A 10-32 fastener can have many different torque values depending on material, lubricated or dry, tension or shear, or whether you are turning the bolt or nut. Once again, it's a matter of knowing when and why you should be using a particular process.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
|

10-22-2015, 10:44 AM
|
 |
|
|
Join Date: Mar 2014
Location: Prescott, AZ
Posts: 739
|
|
I don't believe it's the sealant as much as it's the practice. ANY sealant used wrong could potentially cause problems. Yes... you must clean an check the threads on both fittings. It's always best to use a smaller amount of sealant as opposed to "More is better". Never put any sealant close to the last threads, this is where it can leak into the stream. These practices go for fuel, vacuum, pressure, pitot, static... Any connection.
Looking at the picture Dan posted it's obvious none of these listed practices were observed. It's a very tragic lesson for everyone to learn. This goes with all installation practices. I see this way too often; nicked tubing, over bent tubing, strained connections, misuse of RTV, way too many Adel's, duct tape, auto wires... This list is too long. Common sense.
|

10-22-2015, 11:02 AM
|
 |
|
|
Join Date: Jul 2013
Location: US
Posts: 2,251
|
|
Quote:
Originally Posted by ccrawford
I've been doing this as well, just a bit on the threads and ensuring that no Fuel Lube is on the sealing surfaces. (Which is why I asked the question about the AN fittings earlier). The fact that this would impact the torque brings up an excellent point.
|
Add me to the list of people who did this to prevent galling the fittings.
|

10-22-2015, 11:13 AM
|
 |
|
|
Join Date: Jul 2013
Location: US
Posts: 2,251
|
|
BTW:
http://static1.squarespace.com/stati...60_install.pdf
(from this website: http://www.fdatasystems.com/fc-10/)
Quote:
When assembling fittings into the 1/4? NPT inlet and outlet ports do not exceed a torque value of 25 ft.-lbs.
Do not use Teflon tape in an aircraft fuel system. Use ?Fuel Lube/Ez Turn Lubricant?
|
Hmmmm....
And just to add
Quote:
|
EZ Turn is a revolutionary sealant and lubricant for oil and fuel line valves. Resistant to high temperatures, it is especially effective where high octane fuels and aromatics are present.
|
http://www.skygeek.com/united-ez-turn-fuelube.html
Last edited by RV7A Flyer : 10-22-2015 at 11:24 AM.
|

10-22-2015, 01:55 PM
|
 |
|
|
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
|
|
Quote:
Originally Posted by RV7A Flyer
|
And from the same source, but covering the FloScan sensor, which appears to be a cast aluminum rather than the machined block that is the red cube -
? When assembling fittings into the 1/4? NPT inlet and outlet ports do not exceed a torque value of 15 ft.-lbs. (180 in.-lbs.) or two
full turns past hand tight, which occurs first.
? Do not use Teflon tape in an aircraft fuel system. Use ?Fuel Lube?
? The transducer should be mounted down stream of a fuel filter.
10 ft.-lbs. less torque for the FloScan over the red cube.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
|

10-22-2015, 02:18 PM
|
 |
|
|
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
|
|
If it is anything like the JPI Fuel Flow Transducer, which I thought was FloScan, don't use Fuel Lube. It can migrate into the fuel stream and gunk up the impellor. Not inherently dangerous, but not cheap to replace. I am surprised to see it recommended.
In most applications, Fuel Lube is a great lubricant for Pipe Threads that you do not need to clock, as a gasket dressing (awesome for that), and for sticking the odd stack of washers and nut together in those tight spots!
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 05:22 AM.
|