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  #1  
Old 07-26-2019, 09:29 AM
jeffwhip jeffwhip is offline
 
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Location: Phoenix
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Default Torque Setting Fuel Vent Line

I was wondering if someone could please give me the torque setting for the AN818-4D and the AN924-4D fittings on page 18-6 for the return fuel line fittings.

According to pg 9-19 in the FAA AC4313-1B Table 9-2 Tube data, the torque setting for this 1/4" tubing is between 50 (min) and 65 (max) Inch/Ibs. I assume these values are for the 5052 tubing found on certified aircraft. I can't find torque values for the softer tubing. Before I got to the min (50 Inch/Ibs) it felt too tight so I backed off.

Thanks in advance!
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Old 07-27-2019, 07:25 AM
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From our kit manufacturer:https://www.vansaircraft.com/wp-cont...m_Fittings.pdf
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Old 07-28-2019, 08:23 PM
jeffwhip jeffwhip is offline
 
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Thanks Patrick!
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Old 07-28-2019, 09:26 PM
Captain Avgas Captain Avgas is offline
 
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Quote:
Originally Posted by jeffwhip View Post
I was wondering if someone could please give me the torque setting for the AN818-4D and the AN924-4D fittings on page 18-6 for the return fuel line fittings.

According to pg 9-19 in the FAA AC4313-1B Table 9-2 Tube data, the torque setting for this 1/4" tubing is between 50 (min) and 65 (max) Inch/Ibs. I assume these values are for the 5052 tubing found on certified aircraft. I can't find torque values for the softer tubing. Before I got to the min (50 Inch/Ibs) it felt too tight so I backed off.

Thanks in advance!
Hi Jeff, you need to be careful here. You can get a lot of dangerous advice on VansAirforce. Firstly I think the reference to the data on Vans Aircraft (the Aeroquip data) is probably wrong for your application. That data is for grade 6061 aluminium to grade 6061 aluminium fittings. However you seem to be interested in a grade 6061 fitting to a flared aluminium tube. In that case your original assumption would be entirely correct and you should use the AC43.13 data (table 9.2) originally referenced. For -4 that would be a torque of 50-65 inch pounds. However, again, as you rightly surmised, those torques are for aluminium aviation grade 5052 tubing. On the other hand the stuff that Vans supplies is cheap 3003 grade and it’s considerably softer ( generally used for commercial aircon systems). So in that case I would use a slightly lower torque...maybe change the 50 min to be 50 max.
I think you have been very much on the right track in your original post. The number of builders who have serious problems with “creamed” 3003 fuel and brake line tubing flares leading to failure is alarming.
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Last edited by Captain Avgas : 07-29-2019 at 08:25 AM.
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Old 07-29-2019, 08:38 AM
RV Jerry RV Jerry is offline
 
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I?m curious why more builders don?t double flare tubing , makes the flare much stronger and not as likely to get damaged being torqued
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Old 07-29-2019, 08:49 AM
PilotjohnS PilotjohnS is offline
 
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Default Double Flare

I would love to double flare everything, but I had a hard time finding the tooling. Most double flares I did at work were on a stand alone machine that I had to bring the work to, not on a tool I could take to the plane. My search for the proper tool proved futile, so I gave up and am going with careful construction and inspection of single flares instead. YMMV JMHO

Thanks for the data above on the material. I think for the fuel lines, I will buy the aviation grade tubing, or have TSflightlines make these tubes, rather than use the soft aluminum in the Vans kit. All fuel lines firewall forward will be stainless anyway.
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Last edited by PilotjohnS : 07-29-2019 at 08:51 AM.
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Old 07-29-2019, 09:09 AM
coffeeguy coffeeguy is offline
 
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I'm about the same place, going to be installing the vent line shortly and I had the same question about torque. Just went to the aviation section at Ace hardware to buy Permatex #2 for the thread sealant. Does anyone put a small dollop of proseal on the vent line at the bushings to keep them from rattling around?

Jeff
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Old 07-29-2019, 11:10 AM
gasman gasman is offline
 
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Quote:
Originally Posted by coffeeguy View Post
I'm about the same place, going to be installing the vent line shortly and I had the same question about torque. Just went to the aviation section at Ace hardware to buy Permatex #2 for the thread sealant. Does anyone put a small dollop of proseal on the vent line at the bushings to keep them from rattling around?

Jeff
Do not use anything on the flair fittings or nuts that are not taper thread (pipe thread).
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Old 07-29-2019, 11:31 AM
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Bill Boyd Bill Boyd is offline
 
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Default Just a side-question

What good does backing-off do when a fitting (or fastener) has already been over-torqued? Is the damage already done, or is there benefit from reducing the preload by backing off the setting? I'm not sure how elastic these things are but I'd like to know; I've over-torqued a few things myself but always thought that meant throw them away and start new (bolts, not flare fittings).
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  #10  
Old 07-29-2019, 08:56 PM
coffeeguy coffeeguy is offline
 
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Quote:
Originally Posted by gasman View Post
Do not use anything on the flair fittings or nuts that are not taper thread (pipe thread).
Thanks, I was looking thru the chapter 5 instructions and saw the note to use Permatex #2 or Tite-seal. I see another section for aluminum tubing. Here is what they had to say about torque.

Slide the AN818 nut over the far end of the tube and engage the threads on the AN fitting. Tighten to the specified torque. You
should have a Standard Aircraft Handbook with the torque tables for these things. (assuming aluminum fittings, for 1/4 tubing it is
40-65 inch-pounds, for 3/8 tubing it is 75-125 inch-pounds.) Later, you can leak test the system.
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