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  #1  
Old 06-21-2018, 06:43 PM
rvmv rvmv is offline
 
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Location: Marietta, GA
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Default Fuel Lines near exhaust pipes. How close is too close?

I've started my io320 install in my 9a and, in a few places the fuel lines come within 1 inch of the exhaust pipes. Seems too close but don't see any other way. Standard fire sleeved lines. Planning on heat shields for the tight spots. Too close? Thanks
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  #2  
Old 06-21-2018, 06:51 PM
pjoshyjosh pjoshyjosh is offline
 
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I fly a 9A that I bought last year. I'm wondering the same thing. I seem to get low fuel pressure intermittently. I am going to go download my Dynon data from last weekend's flight to see if it correlates to any specific cylinder EGT. I do get a warning and then flip on the electric pump. Sometimes it stays high sometimes it goes back low after turning pump off.
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  #3  
Old 06-21-2018, 07:06 PM
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Carl Froehlich Carl Froehlich is online now
 
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Canít reroute the fuel line to get more clearance?

You can also add a radiant heat shield on the offending pipe: http://vansaircraft.com/cgi-bin/stor...t=heat-shields

Carl
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  #4  
Old 06-22-2018, 04:03 AM
rvmv rvmv is offline
 
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found this in Tony Bingelis' Firewall Forward p155.

"Fuel lines should be separated from hot exhaust stacks by a minimum distance of 1 1/4 inch to prevent heat damage and possible fuel vaporization."
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  #5  
Old 06-22-2018, 04:13 AM
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ronschreck ronschreck is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
Canít reroute the fuel line to get more clearance?

You can also add a radiant heat shield on the offending pipe: http://vansaircraft.com/cgi-bin/stor...t=heat-shields

Carl
You can make these heat shields yourself quite easily. I have several all over my exhaust system to protect oil and fuel lines as well as throttle and mixture cables. They do a great job and I have had no issues with fuel lines passing within an inch of the exhaust when it is protected by this sort of shield. Sometimes there is no other way to route lines and a heat shield is the best answer.
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  #6  
Old 06-22-2018, 04:38 AM
rvmv rvmv is offline
 
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Thanks, also found this previous post by mahlon r

"Check out AD 95-26-13. It is on oil cooler hoses and routing of them. Although not fuel lines per say, the lines are made of the same material and the FAA says maintaining a 2 inch clearance between oil cooler lines and straight exhaust pipes with no heat shield on the pipes and only fire sleeve on the hoses is acceptable. I would think the same clearance would be acceptable with any fluid carrying line and an exhaust pipe, as far as line clearance for proximity to a heat source and line deterioration from it. I think they do want you to check the line for flexibility every 100 hours at that clearance.
Just a point of reference, that might be helpful.
Good Luck,
Mahlon"
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  #7  
Old 06-22-2018, 07:25 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by rvmv View Post
"Check out AD 95-26-13. It is on oil cooler hoses and routing of them. Although not fuel lines per say, the lines are made of the same material and the FAA says maintaining a 2 inch clearance between oil cooler lines and straight exhaust pipes with no heat shield on the pipes and only fire sleeve on the hoses is acceptable.
Note that in the same document, the FAA also recommends 100 hr repetitive inspections and requires 1000 hr replacements. And it doesn't mention what type of hose, i.e.rubber or plastic liner.

Personally I don't think there is a reason to ever be closer than 2". There are generally a lot of ways to run a fuel line.

BTW, remember that oil has a very low vapor pressure, not at all like fuel.
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  #8  
Old 06-22-2018, 09:12 AM
TS Flightlines TS Flightlines is offline
 
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DONT rely on firesleeve, integral silicone firesleeving or heat shields to protect the hoses over good routing and installation. We know of one case where a firesleeved teflon hose laid on the exhaust for +- 100 hours. Firesleeve was darkened under the burned silicone, and the sleeve frayed from rubbing on the exhaust. The stainless braid was a light brown color. But the teflon liner wasnt damaged and the hose even pressure tested ok.

BUT DONT assume that since its firesleeved it will 'fix' a questionable installation. The more room the better.

Tom
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  #9  
Old 06-22-2018, 09:32 AM
rocketman1988 rocketman1988 is online now
 
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Default fuel line...

You said:

"Personally I don't think there is a reason to ever be closer than 2".

Maybe you would like to look at an RV-10 with the EFII system, Showplanes cowl/induction and Custom Aircraft exhaust. Short of running the line from the right side fuel rail straight forward, down and around the induction system, along the inside surface of the cowl, that line is going to be within two inches of the #2 exhaust somewhere...

I made a heat shield similar to the one posted above and tried to make the section parallel to the exhaust pipe as short as possible. It is about 1" from the heat shield. Where it crosses the exhaust, it is about 1 3/8" from the pipe. I'm using integral fire sleeve fuel line (Thanks, Tom!) and I put an additional short length of fire sleeve over these areas...
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  #10  
Old 06-22-2018, 11:37 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by rocketman1988 View Post
You said:

"Personally I don't think there is a reason to ever be closer than 2".

Maybe you would like to look at an RV-10 with the EFII system, Showplanes cowl/induction and Custom Aircraft exhaust. Short of running the line from the right side fuel rail straight forward, down and around the induction system, along the inside surface of the cowl, that line is going to be within two inches of the #2 exhaust somewhere....
Plumbing weld-on ports or primer ports? There is probably a difference in radiant exposure, but either way, the high recirculating flow would cool the hose from the inside out, so it seems to work.

As you know, the other EFI brand injects from the top of the heads, with
no fuel lines near exhausts.

I assume the OP is plumbing a constant flow fuel control, which requires two lines, and one is very low pressure. This is simply one of those things where more is better, "more" being distance. Acceptable is largely opinion.
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