Coupling Old Copper Fuel Lines

[Jammin']

I have heard from a number of people that the 47 year old copper fuel and water lines are brittle and can not be flared. I would like to clean up the generator fuel supply and return lines which would require mating them to rubber lines. What is the best way to do this? Can I slide a rubber line over the copper and double or triple clamp it? Is there a better way?

 

[Cricket]

If they're too brittle to flare then replace the lines, at the least, back to the valves.
Slipping hose over copper tubing and then hose clamping should only be used in an emergency to be able to get going.

 

[rustybucket]

If they're too brittle to flare then replace the lines, at the least, back to the valves.
Slipping hose over copper tubing and then hose clamping should only be used in an emergency to be able to get going.

What Cricket said, I'd trace them back to the valves and replace the entire run with a good quality hose (from a hydraulic shop, not autozone)

 

[Westfield 11]

Can you anneal the ends you want to flare? I’ve annealed many copper washers on drain plugs of cars and motorcycles. It might be a bit tricky on the fuel lines, but the water should be no risk.

 

[Jammin']

Are compression fittings out of the question?

 

[racclarkson@gmail.com]

I was going to also suggest annealing.

Compression fittings are a no-no.

 

[Cricket]

You've got 47 year old brittle copper lines, they are going to be like that for the entire run, don't fool around replace them.
There may be an easier way to run the new lines than how Hatteras installed them, worth looking into.

 

[Fanfare]

I don't know if the old copper is too brittle to flare or not, but I can recommend a cheap way to check--Try one and see! (I think I would start with water.)

 

[Scarlett]

I just did new flares on my copper lines, no problem at all and mine are 46 years old. So I agree try it. John

 

[Briankinley2004]

I replaced some sections of my 35 year old copper steering lines using flares. It was brittle in the bilge but I found good copper in the ER to splice to. Also make sure to use the USCG Flame resistant fuel hose if not going copper. Not just the good stuff from the auto place. The true USCG fire rated hose is hard to find off the shelf even at a hydraulic shop.

 

[davidwigler]

I was able to cut and flare the 42 year old water lines to relocate the water heater and to add shutoff valves at each sink. No problem.

 

[kingsley_oasis]

I have completed several flares without issue. If it would not flare it was way to fragile to keep anyway.
The weakness I always found was easy to see from from outside corrosion caused by mix of water, bad grounding, and dissimilar metals. problem could be very localized, I think water being the main contributor

 

[Westfield 11]

I don’t see how clamped and secured copper lines could become work hardened. All they do is lay next to the bulkhead. If they were unsupported and vibrating, then yes, they will become brittle, but not simply from aging. Corrosion is a different story, but clean correctly secured copper should last nearly forever without embrittlement.

 

[oscarvan]

embrittlement.

HAH, made me Google that and learned a new word...., right up there with "lubricity".... Cool!

Embrittlement is a loss of ductility of a material, making it brittle. Embrittlement is used for any phenomena where a hostile environment compromises a stressed material's mechanical performance.

 

[Play'N Hooky Too]

If it is too brittle to flare then I would consider replacing it back to the point where you have good copper. The reason it is "brittle" is because the thickness of the copper has been reduced (eroded away) by corrosion to the point that the tubing wall is so thin that it will just tear when you try to flare it. That is if you can even get the flaring tool to clamp tight enough to hold the tubing.

When I replaced the copper water lines in my '76 46C there were lengths that were corroded to the point that you could just twist them apart with little effort and then other sections that looked like they were put in last week. Those sections were just as malleable as new copper line and could be flared just like new line.

The danger of sliding fuel line over the old corroded copper and clamping it is that if the copper is so thin that it can't be flared, it is thin enough that it could easily be crushed by the force of the clamps.

 

[Pascal]

I was able to cut and flare the 42 year old water lines to relocate the water heater and to add shutoff valves at each sink. No problem.

For water, I use SharkByte fittings. So easy, big time saver. I ve now replumbed the whole boat with new copper and SharkBytes. Some sections are 4 years old now and never had a leak. I’ve even pulled or shaken some pipes while under pressure... not a drop.

 

[Cricket]

Pascal I'm scared somebody is going to take the easy rout and use a Sharkbyte on a fuel line one day.

 

[31FlyCruzr]

Swagelok is the compression fitting that does not leak, overkill for low pressure systems, and pricey, but they don't leak

 

[Jammin']

But are Swageloks acceptable for use on a diesel fuel line? Otherwise, it seems the only option is to try flaring with the possibility that it could lead to full replacement.

 

[Westfield 11]

We used swageloks to install flight test instrumentation on the first 5 C-17’s. Including fluid lines with no leaking. We used cryofit on the 4000psi hydraulic lines, but swagelok everywhere else. I would have high confidence using swagelok on fuel lines on a Hatteras.

One other curiosity is that copper is the only metal that is quenched to anneal, I’m sure you all know this, but I’ve always found that to be an interesting factoid. Heat it to red hot and cool rapidly in water which is also used to harden steels.