Coupling Old Copper Fuel Lines

[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.