stop these compression fitting leaking

[garyfdl]

Originally Posted by Shaneesprit

Do you have a valid reason for saying this?

Re: Previous post #26

https://www.practical-sailor.com/boa...ng-up-our-fuel

[01kiwijohn]

Originally Posted by hd002e

I have these compression fittings in my diesel fuel lines and they leak, it is not kuch but it is enough to make everything greasy and stinky. How do i compat the mess? Any tricks? Thank you!

Is that a little crack that I see at the base of the flare? You may have to cut it off and re-do the flare, with the proper tool.

[Celestialsailor]

Originally Posted by Bycrick

Most of my diesel fuel plumbing is copper tubing with flare fittings. My first boat had hydraulic steering with flare fittings. If they’re done correctly, they don’t need any sealant or tape to keep them from leaking.

Originally Posted by Emmalina

nothing wrong with them but you shouldn't use copper pipe for diesel !

I found out the hard way that copper should not be used with diesel. I added an additive to my diesel and it attacked the copper causing a black crystalline to form as it was eating at the copper. It chocked the flow off when I was entering a harbor breakwater with 5ft. swells.

It's fine for hydraulic steering however.

[P3sailor]

Those are flared fittings. There are copper flared "gaskets" out there. I've used them on aircraft and they do work. But they're not a cure all. I prefer to double flare my lines, which, in my opinion, are the best way to go, don't have to wrench the nut extremely tight and they conform to the nipple well.

[Dieseldude]

Originally Posted by Celestialsailor

I found out the hard way that copper should not be used with diesel. I added an additive to my diesel and it attacked the copper causing a black crystalline to form as it was eating at the copper. It chocked the flow off when I was entering a harbor breakwater with 5ft. swells.

It's fine for hydraulic steering however.

I'd never seen this scaling of copper fuel lines. But this is a good point, so it makes sense to go with steel despite its resistance to bending. A good bending tool with be required. I would take the time to apply a coat of good primer and paint to steel lines. Even if time does not permit for an immediate repair, I would remove it later and paint it. The humid marine environment will eventually rust bare steel line.

[hirondeller]

Poster #40: "But I have seen copper lines on engines that has been there for years, and it has lasted fine." Also read #44



Read post #37 if you think copper is universally OK around fuels. Essentially, it is a regional matter. High sulfur fuels are NOT compatible with copper pipe. In some places it will be OK, others places it will not, that is why the issue keeps arising, with some people saying "It is fine". People are speaking from their own experience, I believe they are well meaning and truthful, but their local advice might be incorrect for others.

[Bycrick]

I suspect that the question of copper vs steel fuel lines depends on whether you’re installing them new (in which case I’d probably design for, and use, steel) or whether I need to rip out by fuel system tomorrow and replace it. That might depend on whether or not I’m using low-sulfur fuel or not.

[Celestialsailor]

Originally Posted by Dieseldude

I'd never seen this scaling of copper fuel lines. But this is a good point, so it makes sense to go with steel despite its resistance to bending. A good bending tool with be required. I would take the time to apply a coat of good primer and paint to steel lines. Even if time does not permit for an immediate repair, I would remove it later and paint it. The humid marine environment will eventually rust bare steel line.

I brought it to the attention of the additive maker and was stonewalled. Getting the draw tube out of the aluminum tank was a challenge. It had grown around the tube. The copper, after I cleaned it looked like craters on the moon with magnification.

I used steel brake line material for the new draw tube and had no further problems.

[Shaneesprit]

Originally Posted by garyfdl

Re: Previous post #26

https://www.practical-sailor.com/boa...ng-up-our-fuel

I am presently involved in a project part of which is replacing a fuel system at a cost of over $1m just for the fuel system upgrade, the existing system has some copper and it’s over a decade old. Fuel flow is minimal.
It’s not the first time I have seen copper pipe on a fuel system, personally never seen an issue, but I wouldn’t of installed in copper in the first place.
Maybe I have copper on my heating oil tank at my house.

[Dieseldude]

Originally Posted by P3sailor

Those are flared fittings. There are copper flared "gaskets" out there. I've used them on aircraft and they do work. But they're not a cure all. I prefer to double flare my lines, which, in my opinion, are the best way to go, don't have to wrench the nut extremely tight and they conform to the nipple well.

While working at ROV hydraulic systems, we kept some copper crush washers in our stock. These were great for quickly solving leaky JIC fitting leaks. But they have limited re-usability cycles. They will not seal badly damaged fittings. Most of the time, they will get you up and running, and if left undisturbed, the joint will be tight for a long time. I've not seen them for flared fittings, as most hydraulic lines are high pressure and use JIC or SAE fittings. SAE fittings use o-rings, so crush washers do not apply. JIC fittings would be overkill for low pressure fuel, as would be SAE.


Double flared joints will offer the benefit of second layer to the joint to provide a crush washer effect, so in my view, a double flare is superior. For vehicle brake systems, a double flare or metric bubble flare is required by law. Single flare brake joints are considered as unsafe. But brakes are under hundreds of pounds of pressure. I've not seen it yet, but some boat fuel systems may have metric bubble flare fittings. So one must identify fittings with certainty before purchasing a flaring tool and spare fittings.



Back to the steel vs. copper line discussion. Steel line can easily mar the surface of brass flare fittings as the steel can bite into the brass. So one must keep some spares on hand and be prepared to use a new fitting if disturbed.

[Bowdrie]

Lots of talk about brake lines.
Yes, brake lines use a double-flare, but they also use "inverted" flare fittings that are generally made from steel and have no resemblance to a "regular" flare fitting/nut.
If one wants to make good quality flares get an "Imperial Eastman Rol-Air" flaring tool.
They don't crush the tubing shoulder in the die, and the faceted head of the tool burnishes the tubing.
Might as well get an Imperial Eastman tube cutter also.
Standard tools of use for decades in the HVAC field.
Use forged nuts.

[AKA-None]

Originally Posted by Bowdrie

You make a good point.

Going thru the "Permatex" products, (and perhaps I missed something,) I found only one product that had diesel listed in the MSDS data.

That is part#80632, commonly available at your favorite auto parts store.

It's a paste with PTFE, and I've had good success with it.

I'm sure their are other brands, I'm just used to the Permatex product line.

Their "Aviation" sealant can give good service, but it it's messy to use, it leaps right out of the bottle and gets over everything.

Ranks right up there with 5200
It works but is really sticky and semi permanent

[Sand crab]

Originally Posted by 01kiwijohn

Is that a little crack that I see at the base of the flare? You may have to cut it off and re-do the flare, with the proper tool.

Yup I mentioned the same thing in post #14. I think it was taken apart one too many times which probably softened or distorted the copper. Here's that pic again.

[flightlead404]

Originally Posted by Chotu

They are one of the most reliable ways to seal things. ...
If you have properly formed the flare using the right tool,

This part is critical. I've made 100's of these fittings for fuel lines, although with aluminum tube not copper.

Its critical to:

1) Get a square cut on the end of the tube
2) Smooth that cut end down so there's no cuts, nicks, dings, jags etc etc
3) Get just the right flare, the better more expensive tools are invaluable here. Over flare it and the cone will split, under flare and it won't provide the right sealing surface. Practice makes perfect here.
4) Use the right flare. There are a variety of different flare angles used in different applications.

[Dieseldude]

Originally Posted by Sand crab

Yup I mentioned the same thing in post #14. I think it was taken apart one too many times which probably softened or distorted the copper. Here's that pic again.

Good points SC. Over time, copper flare joints can deteriorate. Repeated dismantle and re-assembly can take their toll as will years of vibration. Often the joint was not made correctly to begin with. Sometimes the tubing is not properly secured, so stresses and vibrations concentrate at the joints. Malleable copper can spread out and thin.



But copper actually tends to harden under compression rather than soften. Of course it becomes less compressible and will not thoroughly seat and seal. It can be annealed by heating with a torch to red hot. There is debate on whether to quench in water or cool slowly. I have always opted for slow cooling of copper sealing washers. Have never needed to anneal a flared joint though. This is called annealing. Annealing of steel always requires slow cooling. So I use the same procedure for copper. Quenching causes rapid uneven cooling as the "cold front" progresses along the metal. This may cause uneven stresses. For emergency repairs when a flaring tool is not available, or the old tubing is too short to cut back for a new flare, annealing the old joint might be a temporary fix. Of course any fuel must be drained from the line. Residual fuel stuck to the inner wall is a hazard. Best to remove the whole line and heat outdoors. But that also means disturbing a second joint.



When renewing flared joints, the fitting itself should be examined for any surface gouging or raised burrs and lumps. Of course such damage will require a new fitting. The very best quality flaring job will fail if the fitting is burred or gouged. It is always good to have a hand full of spare flare nuts and fittings aboard.