Did you use any oil on your flare fittings??


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Good call. Oil is an excellent torque multiplier! I've also had a bad lineset. The tube kept on splitting at the flare every time I tried to flare it. Upon inspection, it looked like the 3/8" suction line (yeah, a small mini split) had a seam down it. Obviously a defect.

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would it be on the outside or inside of the flare? I always clean the mating surfaces with isopropyl and put some nylog there... Why would oil multiply the torque? Torque is torque and should be "generated" by the compression force of the mating surfaces, IMO?!

it was like witched today and I was already running short on the 1/4 line... finally the 4th attempt worked (and no issues on the 1/2 line).

 

The oil is just a lubricant that helps form a good bond and allows for slippage. I put a dab on the face of the flare the back of the flare and the threads both male and female. And proper torque that I’ve always been told on brass is index the points on the nut and fitting then make a 1/6 turn. That means take your index point and move it to the next point. I’ve never put a torque wrench on a brass flare fitting. And I’ve messed with some pretty big flares


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Still could have been a bad spot in. The copper.


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btw does anyone use these blue "flare seal" gaskets as sold on ebay?

Do they work?

 

Nylog Or oil!

 

I use vacuum pump oil.


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is the blue gasket thing useful? it seems to contain Locite

 

If the end of the coper tube is not debureed well enough the tube will split when flared (creats a high stress stop in the copper). The potential for splitting becomes greater the smaller or thinner the tube is. If the tube is hard it will split. Many people apply too much force when flaring 1/4" tubing and cracks the copper, which is typically found when tightening the flare nut or when it is vacuum/leak checked. What makes the seal in a flare fitting. It is the conpression forces created by the flare nut on the copper tube to the fitting. Too much force by nut and fitting and the copper fails. What is the primary thing that effects torque and making a good seal? Friction. Oil reduces friction, look at a torque chart sometime find a non-lubricated and a lubricated torque chart. You will find every tme for every size the lubricated torque value is lesser.

 

Any lubricant will change a torque value. Sometimes a lot. The value for a bolt with oil on the threads has a multiplier of .55.
A flare should be oiled. This is standard procedure. A flare breaking is likely because of no oil. Even with a lubricant the torque value should be adjusted. I would expect the manufacturer should have these values.
A problem might be had if the copper is too hard but that should be seen when the flare is being made. If this is suspect you can anneal the copper first. Heat to a dull red and let it cool naturally then flare.

 

it didnt split... it came off as a copper ring inside the fitting, with no visible split. And I'm sure the torque was correct (as specified by the manual).

 

Using an automotive torque wrench with a crowsfoot? Leverage add to torque...

The torque tool for the minis is calibrated for the supplied "crow foot"

...and they do spec a pot load of lb-ft of torque!

 

not if you put it at 90°, then it is nearly the same

 

What happened to the days when a flare was simply tightened.
Your flare broke. I imagine your flare tool is the correct angle. There are several angles out there. For a flare to appear as you said, the flared portion braking from the pipe would seem to indicate that the flare moved and the pipe didn't. The flare nut grabbed the flare and broke it. If true there was no lube. I'd inspect the brake closely with a magnifier to see the way the flare broke.
What was the torque and did the manual specify what to lube it with. The type shouldn't matter as it's only aiding the sealing. Just to check if the manual had a torque + lube.

I had an electrician tell me of someone tightening a flare and the pipe twisted inside the insulation.

 

btw can I double flare on HVAC lines?

 

Yes.

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it didnt split... it came off as a copper ring inside the fitting, with no visible split. And I'm sure the torque was correct (as specified by the manual).

It is possible that the tubing is too hard, is it soft annealed and bent easily by hand (soft) or does kink (hard) when you try to bend it. However most times I have seen the cone break off it is because too much force was used right at the very end, you know the Umph that got it.

btw can I double flare on HVAC lines?

Just curious why would you want to? A double flare is for high pressure (like brakes and above 5000 psi) and usually steel and the fitting are different. I don't believe you can double bend copper without damageing in. They do make copper seal cones that go between a steel flare fitting and steel nut but these are typically used in hydraulics and greater than 3000 psi

 

double flare would resist higher torque

 

Why do you say that? The copper is still the same thickness, The thickness whereyou explained it broke would be the same therefore no additional strength

 

Don't put anything except refer oil on the flare mating surface. Anything. A few drops of refer oil on the flare where it meets the nut. Tighten until you say UGH.
I've only used a torque wrench on my bike but if that's what they want, go.
I have never broken a flare on a line set but have had it happen on very small tubes. Over-tightening but more likely movement of the tube causing stress at the nut.

I never used nylog but I know some here do. Don't know why. A proper copper to fitting flare won't leak. The flare has to be wide enough to seal. The nut should just fit over the flare.
When I worked in aviation I dealt with hydraulic systems that exceeded 1500 psi. Skydrol systems were even higher. The only thing present on the fittings was hydraulic fluid. WE couldn't have any leaks or the aircraft would have been grounded.
I have to assume your failure was procedure. The nut has to slide over the flare in a smooth unrestricted way as it's tightened.