Metal hydraulic line keeps blowing

[North Idaho Wolfman]

Buy the tubing (you can buy tubing with a thicker wall) and a bender, I did exactly that years ago.
You can get whatever end you need to weld onto the tube.

 

[Runs With Scissors]

Did you read the very first post in this thread? The op clearly states where the pinholes are and also that he explored the idea of replacing the steel lines with soft hoses. The very first post no less!!

Either too much, or not enough covffee…...

 

[Hugo Habicht]

You can get whatever end you need to weld onto the tube.

I typically reuse the fittings of the old line. Cut off the pipe at the fitting and drill out the rest.

They should be strong enough and fit perfectly to the tractor side (one side of your pipe seems to be thread, but the other fitting looks non-standard). You may have to drill the hole slightly bigger if the new pipe has higher outside diameter due to the increased wall thickness.

 

[PoTreeBoy]

Shouldn’t this be a WARRANTY Item?

Yeah, I agree. The tractor itself may be out of warranty, but the repair parts should have some kind of inferred warranty.

@Stone'd Mason, do you have the old parts and receipts maybe? I think it's time to escalate the issue. If you can make a temporary fix so you can use the tractor, I'd press the dealer to set up a meeting with the Kubota representative to present the evidence and 'what are you going to do about it?" Don't just leave the parts with the dealer, lest they disappear.

I don't think the problem is due to gross overpressure for two reasons; 1. I think you'd see some damage to one of the hoses, 2. Rupture from overpressure usually, in my experience, results in a split, not pinholes. This is probably welded, not seamless, tubing. The tubing is rolled from a continuous flat strip and welded, using the resistance welding process I'd think. That process has been used a long time, but it requires close process control to produce top quality.

 

[McMXi]

Rupture from overpressure usually, in my experience, results in a split, not pinholes.

Hoop stress vs. axial stress .... yep. Pinholes in metals are typically due to physical impact of some form e.g. abrasion or cavitation erosion, or they're caused by corrosion. Corrosion should be easy to rule out (or rule in) based on the appearance of the outside wall of the tube. This is why I asked about the nature of the pinholes whether they're forming on the inside or outside of the tube.