Can you braze a hydraulic line?

[RickB]

What kind of pressures can a brazed patch handle? I don't know much about brazing but hydraulics run such high pressures that I don't think I would even try to weld on them let alone braze. I would just replace the line with a flexible hose built for hydraulics. It would suck to have it break down "in the field" with no way to get it back to the shop.

Lack of experience and subject knowledge never deters a TBN member from commenting.

 

[IndyJay]

Lack of experience and subject knowledge never deters a TBN member from commenting.

Then what would we have for entertainment?

 

[RickB]

Then what would we have for entertainment?

There is that.

 

[Texasmark]

One of the metal hydraulic lines for my dozer split. My neighbor happened to stop by while I was taking it off and he said that he could weld it with a coat hanger. He used a gas acetylene torch and the metal coat hanger, and it's held perfectly for over a decade now.

When I was in my 20s, the local muffler shop did custom exhaust systems. Their acetylene torched brazing accessories were a pair of sunglasses shaped welding goggles and coat hanger sized steel wire, straight for about a foot and few inch bent over at 90*. Had several lifts like used to be a service stations for access.

 

[lpakiz]

To whoever was interested in gas welding steel, I've done it quite a bit back in the day. I worked for a gravel hauling company and I didn't have access to an arc welder or generator in the pits.
Yes, I've used coat hanger for filler rod. As far as getting it clean, its a non-issue, because when you gas-weld steel, you are truly melting the base metal, as opposed to brazing, soldering or silver soldering, which relies on adhesion only. I guess we could add glueing to the list of things that need to be clean, but mild steel--not necessary. Of course, you can't have scale 1/4 inch thick, but if you did, youre not hot enough to join steel or add filler rod until that junk is all gone--burned away.
Actually, in welding class in Tech School, we learned to gas weld without filler rod. We just fused the two edges together. With a large enough tip, 1/4" could be done! It's kinda neat to see the molten iron from each piece "jump" to the middle of the seam. Then you weave and carry that little ball of molten metal right up the seam. If you want a seam with absolutely no depression, you can add filler rod.
And when the equipment companies TIG weld thin Maple Syrup equipment seams, no filler rod is used unless there are major fitment issues, (and they guy doing the shearing and bending is going to hear about it) or a burn-thru. This material is 22 gauge, so a steady hand and a keen eye (not mine anymore) is mandatory.

 

[Ken Kegris]

Why not just put a new end on the hose.

 

[Boss 302]

Good job and a lesson learned, keep up the good work

 

[Trauma47645]

Regarding the issue of overheating the steel tube, my silver rod melts well below 1500° so the tube never even got to dull Cherry. It just barely got shiny.

 

[Baby Grand]

As Ipakiz noted:
<snip>
Conclusion-- the bronze filler rod just didn't have the tensile strength to withstand the pressure. The steel patch did.
Ever since, I've never attempted to repair a split or crack without incorporating a steel patch.

Strongly recommend this site:
Braze School and Training | Lucas Milhaupt
In particular the Principles of Joint Design section.
My first choice (if possible) would be to cut a section out of the tube and make up a steel tube fitting that bridges the gap with a tubular lap joint at both ends - like an elbow fitting used in copper plumbing. If that won't work, then a patch that fits around the tube as close to 360 degrees as you are able to get it. Try to get the fit gap within recommended range - typically .003-.005 loose, but will depend on tube/patch and filler materials. You want the braze to be loaded entirely in shear, if possible. Also, keep in mind the system pressure in a hydraulic circuit is going to be high, if you're on the supply side. You also need to consider what type of shock load factor to apply, based on how flow is affected by sudden flow changes - pump "ripple", valve operating speed and system damping. In-other-words, over build it.

 

[rScotty]

Need to remember wrapping with wire trick before brazing. SS safety wire?

I've got to remember that trick, too. It's a good one.
The resulting composite of steel and silver stands a decent chance of being better than either alone. I'd love to see some formal testing.
rScotty