Can you braze a hydraulic line?

[IndyJay]

A coil #9 wire has many uses! Its more feline than coat hangers.

coil #9 "more feline" as in 9 lives?

 

[jaxs]

I didn't think much about it the first time someone claimed to gas weld steel hydraulic line with clothes hangers as filler. After hearing it again I'd like to ask (A) How many others here can and do gas weld steel hydraulic line with clothes hanger filler? (B) Foremost,will one or more of you expand on the proceedure? Does clothes hangers melt at a temperature low enough so there's a margin until line melts or do you melt parent metal as well? How do you prevent damaging or even collapsing line? Is any hanger suitable and if not,how does one tell? Is there filler available at welding supplies that is equal or better? Most everyone is impressed with OP's brazing repair which is a feat to pull off without contaminating inside line. Welding take's things to a higher level that would be good to know for a few other applications.

 

[Egon]

coil #9 "more feline" as in 9 lives?

Ahh. Flexible!

 

[John0829]

Using a clothes hanger ( done it many times ) is the same as using mild steel gas rods, I prefer to use the mid steel rods but clothes hanger are handy if you happen to be out of the other. Using gas is the same as any other welding you have to learn to read the metal to not get it to hot and burn through or not getting it hot enough to stick. Personally I REALLY enjoy gas welding and brazing, the biggie as with any welding is get it CLEAN if you want it to work.

 

[blueman2]

I am a refrigeration tech so I will be applying my practices and tools to this. I will be using an air acetylene turbo torch with a rosebud about the size of your thumb nail. I usually have no problem doing up to inch and an eighth copper with an MC tank. Most of my experience with steel is brazing copper lines into steel king valves on compressors. We use a paste flux on the mating surfaces and then a 45 to 55% silver alloy brazing rod. Or a hollow core brazing rod with flux inside. I will blast the oil out of the tube with nitrogen and then set my regulator to bleed a low pressure feed of nitrogen through the tube while I heat it up. Probably float the high silver and flux combo all over the top of the trouble area because it is runny, and then switch to the 15% silver alloy brazing rod to cap it because it will build up a patch better. Bleeding the nitrogen through the tube while I heat it will eliminate any oxygen in the line that could allow any residual hydraulic fluid to catch fire, and prevent oxidation and pollution on the inside of the pipe. My first challenge is a bit embarrassing, as I attempted to bubble gum the leak first, so I will have to get the epoxy patch off of the area and get it back down to clean metal. I will document what I do and report back in a day or so.

I have brazed a hydraulic fitting with flux coated silver brazing rods. The ones I have seen are coated with either red, white, or blue depending on the mfr. It worked fine

 

[Kschwennsen]

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.

 

[Gord Baker]

I am a refrigeration tech so I will be applying my practices and tools to this. I will be using an air acetylene turbo torch with a rosebud about the size of your thumb nail. I usually have no problem doing up to inch and an eighth copper with an MC tank. Most of my experience with steel is brazing copper lines into steel king valves on compressors. We use a paste flux on the mating surfaces and then a 45 to 55% silver alloy brazing rod. Or a hollow core brazing rod with flux inside. I will blast the oil out of the tube with nitrogen and then set my regulator to bleed a low pressure feed of nitrogen through the tube while I heat it up. Probably float the high silver and flux combo all over the top of the trouble area because it is runny, and then switch to the 15% silver alloy brazing rod to cap it because it will build up a patch better. Bleeding the nitrogen through the tube while I heat it will eliminate any oxygen in the line that could allow any residual hydraulic fluid to catch fire, and prevent oxidation and pollution on the inside of the pipe. My first challenge is a bit embarrassing, as I attempted to bubble gum the leak first, so I will have to get the epoxy patch off of the area and get it back down to clean metal. I will document what I do and report back in a day or so.

Save your consumables and time. Buy a new line. You will never get the oil film removed from the inside. Procedure is correct, job is wrong.

 

[ovrszd]

Save your consumables and time. Buy a new line. You will never get the oil film removed from the inside. Procedure is correct, job is wrong.

Go back to the beginning. He described that the machine would have to be majorly disassembled to remove/replace the line. And I think he mentioned he has the new line onhand.

 

[Menagerie-Manor]

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.

Back in the day when going thru my apprenticeship in the pipe welding shop we performed burst testing on brazed copper tube and not once did a brazed joint fail at over 5000 psi, typically the tube would fail with a split similar to a frozen pipe.

 

[lpakiz]

Since we are relaying old "war stories" I'll tell you my experience.
i worked for a construction company as a mechanic. (1975?)
One day, the foreman tells me the D8 (Caterpillar bulldozer) has a split in a steel hydraulic line. The line was at least 1" diameter, maybe 1 1/4. Easy place to get at, right above the track, and the split was right on top.
I applied a patch of brazing rod to it. Looked good. The next day, it leaks again. The bronze filler rod had split exactly where the original split was.
I applied another patch of bronze brazing rod, this time about 1/4" thick, 3/4" wide, 3" long. Good looking patch, I used a weaving techinque. That second patch was a thing of beauty.
Next day, leaks again. My beautiful brazed patch was again split right where the original crack was. No problem on the bonding, the bronze flowed on and adhered perfectly. Formed a beautiful bead. Just cracked that nice patch.
So the next day, I melted off the bronze, formed a steel patch from some 16? gauge steel and brazed that on. End of problem.
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.

 

[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