brazing or silver solder for steel hydraulic line repair

[chuckinnc]

I need to repair a hole in a 1/2" od hydraulic line. I have done lots of arc
welding and electrical soldering but nothing with brazing brass rods or hi temp silver solder. I need repair a leak on a steel (Chinese) hyd line of a small dozer and need to know which would be the easiest way for a amateur?

[warmstrong1955]

I've repaired a lot of hydraulic tubes on mining equipment in the past. If you can, weld it or get it welded.

It really depends on how the hole got there.
If it failed because it cracked, brazing will work for a temporary fix, but is generally not a good permenant fix. A crack is caused by flexing, and it will eventually re-crack thru the brass. This will make it harder to weld later.
I have brazed small adapters on tubes, for checking pressures, and have patched holes caused that were rubbed through them, with a steel patch brazed on over the hole. Only time I've brazed them, is when I haven't had the right welding machine available. I get a new one on the way for replacement later. I've never tried silver solder.

Best method is to weld them, heliarc or a small wirefeed.

[chuckinnc]

This is a small 6500lbs Chinese dozer and the pipe has metric fittings so I really need to repair it. Its on the left to right blade adjust and is only
3/8" tube. Im not sure this stuff will stand up to welding? Ive been told
sliver solder brazing would work, the thing only runs 2200 max psi.
The plant I work at is shutting down so I need to start doing repairs myself, just wanted to know which methoid would be easiest for a amateur
to learn, brass or silver brazing or maybe wire feed?

[warmstrong1955]

3/8" tube.... a little guy. I'm used to 3/4" & bigger.....

Assuming you're new to all, brazing or silver soldering are the easiest to learn. Metal prep is the most important aspect. Neither like oxidation, and especially oil about. Gettin' things clean is important, but also important for welding as well.

For a 3/8" tube, or any size for that matter, heli-arc would be best. I've repaired 1/8" tubing for pilot & brake systems with heliarc, and up to 2" diameter HP tubes.

On smaller diameters, wire feed is do-able, easier as they get bigger & thicker, but will be more difficult if you're new at it. I've done some 1/2" tubes with my little Miller 115V wirefeed not too long ago. It seems to get a bit tougher as the bifocal prescription changes too....not sure what that's about.

Again, if it's a fatigue failure, especially if it's in a bend, it will fail again later if brazed or silver soldered. If it's a hole that was worn in the thing, especially in a straight section, then it's not so critical. For something like a sidehift or tilt on a dozer, that see's an intermitant pressure load, it may last quite some time, and may be adaquate for you. The type of repair that will work depends a lot on why it failed. Also to be noted, the smaller the diameter, the higher the pressure the tube, and/or any type of repair, can withstand.

Got any pics?

Bill

[dly31]

Regardless of how you make the repair, if possible put something inside the tube to prevent the material from running into the tube. Since my welding skills are not up to welding it, I would probably split a short piece of tubing, clean everything real good, fit the piece around the defect, and braze it. I think hard "silver solder" would be suitable also. It would be real easy to over heat the patch so keep most of the heat on the line.

Don Young

[Sandman north]

I have repaired a few hydraulic lines and I prefer brazing or silver soldering with 45% silver not the cheep stuff.
And not welding.

In this case with a hole I would solder on a patch and (cleanliness is holy ) I like to sandblast the surface, remembering to get all the sand out after.

pros and cons

Silver solder gives a good strength and if you can solder its easy and the lowest temp.

Brazing also good slightly higher temp.

Against welding a pipe: strong enough but down the road it may crack due to vibration and hydrogen embrittlement.

MY 2 cents worth

[Russ Hanscom]

Second the split sleeve method.

[LarryMck]

I agree with Russ with making a sleave and cutting the tube and puting a sleave over it. Keeping it clean and removing all the oil is key to making a good repair. you could silver solder the sleave or weld it with a mig or tig welder. Stick is duable but you have to be fast to prevent under cut or melting another hole in the line. More and more hydraulic shops are starting to cary metric fittings. A good one may be able to make a new line or maybe a hose.

I have made BSP to JIC addapters before on my lathe. There is a formula in the Machiniest Handbook to calculate safe working pressue based on wall thickness. Just have to remember that BSP is 55 Deg. VS 60 Deg on your threading tool.

Below is a link to help Identify hydraulice fittings.

http://www.hfifluidpowerproducts.com/Pa ... guide.html

[steamin10]

In todays age, any good hose shop should be able to swage a new end on the old hose, provided it is of sufficient remaining life. Bent and detailed lines can be fabbed to mimic the original, and be extended for the material lost in the conversion. That, or a new line made for the job, would be my first choice. Hoses are really cheep, and it is 'done right'.

If I had to do a bench repair, high quality silver braze, or even bronze rod would work well, given you dont melt the base tubing in the process. IMHO it is safer to master than welding pressure tube or pipe. A braze that fails on 22oo psi, can be rebrazed with little trouble. Oil being the biggest problem.

Just my .02 Thanks.