I'll let the pics do most of the talking, but I'm repairing an espresso boiler for a good friend. It had a brass tube running through it that tore up from a crack. I'm replacing the old tube with a copper tube. I have 4 "welds" to make. 2 "welds" for the brass end caps on either side of the copper tube. Then I have 2 fillet "welds" that will connect the tube to the boiler.
So far I've run into oxidation issues on the test piece. As I heat up the tube it becomes oxidized to the point that the ground doesn't work anymore causing the arch to die out. Should I be using deoxidized copper? I can get it, but it's twice the price of the already pricey common copper tubing.
Another question is regarding filler metal. Because brass will gas out zinc and all, when heated up, should I switch from Aluminum-bronze filler to this blockade stuffhttp://www.harrisproductsgroup.com/en/P ... ckade.aspx. I can also get a hold of regular copper-phospherous brazing rods, but I need something that will set up for the 2 fillet/socket "welds".
I've used Blocade for lots of stuff! Works great. I've used it with oxy acetylene and with just a tig rig. Don't need flux. I've done steel to copper. Copper to copper. Brass to copper. Brass to steel. Flows real nice.
Poland308 wrote:I've used Blocade for lots of stuff! Works great. I've used it with oxy acetylene and with just a tig rig. Don't need flux. I've done steel to copper. Copper to copper. Brass to copper. Brass to steel. Flows real nice.
Sounds good, I haven't done this and was just going by Harris's chart
I've used the flux for 45% silver braze but only 1 time when it was a 70 year old steam coil that was contaminated with minerals from the water. The tube wall was so thin I couldn't sand it clean and still have metal to work with. If you use a flux make sure it can handle the higher temps associated with brazing.
The first time I used it it was specifically because of its low melting point. That's one of its great features for working on thin stuff. It will wet out like a solder but if you feather your heat you can build it up almost like a weld. It has sort of a shiny black look to the finished joint.
Tried some phosphorous copper brazing rod. It didn't melt through so good on that front. It didn't cook up some oxides though. Not as bad as the first time, but I dunked it acid in between the brazing.
One thing I'd like some confirmation or refutation of some kind on is the "weld" pool. I tried dabbing too early and it balled up, but then it reeaaallly wet out like a puddle and from there on it was hot and fast. I was worried that I was melting the base metal, but back side didn't seem to indicate that.
Any extra thoughts about this before buy up some blockade that seems to have a slightly lower melting point.
Also, this boiler will see 9-12 bar, while the pump is on, but 2.5 bar after that. Any caution on the pressure?
I don't think that pressure will be an issue. Most braze joints I've done and researched are rated at 800 psi plus. http://www.harrisproductsgroup.com/~/me ... deSpec.pdf
If you look at one of the spec sheets for the blocade you will see they cycle tested it at 600 psi and 300 deg f. Then up to 2500 psi with no failures. I've used it to repair steam coils that ran 50-75 psi stem. No issues.
I finally got my hands on the Blockade. Wasn't expecting a grey colored rod, although the original braze had grey filler metal so may be something similar to the original.
What amperage range would you suggest? I had no foot pedal so I tried 120 on the first fat blob, then 70amps for second attempt. 70 seemed fine. I just moved to quickly because I thought it was going to overheat again. I'm happy to see less overall heat inputed. I think this should work out fine.
Any final suggestions or considerations before I attempt the repair on the next work day?
So I got it all welded up. Before someone points it out, I am not proud of the welds. I was running really low on giveafuckitude. I don't know why, but I just wanted it out of my way. BUT it holds pressure! All hail the immortal booger-welds.
Thanks a ton for the input and hand holding. I can't wait to have good espresso!
I know this thread is 6 years old, but I have a very similar espresso boiler with the same internal failure. Before I go about trying the same repair that you did, I was wondering if there is anything that you would do differently, either in cutting out the old tube, or in doing the repair braze/weld? For me, this will probably be the only time I do this sort of job, so any advice or tips on getting good results is appreciated. Thanks.
Last edited by Harmonic on Tue Oct 26, 2021 11:55 am, edited 1 time in total.
I can’t speak for the original poster, but any time your dealing with thin metal. That has been exposed to boiling water, then your biggest enemy will be the mineral deposits. Often there on the back side where it’s nearly impossible to clean off.
