Questions Regarding Brazing & Techniques

You will need a higher temperature if you want to braze. I would go with a high melting point silver solder like 97.5% Pb, 1.5% Ag and 1% Tn with Rury fluid flux. Temperature is 590° to 595°. Brazing needs 1000°+. Soldering can be done with a MAPP torch. The parts to be joined MUST be free of any impurities like grease from fingerprints.

You are right, brazing copper will probably be impossible due to melting of the copper, but silver soldering will be fine......

Cleanliness, wide joints (bell parts and file to increase the wetted/soldered area) and the right paste/flux are required, then the joint almost makes itself!!

Silver soldering is a nice method of working......it was my favourite for years. Now I prefer Stainless Steel welding........having bought a MIG welder 2 years ago!!

Those flat rods the ac guys use are fantastic. I think they are 5% silver. They use a pure acetylene torch, a real whistler. The technique is easy, no flux necessary. Tip: splice a new rod to the old when it gets short, use it all. Just leave the old one stuck to the job to keep it steady while splicing on a new one. The rods are expensive.

Several choices here.

http://www.harrisproductsgroup.com/consumables/alloys.asp?id=31

Off hand, this looks pretty good.

I've had good luck brazing with a MAPP torch (steel or iron with brass)

Stay-Silv 15 For many years the standard of the industry, the 15% silver alloy has proven its value. This filler metal is excellent for situations in which close fit-up does not exist, and where agitation and vibration in service are involved.

The phosphorus content serves as a "self-fluxing" agent in joining copper to copper. When brazing brass to copper or brass to brass, use STAY-SILV White brazing flux.

Hello Everyone!

I want to thank everyone that responded to my questions. Your answers were invaluable. I think for now I will stick with soldering the copper pipe and fittings with a tin/silver solder using the MAPP gas. Most of my work will be this type of soldering. When it comes to copper-to-brass connections I've elected to use standard treaded joints, just to simplify things. Most of the brass parts are either full ball valves, automatic air release valves, check valves, flow meters and what not.

Andy, I see you bought a Mig Welder too, eh!!??? Fun isn't it!!!??? Although I've never welded stainless steel, it sounds awfully inviting, just to play around with in the garage. What you'd really get a kick out of is using a good heavy duty Plasma Torch. I bought one last year to me help fabricate the pieces going into my DIY self-designed two-story steel tool shed/storage building. It's been invaluable for cutting up huge slabs of structural steel plate, rod and bars!!! Man, it's a hoot!

Also invaluable is the standard arc welder and resistance spot welder. I'll never go without either again. Both came in handy last weekend when my best friend shows up at my doorstep asking me to help him fabricate a new galvanized steel chimney cap for this house. In no time flat we had it done!

Again, many many thanks to all that have assisted me here. Have a great fall weekend folks!

It sounds like you have a great shop and you probably already have a torch rig but if not you would learn to really appreciate a small oxy/acet tote with a small amount $$ of 15% and 45% Sil-fos on board.

You'd be able to cut or braze almost anything... almost anywhere... just make sure to read about the fumes.

http://www.silfos.com/index.html

Actually, if he just wants to braze, oxy / propane is a good choice. It has a softer, paint brush type flame that heats a broader area more evenly. Not good for welding, though it's excellent for cutting because the stand-off distance between the cutting tip and the work is much less critical than oxy / acetylene or oxy / mapp. Just make sure that the outfit bought is for propane; special regulators, seals and hoses.

At nearly 600 degrees, I'd still go with braze. As previously posted, phos-copper is an especially good choice because flux is not needed on copper to copper joining. A flux coated low fuming bronze will work, but you end up having to heat your work to 1,400 - 1,600F which is just a few hundred off the melting point of copper.

Thats good info. I for one give you a GA......not off topic!!

Hello Ed,

I understand and appreciate your thoughts and concerns regarding my solar collector, especially when it comes to safety issues. But I think I may have to do some clarification here as there seems to be a misconception or misunderstanding in regards to what I'm trying to accomplish.

The evacuated solar energy collector tubes that I'm using in my system are NASA surplus. This type of solar energy collector system is one of the most efficient types and can be found on roofs all over the world. If you're not familiar with them, let me please explain the inner workings of the tube, etc. They're made of borosilicate glass by Owings-Illinois Glass Co. for SunPak. There is an outer tube and an inner tube with a gold film coating on it. There is a vacuum between the two tubes. Inside the inner tube is a 3/8" OD refrigerant copper tubing "heat pipe" that runs the entire height of the inclined tube and it's sealed at the bottom with an end cap. At he top of the heat tube is a 6-inch long x 5/8-inch OD copper expansion tube (same fitting as used for water hammer), also known as a "heat bulb". Prior to this fitting being soldered onto the top of the heat pipe, a very small amount of MEK or acetone is poured in, and then the heat bulb is soldered to the heat pipe, thus producing a slight vacuum. There is no water present inside the heat tube whatsoever, and I think this is where the everyone is confused. The solvents are used because of their relatively low point of evaporization/condensation. As the temp inside the heat pipe the solvent will vaporize and climb to the top and into the heat bulb, where it is cooled by the heat transfer occurring at the contact with the manifold, then the solvent condensates and trickles back to the bottom of the heat pipe. It's acting like a big old fashion coffee percolator in a sense. The heat bulb transfers the captured radiant heat, about 300 degrees F, to a water-filled manifold where contact is made through a dry connection by way of using copper fittings and a heat transfer grease/paste typically used in the electronics industry. There is actually no water contacting the heat bulb per see. The reason I'm using the dry contact connection is for ease of tube removal should any of tubes fail in the future. Now, if I increase the captured radiant energy by either using a mirrored (reflective mylar film lined )concentrator troughs installed underneath the tubes, or by installing curved acrylic-based Linear Fresnel lenses above the tubes, then the temperature in the copper heat pipe will definitely increase. But that's an exercise for me later down the road to experiment with. It will not be installed on the system immediately, so isn't really up for discussion.

Okay, the copper pipe manifold, where multiples of the collector tubes plug into will have water flowing through them, with the maximum water temp regulated at 180 degrees by means of varying the water delivery (flow). The idea here is to get the water hot enough for efficiency sake, but not produce steam in any way. Also, there will be thermocouples relaying the manifold temps to the SCADA system. I'll be using a surplus-ed chemical metering pump where the flow can be varied to maintain water flow and hence water temps.

Basically, the collector tube function like a hybrid Thermos bottle/old fashion coffee percolator. Like I said before, these systems are tried and true and are working all around the world. I'm going the DIY method to save overall costs. I'm only spending about 1/6th what it would normally cost to have a solar contractor come in here and put it on my roof and I'd not even talking about him installing the PC, the SCADA and all the data loggers and black boxes. Most everything I've bought for the system is surplus materials and equipment....I know that my system will outperform the factory/contractor installed one at a fraction of the cost.

Hope this clarifies things for you. Have a great weekend y'all!!!

WOWSERS, I have to get myself one of those oxy/acet totes thingys. That one in the pic looks particularily nice and useful. Whos' the manufacturer and where online can I buy one like it?

Thanks again guys!! WELD-ON!!!!! LOL Get it??? I know I know, very bad pun indeed...my bad!

Ref post 6 .........how come no GA for me...........

I almost gave you a GA for #6, but you showed a burning torch instead of a brazing torch. It's a small point, and a burning torch can be used for silfos, but I'm a stickler for details sometimes. The AC guys use a different torch, just acetylene/air, with a nice diffused flame. Plenty hot, heats up the fitting evenly.

I have a similar combination torch unit myself, and just love it. Got it on e-bay. A potential buyer has to watch out for look-alikes if he wants to use Victor tips. Some sellers will state 'Victor type', but only 'Victor compatable' will work. If you want to follow up your purchase with a nice rosebud or flush-cutting tip, it's harder to find that in the Chinese market.

I am in the trade. Air/acet works for most brazing. When you are doing large diameter pipes or stuck on a roof in -30 deg C only a oxy/acet unit will do it. Very few refrigeration/AC mechanics use air/acet. in this part of the woods. Not hot enough, not fast enough. By the way. Victor makes a great torch.

Wow, did you say minus 30 Celsius? That's frigging cold! My experience was with ac techs here in the tropics, St. Thomas. I got out of the trade because every call was to some God-awful location, hot as hell. Even inside calls to evaporator units was the same problem, hot, hot, hot. You're sweating into your eyeballs so bad you can't see, trying to fix a switch or clean an evaporator. Just about the time it's going again and things are starting to cool off, you're outta there. Sux. Find me a nice cool job somewhere else. I can fix lots of other stuff in better locations! GA, by the way.