Brazing question or two.

[BubBud2]

We have some experiments here at work that are under a Nitrogen purge, from initial warm up of the furnace to cool down. The furnaces run at 1100 degrees C. and the experiments can take days. We are using nitrogen at an alarming rate, so the boss wants me to connect from a dewar manifold panel that is outside to the experimental areas. Using 1 inch 'K' copper the run is about 400 feet or so. There will be reductions in the pipe size to 3/4 inch at the three different experimental areas, then to 1/2 inch through regulators to the experiments. The manifold off the dewar will reduce the pressure to 100 psi. I was told that to silver braze the joints with a nitrogen purge to keep the interior joints from corroding.

Now I am pretty proficient with the torch but what type of brazing filler allow should I use? I was told to use BCuP series, but at what amount of silver? Sorry if this is too vague, but I am not that hip to brazing and the learning curve will be steep for me.

Scott

 

[Tantara]

call your welding consumables salesman.


Brad

 

[MottsRods]

Scott, i wouldn't use anything less than 15% and no more than 25%. If you use less than 15, then it could possibly make the joint brittle. If you use more, then it will make it too soft and not form a good enough bond to withstand the pressures. After being in the HVAC industry for many years, i've learned where and what is best from experience.

 

[e-tek]

Holy ****, I would think the boss would know what to use! Coming here to a "hobbyist" site (MottsRods excellent advice notwithstanding) doesn't seem to be the best course of action!

 

[BubBud2]

Sorry about that, e-tek, I probably should have said that the boss is really a scientist and I am the technician that has to make his ideas fly. I do have ability in the soldering, welding areas, just not that much in brazing. I posed my questions as a way of getting some advice about which way to go. I'm going to talk with some of the maintenance HVAC guys to get a better handle on the situation. I feel it's better to have done a lot of research about this before I get over my head in trouble and have to beg for help. Scott.

 

[e-tek]

Sorry to you too - make sure you don't think I meant that in a negative way. The way your post read, you and your work mates sound like NASA compared to what I know, so I thought it best to ask there!

 

[BubBud2]

No problem e-tek, I get that type of response when I tell people the type of stuff we do here at the lab.
Not too many people know what goes on inside a lab like this, mostly research on a theoretical basis but the group that I work with is R & D. Lots of hands on and I get to put it all together for the scientists. This place is heaven for a guy like me I get to work with all kinds of power and hand tools. I get to fabricate manifolds for gas sampling, wire experiments with 24v up to 480v and each day is something different. Plumbing, electrical, structural, high temp furnaces, eddy current separators, and some stuff that I can't talk about, as it is proprietary and there are patents being applied for some of those ideas. Here are some photos I can show. Scott

 

[MottsRods]

Scott, what is your maximum psi on this system. I have refridgeration systems that carry over 600 psi with soldered joints. But if the system has purge points where it can peak it's psi any higher, you'll want to use brass fittings.

 

[BubBud2]

Thanks for the input MottsRods. The manifold system that the AGA people are installing for us will regulate the pressure down the 100 psi. We don't for see any need to go higher than 100 psi for the experiments we are conducting now or in the future. The nitrogen will be used as a purge for the experiments to help drive off moisture and keep the product from corroding during the process. Scott

 

[MottsRods]

Nitrogen will help some with moisture, and blow any contaminates out of the lines. But to get it 100% moisture free you will have to pull a vaccuum on the lines.