Torch for Silver Soldering Copper Boiler

[Builder01]

I am in the process of flanging the plates for my boiler and I need to get a proper torch for doing the silver soldering. I have a small torch that is fine for annealing the plates and doing small silver soldering jobs, but, it is nowhere near large enough for silver soldering up the boiler. The main boiler barrel is 5" in diameter and 19" long. All of the plates are 1/8" thick.

I would like to have a propane only setup. I have seen several boilers on the internet done this way, so, I know it is possible. I understand the need for a proper "hearth" to contain the heat. There are so many combinations of handles, burners and hoses that I'm not sure where to start. I do like the Sievert torches and they are available in the U.S. from Best Materials in Arizona. Do these setups use ordinary propane tanks like those from Home Depot?

[LVRR2095]

I cannot comment on the Sievert torches.....but I do have to compliment you on the beautiful flange job!

Keith Taylor

[SteveM]

If you have a compressor (and if you don't, you should), you can get propane / air torches that will be hotter than just propane.

Victor lists temperatures here:
http://victortechnologies.com/news/615- ... nd-brazing
1750o F – air-propane
2400o F – air-MAPP
2700o F – air-acetylene
4700o F – oxy-acetylene

Another site has the following:
2200°C = 3992°F, for Propane/Oxygen
2927°C = 5300°F, for MAPP Gas/Oxygen
2700°C = 4892°F, for Acetylene/Oxygen
3200°C = 5792°F, for Hydrogen/Oxygen

You can braze with propane, but not weld, but if brazing is all you are doing, you are good.

You can use oxygen with propane, but the torch has to be made for it. I don't think you can just pump oxygen into a propane / air torch.

Steve

[TrainLarry]

The Sievert torch setup is a good one for propane only silver brazing. With the proper regulator, it can be hooked up to the common 20lb. bar-b-que propane tank, as I did. The system worked well for a 'G' gauge boiler, and with the biggest nozzle could braze a bigger boiler.

Larry

[Bill Shields]

I just finished a 5" diameter boiler for a 1" scale loco using a Sievert on propane with air.

You will need their largest tip , #2944 and a good regulator that will pass a lot of gas (get what Sievert recommends for that tip)

a stack of firebrick to help keep the heat in is helpful...as is a friend with a second torch...

it is often helpful to have one torch to 'keep the heat up' while you use a second one to apply some local heat as needed.

[Builder01]

Thanks for the suggestions and compliment on the flange job. Flanging plates is actually pretty fun!

Bill, so the #2944 tip is good for a 5" copper boiler. This is what I need, a model number. Checking out the Best Materials website, there is not a specific regulator recommended for this burner. I also need a handle and a hose. There is a "kit" on the same page as the 2944 burner. Here's the address:

http://www.bestmaterials.com/detail.aspx?ID=15144

Will this sort of setup provide enough heat for silver soldering a 5" copper boiler? Will this hose connect to ordinary propane tanks?

David

[SteveM]

Will this hose connect to ordinary propane tanks?

The regulator definitely fits a gas grill tank:


Steve

[Builder01]

Hi Steve,

Perfect!

Thanks.

[steamin10]

I would add that given small torches and larger copper, it becomes a battle to keep enough heat in the larger material to work your seam . One method is to preheat the things in moms oven to 500 degrees and quickly bury the uneeded area in kitty litter to keep the heat loss down.

Another method is to drag out the BBQ grill, and work over the 'preheat' of the grill to run your seams. Rock wool or lightweight kiln brick, can help position, and insulate the work.

A spray bottle is handy to freeze a seam for movement, to get at another angle while its hot, moving the setup with welding gloves. Move fast, but not a lot, and get it done in one long heat session.

Dont forget the wire scratcher, to eliminate pinholes. A pointed clothes hanger about 8 inches long, with maybe a hook on the end is good.

The net is full of visuals, good and bad, but no excuse for not watching it being done.

Good work, is not luck. it is a practical learning curve. Not everything goes right, but covering the sideways moves is experieince. You only get that by doing.

[James Powell]

If at all possible, get a friend to help. The big tiger torches (~180k btu/hr) are handy for final silver solders of bigger copper boilers. The bigger Sievert tips will put out enough on their own for up to something in the order of a 4-5" boiler, we did all the work on a much smaller (2 1/2") boiler with one of the medium ones.

MAKE SURE not to use concrete surfaces for such work. They will spall. Possibly explosively. Oww...

Air-Propane is not required for silver soldering copper. Make sure you are using silver solder, not braze, Some of the braze materials react poorly to coal, and need to be avoided. (Sli-Phos)

(& I'd stick to propane and avoid using an O/A to add heat, as with propane it is possible to burn the material, with O/A, you can vaporize poof gone...)

James

[RET]

Hi,

Don & I's experience with the Big Boy boiler taught us several things. Smaller boilers may work with less equipment, but with big ones, the technique needs to be different.

First, while you might be able to do the job with one torch, having someone else play the flame over the boiler for general heating while you concentrate on the area you want to silver solder helps a lot. For us, using a large propane - air torch for general heating and just the wash from an oxyacetylene torch for the actual silver soldering was the best choice. Make sure the oxyacetylene torch has a slightly reducing flame. See the Big Boy thread for a more detailed explanation. It also helps a lot if you do the operation at least partially in the dark (in the garage with the door mostly shut). This way you can see when the work is at the proper soldering temperature (a low red heat) and you will be less likely to burn the copper.

Second, instead of firebrick as Bill says, use insulating brick because it keeps the heat in much better. It helps to build a little structure around the boiler to contain the heat in the parts you aren't presently working on. You'll find that copper sucks the heat away almost as fast as you can put it in and that's where the large general heating torch really helps a lot. The wash from the big torch protects the copper from oxidizing because it creates an oxygen poor region. Make sure the wash from the big torch covers the region you are working on as much as possible.

Third, don't try to rush the process. It takes quite a while for the copper to come up to the proper temperature for a good silver soldering job. This also will reduce the stress in the boiler, both during and after you are finished. Yes, I know copper is ductile, but it still helps to take it slow.

This is what we learned by finding out what doesn't work as we went along.

Richard Trounce.

[Builder01]

Thanks for more suggestions. I understand the basic technique of silver soldering and have done much on small parts. I am looking for a propane only setup. I appreciate technique suggestions, what I am really looking for is model numbers or something specific for burner, handle, regulator and hose. There are many combinations of these parts and it's hard to know where to start. Seivert has a kit sold by Best Materials in Arizona. The link is in a previous message above.

Yes, I understand the importance of building a hearth to contain the heat and the use of a second torch. My smaller torch will become the secondary torch. A large copper boiler acts a giant heat sink and needs to be contained. Insulating bricks are the type to use.

Still hoping for suggestions on specific torches and setups others have used for propane only, silver soldering on a copper boiler. The main boiler barrel is 5" in diameter and 19" long. All of the plates are 1/8" thick.