solder for flash boiler ?

[sanch]

I am attempting to build a flash boiler similar to Green Monti's. I twisted up all the copper and am ready to weld or solder the bottom and top end. Green Monti tig welded his on the bottom. I was wondering if i could get away with solder. I scored half a tube of Sil Fos 5 from an HVAC guy yesterday on the tube it says flow pt. temp. 1325 deg solidus:1190 deg Liquidus:1495
it will be very close to the burner, but i don't think it will be close enough to melt the solder. will this work ? would another product be better ? thanks for any input

 

[BargainFittings]

Remember the temps will only be a only marginally higher than the temp of the liquid / steam inside. The tube and solder will melt very quickly if you run it dry.

 

[sanch]

even if the flow is very slow? making steam

 

[eddie]

Remember the temps will only be a only marginally higher than the temp of the liquid / steam inside. The tube and solder will melt very quickly if you run it dry.

So regular plumbing solder (the kind one would use when plumbing a house) should be okay then?

 

[kladue]

The Sil Phos 5 would work but the heat needed is beyond the mapp gas torches ability to reach easily. A high temp silver braze material would be better, SafetySilv56 with StaySilv flux has a lower melting point than Sil Phos 5 and it will work with the Mapp gas torches. I used that for the brazing of the copper tube to the brass fittings, just need to pour the fire to it as the copper tube is carrying the heat away rapidly. The 430 degree plumbing solder will work, but as GreenMonti found out, it can melt when you are not carefull in the steam mode.

 

[BargainFittings]

Like was mentioned, brazing at higher temps will give you more safety if you run it dry.

 

[sanch]

i have a neighbor that can solder it for me with a big torch. is sill fos 5 better than the others even though it requires more heat to apply? it makes sense to me that the more heat required to braze = the hire the melt down temp. is that the case ?
thanks 4 the input

 

[GreenMonti]

If you can/have access to a torch to do the sil-phos 5. I would do that if cost is a factor. I welded mine just because. If I built another one I would just silver braze it. I wouldn't bother with the welding. All of the work on the top is silver brazed with silvaloy 15.


I also would not use the standard solder. As Kladue mentioned, I found out real quick that the boiler will melt standard solder when making steam. I have seen output temps hotter then I ever intended. Things happen real quick using the FB, and if your solder can't handle the temps.....


Edit; I am not sure what the continuous temp rating is for sil fos 5 but, my silvaloy 15. Even though its brazing temp range is 1300-1500, it is only rated at 300 continuous and 400 degrees for short time periods.

 

[Ranger9913]

I used DynaFlow to braze my flash boiler.

http://www.harrisproductsgroup.com/dynaflow_Stay-silv15.asp

I was able to use a MAPP torch with ease to melt this stuff. No flux is required either. Can fill joints very easily as well. I think it was under $30 for 20 sticks. Should only take you 2-3 sticks to finish everything.