Oxy Propane kit

At the moment I'm in the process of silver soldering my 5" gauge boiler barrel I'm using a Sievert torch and a standard propane cylinder. Even when using a good soldering hearth I'm struggling to get the copper hot enough to produce a good solder flow. Would an Oxy Propane kit overcome this problem ? If so can anybody suggest a suitable kit.

Thanks Peter

CuP alloys do a nice kit.

How big a burner are you using?

Steve

That's not really an either/or question.

Oxy Propane is a high temperature, but localised flame, and can cause issues by melting tubes or tube plates if not used carefully while propane is a slightly cooler flame, but bigger and with a lot more heat capacity.

I would suggest that an oxy propane kit is something useful to have in the workshop for brazing as against silver soldering, but for more heat on a boiler a second propane is probably a better bet and is half the price of the oxy kit. Many of the older designs were produced on the understanding that paraffin blowlamps were to be used and these produced a flame similar to propane not oxy.

If you use a large propane bottle you may be able to get away with using a t-piece with both torches but if you use a small one a second bottle, or exchanging yours for the largest the rules your gas supplier allows might be an idea. A mate to hold the second torch is probably essential too. In my experience do not ask a significant other or partner - just don't ask me how I know!!

But before you try any of these suggestions what burner are you using? - the standard Sievert one is good, but they do a lot of others with far higher outputs and one of these may be the answer.

If you intend to silver solder your firebox stays a cyclone burner could be useful as well.

Edited By Nick Clarke 3 on 16/05/2021 15:26:51

Hi Peter,

You may not need an Oxy Propane kit. A Sievert propane torch should be able to give high enough temperatures for silver soldering (brazing), is your burners outputting enough heat (kW). The burners I use for much of my silver soldering outputs around 7kW, I also have a larger burner that outputs far more heat and is used to silver solder larger items.

Thor

+1. What's wanted is more kilowatts, not higher temperatures. A bigger torch producing more heat by burning more gas. Adding oxygen raises the flame temperature, which is good for cutting and welding, but the flame is too hot for solder and flux.

Agree that a 5" boiler really needs 2 fairly large burners, one for general heating and one concentrated on the joint area, plus effective use of heat insulation, firebricks etc. Soldering the foundation ring is not a job for the faint hearted!

Oxy-propane could replace the concentrated torch heating, but is a more pricey option, could possibly melt the copper if care isn't taken.

You might need a 38mm burner (12kw). Note bigger burners need bigger cylinders, 12kw will work off a 19kg bottle not smaller.

You can get vermiculite 9x4.5x1 blocks cheaply off ebay, I got 12 for £25. You can use them to block cold gaps.

Rockwool roof insulation is blowlamp proof if you can find it

Sounds that you need more heat, I have often used a 20 to 30 kW torches and for a well known 7 1/4 gauge boiler, an even bigger torch. I found that it is best to get the job up to temperature as quickly as possible, as even Tenacity No 5 flux can give up after prolonged heating to get to temperature.

I normally use a very large propane burner for general heat and oxy acetylene for say the tubes in a tubeplate. I find it a quicker system and less liable to destroy the flux in a big job.

You need to know what you are doing with oxy acetylene as you can melt the copper with ease. People like Alec Farmer, nearly always used oxy acetylene with or without a propane torch and I think that he was a better boiler maker than most of us ( disclaimer for the pro boiler maker that frequents the forum!).

Andrew.

Which Sievert burner were you thinking of, there, Dave? The only 38mm one I know is the soft flame burner intended for "cable work and other heat shrinking applications", and it is rated at 15KW.

For big heating jobs I use the Pro88 handle [with pilot flame] and one of the burners in the range 2942-2944. These are rated at 26KW, 43.5KW and 86KW.

Bill,

Bullfinch I assumed Sievert would have a similar one.

I could do with a bigger pure propane burner myself, but for smaller hot jobs I use oxy-propane.
As mentioned above though, it produces a small hot flame for concentrated heat in one spot, but not quite hot enough for welding, where you need a fuel gas other than propane. It will happily melt holes in steel, so use with care.

Because of the cost of cylinder rental or deposit, I picked up a DeVilbliss medical oxygen concentrator, with a flow rate of up to about 5l/min; I think I paid £100.
This is plenty for a small heating torch, but not enough for cutting.

Mine came from ebay/Gumtree as the owner was moving up to a larger setup in a shared workshop.
It's a system favoured by those who make glass jewellery etc.

Tufnell Glass is a well known outfit, who can supply concentrators and torches etc.
https://www.tuffnellglass.com/contents/en-uk/d2.html

I'm using a small lead burner torch, that I had in stock anyway, as well as a conventional BOC torch.
I also bought some specific oxy-propane tips, again off ebay, and made adaptors to use them on the small torch.

Bill

Oxy-Propane does not just produce a small concentrated hot flame if you have the correct nozzle.

I recently was silver soldering some bronze parts with a Benzomatic torch on Mapp gas (Mapp gas is hotter than propane) but had a problem heating the part. I gave up after 5 minutes and tried an oxy-propane torch with a heating nozzle. The nozzle has a row of holes that produces a wide flame and even with gas turned down low took less than 1 minute to heat the part and solder the joint.

Paul.

Hi Peter, some good advice here. It is true the heat comes from the amount of gas burnt. The Sievert torch kit we sell comes with the 2941 burner producing 7.7Kw of heat. By changing your burner to 2941 you go up to 26Kw. There are a couple of bigger burners available, please ensure you have a long neck tube as it gets hot!! On the website www.cupalloys.co.uk we have a small video showing the flame profiles of a few burners. As Andrew says it is common practice to use the propane torch to get near to brazing temperature and then use a more precise torch, eg oxy/acetylene or oxy/mapp.

Hope this is of use.

Shaun.

I have both a Sievert and Oxy/Propane set ups. I tend to use the Oxy/Propane for most things as it brings things up temp very quickly and is very easy to manoeuvre around small objects. I use Hobbyweld oxygen bottles which are £33 for a refill (small bottle) and excluding doing a boiler lasts me about 9 months.

Anyone spot my deliberate mistake? It's the 2942 burner that produces 26Kw.

Thanks for the replies. I purchased a Sievert 3525 cyclone burner, is rated at 10.3 KW which is more than twice what I'm using at the moment. Fingers crossed.

One of the nice things about the cyclone burners [I only have the larger one - the 3525], apart from the way the flame wraps around objects up to a certain diameter, is their relative quietness; they emit a much more muted sound than standard burners of comparable size, so you can solder and hear yourself think at the same time.

Hopefully the 3525 is suited to your present job, Peter.

Hi Peter, I posted a similar question not long ago, some of your replies seem less anti oxy propane than mine. The reason for my question was that my boiler (5" gauge, 4" diameter x about 11" long) was pretty much finished but a low pressure soap bubble test revealed a few leaks. Making the boiler I used a 2943 burner (43kw) eventually, having started off with one about 7kw I think, seemed to take all day to reach temperature by which time the flux was shot. Now a big burner seems like a sledgehammer to crack a nut for sealing up a small leak inside the firebox so wondered about using the propane burner to get some heat into the boiler but oxy propane for localised heat build up quickly around the bit to be re-soldered.

I don't have an oxy propane set but looking at the oxyturbo 200 one, about £220 including oxygen, propane, valves, gauges, hose and burners. Oxygen won't last long but I was hoping with a bit of practice that the operation would only take a couple of minutes. Still wavering on whether to go for it or not, have another test to do, this is about three reheats, so if i still have a leak somewhere I will take the plunge and give it a try.

Bill D.

PS I have a 3525 cyclone burner which is about 10 kw, problem I find is that the heat is soaking away into the boiler as fast as it goes in, gets there eventually of course but still seems an awful lot of heat to put in to the whole boiler just get a few square mm up to temperature.

A friend on mine was perplexed at the logic of having to do this but he is a qualified welding engineer and has a lot of experience in the use of and the science behind methods like oxy acetylene, TIG welding etc.

Bill D.

I purchased a Sievert 3525 cyclone burner and it worked a treat. That the boiler seam sealing strip is now complete. Thanks for all the feedback.