Has anybody successfully managed to dismantle a paraffin stove burner (roarer or silent) into its component parts without damage? I've tried a few times but have been on the verge of melting the brass without loosening the joints. The filler material used at the factory must have had a melting point very close to that of the brass parent metal! I suppose a thermostatically controlled furnace would be the solution but I haven't currently got one at my disposal.
@Blackdog I have tried once Chris, i remember quite a few years back i was repairing a either a stove burner or a blowlamp burner, that had a crack in one of the sil brazed joints and decided to completely remove the top part of the burner, to thoroughly clean it before re brazing and one of the tubes actually melted. I used for this purpose my Sievert paraffin brazing lamp, as it had a large enough flame to cover both tubes, that had the best chance to equally bring both joints to the melting temperature, but unfortunately it failed
Thank you both- confirming what I expected! I need to replace the burner tubes on an old favourite, and have been getting bogged down trying to save as much of the original material as possible. Enough of that, I'll cut the tubes off, drill/file the remains from the head casting, hex fitting and nipple seat, bend and silver solder in some new ones. I'd love to know the composition of the original filler material though. It must have taken some skill to assemble burners without melting the thinner components!
Hi, I successfully transplanted the burner threads, without cutting the tubes. One of the donors: The receiver: The prepared parts: Some dremel work was required to make a perfect fit for the receiver tubes. As visible in the photos, is evident the different shape of the receiver tubes if compared to the donor burner ones. I have to say that the original braze material didn’t “melt” or didn’t look melt like the modern braze rod looks like when reaches the temperature. So no visual help to understand when was the moment to extract the part. Some tapping was required to extract the part and also while heating to individuate the right moment to extract. So, this to say that if you wait to see something melting, probably will be too much heat and the burner brass will melt together with the joint. Not an easy operation by the way… at the required temperature it’s easy to deform the brass parts (fatal for the threads)… so also a strong and firm clamping was not possible during the job. Nicola
The burners are assembled with tight joints and probably also some tension that keeps them all together before the brazing. So, in case of dismantle, the only heat is not enough… the parts need to be mechanically extracted/separated while at the right temperature. I think this is the most complicated thing… with only two hands available Nicola
Thank you @Nicola Francesco Elia, great to see you've managed it, very impressive work! Perhaps I will try again on my expendable burner I was anticipating having to tap the burner apart and made a basic tool to hold the head casting which clamped in a vice, and another to grip the hex nut which I could tap. No go though, perhaps I was being too gentle, I was very conscious of how easily deformable everything was when heated.
@Blackdog in the color scale of temperature, if I remember, the moment was the “glowing orange”, third step after cherry red and glowing red So probably orange/orange-yellow was the range for the loosening of the original joints: Clearly each burner can have different filling material, but I guess they must be all similar.
That sounds right- very close to the melting point of brass! I've done a bit of brass casting and can picture the temperature it 'flops' at, and also managed to melt a brass casting as a youngster during my early days of silver soldering. Granted that was a fine detail casting on a model, but it's still a horrible feeling! It's all a bit nerve wracking with such narrow margins. I imagine the filler was mostly brass with just enough further alloying to bring the working temperature down to something achievable on a production basis.
Yes, I would approach the dismantling part by part… the hex component I think is the simplest to remove because it’s a more solid component that can handle some tapping… The tubes by the way are very delicate and also if I haven’t tried to extract them I guess they would be impossible to grab without squashing them at those temperatures… I would try to wrap the head and hex with some steel wires and use the wires to keep the burner in extraction tension using a vice… then heat the whole burner while opening the vice more to see if the parts can be pulled out by the wires… Not sure if my idea is clear
Nicola’s observation that “the original braze material didn’t “melt” or didn’t look melt like the modern braze rod” is correct. It takes higher temperatures to re-melt braze joints on copper alloys. Manufacturers of brazing rods add certain elements to decrease the rods’ melting and flowing temperature. This allows brazing at temperatures safely below the melting point of the copper parts. Zinc, phosphorus, tin, cadmium, and probably lots of others I forget, reduce the braze rod melting point. They also control the flow and wetting action of the molten metal. Some of these elements are lost to chemical reactions or evaporation during the braze heat cycle. So the completed braze joint stays solid at the temperature originally used. We must use a higher temperature to get it loose. Soldering is a different story. Solder alloys do not change their chemical composition during heating, so we can disassemble and remake solder joints with relative ease.
Just an added detail that might help. Placing the part(s) in ash will hold them still while heating them up. I did that to braze a piece to a flame ring that would have been difficult to hold.
In the US, we have copper phosphorus brazing rods, made especially for doing this kind of work! Bernzomatic | Copper Phosphorus Brazing and Welding Rods | PC3 They also require no flux, a big benefit when doing our kind of work! Murph
Very likely the original filler material contained cadmium. This began to be phased out in the 70s in the UK, and was legislated against completely some time ago. There was a well publicised incident when a worker used an oxy-acetylene set during silver soldering (excessively hot, concentrated flame for this work), vapourising the cadmium content of the filler rod and died from inhaling the vapours.
@Murph et al Bernzomatic | Copper Phosphorus Brazing and Welding Rods | PC3 Will work with a MAPP torch or does one need oxy-acetylene (temperature wise)?
