Hi I have got my hands on a petromax 829 and it has a metal burner nozzle instead of a ceramic one. Should I change this for a ceramic one and what is the difference between the two? Many thanks
In my opinion the ceramic nozzle is much better. If steel would have been better they would have used that in the originals as well. Steel (even stainless) is oxidating in flakes in my experience and would contaminate the mantle.
Many thanks for your reply. After a bit of research I see you are right and so will change it to the ceramic one
The (stainless)steel version was a brainfart I guess. At least for the Petromax lanterns, there where however other companies who had standard a metal burner head. Mind you also a different shape.
But to my knowledge they never used (stainless) steel for the burner heads, as iron oxide is not stable. And the metal mesh that was used in the brass burners (e. g. at Hasag) was often worn, but could be replaced easily. I don't even know from which metal that mesh was made.
Steel has a different thermal coefficient than brass, it expands more than brass and brass being soft will get stretched with subsequent use. Eventually the threads of your mixing chamber will get so stretched that there's a chance your nozzle will simply fall loose and you'd need to replace the mixing chamber above it. The best nozzle are the alumina oxide ones, they have very low thermal coefficient and can take a decent beating, it's harder and tougher than ceramic and leagues better than the clay ones currently sold. If you're worried about stretching out mixing chambers, I guess you can also get a nozzle made entirely of brass, expands and contracts at the same rate with all your brass parts.
@Martin K. , I didn't say stainless. Indeed HASAG did as well as BAT and later on E. Schatz / M. Aschwanden. As far as I know HASAG used steel (?) metal gauze. It was also part of the spare parts. @Dashwood , I guess most of the wear on the burner/J-tube comes from a loose fit and escaping flames. The loose fit comes from the difference in expanding. That is way you always should check if those parts are still well connected.
the connection between the jtube in mixing chamber is not the problem as those parts are brass on brass. It's the mixing chamber and nozzle that should be a concern if you use the steel nozzle. Ceramic, Alumina, or brass is fine.
The geometry, point-location and construction of the Petromax's burner cap is such that, it will be heated to a bright red or higher colour-temperature glow. That indicates estimated temperatures of at least 800°C or higher(approaching that of the flame, ~>1000°C). Under the usual operating environment, almost any metal would tend to oxidize. If thin enough, they'd just burn up. Steels or stainless steels would lose all their 'good or favorable' properties under that condition in the presence of oxygen. The temperature isn't high enough to melt steel or stainless steel but it is high enough to accelerate oxygen-attack on the metal. Ceramics, clays or alumina(Al2O3) and other refractories are oxidation-resistant, since they are already fully oxidized.
An exception, THIS Prabhat has thrown up a plethora of problems to be (successfully) resolved. This solution (photo below) to sloppy ceramic burner threads held, but the threads holding the assembly onto the J-tube were also very poorly formed and sprouted flames past them, then the burner assembly fell off. Replacing the mixing chamber with one from a Petromax provided a strong gas-tight joint with the J-tube, but perverse metal expansion resulted in this fracture of the Petromax ceramic burner. Not wishing to waste a succession of replacements I utilised a stainless steel burner coupled with the Petromax mixing chamber, a combination that is so far doing fine after several lengthy firings. Not shiny steel anymore, but nor has it as yet shed oxide into the interior of the mantle. A solution - temporary? - for the Prabhat but it doesn’t make me an advocate for steel burners, for the reasons already stated in others’ posts. John
