Gas burner suicide

jamespetts · Gas burner suicide

As documented in another thread, I had been having difficulties in getting enough steam out of my boiler, and had traced the difficulty (with the help of other members of this forum) to the heat source, a Bix ceramic gas burner supplied by Forest Classics. Initial suggestions had been to raise the burner to make it closer to the boiler's water-tubes (the boiler is a Stuart 504), and to reduce the jet size from a no. 16 to a no. 8, which I duly did, but without much effect. The burner was not glowing as it ought to be, and the flames were far too big.

I then wrote to the nice people at Maccsteam, who make ceramic burners themselves, and a helpful gentleman replied and suggested that the jet was not properly sealed, the leak reducing the gas velocity and therefore making the mixture far too rich. I duly sealed up the thread with PTFE tape, and it worked very well: the surface of the burner started to glow first red then bright orange within a minute or so of first lighting it. I did also try putting the no. 16 jet back (sealed), but, although it was far better sealed than unsealed, it was not as good as the no. 8, and I could not get the burner to glow properly with the no. 16, so I replaced the no. 8.

To-day, I tried using the burner in the boiler. Although some people had quite strongly suggested moving the burner to the end of the boiler furthest from the chimney to improve heating efficiency, I kept the position as it was (at the chimney end of the boiler) for this test on the basis that it is better to change one variable at a time. At first, everything seemed to go well: the burner lit quickly, and almost immediately started glowing a bight red: so bright, in fact, that the whole inside of the firebox was well illuminated.

In the meantime, since the last run, I had posted on another forum about how to stop the inside of my cast iron cylinders from rusting, and had been advised to fill them with steam cylinder oil after every run. This I had done, but had some difficulty in getting the oil out of the cylinders, having turned the engine over forwards with all the drain cocks open and finding still a significant amount of oil inside. Whilst I had been turning the engine over, even though the drain cocks were open, a quantity of oil had seemed to make its way up the exhaust pipe to the bottom of the chimney, through which the exhaust steam was ventilated. I had resolved to let the pressure of the steam push out the remaining oil.

With this in mind, I was not alarmed (as perhaps, in hindsight, I should have been) when, less than five minutes after I lit the burner, a large quantity of smoke started emanating from the chimney. I had, after all, on my last run, had an oil fire inside the chimney, producing significant amounts of smoke.

Perhaps, on reflection, I ought to have been a little more cautious when I noticed that the whole of the ceramic burner, even underneath, was glowing red hot. I thought at the time, however, that a burner designed to produce a great amount of heat would be designed to withstand that same amount of heat, and thought no more of it; until, that is, I found a few minutes later that the back face of the burner, which, as far as I can gather, had been brazed onto copper-clad steel, had dislodged from its surroundings, the silver solder evidently having melted in the heat.

By this point, the smoke had stopped, and only the back of the burner seemed to be glowing at all (although it was glowing very brightly). The boiler had got up to 25psi (and far faster than before), but was now waning in pressure. The steam engine itself, perhaps invigorated by its internal soaking in oil, ran very well considering the lowness of the pressure, but very little steam was, in the end, produced.

When I removed the burner from the boiler after I had run the steam engine for a little while, here is what I saw:

The paint on this riser can withstand temperatures of up to 450° Celsius

I have just uploaded a video of the whole incident to YouTube:

(If the embedding does not work, here is the link).

I am still baffled as to how a ceramic burner, designed to produce great quantities of heat, can itself overheat so much, with such destructive consequences. I wondered whether the burner was too close to the water tubes, so that a great deal of heat reflected back onto the burner, but all of the Maccsteam boilers are designed to have ceramic burners in very close proximity to the boiler surfaces, in an entirely enclosed environment, so I am perplexed as to why my burner in particular should fail so spectacularly in those circumstances. Is it, perhaps, an inferior burner to the Maccsteam models? Or am I doing something terribly, terribly wrong? Any advice would be very much appreciated indeed.

Florian

Hi James

Ouch.... What the heck?

Looks like the flames had burned in the inside of the burner...

Well... you need a new one i guess....

In your situation, i would give a feedback to the maccsteam people.

Just; what is that stuff in your firebox? is it glass wool? And did you also put it between the watertubes and the boiler? Or does it just look like that in the picture?

Florian

jamespetts

Florian

I think you should let some more "air" to the walls of the firebox. (so that the burner has at least 1.5 cm on each side. It maybe also happened because the heat was stored in your firebox. I also would install the burner a little lower than you had it up to now,
So that there is at least 2 cm to the tubes. (on the lowest point of the tubes)

The flame gets back into the burner (i'm shure there is an expression for this; like "backfire" or something similar ??

)
if something is not right; i don't know what exactly is needed for this but i know that some guys use a fine strainer to prevent the flame getting into the burner.

What do you want to know with "how do you tell" ??

If the burner's from bix, id give a feedback to bix.

And maybe you can ask the Maccsteam people what could have happened.

jamespetts

I took the ceramic off the top of the ill-fated burner, and here is what I found:

The chalky gunk at the far end of the underside of the burner had been blocking up holes: this explains why a semi-circle at the far end never seemed to have any flames:

Interesting construction inside:

The fire evidently got so hot that the ceramic itself melted:

As to Florian's theory about flames being inside the burner, I think that I have worked out how it might have happened: as can be seen at the beginning of the video, I lit the burner, not by holding the match near the top of the ceramic, which is hard to reach, but by holding it near the jet. The flame would then have been sucked into the burner, and lit it. But, unbeknownst to me, it has evidently burned within, as well as on top of, the burner, destroying it from the inside with a quite extreme level of heat (if it is enough to melt ceramic and un-braze a brazed joint, then it must be quite something). That would also account for why it did not destroy itself when I tested it earlier outside the boiler as, being easier to access, I lit the ceramic from the top, not the jet.

The next question is: do I go back to Bix for the burner, or do I get a possibly more solidly constructed one from Maccsteam? I am currently leaning towards the latter (even if the burner suicide was caused by lighting the jet rather than the ceramic, there is still the issue of the glue blocking the holes), especially since it does not cost any more.

Les

Not a pretty sight, but since you had trouble before with that burner I would go and get a new one from Maccsteam.

Florian

I would also get one from maccsteam.
and im shure, they also can tell you how big it needs to be. I thing this size of burner should be just the right size; anyway, go and ask them.

Igniting at the jet is no good idea; that was clear for me...

This will also destroy other ceramic burners! So you shouldn't do this again with any other burner.

jamespetts

Les and Florian,

thank you both for your help. I have e-mailed the helpful man from Maccsteam to place my order.

I shall definitely remember not to light a ceramic burner at the jet end again!

tmuir

Wow that got hot.

I use a similar ceramic material to make jewellery from and I know that can take some heat.
I once balled up some 3mm sterling silver wire and used my ceramic sheet as a back drop to reflect some of the heat back to give me a more even ball.
I directed a Mapp gas burner at the sheet for about 30 seconds and although it did cause a small melt mark on it, it wasn't as big as that one.

MooseMan

For what it's worth, I use a Maccsteam burner in my 3 1/2" marine boiler, and it works a treat.

I think I have a fair idea of what happened...I don't think it matters where you light the gas. The reason these burners work well is that they are catalytic, ie. they accelerate the oxidation by having a large burner surface, which in turn becomes hot, further accelerating things.

Looking into your firebox, the space for the burner seemed very enclosed, with lots of insulating packing, and the only ventilation appears to be the firebox opening and the chimney, creating a through draft....great for coal, but not ideal for gas, as what you created was, I think, a small blast furnace, maybe started off by an oil fire.

I'm not exactly an expert, but I'd suggest you give the burner a bit more space, and possibly make a firebox door, to prevent the trough draft.

xlchainsaw

i agree with mooseman at the end but i believe the burner was defective before this melt down. hard to prove now but due to previous trouble i suspect it could have have been a bit of ceramic cement blocking something(from the factory) or burner blowblack from previous trials melting the inner coil which in turn would cause the burner not to heat all over which was the case before melt down.the burner didnt look healthy prior to the trial . i would be sending it back to the manufacturer complete with the photos! they will likely blame blowback rather than faulty manufacture but it would be good to put it to them.

mogogear

You also described that a fair amount of cylinder oile may have been pushed out - into the chimney- and it could have dripped down into the burner itself.. This could have focused the flame points below the surface of the ceramic..

I think you have more than one factor leading to this "inferno" .........

jamespetts

I am slightly confused by the suggestion that the fact that the burner is enclosed is part of the problem, since many ceramic burners are used in even more enclosed environments: the Maccsteam website, for example, shows burners inside enclosed firetubes, or inside the smoke boxes of locomotive style boilers. Are you sure that it is not the lighting of the gas jet?

Florian

Hi James

But on the examples you just made, the housing of the burner always is free so that the heat can get away. In your case the mineral wool has also stored heat in your firebox instead of cooling the burners housing. I recommend you remove the wool which is lower than the burner (so that the burner gets cooled)

The burner story already made it to the german discussion board where i am also a member. And what i wrote in this answer was also said by some people in this board.