Post by jamespetts on Apr 20, 2008 19:35:45 GMT
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 a number of people here had suggested changing its position to the other side, 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 illuminated.
In the meantime, since the last run, I had posted another thread 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: it can be found here.
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.
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 a number of people here had suggested changing its position to the other side, 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 illuminated.
In the meantime, since the last run, I had posted another thread 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: it can be found here.
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.
...One suggestion, what with all that heat , it would not do any harm, and possibly be wise to do another full Hydraulic check on your boiler integrity.
