Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

So, I’ve been running this boiler and it performs better than any boiler I’ve used, but I noticed recently that the center flue glows orange under heat.

Generally speaking this is bad, as you always want water touching metal under a flame to prevent damage to the boiler.

Is that center flue a different type of metal to withstand higher temperatures, and not melt or blow up?

I have a photo here: [ Guests cannot view attachments ]

The photo ain't the best....but to me it just looks like crap on the super heater tubes that's glowing red, not the actual copper super heater tubes.

It glows red, for sure. Camera just can’t pick it up too well.

Looks to me like perhaps your heater surface is a bit too narrow and your flame a bit too high. The outer thermic syphons are receiving no flame at all, while the ones on either side of the central thermic syphon appear to be "funneling" the oversized flame onto the central syphon. I believe best practice with the ceramic heating elements is to have very little flame above the ceramic surface, while the actual heating is done by the radiant heat, "orange glow" of the ceramic material itself.

This BIX burner is the one designed for the 504 boiler.   I suppose I can lower the flame by turning the gas down, but the fire naturally centralizes.

I do know you don’t want any orange glow in your ceramic. It will incinerate it. You want blue flame with no orange fire or orange ceramic.

I have verified this through BIX and Keith Appleton; unless you’re referring to something else.

I’m not sure if I should raise the burner up higher or lower, or what.


I know the superheater flue has to get very hot and does not touch water, but the silver solder around the superheater flue is touching water.

That would be Orange Glow not bright Yellow or White hot. If you notice in Keith's video, when he says it is just right, the ceramic is glowing with a dull Orange Glow perhaps fringed with a bit of pink, and he doesn't have a large blue flame rising above the surface of the burner, but rather small blue triangles of flame at each hole.

Alright.

I’ll give it a whirl.  I wrote to Stuart about the center flue. I’ll update you with what they say.

Pretty sure there is nothing different about the center thermic syphon. I'm rather certain that all five of them are made just the same.

I just worry about the center flue not having contact with water, and it’s part of a pressure vessel.

Valid concern ..... how about lowering the burner to spread the heat wider?

That’s what Stuart said. They also said not to worry, the burner can’t get hot enough to melt
The center flue.

I did lower it:

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