Black fire cement?

[bungeejumper]

The black enamelled flue pipe on our Rayburn boiler is sealed in several places (or certainly should be!) with fire cement, but it tends to need redoing every year because the standard ready-mixed stuff goes brittle and shakes out into a pile of pale dust. Who'd have thought that half a tonne of cast iron could vibrate that much?

I am about to do the job again (sigh), but the last time we had the boiler serviced, the specialist engineer used some black fire cement that seems to have stayed the course better than the usual stuff. Anybody know what it might have been?

(Important note: We do, of course, have a monoxide detector beside the boiler, or I couldn't sleep at night. Just sayin'. But I do like to be double-sure where flues are concerned.)

BJ

[richlist]

I have a wood burning stove that needs 're-sealing most years. I usually get black fire cement from my local stove supplier but I would think it's readily available online if you don't have a local shop.
The secret to making the cement last more than a year is to not apply it to thickly.

[Loir]

You can get die for colouring it. It's a very black powder.
Mix it in before adding water.

Steve

[DrFfybes]

(Important note: We do, of course, have a monoxide detector beside the boiler, or I couldn't sleep at night. Just sayin'. But I do like to be double-sure where flues are concerned.)
BJ

It isn't the going to sleep that is the problem....

I wonder why they don't use exhaust assembly paste? It is supposed to resist up to 1000C, and if it can live in the exhaust system then it should cope well with vibration.

Paul

[bungeejumper]

It isn't the going to sleep that is the problem....

Amen to that. I had a close call with an anthracite stove in 1970s Berlin that was nearly the end of me. I remember getting sleepy in the early evening, and the next thing I knew I was crawling to the toilet with a thousand pneumatic drills in my head. Broke two teeth while talking down the big white telephone. The neighbours heard the crash and rescued me. I was quite lucky to have woken up at all. Had occasional pounding headaches for several years afterwards, which were not attributable to my youthful lifestyle.

I wonder why they don't use exhaust assembly paste? It is supposed to resist up to 1000C, and if it can live in the exhaust system then it should cope well with vibration.

I'd hazard a guess that it gives off bad chemicals which wouldn't matter in the open-air world of a car but wouldn't be good in a home. Either that, or it seals things up so firmly that you couldn't dismantle stuff without breaking it?

BJ