OT life of insulated chimney

[jim davies]

Just noticed that the stainless insulated chimney for my wood
stove is running pretty hot to the touch. There is about 12 feet of it,
and it all seems about the same temperature. It's definately cooler than the uninsulated pipe right off the stove but still...

Anyway, my question is how long does this stuff last and is
it normal to get hot like this when old? I'm guessing maybe the
inner liner is perforated...?

[garyphansen]

Clean it and inspect the inside. Replace, if there seems to be a problem. Gary P. Hansen

[Orrin]

A while back I had to replace my insulated stove pipe after 26 years of use. The seams on the inner pipe had come undone.

After removing the old pipe I did a close inspection of it and could see that it wouldn't have hurt to have kept it in service; but I'm glad I replaced it, in spite of the $900 cost.

In the process I discovered a fundamental flaw in insulated pipe. I hope I can explain it in a way that makes sense.

The inner pipe gets much hotter than the outer pipe. It tries to expand radially, but it cannot. It is trapped by the outer pipe and the insulation.

So, when the inner pipe gets hot the only way it can expand is around its circumference. If it expands enough, the edges of the folded seam will "unhook" from one another.

When the inner pipe cools back down, it is highly unlikely that the unhooked edges of the seam will engage one another, again.

Eventually, heat will distort those the edges of the seam and they'll curl inward, exposing the insulation.

I was afraid the insulation would flake alway, but after removal I could see that it was intact. Undamaged. But, it could very well have been.

The lesson to be learned is to not let the fire get too hot nor to allow chimney fires to burn themselves out. If the inner liner gets too hot it is likely to fail. Replacement is very expensive. The rain cap, alone, cost me well over $100 and the only reason I got it that cheaply was because it was used.

Orrin

[jim davies]

I haven't opened up the chimney yet, but examination of the outside shows an accumulation of stuff at the connector between the insulated chimney and the regular stovepipe.

There is a label on some of the segments and although heat affected, the makers name, Selkirk Metalbestos, was readable.

Internet shows they are a pretty big outfit, they are well represented locally and that they claim a lifetime warranty. I have emailed them outlining the situation and await their response.

According to their website, the product is lined with mineral wool and that is what I think has shown up at the lower connector. So, I suspect that one of the segment's inner liner
has perforated [or disconnected as above] and allowed the insulation to fall out and the heat to get in.

I was gonna tear it apart today, but I will wait to hear about the warranty situation.

[Alistair Hosie]

Don't take chances with these type of things your life and the lives of your family are too valuable.Please get someone who knowsabout these things,someone that you can trust to look at it perhaps an expert and take it from there.Alistair

[bruto]

Metalbestos chimney is pretty easy to take apart, so if you can't find an expert who can do it in place, you might be able to disassemble it and inspect the liners one at a time. But first, I'd await word from the manufacturers, to see what kind of warrantee support they have, and what they recommend.

[jim davies]

Good responses, thanks.

I am awaiting word from the mfr. Other than the part going through the roof, the rest is an easy one screw per segment removal.

Living 60km from the closest town makes DIY an easy choice.

[jim davies]

Still waiting for a reply from the mfr. Doesn't say much about there support...

Anyway, got sick of looking at it so I took it appart. One of the sections has a slight amount of buckling in two areas, each about 1-2 inches long. The liner is a bit loose [moves up and down some] but overall it looks okay. All the other sections look good, and since they are still solidly packed with mineral "rock" I can't see a problem. But the sections were darned hot to the touch the last time the stove was lit. If there had been a chimney fire, that would have explained the heat, but there was no sign of that at the time and I can see nothing with it disassembled. The chimney needed cleaning, there was about 1/2 inch of dry, loose flakey carbon inside that brushed out easily. No creosote at all.

I'm thinking I'll just reinstall it...