double wall insulated pipe question

[green acres]

Hello, I just posted this question on yesterdays tractors forum, and was directed to this site for the first time . I installed 8 inch double wall stainless pipe on my stove almost 20 years ago. I have noticed recently that the pipe is hot to the touch { can hold my hand on it 2-3 seconds] It runs straight up through the ceiling and out the roof, I cannot recall if the pipe was that hot when I first installed it. My question, can the inside of the pipe deteriorate and not be visible ? I have looked at both the outside and the inside as mush as possible with a flash light. Thanks in advance Dave

 

[DAKSY]

I'd get a chimney sweep in to run a video camera down the inside in order to determine if the inner
sections are compromised. That's probably the only way to get an accurate look at it...

 

[Hogwildz]

My double wall gets hot on the outside shell. Your only talking about 3/8" or so of insulation between the layers. it won't glow, but it will get hot.
Normal for my set up.

 

[Dave_1]

fwiw mine is metalbestos & will be 30 years old next fall.

Did an inspection 2 years ago & the sections looked good.

But being concerned I called the factory & asked the tech rep what was the normal life expediency.

Was told they knew of customers with 30 years + service & were still going.

Yes, it gets hot. That's the reason why there is to be 2" clearance to combustion surfaces.

Come spring take it apart on a sunny day clean it & inspect it for any pits.

Good luck with it.

 

[grizzly2]

Be aware that some double wall stainless chimney pipe have galvanized steel ends. Water gets between the two pieces of pipe and rusts the ends out. Then water gets between the two layers of pipe and soaks the insulation. Each occurance I have seen has been on pipe above the roof flashing, not surprisingly. I just thought this was related to to topic, though not your hot to the touch problem.