Liners...Pre-fab vs. Custom

[boatboy63]

Since I have been reading around here for the past week or so, I have learned alot. I got to reading about liners last night and am confused. After looking on ebay, I saw where most 6" liner kits are somewhere in the neighborhood of $350-700+. After reading further into it, I saw where most of them are only .005" thick. This is 5 thousandths of an inch, which is about the same thickness of a hair. The thickest I saw was .014, which would be about the thickness of a razor blade. This just doesn't seem very assuring to me, since it is so thin.

I know these are stainless steel, but just wondering why someone couldn't make their own rigid one out of 6" steel tubing/pipe. It shouldn't be a problem to get this in a 1/8" thickness, which would be .125" or 9 times the thickness of the thickest I saw. I then thought about the pre-fab liners being stainless steel and probably having a higher melting point. After a little research, I found that stainless has a melting temp of around 2500-2600°F. Mild steel, which is what the steel tubing is made from, has a melting temp of 2730°F. Advantage...mild steel. The next issue is that stainless will not rust, if it is the right type. Mild steel will. Advantage...stainless. The counter argument for mild steel would be that it is 10x as thick. Also, the mild steel would be coated with a slight coat of creosote within a week, which would inhibit rusting internally. The outside of it could be painted with high temp paint to preserve it.

The mild steel tubing would cost alot less and be much stronger. Could somebody tell me what I am missing here?

 

[mikeyny]

first thing that comes to mind is 9x thicker equals 9x the weight. Maybe a bit overkill, err, over weight.

 

[DaveBP]

The mild steel tubing would cost alot less and be much stronger. Could somebody tell me what I am missing here?

I think what you are missing is faith in metallurgy. It's not the melting temperature that's important but the ability to resist long term corrosive effects of the gases that condense in the pipe.

The flue liners that I'm familiar with are the corrugated flexible types. They come in different alloys of stainless steel. 316 stainless is the type I've seen rated for coal exhaust so it can take the potentially high sulfur (very corrosive) fumes and I think it is probably the best alloy for this use. Even if only a few thousandths thick it will outlast mild steel, especially if this chimney is outside the building wall.

And it will be easy to snake down a chimney compared to a rigid, straight pipe. Did you figure in the cost of the crane for the steel tube? Even at 1/8" wall thickness it's 8 lbs/ft.

 

[Gooserider]

Wood smoke / creosote is HIGHLY corrosive - it will rot out a mild steel liner in very short order, which is why it is a serious code violation to put steel stove connector pipe in a location where it can't be readily inspected...

As a comparison, you can get single wall rigid stainless connector pipe, which has about the same thickness as black steel connector pipe - the SS pipe is hard to find because it's about 2-3x the cost of black steel - however the difference is that if regularly used, the black pipe will rot out in just a few years, while the stainless will last just about forever...

Gooserider