Rotting Steel Chimney Pipe - Causes and Remedies.

 
lonerinalaska
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Post by lonerinalaska » Sun. Jul. 17, 2016 9:20 am

I have a Harman TLC 2000 coal stove. I have been using the stove for 5 years. I designed and had my chimney fabricated. I used 6" steel (presumably cold roller) and I believe it was 3/16" thick, 18' long. About halfway through this last winter, I noticed what appeared to look like burnt spitwads sporadically appearing on the stove pipe. Come to find out, the pipe was rotting. I just took the pipe out and in some areas the steel was paper thin. The internal part of the stove around the top loading hatch is also slowly burning away, though much slower. The rest of the stove appears to be in good working order. I also noticed on the pipe that the closer to the top,the thicker the pipe still was.
Throughout some of the winters, we did not have a chimney cap. We would start out with a UL listed store bought one, but they would quickly corrode and blow off after 1 to 2 months. I was never brave enough to traverse our ice covered roof to replace it, so we would leave it until spring. We burn beach coal, bituminous coal that gets washed ashore at a nearby beach. So there is salt on the coal. I also store the coal in the garage, so it is dry.
My question is, what is the likely cause of the rotting pipe? Is it strictly the acid from the burnt coal, or could it have been that water was able to enter the pipe most of the winters and it mixed with the coal smoke. Does regular steel not last long with coal? I just replaced the pipe with 6" well casing, which is substantially thicker and I am hoping to get more than 5 years out of it.
I am trying to find a metal that will last a lot longer so I don't have to replace the pipe many more times before I die. I don't like the thin store bought stuff. I used the heavy pipe so that when I am away from home, I don't have to worry about a chimney fire burning down my house, which up to this last year would have easily handled the fire.
One last question, what grade of steel does Harman use? I have been fairly impressed with the stove, but I think next year I am going to take the stove to a fabricator and have them build a new burn box with much thicker steel, preferably with the same grade that Harman uses.

Thanks for any suggestions and knowledge.


 
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freetown fred
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Post by freetown fred » Sun. Jul. 17, 2016 10:24 am

Tough to say L. Sometimes it just is what it is. Coal, steel quality, etc??????????? I've got a buddy that put up a well casing pipe & has not had a problem for going on 10 yrs. (no cap) Hopefully it'll work better.

 
lonerinalaska
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Post by lonerinalaska » Sun. Jul. 17, 2016 10:34 am

What kind of coal and where did he get it?

 
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freetown fred
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Post by freetown fred » Sun. Jul. 17, 2016 11:43 am

Anthracite--(NUT/STOVE mix) from Pa. a lil south of you!! :) I'm bettin you'll have better luck w/ the well casing no matter what coal you're using. I'm thinkin it's about 1/4 inch thick. You're gonna GET more corrosion with your beach/bit--trick is doin the best ya can with what ya got!

 
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Post by davidmcbeth3 » Sun. Jul. 17, 2016 11:55 am

Flexible v non-flexible? I went flexible .. Hitzer recommended this.

What to do? Replace liner is the solution.

Looking for why...very complicated question.

 
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warminmn
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Post by warminmn » Sun. Jul. 17, 2016 12:31 pm

Salty bit coal is going to be about as bad as it gets corrosion wise. Its hard to beat the price your paying though, which will help make up for your chimney problems. A masonry chimney would be best, but a well casing should last a long while too. Try it and see. Good luck!

 
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Post by ONEDOLLAR » Sun. Jul. 17, 2016 1:41 pm

warminmn wrote:Salty bit coal is going to be about as bad as it gets corrosion wise. Its hard to beat the price your paying though, which will help make up for your chimney problems. A masonry chimney would be best, but a well casing should last a long while too. Try it and see. Good luck!
Loner... WELCOME TO NEPA!! You are not alone on this site. At least when it comes to members in Alaska. There are a few and one just moved up there. Glenn Harris.

I would say the combination of the bit coal with salt and then add the moisture and the recipe is there for rust and lots of it. The well casing is a great idea but I think if you can put in a masonry chimney with a terra cotta liner your problems will forever be solved. That a FREE coal and you are on EASY street for heat! WOO HOO!!! :lol:

Just curious but what is the frost line in your neck of the woods. Here in New England it is 3 feet. I would imagine a solid footer for a chimney in your area would need to be pushing 5 feet to account for frost heave.


 
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Lightning
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Post by Lightning » Sun. Jul. 17, 2016 3:05 pm

A stainless steel chimney cap would last much longer. With us guys that use anthracite coal the problem is fly ash. Our breed of coal is rich with sulfur compounds that when mixed with moisture creates sulfuric acid. I can't say for sure if your coal would be sulfur rich or not.

As for your well casing chimney pipe, my preventive maintenence would be to climb on the roof every spring and hose it out real good to wash away any fly ash that is clinging to the sides of the pipe. This is what I do with my stove pipe between the furnace and chimney. Of course I disconnect it all beforehand.

 
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Post by lonerinalaska » Mon. Jul. 18, 2016 4:20 am

Putting in that kind of chimney is completely impossible with my set up. I was contemplating some kind of cement or clay liner that would fit perfectly inside of my well casing, I just want to know that the clay or cement will last most, if not all, of my remaining years (hopefully another 30-40). I figure the steel casing around the clay / cement will give it rigidity and chimney fire resistance qualities that I want. I would assume this type of setup would make the steel last just as long.

Do you know of any websites that might offer the kind of liner I'm looking for?

In my area the frostline is 4-6 ft, probably less most years. Our winters are long, but quite mild compared to the rest of the state.

As far as chimney caps go, I took the left over well casing and making a "T". This design has worked out perfectly last year.

 
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freetown fred
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Post by freetown fred » Mon. Jul. 18, 2016 7:47 am

L, if that well casing is 1/4" as I'm familiar with--you're not gonna get any more rigid. 30-40 yrs??? You're talkin mason now! What's your casing diameter & thickness?

 
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Post by McGiever » Mon. Jul. 18, 2016 8:02 am

L, any way you can insulate that chimney pipe?

The less the exhaust gases cool off the less condensation into corrosive liquid.
Keep that corrosion in vapor state to be expelled into air and not condensed so much into liquid state inside your stove pipe. :idea:

 
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Post by blrman07 » Mon. Jul. 18, 2016 8:38 am

I never heard of sea coal or beach coal until this post. :shock: I looked it up and sure enough it's a legit source. Several theories abound from coal being liberated from pre WWW2 ships rotting away and the coal getting washed out, to underwater seams being broken up by wave action. I watched a video about a guy that makes a living going to the beach and shoveling up coal, bagging it and selling it. The government tried to ban it but couldn't because the beaches were public property and they were providing a service by cleaning the beaches.

Nuts huh.....I can assure you that if that happened in the lower 48 the government wouldn't ban it, they would figure out how to tax it. :mad:

 
lonerinalaska
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Post by lonerinalaska » Mon. Jul. 18, 2016 9:03 am

McGlever - My chimney is not insulated and the design doesn't really lend itself to insulating it. What you said seems logical, but in reality it seems to work the opposite. The top of my chimney, which is obviously outside, had very little wear, whereas the bottom of the stack had the worst corrosion. The stove probably averages 200-300 F throughout the winter, with occasionally hot bursts like in the morning to get the chill out or when we have lots of cardboard or other stuff to get rid of. Here in Alaska, we don't have trash pickup, but rather there are several dumps throughout the borough were people can freely dispose of there thrash. Much to my wife's dismay, I'd rather burn our burnable waste and heat the home, rather than pay for gas to drive to the dump.

brlman07 - Your theory sounds interesting, but the source of the coal is from one of the largest seams in the world. The seam is about 1/4 mile wide and is located under the Cook Inlet on its west side. Stormy weather breaks it loose and it gets washed ashore. I don't have an old beater truck right now, so I pay someone about $125 a truck load (about 1.25 tons). I go thru 5-6 truck loads over about an eight month period. Right now, thanks to tree huggers and the like, the coal cannot be commercially accessed People on the Kenai have been using this source to heat there homes since at least the 1940's.

Freetown Fred - Ya, this new pipe is 1/4". I think the next time I have to replace it, I'm going to use some of the 316Ti flue liner on the inside of the well casing and see what kind of results I get.

Meanwhile, can anyone tell me what grade of steel Harman (currently Legacy) uses on there coal stoves? 304/304L, 316/316L, 316Ti, basic run of the mill carbon steel? You'd think the internet could answer this, but I haven't been able to find anything.

 
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Post by franco b » Mon. Jul. 18, 2016 9:30 am

I think the corrosion is from condensation. Because the pipe is so cold it is occurring low down and the upper part then is drier.

I like the idea of an inner liner which will insulate to a degree as well depending on how well it traps air from circulating between the inner and outer walls.

A well sealed chase on the outside of the pipe should also help.

 
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Post by Lightning » Mon. Jul. 18, 2016 5:16 pm

franco b wrote:I think the corrosion is from condensation. Because the pipe is so cold it is occurring low down and the upper part then is drier.
Such a smart man :)


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