Welded pipe and expansion rates

[Sutol]

I'm going to weld together some 3inch dia pipe as a new chimney for my stove in the garage.

the pipe is to go up from the stove for about 3 feet then diagonally across the back wall for about 12 feet then up and out of the roof for about 4 feet.

The reason for going across the wall is that the pipe acts like central heating for the garage as it runs along the back wall.

The pipe we are replacing is stainless flexi pipe usually used as a liner in a brick chimney and it is getting past its sell by date due to the extreme heat from the stove.

My worry is that the solid metal pipe will expand and move horizontaly along the wall and then will disturb the roof where it goes through as it will no longer line up.

Am I worrying about nothing?

 

[bearcreek paul]

3 in pipe is small for a for a stove.I had a Franco belge coal stove that used a 4 in stove pipe and that's the smallest that I have herd of.
Your best way to do it would be to run it straight up. You would pickup some heat from running it the way you wanted to but it might affect your draft.
The smallest pipe I run now is 6 In and that is on a stoker with an inside chimney that does not get too cold and only has 1 elbow in it.
As far as expansion you should have no worries.

 

[Shield Arc]

How about buying one of these, and reducing it down to 3-inch?
Magic Heat 6" Wood Stove Heat Reclaimer | WoodlandDirect.com: Wood Stove Accessories, Wood Stove Fan, Fans & Heat Reclaimers

 

[deereman75]

You might want to put a piece of flex hose in it for an expansion joint, that was it could expand without causing a problem.

 

[yomax4]

I agree on the draft. You would likely have to force draft it somehow. We did that type of thing with an ice fishing shack and the small pipe wouldn't draft until we took out an elbow or two. As far as going through the roof, You could always run it through a 4" pipe where it goes out. It may expand some but I would think more in the area of the elbows and not too bad. Probably be a little longer when it's up to temp.

 

[rjmack]

forget using sch 40 pipe for woodstove.

there is not enough heat in the flue gas to keep the inside of the pipe clean... the thicker pipe just dissipates too much heat. it will probably soot up and plug very quickly. i tried it with 6" and it didn't take two weeks to plug up at the elbow.

the thin stove pipe is much better, iirc the smaller diameters are for n/gas propane etc.

 

[Sutol]

I have used 3inch pipe before and it worked fine

The pipe was about 15 feet high and went through the wall at about eight feet at a 45 degree angle.
The stove was a converted propane gas bottle with a flue regulator (butterfly) and an air flow regulator at the bottom of the fire so as it could be shut down to burn nice and hot.

The pipe I have at the moment is 5 inch and works fine with no sooting up, it has been in the garage for about two years. It was put in as a temporary thing to get heat in there.

I think the 3 inch will work fine with the very dry wood that we burn, just worried about the pipe expanding between the stove, along the top of the spanners and tool boxes and ending up 4 inches longer and distorting the hole in the roof which will be a tight fit to keep water out.

 

[SandburRanch]

I'm going to weld together some 3inch dia pipe as a new chimney for my stove in the garage.

the pipe is to go up from the stove for about 3 feet then diagonally across the back wall for about 12 feet then up and out of the roof for about 4 feet.

The reason for going across the wall is that the pipe acts like central heating for the garage as it runs along the back wall.

The pipe we are replacing is stainless flexi pipe usually used as a liner in a brick chimney and it is getting past its sell by date due to the extreme heat from the stove.

My worry is that the solid metal pipe will expand and move horizontaly along the wall and then will disturb the roof where it goes through as it will no longer line up.

Am I worrying about nothing?

*****************************************************
From Fire Engineering - "Steel will expand from 0.06 percent to 0.07 percent in length for each 100oF rise in temperature".
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According to those calculations about 3" of room for expansion at the roof opening would be sufficient.

 

[Sutol]

*****************************************************
From Fire Engineering - "Steel will expand from 0.06 percent to 0.07 percent in length for each 100oF rise in temperature".
----------------------------------------------------------------------

According to those calculations about 3" of room for expansion at the roof opening would be sufficient.

But then it would leak

I've come up with a solution, I'm going to place the burner on a wheeled base so that it can move as the pipe expands and this will solve the problem of the roof opening.

clever eh

 

[Sandlot]

I would say an expansion joint should be used. Something like this.
McMaster-Carr