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Post by spinal on Sept 21, 2012 13:24:30 GMT
Looking for a flue pipe... found some stainless steel stuff, but it's quite expensive at £40 a meter.
On the other hand, I can get galvanised pipe for £10 a meter...
That said, I'm worried about the zinc fumes... what's the consensus?
(while on topic, what's the suggested diameter? I'm thinking 8" pipe?)
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Post by faz on Sept 21, 2012 15:45:44 GMT
I wouldnt worry about zinc fumes. Firstly, it probably won't get hot enough in the flue for zinc oxide fumes to form. Secondly, even if it does, you don't breathe in the fumes that come out of your chimney.
Unfortunately, a bigger issue is likely to be corrosion. Once the flue gets hot it is likely to suffer from corrosion, and a rusted out metal flue wil be a pain to replace. Are you planning on having it inside a brick chimney or visible?
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Post by spinal on Sept 21, 2012 16:03:26 GMT
Brick chimney or visible: neither  It'll be inside the enclosure (so difficult to replace... and if it corrodes the loose vermiculite won't have anything to hold it back)... That said - shouldn't the galvanisation protect it from corrosion? M. |
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Post by faz on Sept 21, 2012 16:43:07 GMT
It will, but galvanised products don't last forever. It will all depend on how damp the duct gets, and any corrosion that might occur due to acidic compounds sitting in the duct. If your duct is going to be impossible to replce, and you cannot tolerate a failure, then I think you need to go with the stainless.
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Post by spinal on Sept 21, 2012 17:03:37 GMT
I just ordered a "enamelled" flue - something apparently used for AGA cookers...
I may also put some 5:1 vermicrete around it, so if it does end up rusting away, the vermicrete should hold the rest of the loose vermiculite out...
M.
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Post by cannyfradock on Sept 21, 2012 17:41:02 GMT
Spinal I think £40 is good when "buying" a new chimney. The ideal thing is double walled insulated s/s flue. Is this what you can get for £40?. The cheapest I've seen for 1 meter length plus cowl and base flange is  ? £140. It's always good if you buy a set to have them before you create the vent. The flange just stops the heat from transferring to the outer sleeve. A 1 meter length can be "tampered with" ..with the help of an angle grinder to create the same affect. I've managed to buy mine (2 so far) at scrapyards. Mine cost £8. I've also used an upside down flower pot.... There is an exact equation which will calculate the vent diameter size, compared to the cubic area of your dome.......I haven't got a clue what it is though. Minimum should be 6" for a 36" oven. A lot of people buy the 7" s/s flue but the internal diameter is only 5"..I have also used one of these on a 36" oven.......it still works fine. Terry |
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Post by spinal on Sept 21, 2012 18:04:39 GMT
I'm not using a double-walled flue as I don't have an exposed chimney; my single walled chimney is buried inside my build, and covered by loose vermiculite on all sides. The thinnest insulation will be about 20cm of loose vermiculite and then a line of bricks (and the thickest will be almost 2m of vermiculite before the bricks). If I have some spare blanket, I may wrap it in that first with some rigidizer instead of the vermicrete.... I'm going to use 8"x36" for my flue (8" being the internal diameter) - so that should be plenty big  M. |
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? £140.