smokeyCityTeacher wrote:Since I have a lot of galv pipe around Im hoping that stack temps of less than 300 will be safe.
It should take twice that with no trouble, the galvanized starts to go away at 700-800* range depending on if it is hot dipped or electrically coated IIRC. Coal isn't a big deal, wood is because it can get much hotter in a hurry.
As long as the coating looks normal, it isn't an issue. Once it gets toasted, the pipe will pinhole like crazy and it is difficult to tell. It will etch itself very thin like paper in a short time and eventually crumble.