And damage due to overheating due to scale formation, and damage due to abrasion by products of combustion? >From: "Charles & Dorothy Brumbelow" <cbrumbelow@xxxxxxxxxxx> > >Authoritatively, someone else will need to speak. Intuitively, I would say >they are for at least two reasons -- bureaucratic comfort factor and >possibility of fatigue failure from the hot/cold/hot/cold flexing. Charles MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.