Question 428Steam Plants - Assistant Engineer

The correct answer is A) dirty firesides or watersides. A higher than normal stack gas temperature could indicate dirty firesides or watersides, which reduce the heat transfer efficiency of the boiler. Fouling on the firesides or watersides acts as an insulator, preventing the heat from being effectively transferred to the water, leading to higher stack gas temperatures. The other options are incorrect because they do not directly impact the stack gas temperature. Eroded water screen tube walls (B), inner or outer casing leakage (C), and defects in burner cone refractory (D) may have other effects on boiler performance, but they are not the primary causes of higher than normal stack gas temperatures.