Question 198Steam Plants - 1st Asst/Chief

The correct answer is A) water trapped between tubes and refractory. Cratering and water tracking in boiler tubes is caused by water trapped between the boiler tubes and the refractory (the heat-resistant lining of the boiler). This trapped water causes localized corrosion and erosion of the tube metal, leading to the formation of craters and water tracks on the tube surface. The other answer choices are incorrect because: B) burning a fuel with a high vanadium content can cause different types of fouling and corrosion, but not specifically cratering and water tracking; C) soot corrosion is a different type of corrosion mechanism; and D) baked-on slag deposits can also cause different types of issues, but not the specific problem of cratering and water tracking.