Question 211Steam Plants - 1st Asst/Chief

The correct answer is A) decrease refractory maintenance. Water wall tubes in a boiler furnace help to protect the furnace refractory, which is the heat-resistant material lining the inside of the furnace. The water flowing through the tubes helps to cool the refractory, reducing the amount of wear and deterioration it experiences over time. This decreases the frequency and cost of refractory maintenance, making option A the correct choice. The other options are incorrect because water wall tubes do not directly reduce combustion rates (B), increase furnace size (C), or reduce furnace temperature (D). The primary purpose of water wall tubes is to protect the furnace refractory, not to alter the fundamental combustion or heating characteristics of the boiler.