Which of the following is NOT a purpose of the feedwater tank?

The feedwater tank serves several important roles within a boiler system, but cooling down the steam is not one of them. The primary purposes of the feedwater tank are to store feedwater, allow for the settling of impurities before the water enters the boiler, and preheat the feedwater to improve efficiency and reduce thermal shock on the boiler components.

When feedwater is stored in the tank, it can help maintain a consistent supply for the boiler while minimizing fluctuations in pressure and temperature. The tank also provides an environment where heavier impurities can settle out of the water, improving the overall quality of the feedwater and protecting the boiler from potential damage. Additionally, preheating the feedwater can improve the efficiency of the boiler operation by reducing the energy needed to convert water into steam.

Cooling down the steam, however, is not a function of the feedwater tank. Instead, this process typically occurs in other components of the steam system, such as condensers, where steam is cooled and condensed back into water. Therefore, the answer identifies the correct statement, as cooling down steam is not intended within the design or function of a feedwater tank.