Question 420Steam Plants - Assistant Engineer

The correct answer is C) remove floating impurities from boiler water. The boiler surface blow is used to remove floating impurities and scum from the boiler water surface. This helps maintain the boiler water quality and prevent the buildup of deposits that can reduce heat transfer efficiency and potentially damage the boiler. The other answer choices are incorrect because: A) the boiler surface blow does not directly affect boiler alkalinity, B) it removes floating impurities rather than precipitated solids, and D) it does not disrupt circulation in a steaming boiler.