Question 390Steam Plants - Assistant Engineer

The correct answer is C) Boiler water should have a reserve of phosphates. Phosphates are added to boiler water to control the precipitation of hard scale-forming minerals like calcium carbonate. By maintaining a reserve of phosphates in the boiler water, these minerals are precipitated as soft, sludge-like deposits that can be more easily removed, rather than forming a hard, adherent scale on the boiler surfaces. This helps to maintain efficient heat transfer and prevent damage to the boiler. The other options are incorrect because: A) Slightly acidic boiler water can actually increase corrosion, B) High water hardness will lead to more scale formation, and D) Hydrazine is used to remove dissolved oxygen, not to control scale.