Question 370Steam Plants - Assistant Engineer

The correct answer is D) prevent hard scale formation. Maintaining an adequate phosphate reserve in boiler water helps prevent the formation of hard scale deposits on the boiler's internal surfaces. Phosphates act as scale inhibitors, keeping minerals in the water suspended and preventing them from adhering to the boiler surfaces. This helps maintain the boiler's efficiency and prevents damage from scale buildup. The other options are incorrect because they do not directly address the purpose of maintaining a phosphate reserve. Removing dissolved oxygen, reducing blowdown frequency, and maintaining a neutral pH are important for boiler water treatment, but they are not the primary reasons for having a sufficient phosphate reserve.