Question 38Steam Plants - Assistant Engineer

The correct answer is B) a water seal line to the packing gland. The water seal line provides a positive pressure at the packing gland, which prevents air from being drawn into the pump casing. This is an important mechanism to maintain the pump's efficiency and prevent air from entering the system. The other answer choices are incorrect because: A) The vacuum in the pump suction would actually draw air into the pump casing through the packing gland if there was no water seal. C) Special packing in the stuffing box alone does not prevent air leakage - a water seal line is still required. D) An air seal line from the compressed air line would pressurize the packing gland, but does not provide the same positive sealing effect as a water seal line.