Question 391General Subjects - Assistant Engineer

The correct answer is C) a liquid seal. A liquid seal in the stuffing box prevents air leakage between the shaft and the packing. The liquid seal is created by the pressure of the liquid being pumped, which forces the packing against the shaft, creating an effective seal. This prevents air from being drawn into the pump through the stuffing box. The other options are incorrect because: A) lantern rings only provide a path for lubrication, not a seal; B) a compressed packing gland alone does not prevent air leakage; and D) the stuffing box gland tightens the packing, but does not create a liquid seal.