What is the mechanical device used to control leakage from the stuffing box of a pump?

• A. Gasket
• B. Mechanical Seal
• C. O-ring
• D. Packing

Answer: (B)

In a pump, sealing around the rotating shaft inside the stuffing box is what stops fluid from leaking out. The device that achieves this is a mechanical seal. It works by bringing two smooth, opposing surfaces (one attached to the shaft and one to the stationary housing) into close contact and using springs or other loading to keep them pressed together as the shaft turns. This tight, continuous seal minimizes leakage far more effectively than packing alone.

Packing, the other common method inside a stuffing box, consists of filling material around the shaft that is continually compressed by a gland to seal. It can leak over time and often needs frequent adjustments, whereas a mechanical seal provides a more reliable, maintenance-friendly solution. Gaskets and O-rings seal joints in other parts of machinery but don’t serve as the primary shaft seal inside a stuffing box, making them unsuitable here.