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

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)

Sealing the pump shaft to prevent leakage from the stuffing box is the idea behind this question. A mechanical seal is the device designed for that purpose. It creates a tight, dynamic barrier between the stationary housing and the rotating shaft by using mating seal faces pressed together (often with a spring) and sometimes a barrier fluid to keep things lubricated. This arrangement minimizes leakage under pressure and wear far better than packing, which relies on compressing a packing material around the shaft and can still leak as it wears. Packing is the material placed inside the stuffing box to seal around the shaft, not a mechanical sealing device. Gaskets seal flat joints, not the shaft inside a stuffing box, and O-rings are general-purpose seals used in various places but not the specific mechanism used to seal the shaft in the stuffing box. So the device intended to control leakage in this setup is the mechanical seal.