Which part of a belt-driven non-hermetic compressor is most likely to leak if the compressor has not been used for several months?

• A. Piston rings
• B. Crankshaft bearing
• C. Sealing gasket
• D. Rotating shaft seal

Answer: (D)

Long idle time makes the rotating shaft seal the most likely leak path on a belt-driven non-hermetic compressor. The seal sits where the shaft exits the compressor housing and is designed to keep refrigerant in while the shaft spins. When the unit sits unused for months, the seal relies on a thin oil film and precise mating surfaces; without operation, that film can deteriorate, the seal material can dry out or crack, and clearances can change with temperature cycling. This creates a gap for refrigerant to escape around the shaft.

Piston rings seal the internal compression inside the cylinder and mostly affect performance when the compressor is running; if they wear or fail, you’d see degraded compression and possible internal leakage, not a straightforward external refrigerant leak after a long period of inactivity. The crankshaft bearing mainly supports the moving parts and would more likely contribute to oil leaks or mechanical noise rather than a primary refrigerant leak to the outside. A static sealing gasket can degrade with age, but the most direct and common external leakage path after long idle is the rotating shaft seal.