In some refrigerating systems with an external open-type motor to drive the compressor, the crank case seals to seal the ______.

• A. shaft
• B. piston
• C. crank
• D. bearing

Answer: (A)

When a compressor is driven by an external open-type motor, the drive shaft passes through the crankcase wall. A seal is placed around that shaft to keep refrigerant from leaking into the motor housing and to prevent oil from escaping along the shaft. This keeps both the lubrication in the crankcase and the motor area clean and free of refrigerant, ensuring reliable operation. The other components—piston, crank, or bearing—don’t involve the shaft seal, so the seal’s purpose is specifically to seal the drive shaft.