______ are positive displacement pumps that can pump air as they operate.

• A. Diaphragm pump
• B. Priming pump
• C. Gear pump
• D. Centrifugal pump

Answer: (B)

Positive displacement pumps move a fixed amount of volume with each cycle, so they can push air as part of their operation. A priming pump is designed specifically to remove air from the suction line and prime the main pump, which means it deliberately displaces a known volume of air through the discharge side. That makes it a positive displacement device that can pump air as it operates, exactly what priming requires.

Diaphragm pumps are also positive displacement and can move air, but they aren’t described here as priming devices. Gear pumps and centrifugal pumps mainly handle liquids; they aren’t used to pump air during normal operation, especially not as the primary function.