Which pump is a positive displacement device that uses meshing gear teeth to move liquid?

• A. End Suction Pump
• B. Horizontal Pump
• C. Gear Pump
• D. Fire Pump

Answer: (C)

A positive displacement pump moves a fixed amount of liquid with each rotation. A gear pump achieves this by using two meshing gears that trap liquid between their teeth and the housing as they rotate. That trapped liquid is carried around from suction to discharge, so each revolution pushes a precise amount, giving flow that follows the pump speed rather than the system pressure (within limits).

End suction and horizontal pumps are typically centrifugal devices, which rely on converting rotational energy into velocity and dynamic head, so their flow depends on system pressure and head rather than a fixed per-revolution displacement. Fire pumps are a classification often associated with centrifugal units used for firefighting, not by a gear-into-housing mechanism.

So the gear pump is the one that uses meshing gear teeth to move liquid and functions as a positive displacement device.