Which pump is a positive displacement pump characterized by the use of gear teeth and a casing to displace liquid?

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

Answer: (C)

Gear pumps are a positive displacement pump that uses intermeshing gear teeth inside a sealed housing to trap and move a fixed volume of liquid. As the gears rotate, liquid is captured in the spaces between the gear teeth and the casing and carried from the inlet to the outlet. Each revolution displaces a set amount of liquid, giving a constant volume flow independent of discharge pressure (up to the pump’s limits). The casing forms the sealed cavities that make this deliberate displacement possible.

This contrasts with end suction or centrifugal pumps, which rely on an impeller to add velocity to the liquid and push it through the system; their flow depends more on system head and pressure rather than a fixed per-revolution displacement. Orientation like horizontal doesn’t define the pumping mechanism, and “fire pump” describes the application, not the mechanism. The gear pump’s defining feature—gear teeth moving liquid within a casing to achieve displacement—matches the description perfectly.