What type of pumps are piston, diaphragm, and gear pumps classified as?

Piston, diaphragm, and gear pumps are classified as positive displacement pumps because they work by trapping a fixed volume of fluid and then forcing that volume into the discharge pipe or system. This type of pump operates by generating a specific flow rate at a given pressure, which is characteristic of positive displacement mechanisms, allowing them to efficiently handle varying fluid viscosities and maintain delivery pressure regardless of the resistance encountered in the delivery system.

In contrast, centrifugal pumps utilize rotational energy to move fluids, relying on the centrifugal force to create flow, making them fundamentally different from positive displacement pumps. The other choices, pressure pumps and flow pumps, are more general terms that could encompass various types of pumps including both positive displacement and centrifugal pumps, but they do not specifically identify the core mechanism of operation as clearly as the term positive displacement. Hence, the classification of piston, diaphragm, and gear pumps as positive displacement pumps is accurate and reflects their operational characteristics.