Pump
a device which applies mechanical force and motion to a liquid, creating hydraulic fluid power. Pumps are divided into two categories:
| Positive displacement | pumps force liquid to flow in volume proportion to increasing and decreasing pump volume, as in reciprocating and rotary pumps. Reciprocating pumps use pistons, plungers or diaphragms to increase and decrease fluid volume. Rotary pumps use a rotating gear, vane or screw to force liquid from the pump. |
| Centrifugal pumps | also called kinetic pumps, provide smooth non-pulsed flow and adjustible flow velocity. Liquid flow is established through centrifugal force created by a rotating impeller, as in radial flow and axial flow centrifugal pumps. In a radial flow pump, fluid enters the pump at the impeller rotational axis and is forced outward by vanes. In an axial flow pump, a propeller or screw moves fluid down the axis of the pump, parallel to the shaft. |