This chapter begins with a description of the liquid-transportation process. This is followed by a summary of the different pump designs, features, and accessories, such as variable-speed drives. In the transportation of liquids, impeller velocity or displacement force imparts a head (pressure rise) that moves the liquid through the resistances of the pump cavities and of the process. In the pressure or flow controllers of pumping systems, the use of the integral mode is essential because these systems are noisy, multi-capacity processes. In positive displacement pumps, a piston or plunger inside a cylinder is the driving element as it moves in reciprocating motion. Metering pump flows can readily be adjusted by changing the length and number of strokes of the piston. A calibration chart must therefore be drawn for the pump under actual operating conditions. In addition to multiple pumping heads, a pulsation dampener can be used on the pump discharge to smooth the flow pulsations.