Publisher Summary This chapter focuses on drivers for moving chemical process equipments, which include electric motors, steam or gas turbines, and internal combustion engines. The three main classes of electrical motors are induction, synchronous, and direct current. Induction motors are the most frequent used because of their simple and rugged construction, and simple installation and control. They are constant speed devices available as 3600 (two-pole), 1800, 1200, and 900rpm (eight-pole). Synchronous motors are made in speeds from 1800 (two-pole) to 150 rpm (48-pole) and they operate at constant speed without slip. They are the obvious choice to drive large low speed reciprocating compressors requiring speeds below 600 rpm, however they are not suitable when severe fluctuations in torque are encountered. Direct current motors are used for continuous operation at constant load when fine speed adjustment and high starting torque are required. Turbines utilize the expansion of steam or a gas to deliver power to a rotating shaft. Salient features of these equipments are high speed rotation, adjustable speed operation, nonsparking and consequently nonhazardous operation, simple controls, low first cost and maintenance, and flexibility with regard to inlet and outlet pressures. Gas expanders are used to recover energy from high pressure process gas streams in a plant when the lower pressure is adequate for further processing. When a low cost fuel is available, internal combustion drivers surpass all others in compactness and low cost of installation and operation.