Fluid-handling or transfer devices are not basically concerned with the modulation or transfer of power, but only with the movement of fluid.

When the force on the plunger is reduced, the spring extends the plunger once again. This is termed a cycle. Spring-loaded plungers can handle from one to several thousand cycles.

Linear-motor driven plunger pumps are most efficient at transforming mechanical energy to hydraulic work in low-producing and highly deviated wells.