Hydraulic pumps convert mechanical energy (from a motor or engine) into fluid energy. They are called positive displacement pumps. There are two very broad categories of pumps that are commonly used, known as fixed displacement and variable displacement types.
Most systems using a fixed displacement pump are simpler in design and requirement, and are less costly. Alternatively, systems using variable displacement pumps are generally for multiple actuator projects and jobs that require simultaneous movement of cylinders and motors. These systems also often require variable speed functions, and are generally more sophisticated. They require the control valves and pumps to be made together.
Broadly speaking, pumps have three types of construction (gear, vane and piston) within the two aforementioned categories. Through Statewide Hydraulics, you’ll find the gear pumps have fixed displacement capacities, while the vane and piston pumps are available as both variable and fixed displacements.