The pump can be used to pressurize fresh liquid in what would be called an open loop system, or to re-pressurize fluid after it has driven a motor, known as a closed loop system. In both cases, pump types are matched to certain applications and have different specifications to fit into any process design scheme. Let us take a look at the different types available to engineers and industry.

 

Fixed Displacement

 

A fixed displacement hydraulic pump has a set flow through depending on the design parameters. These pump types are more simple, less expensive, and easier to maintain. These benefits come at the expense of the flexibility to change the operating parameters to meet process needs.

 

The basic type is the gear pump. Pressure is created by pushing the working liquid through a pair of gears toward the outlet. These gears can be run in a line, or nested within each other to improve performance and reduce noise levels.

 

A screw pump forgoes the use of gears and instead uses a pair of Archimedes spirals. These appear as screws with very large grooves. The working liquid picks up pressures as it flows through the rotating screws. These pumps are well suited for higher flow rates at a relatively low pressure.

 

Hydraulic pumps come in such a wide variety in order to fit into any process and any budget. Simple, fixed displacement pumps work very well for a process that does not have variable operating parameters. Variable displacement models are well suited for more flexible processes and can also be connected to multiple machines by increasing the output based on the number of machines running.