34 Fluid Power
Functions of Fluid Power
Systems
Fluid power systems are made up of compo-
nent groups containing parts designed to perform
specific tasks. These component groups act together
to perform the work desired by the system designer.
The work may involve simple or complex tasks, but
the component groups perform specific system
functions that are basic to all fluid power systems.
There are five functions that are basic to system
operation of any fluid power system, Figure 2-1:
■ Energy conversion.
■ Fluid distribution.
■ Fluid control.
■ Work performance.
■ Fluid conditioning.
Each of these functions must be performed by a
fluid power system if the system is to operate
efficiently and provide a reasonable service life.
The operating environment, power output, and
complexity of the system establish the number
of components required to perform a particular
function.
Energy Conversion
Fluid power systems do not generate energy,
but transform it into a form that can be used to
complete a task. The process begins with a prime
mover pressurizing a fluid. It ends with an actua-
tor using the energy stored in the pressurized fluid
to perform work.
Fluid Distribution
The operation of fluid power systems requires
the distribution of fluid to the components in the
system. Various types of lines are involved in this
function. Valves and other components also serve
to assist in fluid distribution.
Fluid Control
Fluid power systems require the control and
regulation of the fluid in the system to perform the
tasks desired by the system designer. A number
of different components are used to control fluid
flow rate, direction, and pressure in a system. Con-
trol of these three elements allow the system to
provide the desired operating characteristics.
Work Performance
Using the energy stored in the pressurized
fluid of the system is the primary function of a fluid
power system. This process involves actuators that
convert the energy stored in the fluid to linear or
rotary motion to perform the desired work.
Fluid Conditioning
Fluid power system performance and ser-
vice life require a fluid that is clean and provides
lubrication to system components. This function
involves storing fluid, removing dirt and other
contaminants, and maintaining proper system
operating temperature.
Structure of Fluid Power
Systems
The physical appearance of fluid power sys-
tems vary considerably, depending on the type of
fluid used, application, and power output. How-
ever, each system is structured using component
groups that perform the various system func-
tions. The structure of typical fluid power systems
involves five component groups, Figure 2-2:
■ Power unit.
■ Actuators.
■ Conductors.
REQUIRED SYSTEM
FUNCTIONS
FLUID
CONTROL
ENERGY
CONVERSION
FLUID
CONDITIONING
FLUID
DISTRIBUTION
WORK
PERFORMANCE
Figure 2-1. The basic functions of a fl uid power
system.