42 Fluid Power
is controlled by the size of the passageway open-
ing. Adjusting the size of the passageway varies the
flow volume, which controls the speed of system
actuator(s). The larger the opening, the higher the
volume of flow through the valve and the higher
the speed of the actuator(s).
Fluid Conditioning Devices
Various devices are used to assure the system
fluid is free of contaminants and operating within
an acceptable temperature range. Proper care of
the fluid has a major effect on the performance
and service life of components and the overall sys-
tem. The type of conditioning devices required in
a system is directly related to the complexity of
the components and the environment in which the
system operates.
Filters are the most common conditioning devices
incorporated in fluid power systems, Figure 2-17.
They remove foreign particles and other contami-
nates. Filters are located in various places of a sys-
tem to safeguard specific components, as well as
the overall system. Three typical locations are:
■ In the intake line for the system.
■ In high-pressure working lines.
■ In the lines that return fluid from system
actuators.
A basic filter consists of a filter housing, filter ele-
ment, bypass valve, and ports to connect the filter
into the system.
Many different filter designs are used in fluid
power systems. In a typical basic filter, fluid enters
the filter housing through the inlet port, is routed
Diaphragm
assembly
Positive
bias
spring
Supply
valve
Inlet port
Outlet port
Inner valve
assembly
Aspirator
tube
Figure 2-15. A pressure regulator is used to set the
operating pressure of a pneumatic system worksta-
tion. (Fairchild Industrial Products)
A B C
Closed Partially Open Wide Open
Figure 2-16 Fluid fl ow through a fl ow control valve is adjusted by varying the size of an orifi ce in the valve.
A—In the closed position, fl uid does not fl ow. B—With the orifi ce partially open, restricted fl ow is allowed
through the valve. C—When the orifi ce is fully open, fl ow through the valve is not restricted.