RETURN
LINE
FILLER
AIR
STRAINER
OUTLET
FILTER
TO PUMP
BAFFLE PLACED BETWEEN
DRAIN
INTAKE AND DISCHARGE LINES
PLUG
PREVENTS EXCESSIVE TURBULENCE.
CLEANOUT
SIGHT GLASS FOR
ASf08005
OPENING
CHECKING FLUID LEVEL
Figure 8-5.--Typical hydraulic reservoir.
four-way, two-position valve used to select either the
actuating mechanisms. There are several ways to
classify hydraulic pumps. One common way is by the
test stand reservoir or the aircraft reservoir.
source of power used to operate the pump. Pumps that
Yo u r p r i m a r y c o n c e r n i n s e r v i c i n g a n d
are driven by electric motors, gasoline engines, or
maintaining hydraulic reservoirs is cleanliness.
diesel engines are referred to as power pumps. Pumps
Although servicing a reservoir is a simple operation,
that are manually operated are referred to as hand
certain procedures and precautions must be followed.
pumps.
Specific directions are contained in the applicable
Hydraulic pumps may also be classified by the
service instruction manual. In addition, some
type of design used to create the fluid flow. In this
reservoirs are provided with a placard or information
sense, there are three main types: centrifugal, rotary,
plate, which is located on or near the reservoir. This
and reciprocating. As the centrifugal style pump finds
placard or information plate contains detailed
little use in support equipment, it will not be discussed
information necessary for servicing the reservoir.
here.
This includes such information as reservoir capac-
ity, fluid type, and caution notes.
Terms such as fixed displacement and variable
displacement are used to classify pumps. Fixed
Servicing a reservoir is accomplished by a
displacement pumps discharge the same volume of
hydraulic servicing unit or cart. Figure 8-7 illustrates
f l u i d e a c h c y c l e a t a g i v e n s p e e d . Va r i a b l e
the Fluid Service Cart, Model 310, a 10-gallon capac-
displacement pumps are constructed so that the
ity unit. There are also 1-gallon, 3-gallon, and
volumetric output can be varied. Fluid Power,
55-gallon models. Each model is equipped with a
NAVEDTRA 14105, provides detailed information on
3-micron absolute filter.
pump classification. You should read Fluid Power in
conjunction with the following text for a complete
HYDRAULIC PUMPS
understanding of pump classification.
To accomplish work, fluid power systems require
It is important that you understand what is meant
some means of providing a flow of fluid. In hydraulic
by the terms volume of output and pressure in hydraulic
systems, pumps satisfy this requirement.
pumps. Hydraulic pumps are normally rated in terms
The heart of any hydraulic system is its pump, as it
of their volume of output and pressure. The volume of
is the pump that generates the force required by the
output is the amount of fluid the pump can deliver to its
8-6
