uses hydraulic or pneumatic medium. The basic
components are as follows:
Strainers and filters
Control valves (directional and relief)
Actuating devices (cylinders)
Lines (pipe, tubing, or flexible hose)
Connectors and fittings
Sealing materials and devices
Several applications of fluid power require only a
simple system; that is, a system which uses only a few
components in addition to the basic components.
A properly constructed reservoir (fig. 3-6) is more
than just a tank to hold oil until the system demands
fluid. Is should also be capable of the following:
1. Dissipating heat from the fluid,
2. Separating air from the oil, and
3. Settling out contamination in the oil.
Ideally, the reservoir should be high and narrow,
rather than shallow and broad. The oil level should be
as high as possible above the opening to the pump
suction line. This condition prevents the vacuum at the
line opening from causing a vortex or whirlpool effect.
Anytime you see a whirlpool at the suction line
opening, the system is taking in air.
As a rule of thumb, the reservoir level should be
two to three times the pump output per minute. By this
rule which works well for stationary machinery, a 20-
gpm system would require a 40- or 60-gpm reservoir.
However, this is not possible for mobile equipment.
You are more likely to find a 20- or 30-gallon tank to
support a 100-gpm system. This is possible because
mobile systems operate intermittently, rather than all
the time. The largest reservoirs are on mobile
equipment. These reservoirs may have a 40- or 50-
gallon capacity, capable of handling more than 200-
The reservoir must be sized to ensure there is a
reserve of oil with all the cylinders in the system fully
extended. The reserve must be high enough to prevent
a whirlpool at the suction line opening. Also, there
Figure 3-6.Typical hydraulic reservoir.