SUPPLY PRESSURE AND RETURN CIRCUIT
The supply pressure and return circuit is made up of
directed through an external filter located inboard of
three (3) separate circuits which route oil from the
the hydraulic reservoir. Both filters incorporate a
hydraulic pumps to the directional control valves for
bypass feature allowing oil to bypass the filter when
the individual operating circuits.
the element is clogged and back pressure exceeds
pressure and return circuit consists of the reservoir,
25 psi (172.3 kPa). Gauges on the front of the filter
a three section hydraulic pump, pump disconnect, oil
heads show the amount of filter restriction present.
cooler, two oil filters, and a 15 port hydraulic swivel.
The operating circuits description and components
begin with the circuits directional control valve.
An air cooled hydraulic oil cooler is mounted on the
HYDRAULIC RESERVOIR AND FILTER.
right side of the superstructure. The oil cooler
consists of a hydraulic radiator, and fan-mounted on
The hydraulic reservoir is mounted on the left side of
an electric motor. The fan draws cool air through the
the carrier frame and is held in place by two retaining
cooling fins on the radiator.
straps, refer to Figure 2-8-3. The reservoir is all-
steel and has an internally-mounted full-flow filter
A temperature switch installed in the return manifold
and an integral baffle that helps cool the oil and
controls the operation of the fan motor. When the
temperature of the oil reaches 120F (48.8C) the
prevent foaming. The reservoir has a capacity of
approximately 73 gal. (276 l) total; 64.4 gal. (244 l) to
switch's contacts close and energize the fan motor
the full level, with a low level of 60 gal. (227 l).
relay to actuate the fan motor.
Oil flows through the two individual tubes at the back
of the reservoir to the hydraulic pump. The majority
of the return flow enters directly into the return filter.
A drain plug located in the bottom of the reservoir is
Section One of the hydraulic pump supplies the main
magnetized to collect metal particles from the oil,
hoist circuit. Oil flowing from the valve bank returns
should the oil become contaminated.
to the return manifold.
A sight level gauge is located on the side of the
reservoir to indicate oil level. A screw-on breather
located on the top of the reservoir allows air to enter
Section Two of the hydraulic pump supplies the lift
or exhaust from the reservoir. It is most important
and telescope directional control valves. Oil flowing
that the breather be kept clean to prevent damage to
from the valve bank returns to the reservoir.
the reservoir. A filler cap located on the top of the
reservoir is used when hydraulic oil is added to the
Section Three of the hydraulic pump supplies the
The oil filter housing located inside the reservoir,
integrated outrigger valve which controls the
contains a replaceable 10 micron filter element. To
outrigger circuit and the superstructure rear steering
gain access to the filter element, unbolt the filter
circuit. Bypass flow from the integrated outrigger
head. Most of the oil returning from the system is
valve supplies the pressure reducing valve, which in
directed to the filter. The oil passes through the filter
turn divides the flow to supply the swing system and
element and to the outlet at the bottom of the filter
the hydraulic remote controllers.
bowl. Oil returning from the steering circuit is