Supply Pressure And Return Circuit; Description - Manitowoc Grove RT765E-2 Service And Maintenance Manual

RT765E-2 SERVICE MANUAL

SUPPLY PRESSURE AND RETURN CIRCUIT

Description

The supply pressure and return circuit is made up of several
circuits which route hydraulic oil from the three hydraulic
pumps to the directional control valves for the individual
operating circuits. The supply pressure and return circuit
consists of the reservoir and integral filter, three hydraulic
pumps, a hydraulic oil cooler and a 10-port hydraulic swivel.
Refer to Hydraulic Pumps in this section for descriptions and
maintenance instructions for each hydraulic pump. Refer to
Swing System, page 6-1 for description and maintenance
instructions for the hydraulic swivel.
The supply pressure and return circuit uses Ports 5, 6 and 8
for pump supply and the dual Port 4 for return. Each
operating circuit's description and components begin with
the circuit's directional control valve.
Hydraulic Reservoir And Filter
The reservoir (Figure 2-1), attached to the right side of the
carrier frame has a capacity of 150 gal (568 l).
The all-steel reservoir has an internally mounted full-flow
filter Figure 2-2 and integral baffles that help cool the
hydraulic oil and prevent hydraulic oil foaming.
Hydraulic oil flows through two tubes at the lower rear of the
reservoir to the three hydraulic pumps. Almost all of the
return flow goes through the filter at the top of the reservoir.
The return line that goes directly into the reservoir (instead of
through the filter) is from the No. 10 port (drain) of the 10-port
swivel.
T h e r e a r e t h r e e t e m p e r a t u r e s w i t c h e s ( 4 , 6 a n d 7 ,
Figure 2-3), located in the tube that routes return oil to the
hydraulic oil return filter in the reservoir. Switches 6 and 7 are
part of a circuit that controls the oil cooler fan speed; refer to
Oil Cooler, page 2-15 for more detailed information on the
operation of these switches.
The third temperature switch (4) is part of a circuit that will
alert the operator to a high hydraulic oil temperature
condition. The switch is normally closed and will open and
cause the circuit to lose ground when the hydraulic oil
temperature exceeds 190°F (88°C). When the circuit loses
ground, the CAN bus system will turn on power to illuminate
the Hydraulic Oil High Temperature Indicator in the gauge
display in the operator's cab. See Section 3 - Operating
Controls and Procedures, in the Operator's Manual for
details of the Hydraulic Oil High Temperature Indicator.
A magnetized drain plug in the bottom of the reservoir
collects metal particles from the hydraulic oil if it becomes
contaminated.
A sight gauge is located on the front end of the reservoir to
indicate hydraulic oil level.
GROVE
A filler neck and breather on the top of the reservoir are for
filling the reservoir and for venting it. The filler neck includes
a strainer for catching contaminants and gaskets to prevent
leaking. The breather which screws onto the filler neck,
allows air to enter or exhaust from the reservoir. It is most
important that the breather be kept clean to prevent damage
to the reservoir. A breather guard protects the breather and
filler neck.
A large round access cover on the top of the reservoir
provides access for cleaning. The cover is bolted to the top
of the reservoir and has a gasket to prevent leaking. The
access hole can also be used to fill the reservoir after it has
been completely drained.
The hydraulic oil filter is located in the reservoir. It bolts to the
top of the reservoir. The filter housing contains a replaceable
filter element. Returning hydraulic oil flows through the filter
head, through the filter element, and into the reservoir.
A gauge on the filter head indicates how restricted (clogged)
the filter element is. When back pressure caused by a dirty
filter element exceeds 25 psi (170 kPa), the filter head's
bypass feature functions to allow the hydraulic oil to bypass
the filter element and flow into the reservoir through the
bypass outlet instead.
1
12
11
7675
Item
1
2
3
4
5
Published 9-04-2014, Control # 422-08
HYDRAULIC SYSTEM
2
3
8
9
10
Figure 2-1 Table

Description

Cover
Fill Cap/Breather
Return Filter
Temperature Switch- High Oil Temp.
Indicator Light
Return Hose
2
4
5
6
7
FIGURE 2-1
2-9