used is shown in figure 8-25. The system consists
pump and the attached or gear hydraulic pump are
running. The electric or motor operated pump normally supplies the
of an HOPM; a gear-driven attached or gear hydraulic
hydraulic oil flow, while the attached or gear pump flow
pump; the manifold block assembly of the con-
is returned to the sump tank by the unloading
trol valve; and associated piping, valves, and
valve. The check valve prevents the electric or motor operated pump
fittings.
discharge from entering the attached or gear pump. If the
electric or motor operated pump fails or the pressure drops below
Hydraulic Oil Power Module
minimum, the pilot-operated unloading valve
directs the flow from the attached or gear pump to the
The HOPM is located adjacent to the MRG.
electric or motor operated flow path. In this mode, discharge from the
It contains the motor-driven, screw-type electric or motor operated
attached or gear pump is prevented from entering the electric or motor operated
hydraulic oil pump, a suction strainer, two
pump by the electric or motor operated pump check valve.
d u p l e x filters, and a pressure control
The hydraulic oil flow next enters the relief
assembly. It also contains a duplex
and sequence valves. An unloading valve is used
control oil filter, two gauge panel assemblies with
to maintain system pressure. The sequence valve
associated instrumentation, a manual bypass
acts to maintain a minimum hydraulic oil pressure
valve, and interconnecting piping and fittings.
of 350 psig at the inlet of the control oil pressure-
The motor-driven electric or motor operated hydraulic pump draws
reducing valve. High-pressure oil for the propeller
oil from the sump tank through a foot valve and
hub leaves the sequence valve at a pressure of 200
a suction strainer. The foot valve allows oil flow
to 600 psig. If the oil pressure exceeds the
in one direction only, thus preventing the
maximum limit of 1,000 psig, the relief valve
backflow of oil from the pump to the tank when
opens and excess pressure is bled off to the sump
the pump is shut down. The suction strainer is
tank. Oil from the pressure-reducing valve
a telltale, bypassing type of strainer. An indicator
(control oil) flows at reduced pressure (10 gpm
on the strainer indicates the degree of clogging.
at 350 psig nominal). It flows through a
If the indicator is ignored and the degree of
duplex filter to the control oil section of the OD
clogging becomes extensive, the oil is internally
box. If the control oil pressure exceeds 600 psig,
bypassed around the strainer element. The
the auxiliary relief valve opens and the excess
hydraulic pump delivers 160 gpm at up to 1,000
pressure is bled off to the sump tank.
psig. From the pump, the oil flows through a
A manually operated bypass valve is located
duplex filter to the pressure control
in a line between the sequence valve discharge and
assembly. An air bleed valve, located between the
the return line to the sump tank. This valve is
pump and the filter, automatically purges
normally closed during operation.
entrapped air from the system. It also aids initial
A spring-loaded check valve is located in the
start-up and priming of the pump.
hub oil return line between the OD box and the
You can start or stop the HOPM electric pump
motor from the CCS or from a local motor
HOPM. It maintains the return oil pressure
between 28 and 35 psig during system operation.
controller located adjacent to the HOPM. The
It assures a positive pressure on the return line
motor controller has a two-position transfer
during system shutdown. At this time, the CRP
switch with the positions labeled LOCAL and
head tank provides the only source of return line
REMOTE. The LOCAL position allows the
pressure.
electric pump motor to be operated from the local
The attached or gear hydraulic pump is a vertically
controller and at the same time inhibits operation
mounted, screw-type pump identical to the motor-
from the consoles. The REMOTE position allows
driven electric or motor operated pump. It is driven by the MRG. The
the electric pump motor to be operated from the
consoles, while inhibiting operation from the local
pump draws oil from the sump tank through a
foot valve and suction strainer identical to those
controller.
in the electric or motor operated pump system. The discharge from the
The pressure control assembly (seen in fig.
attached or gear pump flows through a duplex
8-25) regulates the HP (power) oil and control oil
filter, located in the HOPM, to the pilot-operated
that is supplied by the HOPM. The assembly
unloading and check valve.
consists of a pilot-operated unloading valve and
check valve together in one housing, a motor-
driven pump check valve, a relief and sequence
Oil Distribution
valve together in another housing, a pressure-
As discussed earlier, there are three oil systems
reducing valve, and an auxiliary relief salve.
common to all CPP/CRP systems. They are the
During normal operation, both the electric or motor operated HOPM
8-38
