disengage the manually operated attached CRP
sleeve gear coupling and engages the sliding gear
hydraulic oil pump coupling while the reduction
with the sleeve on the pinion shaft. The engage-
gear is in operation. However, you can dis-
ment lever position is marked on a plate on the
connect the pump drive couplings while the MRG
drive housing under the lever handle. The
is in operation if an emergency occurs.
handle can be locked in either the ENGAGED or
DISENGAGED position (see detail A on fig.
Electrostatic Vent Fog Precipitator
8-12). No remote status indication is provided. A
photoengraved plate should be visible, adjacent
The electrostatic vent fog precipitator is
to the unit, with the following caution message:
mounted in the lube oil system vent piping. The
purpose of the vent fog (mist) precipitator is to
remove entrained oil mist from the MRG vent air
CAUTION
before it is discharged into the engine room. The
mist precipitator is a two-stage, electrostatic type,
Do not attempt to engage or disengage the
capable of removing 95 percent of the entrained
manually operated attached lube oil pump
oil from the vent air at an airflow rate of 10 cfm.
drive coupling while the reduction gear is
It has a charging element (ionizing section), a
in operation.
collecting element (collecting section), and an
integral power supply. The power supply converts
T h i s action will result in equipment or
the input voltage, which is 120-volt, single-phase,
personnel casualties. However, you can dis-
60-hertz, to l0,000-volt dc.
connect the pump drive couplings while the MRG
Figure 8-13 shows the operating principle of
is in operation if an emergency occurs.
the vent fog precipitator. In operation, the MRG
The drive unit has a drive assembly housing,
vent air enters the precipitator through a flame
a horizontal drive shaft, a spiral bevel gear set,
arrestor mounted in the inlet plenum. The oil
and a vertical drive shaft. The horizontal shaft
particles in the vent air are electrically charged
drives the vertical drive shaft through the set of
(positively,) as they pass through an ionizing
spiral bevel gears. The vertical drive shaft drives
section. In the ionizing section, a high con-
the attached pump through an extension shaft.
centration of ions emanate from the ionizer
The extension shaft is attached to the pump and
electrode suspended in the center of and at the
the drive unit through flexible couplings. The
entrance to the collector tube. The ionizer
pump drive and disconnect coupling unit is
electrode is charged with high-voltage dc and the
lubricated by sprays from the MRG lube oil
collector tube is electrically grounded.
system. The vertical couplings are grease-
The positively charged oil particles then pass
lubricated.
into an electrical field set up within the collector
tube. The field is created by a positive, high dc
Controllable Reversible
voltage being applied between the high-voltage
Pitch Hydraulic Pump
tube and the collector tube. The positively charged
oil particles are attracted and adhere to the wall
The backup hydraulic oil pump for the CRP
of the negative (grounded) collector tube. As more
propeller is attached to the MRG. It is driven by
particles collect on the collector tube wall, they
the lower outboard second-reduction pinion
form an oil film, which runs down the wall into
through a manually operated, connect/disconnect
the inlet plenum. From the inlet plenum, the oil
type of coupling and spiral bevel gear right-angle
drains into the MRG. The cleaned vent air is
drive assembly. The coupling/drive unit is similar
discharged into the engine room.
to the coupling drive unit for the attached
The air discharged from the precipitator
lube oil pump. The main difference is that the
originates primarily from changes in operating
horizontal bevel gear on the coupling/drive unit
conditions that cause temperature changes in the
is mounted on the MRG side of the vertical bevel
MRG. Expansion and contraction of the oil and
gear to give opposite rotation to the output shaft.
air inside the MRG result in air being aspirated
The output shaft is coupled to the pump through
into the gear case. Other possible sources of
a flexible coupling. The attached CRP hydraulic
aspiration of air are moving HP and LP areas
oil pump is similar to the hydraulic oil power
inside the case (caused by rotation of the gears),
module (HOPM) motor-driven pump, which we
which result in aspiration of air, gasket and seal
will discuss further along in this chapter. During
leaks, and strainer changing.
normal operations, NEVER attempt to engage or
8-22
