Figure 8-26.--Control valve manifold oil flow.
leaking past the blade seals and into the hydraulic
to the propeller is shut off, the check valve
system. Hydraulic oil continually fills the head
prevents the head tank from draining back into
tank from the return oil chamber and flows back
the sump. The head tank then provides sufficient
pressure to prevent seawater entry through the
to the sump through the overflow line when the
hub seals since it is 4 to 6 feet above the ship's
HOPM is providing HP oil. This head tank
waterline.
circulation is caused by the return check valve in
the return oil line. When the HOPM is operating,
ELECTRONIC PITCH
the check valve maintains approximately 28 to 35
CONTROL SYSTEM
psig in the return oil chamber. Since 28 to 35 psig
is greater than the head pressure caused by the
tank height, return oil continuously fills the tank,
The pitch of the CRP propeller is established
electrically through the electrohydraulic pitch
and it overflows back to the sump. When HP oil
8-41
