HYDRAMECHANICAL PROTECTIVE SYSTEM
Engine lubrication oil (under pressure) is sent to
the oil reservoir for the shutoff control. The reservoir
keeps the correct level of oil for the system and drains
the excess oil back into the engine. This gives a
constant oil supply to the system.
An oil pump and pressure relief valve (located in
the shutoff control group) supplies oil flow and pressure
for the protective system hydraulic circuits.
There are two main hydraulic circuits in the protective
COOLANT TEMPERATURE PROTECTION
system. One circuit is for the fuel shutoff and the other is
13. Aftercooler housing (coolant inlet). 15.
for air inlet shutoff. A constant flow of oil through the air
Thermostatic pilot valve. 16. Housing (below
inlet shutoff circuit removes (bleeds) air and keeps the
lines full of oil to give a minimum time for system
response. If a fault condition occurs, the oil pressure in
one or both hydraulic circuits is increased to operate an
actuator to shutdown an engine or activate an alarm.
HYDRAULIC CIRCUITS (EARLIER)
(Without Check Valves In Diverter Valve)
The schematics that follow, show only hydraulic
actuators that are filled to cause engine shutdown. The
fuel shutoff actuator can be replaced with an electric
the use of a pressure switch.
NOTE: Some of the schematics show only the
GOVERNOR SHUTOFF ACTUATOR
components needed for explanation and do not show the
(Woodward UG-8 Governor Shown)
complete hydramechanical protective system circuits.
9. Oil line to thermostatic pilot valve. 10. Oil line to
fuel shutoff actuator. 17. Fuel shutoff actuator.