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 HYDRAMECHANICAL PROTECTIVE SYSTEM
SYSTEMS OPERATION
SCHEMATIC NO. 16 (OVERSPEED CIRCUIT)
2. Emergency manual shutoff valve. 3. Selector valve. 5. Speed sensing valve spool. 8. Low speed oil
protection valve. 9. High speed oil protection valve. 10. Oil pump. 11. Oil pressure relief valve. 13. Oil
pressure switch. 14. Orifice. 15. Diverter valve orifice. 16. Remote normal shutoff valve. 17. Fuel shutoff
actuator. 18. Diverter valve. 19. Engine oil pressure orifice. 20. Start-up override valve. 21. Thermostatic pilot
valve. 22. Air inlet sequence valve. 23. Pilot operated two-way valve. 24. Fuel shutoff sequence valve. 25. Air
inlet shutoff. 26. Air inlet shutoff actuator.
3. Oil from fuel shutoff sequence valve (24) goes to
the inlet of diverter valve (18) then to orifice (15)
in the valve spool. The oil goes through orifice
(15) and goes to the system drain through two-
way pilot operated valve (23). The pressure of
the oil is lowered after the oil goes through orifice
(15), this causes the oil pressure to move the
diverter valve spool against a spring force and
connect the fuel shutoff actuator oil circuit to the
system drain.
Thus, the actuator will not
shutdown the engine. Engines with electric shut-
off solenoids on the governors have a pressure
switch installed in the diverter valve outlet for the
shutoff actuator. The pressure switch will not
shutdown the engine until system oil pressure is
directed to it.
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