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 HYDRAMECHANICAL PROTECTIVE SYSTEM
SYSTEMS OPERATION
If the engine oil pressure decreases to 205 kPa
LOW OIL PRESSURE OR HIGH COOLANT
(30 psi), the spring force on high speed oil protection
TEMPERATURE FAULT
valve (9) will move the valve and stop the oil flow to
drain. The pressure of the oil will become equal onj both
Make Reference to Schematic No. 18
sides of orifice (14) and oil pressure switch (13) senses
760 kPa (110 psi). The normally open switch closes and
Under normal operation at low engine speeds,
activates an alarm.
the engine oil pressure must be 140 kPa (20 psi) to
move low speed oil protection valve (8). The fuel shutoff
For the engine coolant temperature circuit, a
circuit oil can then flow from pump (10) at 760 kPa (110
ther- mostatic pilot valve (21) is connected to the engine
psi) through orifice (14), oil pressure switch ( 1 3), low
oil pressure supply. Thermostatic pilot control valve (21)
speed oil protection valve (8), selector valve (3) and pilot
is normally closed.
operated two-way valve (23) to drain.
NOTE: The sensor of thermostatic pilot valve (21) must
If the engine oil pressure goes below 140 kPa
be below the water level in the coolant manifold to
(20 psi), the spring force on low speed oil protection
operate correctly.
valve (8) will close the valve. The oil flow in the circuit is
then stopped and can not flow to drain. The pressure of
When coolant temperature increases to 99C
the oil will become equal on both sides of orifice (14) and
(210F), thermostatic pilot valve (21) will open. This will
oil pressure switch (13) senses 760 kPa (I 10 psi). The
let oil in the circuit go to drain and cause a decrease in
normally open switch closes and activates an alarm.
engine oil pressure at low speed oil protection valve (8)
and high speed oil protection valve (9). The valves close
At approximately 70% of engine full load speed,
and stop oil flow through orifice (14). The pressure of
the oil pressure protection changes from the low speed
the oil will become equal on both sides of orifice ( 14)
range to the high speed range.
and oil pressure switch ( 13) senses 760 kPa ( I10 psi).
The normally open switch closes and activates an alarm.
When the engine speed increases to the high
speed range, speed sensing valve spool (5) will be
NOTE: When the engine is started, the low oil pressure -
moved up by the flyweights. This will send pilot oil to
high coolant temperature alarm will be activated for a
selector valve (3). This will close selector valve (3) and
short time until the engine has enough oil pressure to
re- move low speed oil protection valve (8) from the
open low speed oil protection valve (8) or' high speed oil
circuit. The oil must now flow to drain through high
protection valve (9).
speed oil protection valve (9) and pilot operated two- way
valve (23).
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