How to test and adjust the pilot safety valve of Caterpillar 320C excavator 

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 (1) Park the machine on flat ground. 

 (2) Turn off the engine. 

 (3) Release the pressure of the hydraulic system, refer to the "Pressure Relief of the Hydraulic System" section.  

(4) As shown in Figure 2-3-169, connect a 6000kPa pressure gauge to the pressure measuring joint 30.

  (5) Start the engine.  

(6) Set the machine control volume as follows: the engine tachometer is set to 10, and the AEC switch is set to OFF. See the "Engine Performance Testing" section for engine RPM setting.  

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  (7) Increase the hydraulic oil temperature to (55±5)℃. 

 (8) Check the setting of the pilot safety valve at pressure measuring joint 30. 

 (9) The pilot safety valve should be set at (4100+200) kPa. If the setting value is not within the technical specifications, adjust the pilot safety valve.  

(10) To adjust the pilot safety valve, loosen lock nut 28. 

 (11) Rotate the positioning screw 29 until the pressure gauge connected to the pressure measuring joint 30 reads (4100±200) kPa. Note: Turn the set screw 29 clockwise to increase the pressure; turn the set screw 29 counterclockwise to decrease the pressure. Be sure to make final pressure adjustments as pressure increases. 

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 (12) Tighten the locking nut 28 to a tightening torque of (49±4.9) N.m. Note: Normal operation of the engine and pump is required when making pressure adjustments. If the pressure adjustment result is incorrect, check the engine and pump characteristic curves.