How to temporarily adjust the main safety valve of the Caterpillar 320C excavator
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(Note: The main safety valve needs to be temporarily adjusted before adjusting any pipeline safety valve.)
1) Park the machine on flat ground.
2) Shut down the engine.
3) Release the pressure in the hydraulic system, refer to the “Pressure Relief of the Hydraulic System” section.
4) As shown in Figure 2-3-167, connect a 60000kPa pressure gauge to the pressure measuring joint 1. Connect a 60000kPa pressure gauge to pressure measuring joint 2.
5) Connect a 6000kPa pressure gauge to pressure measuring joint 3.
6) Start the engine. 2023 CAT ET 2023A 2022A & 2019C Full Service Download and Installation Service
7) 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 settings.
8) Increase the hydraulic oil temperature to (55 ±5)°C.
9) Slowly move the bucket’s control lever to the BUCKET OPEN position (the bucket cylinder piston rod is in the fully retracted position).
10) Check the pressure setting of the main safety valve at pressure measuring joint 1.
11) Return the bucket control lever to the NEUTRAL position.
12) The pressure setting value of the main safety valve should be (34300 ±490) kPa. If the pressure
setting of the main safety valve is not within specifications, adjust it to the correct value before
proceeding to step 13). See “Main Relief Valve Testing and Adjusting”.
13) As shown in Figure 2-3-168, loosen the locking nut 5 and adjust the screw 4.5 turns clockwise.
Tighten the lock nut 5 to the specified tightening torque. NOTE: Be sure to make final pressure
adjustments as pressure increases.
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