SYSTEM / Control System Pressure Increase Selection Control When Trav- eling, Power Digging Control Purpose: Applies back-pressure to the main relief valve and increases main relief pressure. Operation: 1. When the pressure sensor (travel right or left) detects travel pilot pressure or when the power digging switch is turned in the ON position, MC activates solenoid valve unit (SG) (for eight sec- onds with the power digging switch ON). 2. Pressure oil from the pilot pump flows to the back of main relief valve. 3. Pressure oil compresses the spring of main relief valve and increases relief pressure. (Refer to the Control Valve group / COMPONENT OPERA- TION.) NOTE: Main Relief Pressure:
During normal operation: 31.9 MPa (325 kgf/cm 2 , 4638 psi) During pressure increasing operation: 34.3 MPa (350 kgf/cm 2 , 4987 psi) T2-2-44