3.
BOOM PRIORITY SYSTEM ARM CYLINDER BUCKET CYLINDER BOOM CYLINDER SWING MOTOR ps1 T3 T4 ps2 T1 T2 TRAVEL MOTOR pa11 pa10 B5 DR1 pc1 pb9 A5 pb5 B9 A9 TURNING JOINT ARM2 pb9 pc1 pa5 (34,2) P2 BUCKET B8 A8 pa9 pb8 (34,1) DR2 pa11 pa8 pc2 A7 pb3 pb7 pa3 pa7 B7 pc2 pc7 BOOM1 A6 B6 pc6 TRAVEL-RH pb6 pa6 STRAIGHT TRAVEL P3 RCV PEDAL P T TRAVEL P2 pa6 pb6 pb1 pa1 (4) (1) (2) (3) SWING ARM BUCKET BOOM P T P T Dr#, dr# A1 A2 FRONT PUMP REAR PUMP PILOT PUMP Pk (T/Joint) PH (MCV) (4) (1) (2) (3) a b d e f g h j c d1 h1 PS PS PS (4) (1) (2) (3) A5 A1 A2 A3 PG (S/Motor) pb5 pa2 pb2 pa9 pb8 pa8 pa7 pb7 h2 P3 P2 P4 PP(MCV) HYDRAULIC TANK T(dr1) P1 LINE FILTER RELIEF VALVE 900L3HC04 When carrying out the combined operation of swing and boom up, the boom up operating speed is lowered then normal operation.
To increase working efficiency, swing speed reducing system is used. When the RH control lever is pulled back to the boom up position, the pilot oil from pilot pump flow into Pc6 port in main control valve through pa7 port. Pc6 oil pressure moves swing reducing spool to upper direction and oil flow rate to the swing motor decreased. Then, the boom up speed is increased. This is called the boom priority system. 3-8 p B B A A D p p ARM1 a5 PO B4 A4 1 OPTION 1 R7 c7 A3 B3 b3 B2 pa3 BOOM2 A2 pb2 SWING DR3 pa2 pc6 B1 A1 pp ab 11 TRAVEL-LH pr1 P1 PSPT PP PA PH SH PS