a 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. The pilot oil from pilot pump flow into Pc6 Pc6 port in main control valve. Pc6 Pc6 oil pressure moves boom priority spool to upper position and oil flow rate to the swing motor decreased. Then, the boom up speed is increased. This is called the boom priority system. 3-9 .
BOOM PRIORITY SYSTEM DA R M RB U C K E T EB O O M C Y L IN E R C Y L IN D E C Y L IN D R S W IN G M O T O R ps1 T3 T1 T2 T4 ps2 pa11 pa10 DR1' DR1 pc1 T R A V E L M O T O R B5 A5 B9 A9 pb5 ARM 1 pb9 ARM 2 p Ba 45 pa9 B8 A4 A8 pb4 pb8 BUCKET pa8 pa4 OPTION DR2' DR2 A3 pc2 A7 B3 B7 B2 p pb a3 3 BOOM 2 Dpb R7 4 BOOM 1 pc7 A2 pa7 B6 pb2 DR3 SWING A6 pa2 B PO RIO OM RITY pb6 B1 pc6 SPOOL TRAVEL(LH) pa6 A1 pb1 pa1 pr1 TRAVEL(RH) TRAVEL STRAIGHT TRAVEL P T P3 P1 PSPT PP PA PH P2 PS (2) (1) (4) (3) pa6 pb6 pb1 pa1 CROSS ASSY ING P T ARM BUCKET P T BOOM P1 T1 P2 T2 P U MA 1 P P U M PA 2 PP MILO PT P3 T3 U P T dr# 1) (3) (2) (4) (3) (1) (2) (4) A B D E F G H J F PH (T/JOINT)(MCV) c b d1 d e2 e f1 f g g1 h h1 j j1 A5 A2 A1P4 Pi(D/C VALVE) b2 PS pa2 PS PS PS PS PS PS P3 PP(MCV) Td# P2 P(2-EPPR) P pb5 pb9 B CA (Td#)T P1 H Y D R A U LIC T A N K pa5 pc1 pa9 pb8 pa11 pa8 pa3 LINE FILTER pc2 pb7 pb3 pc6 pa7 480A3HC04 A5 pb5 ARM 1 pa5 B4 A4 pb4 pa4 OPTION A3 B3 pb3 B2 pa3 BOOM 2 A2 pb2 BOOM PRIORITY SPOOL TRAVEL(LH TRAVEL STRAIGHT A6 pb6 pa6 ) P3 P2 T ARM B (2) (4) B D E 1) (3) A (3) (1) (2) F G H J c b2 PS pa b d1 d e2 e f1 2 PS PS PS f g g1 h h1 j j PS PS CROSS ASSY P1 P2 P3