SECTION 3 HYDRAULIC SYSTEM Group 1 Hydraulic Circuit - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-1 Group 2 Main Circuit - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-2 Group 3 Pilot Circuit - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-5 Group 4 Single Operation - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-12 Group 5 Combined Operation - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-22

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GROUP 1 HYDRAULIC CIRCUIT T(dr2) 28 25 Pd2 Pc2 Pc4 0 Pa2 0 Pb2 0 T P A B D E G F H J (2) (4) (3) (1) SWING ARM BUCKET BOOM 7 5 6 (RG) Dr SRG ARG SH R/G R/G T Pm1 (Pump) Pm2 (Pump) Pd4 0 27 SH SGo GB PG A2 A1 Au Dr(R7) Pm2 Ps Pm2 Ps 22 Pa5 Pb5 (3) (1) (2) (4) Pm1 Pm1 T Pk (T/Joint) B(CW) Mu A(CCW) GA P1 P2 T1,T2 T1,T2 P2 P1 A1 A2 ACC 23 3 12 DR P 4 P1 P2 P3 P4 C A D B 21 Po1(MCV) PG(S/Motor) Pd1 Pc1 Pb1 Pa1 (1) (2) Pk S/Motor DB (3) (4) TRAVEL 26 15 17 Dr#,dr#,R# 19 14 18 M 13 P01 DR0 Pc4 Pd4 0 20 16 24 Pd1 Pc1 D1 Pd2 Pc2 DR2 0 DR3 Pd5 Pc5 Pi1 (Fl,MCV) Pi2 (Fr,MCV) STRAIGHT TRAVEL Ptr TRAVEL (LEFT) C1 SWING D2 C2 V3 BOOM UP Pa2 1 Pc3 Pc4 1 D4 C4 OPTION-B D5 C5 3-1 Pm1 ARM1 Dr a2 a1 1 T1 P2 P1 BC COMP.

Rs CK1 A1 A2 B1 B3 a4 Psv Pu NRV2 Pn2 Pn1 MRV BOOM REGENERATIION CUT NRV1 A3 a3 Pm2 TRAVEL (RIGHT) ARM2 OPTION-A BUCKET Pa1 A1 Pb1 B1 Patt P02 DR1 Pb2 1 A2 B2 1 Pd4 Pb3 Pc4 2 BREAKER Pa4 Pb4 B4 CK2 Pb5 A5 B5 2 24 Pa5 Pa2 Pb2 0 D21073HS01 0 SECTION 3 HYDRAULIC SYSTEM 10 11 8 9 1-CARTR' V/V 28 27 Shockless V/V 26 LAST G.FILTER 25 TERMINAL PRESSURE S/W 24 ACCUMULATOR 23 22 2-CARTR'V/V LINE FILTER 21 20 SPIN FILTER 19 STRAINER ASSY ELEMENT-RETURN BYPASS VALVE 18 17 AIR BREATHER 16 OIL COOLER 15 HYD.TANK ASSY 14 CHECK V/V 13 CHECK V/V 12 TURNING JOINT 10 11 ARM CYL BUCKET CYL BOOM CYL(R/H) 8 9 BOOM CYL(L/H) 7 RCV PEDAL 6 RCV LEVER(R/H) 5 RCV LEVER(L/H) 4 TRACK MOTOR 2 3 M.C.V SWING MOTOR PUMP 1 1 Main pump 2 Main control valve 3 Swing motor 4 Travel motor 5 RCV lever(LH) 6 RCV lever(RH) 7 RCV pedal 8 Boom cylinder(LH) 9 Boom cylinder(RH) 10 Arm cylinder 11 Bucket cylinder 12 Turning joint 13 Check valve 14 Check valve 15 Hydraulic tank 16 Oil cooler 17 Air breather 18 Bypass valve 19 Strainer 20 Spin filter 21 Line filter 22 Solenoid valve 23 Accumulator 24 Pressure switch 25 Shuttle valve 26 Last guard filter 27 Shockless valve 28 Solenoid valve SECTION 3 HYDRAULIC SYSTEM GROUP 1 HYDRAULIC CIRCUIT

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GROUP 2 MAIN CIRCUIT The main hydraulic circuit consists of suction circuit, delivery circuit, return circuit and drain circuit. The hydraulic system consists of one main pump, one control valve, one swing motor, four cylinders and two travel motors. The swash plate type variable displacement axial piston pump is used as the main pump and is driven by the engine at ratio 1.0 of engine speed. 1. SUCTION AND DELIVERY CIRCUIT To cylinders To motors Main control valve To oil cooler To hydraulic oil tank Main pump Suction filter Hydraulic oil tank (210-7) 3-03 The pumps receive oil from the hydraulic tank through a suction filter.

The discharged oil from the pump flows into the control valve and goes out the tank ports. The oil discharged from the main pump flows to the actuators through the control valve. The control valve controls the hydraulic functions. The return oil from the actuators flows to the hydraulic tank through the control valve and the oil cooler. 3-2

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2. RETURN CIRCUIT Check valve(2) 1.5kgf/cm 2 Full flow filter Oil cooler Main control valve Actuators Check valve(1) 3.0kgf/cm 2 Bypass relief valve 1.5kgf/cm 2 21073CI01 All oil returned from each actuator returns to the hydraulic tank through the control valve. The bypass check valves are provided in the return circuit. The setting pressure of bypass check valves are 1.5 kgf/cm 2 (21 psi ) and 3.0 kgf/cm 2 (43 psi ). Usually, oil returns to the hydraulic tank from the left side of control valve through oil cooler. When oil temperature is low, viscosity becomes higher and flow resistance increases when passing through the oil cooler.

When the oil pressure exceeds 3.0 kgf/cm 2 (43 psi ), the oil returns directly to the hydraulic tank, resulting in the oil temperature being raised quickly at an appropriate level. When the oil cooler is clogged, the oil returns directly to the hydraulic tank through bypass check valve(1). The full-flow filter and bypass relief valve are provided in the hydraulic tank. The oil returned from right and left side of control valve is combined and filtered by the full-flow filter. A bypass relief valve is provided in the full-flow filter. When the filter element is clogged, the bypass relief valve opens at 1.5 kgf/cm 2 (21 psi ) differential pressure. 3-3

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