BAIC Hydraulic System Service Manual PDF - HX900L Technical Guide (EN)

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 GROUP 1 HYDRAULIC CIRCUIT SECTION 3 HYDRAULIC SYSTEM SECTION 3 HYDRAULIC SYSTEM 1 Main pump 2 Main control valve 3-1 Swing motor 3-2 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 22 30 30 9 8 E PS Pi1 T(dr3) V2 11 10 T(dr2) E V2 Pi1 31 pa10 B9 A9 pb9 pa9 B8 A8 pb8 pa8 DR2 pc2 A7 B7 pb7 pa7 B6 A6 pb6 pa6 2 2 Travel(RH) (Pi2,Shuttle) (Pi1,Suttle) Arm 2 Bucket Boom 1 ps1 ps2 T3 T1 T2 T4 Arm 1 Option Boom 2 Swing pb4 A4 pa4 pb3 B3 B1 pc6 pa11 pc1 DR1 B5 A5 pb5 pa5 PO B4 (34,2) B B1 A A1 pc7 DR7 (34,1) A3 B2 pa3 A2 pb2 DR3 pa2 A1 PG SH PB B(CCW) TRAVEL (FW-LH) (BW-LH) (FW-RH) (BW-RH) A1 (43) A3 (43) P PG(S/Motor) PP(MCV) pb1 pa1 (3) (4) (3,F) (1,G) A1 A2 FC1 FC2 3-1 3-2 38 36 C A2 A3 41 24 26 G.P PS P T P T P T pb6 pa6 (1) (2) (2,D) (4,E) (3,B) (1,A) (Boom Down) A1 A2 A5 P4 P3 P2 P1 TRAVEL 1/2 SPEED POWER BOOST SAFETY LEVER A(CW) 35 37-1 37-2 B P2 T 7 26 6 26 5 26 T DB M PA A1 SWING ARM BUCKET BOOM (2,H) (4,J) h2 42 PH (MCV) G2 G1 P2(BW) P1(FW) A B D E F G H J PS PS c d1 h1 24 24 24 24 pb2 pa9 pa7 (Boom Up) Pk (T/Joint) PG R/G 12 P1 f g a b d e e2 PS pb8 pa8 (Bucket In) (Bucket OUT) ITEM PORT ITEM PORT J1 J3 J4 J2 D J E H SH PB PA B(CCW) LH RH R/G Dr Pk B A D C P Dr PS (Arm In) FROM TO 2 4 2 4 M1 M2 M3 M4 50 25 21 T(dr1) 4 4 Pi Pi ( ,A5) 21 P T (1) (2) Pb4 pb5 (Arm Out) 5 6 50 Dr G2 G1 26 34 Pa4 (Swing CCW) pa2 (Swing CW) J1J2J3 J4 ISO M1M2M3M4 A(CW) P2(FW) P1(BW) DB M 25 48 SECTION 3 HYDRAULIC SYSTEM GROUP 1 HYDRAULIC CIRCUIT 10 T(dr2) E V2 Pi1 31 (Pi1,Suttle) (Pi2,Shuttle) 2 ps1 T3 T1 T2 T4 ps2 (Pi1,Suttle) (Pi2,Shuttle) 2 ps1 T3 T1 T2 T4 ps2 pa11 DR1 pc1 B5 A5 pb5 Arm 1 pa5 PO B4 (34,2) A4 B B1 pb4 A A1 pa4 Option (34,1) DR7 pc7 A3 pb3 B3 pa3 Boom 2 B2 A2 pb2 Swing DR3 pa2 B1 pc6 A1 pb1 Travel(LH) pa1 pr1 PT P1 24PS 28 14 13 IN D R #,dr# 16 Dr OUT pa11 DR1 pc1 B5 A5 Arm 1 2 pa10 B9 A9 PO B4 A4 B1 pb4 A1 pa4 Option DR7 pc7 A3 B3 pb9 Arm 2 pa9 B8 A8 pb8 Bucket pa8 DR2 pc2 A7 B7 pa3 Boom 2 B2 A2 pb2 Swing DR3 pa2 B1 pc6 A1 pb1 Travel(LH) pa1 pr1 PT P1 24PS PP PA PH pb7 Boom 1 pa7 B6 A6 pb6 Travel(RH) pa6 P3 P2 24 PS 22 23 a1 a2 PS Psv1 PS PS Psv2 a A1 A2 a4 1 26 Pi1 PS 23 M 27 OUT IN Dr1,r2 B1 D r3,r4 5 26 20 19

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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 main control valve, two swing motors, four cylinders and two travel motors. The swash plate type variable displacement tandem 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 Suction strainer Main pump Hydraulic oil tank 140L3CI01 The pumps receive oil from the hydraulic tank through a suction strainer.

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

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2. RETURN CIRCUIT Full flow filter Oil cooler Check valve(2) 1.5kgf/cm 2 Main control valve Actuators Check valve(1) 5.0kgf/cm 2 Check valve(3) 1.5kgf/cm 2 8007A3CI01 All oil from each actuator returns to the hydraulic tank through the main 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 5.0 kgf/cm 2 (71 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.

The oil pressure exceeds 5.0 kgf/cm 2 (71 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 from right and left side of control valve is combined and filtered by the return 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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