W345B Series II Material Handler Hydraulic System Main Hydraulic System Caterpillar


Main Hydraulic System
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1.1. Schematic for Main Hydraulic System
2.1. Hydraulic Pump Flow

Schematic for Main Hydraulic System




Illustration 1g00810508

Hydraulic schematic

(1) Left swing motor

(2) Right swing motor

(3) Left travel motor

(4) Right travel motor

(5) Grapple cylinders

(6) Boom cylinders

(7) Stick cylinders

(8) Left travel brake valve

(9) Right travel brake valve

(10) Boom lowering control valves

(11) Stick lowering control valves

(12) Stick drift reduction valve

(13) Swivel

(14) Main control valve

(15) Pressure switch (implement or swing)

(16) Pressure switch (travel)

(17) Boom raise pressure switch

(18) Solenoid valve (grapple)

(19) Pilot control valve (travel)

(20) Main relief valve

(21) Pilot control valve (swing or stick)

(22) Accumulator

(23) Pilot control valve (boom)

(24) Pilot filter

(25) Grapple rotate motor

(26) Rotate control valve

(27) Grapple rotate pump

(28) Oil cooler

(29) Slow return check valve

(30) Bypass check valve

(31) Drain filter

(32) Hydraulic activation control valve

(33) Return filter

(34) Radiator

(35) Cooling pump relief valve

(36) Fan motor

(37) Hydraulic tank

(38) Solenoid valve (fine control)

(39) Solenoid valve (travel speed)

(40) Solenoid valve (swing)

(41) Proportional reducing valve

(42) Pilot relief valve

(43) Pilot oil manifold

(44) Lower pump

(45) Upper pump

(46) Automatic travel speed change valve

(47) Cooling pump

(48) Pilot pump

Hydraulic Pump Flow




Illustration 2g00810889

Pump compartment

(44) Lower pump

(45) Upper pump

(49) Housing

(50) Outlet line (upper pump)

(51) Outlet line (lower pump)

This machine is driven and controlled by the following systems.

  • The main hydraulic system supplies oil to the cylinders and motors of the machine.

  • The pilot hydraulic system supplies oil to the control circuits.

  • The electronic control system controls the output from the engine and the pump.

  • The cooling system supplies oil from the cooling pump to fan motor (36). The fan creates an air flow in order to cool the hydraulic oil and the coolant.

The main hydraulic system oil is supplied by lower pump (44) and upper pump (45). Pumps (44) and (45) are variable displacement piston pumps. Pumps (44) and (45) are identical in performance. Lower pump (44) is directly connected to the engine by a flexible coupling. Pumps (44) and (45) are mechanically connected in parallel through gears. Gear type pilot pump (48) supplies oil to the pilot hydraulic system. Gear type pilot pump (48) is directly connected to lower pump (44) by a gear. All engine output is used to drive these three pumps.

Each of the main pumps outputs approximately 360 L/min (95 US gpm) of hydraulic oil at no load. The pilot pump outputs approximately 41 L/min (10.85 US gpm) of hydraulic oil at no load. When a load is placed on the machine, the hydraulic oil is supplied to the main hydraulic circuit.

When the load increases, the delivery pressure increases and the oil flow rate decreases. The system maintains constant hydraulic horsepower even though the delivery pressure and the oil flow rate change. The hydraulic horsepower is approximately identical to the engine horsepower.

The hydraulic oil of the cooling system is supplied by cooling pump (47). Pump (47) is a fixed displacement piston pump. Fan motor (36) rotates at high speed. High cooling capacity results due to the delivery pressure of cooling pump (47).




Illustration 3g00810903

Main control valve compartment (view from front of machine)

(20) Main relief valve

(52) Left control valve body (lower pump)

(53) Right control valve body (upper pump)

The oil from lower pump (44) and upper pump (45) enters left valve body (52) and right valve body (53) of main control valve (14). When no work is being performed, pump oil flows through the main control valve and the oil returns to hydraulic tank (37). The main control valve sends a negative flow control signal to each main pump in order to destroke to the minimum output flow.

If an operation is being performed, main control valve (14) directs pump oil to the respective cylinders (boom, stick, and grapple) and/or motors (swing and travel). Main control valve (14) contains numerous valve stems, passages, check valves, and orifices in order to carry out a single operation or a combined operation. The working pressure of the main hydraulic system is restricted by main relief valve (20). The main relief valve is set for a maximum oil pressure of 33830 to 34810 kPa (4907 to 5050 psi).

The oil flow from the pilot pump is constant as the oil enters the pilot system. The maximum pressure of the pilot system is restricted by the pressure setting of pilot relief valve (42) .

Reference: For more information about the pilot hydraulic system, see Systems Operation, "Pilot Hydraulic System".

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