PUMP 1R8671 - Caterpillar

Direct Return
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Partial schematicOne-Way / One or Two Pump - Electronic Control with Direct Return (8) Main control valve (14) Hydraulic oil cooler (23) Hydraulic tank (29) Return lineOne-Way / One or Two Pump - Electronic Control with Direct Return System allows the return oil from the work tool to return directly to the hydraulic tank in one-way flow mode. This system is commonly used with hammers.The direct return system allows for a high flow of oil through the work tool by bypassing the return check valves and oil cooler that will cause resistance in the return system.Cooling Circuit
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Partial schematicOne-Way / One or Two Pump - Electronic Control with Direct Return and Cooling Circuit (8) Main control valve (14) Hydraulic oil cooler (23) Hydraulic tank (29) Return line (30) Auxiliary pump (31) Return lineMachines equipped with One-Way / One or Two Pump - Electronic Control with Direct Return System may also be equipped with a cooling circuit. The cooling circuit utilizes an auxiliary pump to circulate oil from the hydraulic tank back through the oil cooler and to the hydraulic tank.One-Way Flow from One Pump
One-way flow from one pump can be achieved by selecting a work tool that requires one-way flow from one pump. The work tool can be selected through the monitor or by the work tool select switch. A typical example is a hammer that receives oil from one pump only.When one pump flow is required to the work tool, the pump supplying the oil can be programmed through the monitor. The following situations are listed to increase controllability of the work tool.
When the work tool with a boom and bucket operation is used most often, the idler pump is recommended as the supply pump.
When the work tool with a stick and swing operation is used most often, the drive pump is recommended as the supply pump.ReferenceRefer to Testing and Adjusting, "Work Tool Parameter - Program" for the tool control system to change the settings for work tool operation.ReferenceRefer to Testing and Adjusting, "One-Way / One or Two Pumps - Electric Control: Default Value of Work Tool Parameters" for the Tool Control System to reference the factory settings.
Table 1
Operation Lever List    
Control     Extension    
Right joystick thumb wheel     Push Forward    
Electric foot pedal     Push Forward    
Electric foot switch     Push ON    
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One-Way Flow from One Pump (idler pump) (1) Tool relief valve (4) Proportional reducing valve (Flow limit 1) (5) Proportional reducing valve (Flow limit 2) (7) Proportional reducing valve (A2 extend) (11) F2.2 stack valve (13) Attachment control valve (14) Attachment control valve (23) Hydraulic tank (25) Idler pump (26) Drive pump (27) Pilot pumpThe following description is made under the assumption that the idler pump is supplying oil to the work tool.When the device for activation listed in Table 1 is pressed, the machine ECM sends a modulated signal to proportional reducing valve (15). Proportional reducing valve (7) allows pilot oil to flow to