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Caterpillar hydraulic excavators serie D
SERV1852-02 August 2008 GLOBAL SERVICE LEARNING TECHNICAL PRESENTATION 320D-336D HYDRAULIC EXCAVATORS TIER III ENGINES MAIN CONTROL VALVE GROUP AND RETURN SYSTEM Service Training Meeting Guide (STMG) 320D-336D HYDRAULIC EXCAVATORS TIER III ENGINES MAIN CONTROL VALVE GROUP AND RETURN SYSTEM AUDIENCE Level II - Service personnel who understand the principles of machine systems operation, diagnostic equipment, and procedures for testing and adjusting CONTENT This presentation provides an introduction and describes the components and systems operation of the 320D-336D main control valve group and return system Additional presentations will cover the machine walkaround, engines, pilot system, pumps and controls, swing system, travel system, and tool control systems in more detail This presentation may be used for self-paced and self-directed training OBJECTIVES After learning the information in this presentation, the technician will be able to: identify the components and explain the operation of the 320D-336D hydraulic excavators main control valve group and return system, and diagnose problems in the main control valve group and return system REFERENCES 320D Hydraulic Excavator Specalog 323D L and 323D LN Hydraulic Excavators 324D Hydraulic Excavator Specalog 325D Hydraulic Excavator Specalog 328D Hydraulic Excavator Specalog 330D Hydraulic Excavator Specalog Machine Monitoring System - Systems Operation Self-study "300D Series Hydraulic Excavators, 345C Hydraulic Excavator, and 365C & 385C Large Hydraulic Excavators iTIM " '300C' Series Hydraulic Excavators-Electronic Control Systems" iTIM "325C Hydraulic Excavators-Hydraulic Systems" 325D Hydraulic Schematic Estimated Time: Hour Illustrations: 22 Form: SERV1852-02 Date: August 2008 © 2008 Caterpillar AEHQ5856 HEHH3327 AEHQ5663 AEHQ5665 AEHQ5706 AEHQ5667 RENR8068 SERV7032 SERV2693 SERV2701 KENR6157 SERV1852-02 08/08 -3- Text Reference Main Control Valve Group TABLE OF CONTENTS INTRODUCTION Main Control Valve Group .6 Additional Components 15 Return Hydraulic System 24 CONCLUSION 29 SERV1852-02 08/08 -4- Text Reference Main Control Valve Group PREREQUISITES "Fundamentals of Mobile Hydraulics Self Study Course" "Fundamentals of Power Train Self Study Course" "Fundamentals of Electrical Systems Self Study Course" "Fundamentals of Engines Self Study Course" TEMV3002 TEMV3003 TEMV3004 TEMV3001 NOTES Nomenclature Change: During the fourth quarter of 2008, the 325D and 330D nomenclature changed The 325D became the 329D and the 330D became the 336D for most arrangements The exceptions are as follows: - The nomenclature for the 325D MH and 330D MH did not change - The nomenclature for the 325D FM and 330D FM did not change - The 325D HD HW did not change into 329D HD HW This model is being discontinued However, the 330D HD HW changed to the 336D HD HW SERV1852-02 08/08 -5- Text Reference Main Control Valve Group MAIN CONTROL VALVE GROUP AND RETURN SYSTEM Stick Cylinder Bucket Cylinder Swing Motor Main Control Valve Group Pilot Control Valves Priority Valves Pilot Manifold Pilot Pump Fan Motor Boom Cylinders Travel Motors Main Hydraulic Pumps M Fan Pump Tank The Fan Motor and Pump are only used on the 330D and 336D INTRODUCTION The main hydraulic system is a Negative Flow Control (NFC) System that supplies hydraulic power at high pressures and high flow rates to perform work Two main hydraulic pumps supply oil to the main control valve group The individual hydraulic circuits are controlled by valves in the the main control valve group The main hydraulic system supplies the following circuits: - swing - stick - left and right travel - bucket - auxiliary - boom Oil returning from these circuits flows back to through the return system to the hydraulic tank SERV1852-02 08/08 -6- Text Reference Main Control Valve Group 10 11 13 12 Main Control Valve Group The main control valve group is located in the center of the upper structure of the machine The main control valve group receives pilot oil signals from the operator controls in the cab Each pilot signal then causes the appropriate control valve to shift in the correct direction When a control valve shifts, oil flows from the main hydraulic pumps to the appropriate hydraulic cylinder or hydraulic motor to perform work The medium 320D-336D main control valve is similar to the medium 300C Series valve The components shown above include: - right side NFC relief valve (1) - main relief valve (8) - stick (2) - left travel (9) - boom (3) - swing (10) - bucket (4) - stick (11) - attachment (5) - boom (12) - right travel (6) - auxiliary valve for tool control (13) - straight travel valve (7) SERV1852-02 08/08 -7- Text Reference Main Control Valve Group MAIN CONTROL VALVE NEUTRAL Boom Stick Swing NFC Signal Pressure for Idler Pump Left Travel Parallel Feeder Passage Right Travel Attach Bucket Boom Stick NFC Signal Pressure for Drive Pump Drive Pump Inlet Port Idler Pump Inlet Port Return Port NFC Orifice Return Passage Center Straight Travel Valve Bypass Passage Center Bypass Passage Return Passage NFC Orifice The above illustration shows a cross-sectional view of the main control valve group as viewed from the rear of the machine, facing forward The main control valve group is constructed of two valve blocks that are connected together The drive pump provides oil flow for the right side of the main control valve group The idle pump provides oil flow for the left side of the main control valve group The pilot-operated, open-center control valves are of parallel feeder design Because the main control valve group uses the open-center portion of the control valve to generate a NFC signal for the pumps, the oil must have another path to deliver oil to the work ports This is accomplished through a parallel feeder path A parallel feeder path runs parallel to the open-center path and supplies oil to the work port of each implement valve When all of the joysticks and pedals are in the NEUTRAL position, drive pump oil flows through the right pump inlet port to the right half of the main control valve group In the right half of the main control valve group the oil flows two directions; to the center bypass passages, and to the parallel feeder passages SERV1852-02 08/08 -8- Text Reference Main Control Valve Group The oil in the center bypass passages flows in series through the center bypass passage of the travel, the attachment, the bucket, the boom 1, and the stick valves to the NFC control orifice The NFC control orifice allows the oil to return to tank with a restriction This restriction provides an NFC signal pressure which is sent to the drive pump to maintain the drive pump at minimum angle when the control valves are all in NEUTRAL In NEUTRAL this NFC signal is the same as the supply pressure The oil in the parallel feeder passage flows in parallel to the attachment, the bucket, the boom 1, and the stick valves Since all of the valves are in NEUTRAL, the oil in the parallel feeder is blocked by the valve spools, and all oil must flow through the center bypass to the tank The oil from the idler pump flows similarly through the left half of the control valve when all valves are in NEUTRAL SERV1852-02 08/08 -9- Text Reference Main Control Valve Group MAIN CONTROL VALVE GROUP NEGATIVE FLOW CONTROL OPERATION - NEUTRAL Drift Reduction Valve Parallel Feeder Passage Straight Travel Solenoid Stick Regen Valve Boom Bucket Valve Attachment Valve NFC Relief Valve Straight Travel Stick NFC Orifice Swing Right Travel Stick Boom Left Travel Main Relief Stick Unloading Valve NFC Signal Line (Idler Pump) Swing PRV Variable Swing Priority Valve Line Relief and Makeup Valve Parallel Feeder Passage Boom Regen Valve NFC Relief Valve Idler Pump Pilot Oil M Heavy Lift Solenoid Drive Pump Pilot Pump NFC Signal Line (Drive Pump) The schematic for the main control valve group is shown above All of the circuit control valves are in NEUTRAL Oil from the idler pump and drive pumps flows to the straight travel valve From the straight travel valve, the supply oils flow through the center envelop of all of the control valves in NEUTRAL Some of the supply oil also enters the parallel feeder passages Since the control valves are in NEUTRAL the supply oil flows through all of the valves to the tank Some of this oil becomes NFC signal oil and destrokes the two pumps SERV1852-02 08/08 Load Check Valve - 10 - Port A Text Reference Main Control Valve Group Port B CONTROL VALVE NEUTRAL Parallel Feeder Passage Line Relief and Makeup Valve Pilot Valve Pilot Valve Center Bypass Passage Full NFC Signal Control Spool Centering Spring Load Check Valve Control valve operation is similar for all of the valves in the main control valve group The following explanation is for the basic operation of all of the valves in the main control valve group The variations in each individual valve will be discussed later in more detail The control valve above is shown in NEUTRAL The valve spool is spring centered in NEUTRAL when there is no pilot oil pressure directed to shift the spool In the NEUTRAL position, the spool blocks the oil in Port A and Port B Oil flows from the pump to the parallel feeder passage The load check valve is seated because of the pressure differential and spring force present on the load check valve In NEUTRAL, the valve spool allows oil to flow unrestricted through the center bypass passage, which directs a high NFC signal pressure to the pump control valve The high NFC signal pressure causes the pump to destroke to a standby condition SERV1852-02 08/08 - 15 - Text Reference Main Control Valve Group 10 Additional Components The main relief valve (1) is located in the left half of the main control valve group The main relief valve limits the maximum operating pressure of the the travel and implement hydraulic circuits For the NACD market the 300D Series main relief valve has two settings One setting is for the standard maximum pressure and the other setting is for Heavy Lift In all other markets Heavy Lift is optional When energized the heavy lift solenoid (not shown) sends a pilot signal through the line (2) at the top of the relief valve to increase the pressure setting of the main relief valve When heavy lift is selected, the Machine ECM limits engine speed to speed dial and activates the heavy lift solenoid The heavy lift solenoid directs pilot oil to the main relief valve to increase the relief valve setting At the same time the Machine ECM increases the power shift pressure to decrease the pump output flow Decreasing the pump output flow provides increased controlability and hydraulic smoothness during a heavy lift operation The Heavy Lift Mode limits the pumps to a maximum of approximately 60% of the normal hydraulic horsepower Heavy Lift Specs: - Engine rpm for Heavy Lift is the engine speed dial setting - Hydraulic horsepower is limited to 60% of full power during Heavy Lift - Main relief maximum pressure during Heavy Lift is 36000 kPa ± 490 kPa (5225 ± 70 psi) SERV1852-02 08/08 - 16 - Text Reference Main Control Valve Group 11 12 Heavy lift is activated by pressing the heavy lift switch (1) on the soft switch panel (2) in the operators station The heavy lift switch is an input to the Machine ECM The heavy lift solenoid (3) is located near the hydraulic tank and below the main control valve group SERV1852-02 08/08 - 17 - Text Reference Main Control Valve Group STRAIGHT TRAVEL CONTROL VALVE AND MAIN RELIEF VALVE Pilot Oil Main Control Valve Straight Travel Solenoid Parallel Feeder Left Center Bypass Left Heavy Lift Solenoid Main Relief Valve Travel Control Valve Straight Travel Solenoid Center Bypass Right Straight Travel Control Valve Center Bypass Right Main Relief Valve Check Valves Parallel Feeder Right Idler Pump Parallel Feeder Right Drive Pump Center Bypass Left Idler Pump E Drive Pump Parallel Feeder Left Straight Travel Control Valve Pilot Oil Heavy Lift Solenoid 13 The drive pump oil flow enters the main control valve group through the upper delivery line The idler pump oil flow enters the main control valve group through the lower delivery line The drive pump oil and idler pump oil pressures work against the two check valves The oil from both pumps is directed to the appropriate passages by the straight travel valve The check valves ensure that only the higher pressure from the idler or the drive pump flows to the main relief valve The check valves also ensure that flow from the highest supply pressure circuit does not enter the other supply pressure circuit if the pressure is lower For example, if the bucket was being closed at a high pressure and no other function was active, the lower check valve would close The check valve would prevent the drive pump oil from flowing through the center bypass in the left circuit This action ensures that the higher supply pressure is always sensed at the relief valve The relief valve will open when a circuit is stalled, limiting the maximum system pressure SERV1852-02 08/08 - 18 - Text Reference Main Control Valve Group MAIN RELIEF VALVE Heavy Lift Solenoid HEAVY LIFT OFF Heavy Lift Solenoid HEAVY LIFT OFF Heavy Lift Solenoid HEAVY LIFT ON Pilot Oil Pilot Oil Pilot Oil Adjustment Nut Adjustment Nut Lock Nut Lock Nut Lock Nut Lock Nut Spindle Spindle Piston Piston Poppet Unloading Spool Poppet Unloading Spool Orifice Orifice Pump Supply Pump Supply Pump Supply CLOSED OPEN CLOSED 14 The above illustration shows the pilot operated main relief valve equipped with the heavy lift solenoid At lower system pressures the poppet is held against the the seat by the force of the spring System pressure in the passage flows through the orifice into the spring chamber above the unloading spool When the force applied by system pressure is less than the value of the upper spring, the poppet remains seated, causing the oil pressure in the lower spring cavity to equal system pressure The combined force of the lower spring and system pressure holds the unloading spool down As the system pressure nears the main relief valve pressure setting, the force of the system pressure in the lower spring chamber overcomes the force of the upper spring This causes the poppet to unseat, allowing system oil to flow around the poppet to the return passage As the oil in the lower spring chamber flows around the poppet, additional system pressure oil flows through the orifice into the lower spring chamber at a reduced pressure System pressure overcomes the force of the oil pressure in the lower spring chamber and the spring, causing the unloading spool to move upward As the unloading spool moves upward, system pressure oil is allowed to flow to the return passage SERV1852-02 08/08 - 19 - Text Reference Main Control Valve Group The amount of spring force acting on the poppet determines the main relief valve pressure setting Adjustments to the main relief valve pressure setting are made by changing the spring force of the upper spring Heavy Lift increases the maximum system pressure When the Heavy Lift is activated, the Heavy Lift solenoid is energized sending pilot hydraulic oil to the top end of the main relief valve The pilot hydraulic oil pushes the piston down compressing the poppet spring to increase the maximum system pressure To adjust the maximum system pressure turn the adjustment nut in or out To adjust the Heavy Lift pressure setting, the spindle must be turned in or out The Heavy Lift pressure setting should be adjusted first before adjusting the normal relief pressure SERV1852-02 08/08 - 20 - Text Reference Main Control Valve Group LINE RELIEF AND MAKEUP VALVE CLOSED Poppet MAKEUP RELIEF Poppet Spring Spring Inner Spool Inner Spool Outer Spool Spring Chamber Spring Chamber Outer Spool Piston Piston Step Outer Spool 15 The above illustration shows a combination line relief and makeup valve in the closed, relief, and makeup positions At lower system pressures, the poppet is held against a seat by the force of the upper spring The circuit pressure in the passage flows through a cross-drilled orifice in the piston to the spring chamber above the inner spool When the force applied by system pressure is less than the value of the upper spring, the poppet remains seated, causing the oil pressure in the lower spring cavity to equal system pressure The combined force of the lower spring and system pressure keep the inner spool seated As the system pressure nears the line relief valve pressure setting The force of the system pressure in the lower spring chamber overcomes the force of the upper spring This causes the poppet to unseat, allowing system oil to flow around the poppet to the return passage As the oil in the lower spring chamber flows around the poppet, additional system pressure oil flows through the orifice in the piston from the lower spring chamber at a reduced pressure System pressure overcomes the force of the oil pressure in the lower spring chamber and the spring, causing the inner spool to move upward As the inner spool moves upward, system pressure oil is allowed to flow to the return passage ... 32 5D FM and 33 0D FM did not change - The 32 5D HD HW did not change into 32 9D HD HW This model is being discontinued However, the 33 0D HD HW changed to the 33 6D HD HW SERV185 2-0 2 08/08 -5 - Text... equipment, and procedures for testing and adjusting CONTENT This presentation provides an introduction and describes the components and systems operation of the 32 0D- 33 6D main control valve group and return... System - Systems Operation Self-study "30 0D Series Hydraulic Excavators, 345C Hydraulic Excavator, and 365C & 385C Large Hydraulic Excavators iTIM " ''300C'' Series Hydraulic Excavators-Electronic