Chapter 16
Open-Center Hydraulic Systems 379
Overview and Introduction to Open-Center Systems . . . 379
Disadvantages of Open-Center Systems . . . . . . . . . . . . . 381
Advantages of Open-Center Systems. . . . . . . . . . . . . . . 382
Open-Center System Applications . . . . . . . . . . . . . . . . 382
Valves and Designs . . . 382
Series . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
Parallel . . . . . . . . . . . . . . . . . . . . . . . . . . 384
Flow Dividers and Priority Valves . . . . . . . . . . . . . . . . 384
Jammer Solenoids . . . . . . . . . . . . . . . . . . . . . . 384
Varying Cylinder Speeds in Open-Center Hydraulic Systems . . . 388
Tandem Two-Stage Systems . . . 390
Two-Stage Log Splitters . . . . . . . . . . . . . . . . . . . . 390
Tandem Open-Center Loader Backhoe . . . . . . . . . . . . . . 392
Chapter 17
Pressure-Compensating (PC) Hydraulic Systems 399
Introduction to Closed-Center Systems . . . 399
Pressure-Compensating Pump Symbols . . . 400
Pump Frame Designs . . . 400
John Deere Radial Displacement PC Systems . . . . . . . . . . . 400
Inline Axial Piston Pump PC Systems. . . . . . . . . . . . . . . 409
Advantages and Disadvantages of PC Systems . . . 412
Why Open-Center Hydraulic Systems
Do Not Operate at Maximum Pressure . . . 412
Chapter 18
Load-Sensing Pressure-Compensating (LSPC)
Hydraulic Systems 417
Introduction to Load-Sensing Pressure-
Compensating (LSPC) Hydraulic Systems . . . 417
Load-Sensing System . . . 418
Fixed-Displacement Pump Standby Mode . . . . . . . . . . . . . 420
Fixed-Displacement Pump Working Mode . . . . . . . . . . . . . 420
Stall Pressure . . . . . . . . . . . . . . . . . . . . . . . . 421
Signal Network . . . 422
Primary Shuttle Valve . . . . . . . . . . . . . . . . . . . . . 422
Secondary Shuttle Valve. . . . . . . . . . . . . . . . . . . . 422
Diagnosing Secondary Shuttle Valves . . . . . . . . . . . . . . 427
Load-Sensing System with Single-Acting Actuator . . . . . . . . . . 427
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