Pressure-Compensating System . . . 427
Pressure-Compensating Hydraulic Pump . . . . . . . . . . . . . 428
Pressure-Compensated DCV . . . . . . . . . . . . . . . . . . 428
LSPC Systems and Variable-Displacement Pumps . . . 432
Relating Constant-Flow LSPC to Variable-Flow LSPC . . . . . . . . 433
LSPC Variable-Displacement Pump Symbols . . . 433
LSPC Variable-Displacement Pump Modes of Operation . . . 433
Low-Pressure Standby . . . . . . . . . . . . . . . . . . . . 433
Working Mode. . . . . . . . . . . . . . . . . . . . . . . . 437
Stall Mode . . . . . . . . . . . . . . . . . . . . . . . . . 442
Main System Relief in Variable-Displacement LSPC Systems . . . 443
Torque-Limiting Control . . . 444
Corner Horsepower. . . . . . . . . . . . . . . . . . . . . . 444
Jammer Solenoids and Implications of Connecting
the Pump Outlet to a Signal Network . . . 446
Reasons to Use a Jammer Solenoid in an LSPC System . . . . . . . 447
Power Beyond in LSPC Systems . . . 448
DCV Hydraulic Detent Kickout in LSPC Systems . . . 449
Variable-Displacement LSPC System Advantages . . . 451
Variable-Displacement LSPC System Disadvantages . . . 451
Chapter 19
Flow Sharing/Downstream Compensation 457
Introduction to Flow Sharing/Post-Spool Compensation . . . 457
How Post-Spool Compensation Works . . . 460
Why Use a Signal Relief Valve? . . . 463
Flow Sharing with Double-Acting Actuators (Passageways) . . . 465
Operating Pressures in a Downstream-Compensated
System with Demands Met . . . 467
Caterpillar Proportional Priority Pressure Compensation (PPPC) . . . 467
Case Machines with Downstream Compensation . . . 467
721F, 821F, and 921F Wheel Loaders . . . . . . . . . . . . . . . 467
1650K and 1850K Crawler’s Use of an Unloading Valve. . . . . . . . 469
B-Series Motor Grader and 580/590N and SN Loader Backhoes . . . . 469
Other Terminology for Flow Sharing . . . 469
Chapter 20
Excavator Pump Controls 473
Introduction to Negative Flow Control (NFC)
and Positive Flow Control (PFC) Systems . . . 473
Pump Regulators . . . 474
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