Chapter 10
Controlling the System
Pressure, Direction, and Flow 273
Primary Control Functions in a Hydraulic
System 274
Basic Structure and Features of Control
Valves 275
Valve Body Construction and
Function 276
Fluid Control Elements 276
Positioning of Control Valve Internal
Elements 279
Draining Internal Leakage 279
Identifying Normal Valve Position 280
Valve Operation and Springs, Fluid Pressure,
and Fluid Flow 281
Springs and Their Use in Valves 281
Fluid Pressure Used as a Valve
Operator 281
Fluid Flow Used in Valve Operation 282
Pressure Control Devices 283
System Maximum Pressure
Control 284
Actuator Sequence Control 288
Restrained Movement Control 289
Pump Unloading Control 293
Reduced Pressure Control 297
Directional Control Devices 299
Shut-Off Valves 300
Check Valves 302
Three-Way Valves 305
Four-Way Valves 306
Actuation Methods for Directional
Control Valves 310
Holding Position in Multiple-Position
Directional Control Valves 314
Flow Control Devices 314
Fluid Mechanic Concepts Basic to Flow
Control Devices 316
Restrictor-Type, Noncompensated Flow
Control Valves 316
Restrictor-Type, Compensated Flow
Control Valves 318
Bypass-Type Flow Control Valves 321
Flow Divider Valves 325
Chapter 11
Accumulators
Pressure, Flow, and Shock Control
Assistance 331
Basic Functions of an Accumulator 332
Accumulator Design and Operation 333
Weight-Loaded Accumulators 333
Spring-Loaded Accumulators 333
Gas-Charged Accumulators 334
Functions of Accumulator Circuits 337
Storing Energy 338
Dampening Pressure and Flow
Variations 338
Maintaining System Pressure 339
Supplementing Pump Output 340
Selecting and Sizing Accumulators 340
Rated Capacity and Pressure
Ratings 340
Usable Operating Volume 342
Setup and Maintenance of
Accumulators 343
Mounting Position 343
Precharging 343
Working Safely with
Accumulators 345
Chapter 12
Conditioning System Fluid
Filtration and Temperature
Control 349
Need for Fluid Conditioning 350
Contaminants and Their Sources 350
Effects of Contamination 351
System Operating Temperature 351
Controlling and Removing
Contaminants 353
Contamination Control and the
Reservoir 353
Strainers and Filters 354
Locating Filtering Devices in a
System 358
Routing Fluid Flow for Filtration 360
Filter System Maintenance 362
10 Fluid Power