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Chapter 1

Hydraulic Safety 1

Introduction to Safety ...1

Personal Protective Equipment (PPE) ...1

Eye Protection 2

Clothing 3

Hearing Protection 3

Hard Hats 3

Foot Protection 3

Emergency Preparedness ... 4

Fire Suppression 4

Safety Data Sheets (SDS) 6

First Aid Kit and Eyewash Station 8

Fluid Hazards...

8

Fluid-Injection Injuries 8

Burns 11

Combustion 11

Safe Practices for Working with Hydraulic Systems ...12

Before Starting a Job 12

Avoid Heat near Hydraulic Components and Conductors 13

Know the System 13

Hydraulic Environmental Management ...14

Reporting an Oil Spill to the Authorities 14

Fluid Containment 15

Disposal 15

Chapter 2

Hydraulic and Fluid Power Principles 19

Introduction to Fluid Power...

19

Advantages of Hydraulic Systems 19

Disadvantages of Hydraulic Systems 22

Hydrodynamic versus Hydrostatic 23

Hydrostatic Fundamental Principles ...23

Pascal's Law 23

Common Triangles 27

Hydrodynamic Fundamental Principles ...28

Continuity Equation 28

Bernoulli's Theorem 32

Law of Conservation of Energy . . .35

Pump inlet 37

Forms of Energy 38

Work and Power...

38

Conversion Table 40

Chapter 3

j|[t^y$, l^tein^;, mC Product llm^Mm 45

Introduction to Symbols, Drawings, and Product Literature... 45

Pictorial Drawings . . .45

Cutaway Drawings . . .46

Exploded Component Drawings ...47

Graphic Drawings . . .48

Types of Graphic Symbols 49

Colors 59

Combination Drawings ...60

Chapter 4Pumjis 65

Introduction to Pumps . . .65

Non-Positive-Displacement Pumps 65

Positive-Displacement Pumps 66

Fixed versus Variable Displacement 68

Unidirectional and Reversible 69

Open Loop and Closed Loop 70

Gear Pumps ...70

Gear Pump Attributes 71

External-Toothed Gear Pumps 71

Internal-Toothed Gear Pumps 72

Gear Pump Inspection 74

Case Drain 75

Gear Pump Leakage 75

Load-Sensing Gear Pumps 76

Vane Pumps ...76

Types of Vane Pumps 76

Single-Lobe versus Dual-Lobe Vane Pumps 77

Fluid Pressure for Holding the Extended Vanes 78

High-Performance Intra-Vane Pump 78

Cartridges .79

Variable-Displacement Vane Pumps 80

Vane Pump Inspection 80

Piston Pumps ...81

Radial Piston Pumps 81

Axial Piston Pumps 83

Bent-Axis Piston Pumps 89

Piston Pump Attributes 90

Piston Pump Service 90

Piston Pump Inspection 91

Factors Affecting Pump Selection. . .

91

Chapter 5

Fio^ry Actuators 95

introduction to Rotary Actuators. . . 95

Displacement and Direction 96

Torque 99

Operating Pressure 100

Speed 100

Volumetric Efficiency 101

Mechanical Efficiency 101

Overall Efficiency 101

Types of Motors. . .

102

Gear Motors 102

Vane Motors 107

Piston Motors 110

Motor Circuits and Configurations 115

Limited Rotation . . . 118

Chapter 6

Cylinders 125

Types of Linear Actuators. . .

125

Single-Acting Cylinders 125

Double-Acting Cylinders 127

Double-Acting, Double-Rod Cylinders 129

Rams 129

Telescoping Cylinders 130

Cylinder Components and Nomenclature. . .

132

Piston Rings and Seals 132

Gland 134

Rod Rings and Seals 136

Barrel 137

Cylinder Rod 138

Cylinder Loads, Dampening, and Speeds . . . 138

Cylinder Dampening 138

Cylinder Speeds 140

Cylinder Electronic Sensing . . . 141

Valving Designed for Cylinders . . .143

Regeneration 143

Cylinder Drift. . . 144

Metering-ln and Metering-Out Overrunning Loads. . .

147

Synchronizing Cylinders . . .148

Cylinder Safety . . .157

Do Not Attempt to Stall a Hydraulic Cylinder or Motor under Pressure . .

.152

Do Not Attempt to Mechanically Actuate

a Cylinder or Motor while It Is under Pressure 152

Chapter 7

157

Introduction to Pressure-Control and Load-Holding Valves. . .

157

Pressure-Relief Valves. . .

157

Direct-Acting Relief Valves 158

Pilot-Operated Relief Valves 162

Adjusting Valves . . .164

Pressure-Reducing Valves. . .

165

Unloading Valves. . .

167

Pressure-Sequence Valves . . .168

Lift Check Valves . . .170

Load-Holding Valves. . .

170

Pilot-Operated Check Valves 170

Counterbalance Valves 174

Chapter 8

179

Functions of Flow-Control Valves. . .

179

Regulating Speed 179

Regulating Priority 180

Dividing Flow 180

Non-Pressure-Compensated Flow-Control Valves . . .180

Pressure-Compensated Flow-Control Valves. . .

182

Temperature-Compensated Valves. . .

188

Priority Valves . . .188

Excavator Priorities 188

Proportional Flow Divider Valves. . .

189

Excessive Flow Protection. . .

191

Chapter 9

Diirtiiona! Contra halves 195

Purpose of Directional-Control Valves...

195

Types of Hydraulic Control Systems . . .195

Open-Center Systems 195

Pressure-Compensating (PC) Systems 196

Load-Sensing Pressure-Compensating (LSPC)Systems—Pre-Spool Compensation 196

Load-Sensing, Pressure-Compensating (LSPC)Systems—Post-Spool Compensation 198

Excavator Controls 198

Methods of Actuating DCVs . . .200

Manual Control 200

Pilot Control 202

Electronically Controlled DCVs 204

DCV Function. . .

210

Number of DCV Positions. . .

213

Block Design . . .214

Valve Design . . . 216

Spool Valve 216

Seat and Poppet Valve 217

Rotary Valve 217

Cartridge Valve 217

Power Beyond . . .218

Chapter 10

Fluids 225

Function of Fluids . . .225

Transmit Power 225

Remove Heat and Contaminants 227

Seal Oil Clearances 227

Lubricate Moving Components 227

Fluid Properties . . .228

Viscosity 228

Pour Points 233

Stability 233

Preventing Oxidation 234

Anti-Wear 235

Demulsifiers 235

Fluid Types . . . 235

Petroleum Fluids 235

Synthetic Fluids 236

Fire-Resistant Fluids 236

Environmentally Acceptable Hydraulic Fluids 237

Chapter 11

Filtration 243

Introduction to Filtration. . . 243

Strainers. . .

243

Disadvantages of Suction Strainers 245

Strainer Ratings 246

Filters. . .

248

Filter Ratings 248

Filtration by Location. . .

252

Breathers 252

Suction Filters 253

Charge Pressure Filters 253

High-Pressure Filtration 254

Actuator Filtration 255

Return Filters 255

Off-Line Kidney Loop Filtration 257

Types of Filtration by Flow. . .

259

Filter Indicators. . .

260

Choosing How to Filter a Hydraulic System . . .260

Chapter 12

Contamination Control 265

Source of Contamination. . .

265

Contamination from Manufacturing 265

Contamination from Operation 266

Poor Maintenance 266

Reasons for Fluid Analysis . . . 266

Oil Sampling . . .267

Using a Vacuum Pump 269

Using Onboard Sampling Valves 270

Bottles 271

Frequency and Original Sample 272

Cleanliness Standards. . .

272

ISO Range Codes 272

National Aerospace Standard (NAS) 274

Types of Analysis . . .275

Particle Counting 276

Particle Origin Identification 276

Fluid Viscosity 277

Elemental Analysis 277

Water Content 279

Acid Number 279

Additional Tests 279

Improving Contamination Control. . .

279

Storage of Components, Tools, and Test Equipment 279

New Hoses 280

Filtering New Oil 282

Filter Carts 282

Oil Sampling Ports 282

Hydraulic Cylinder Rod Protectors 282

Pressure Taps 283

Oil Drum Covers 283

Reconditioning a Contaminated Hydraulic System 283

Chapter 13Accumulators 293

Functions and Applications . . .293

Store Energy 293

Dampen Pressure Spikes 293

Ease the Buildup of Pressure 294

Maintain a Set Pressure 294

Recover Energy 296

Types of Accumulators. . .

296

Spring 298

Weighted 298

Gas 299

Accumulator Safety . . . 302

Service and Repair . . . 305

Checking Precharge Pressure with a Nitrogen Service Tool 305

Charging an Accumulator with Nitrogen 308

Measuring Precharge Pressure with a Hydraulic Oil Pressure Gauge . ..310

Repair 310

Tools and Accessories...

310

Gas Bottles 311

Safety Fuse 311

Nitrogen Charging Pumps 311

Accumulator Energy Sensors 311

Hydraulic Hybrid Applications ...312

Series Hydraulic Hybrid 312

Parallel Hydraulic Hybrid 312

Hydraulic Hybrid Excavator 312

Chapter 14

Reservoirs and Coolers 319

Reservoirs...

319

Housing 319

Receives and Dissipates Heat 321

Supplies Oil to the Pump's Inlet 321

Provides a Place for Entrained Air to Separate from the Fluid 321

Provides a Place for Contaminants to Settle from the Fluid 321

Reservoir Design and Components . . .322

Vented or Sealed 322

Variable-Volume Reservoir 324

Reservoir Walls 325

Baffles 325

Diffuser 326

Sight Glass or Dipstick 326

Suction Line and Suction Strainer 328

Return Lines 328

Filler 329

Breather 330

Drain Plugs 330

Clean-out Plate 330

Reservoir Shape 331

Reservoirs and Maintenance. . .

332

Heat. . .

333

Coolers. . .

334

Water-Type Oil Coolers 335

Air-Coolers 336

Warmers and Heaters . . . 336

Chapter 15

Plumbinq 341

The Importance of Understanding Plumbing in Mobile Hydraulic Systems ... 341

Types of Plumbing . . .342

Conductors. . . 342

Hose 343

Tubing 358

Pipe 360

Metal-to-Metal Fittings . . .362

Flare Fittings 362

Threaded Pipe Fittings 364

Flareless Fittings 366

O-Ring Fittings . . . 367

O-Ring Boss 368

O-Ring Face Seal 369

Split-Flange O-Ring 370

Quick Couplers . . .371

Noise and Vibration. . .

372

Rigid Conductors and Noise 372

Hose and Noise 373

Chapter 16QRpi-Center Hydraulrc 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 17Pressure-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 SystemsDo 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

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 Connectingthe 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 19Flo* ' Sliiriiip/Gw^istre^P) C^mp' ^: *»on 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 20LmwSm Pump UAttuvs 473

Introduction to Negative Flow Control (NFC)and Positive Flow Control (PFC) Systems . . . 473

Pump Regulators . . .474

Negative Flow Control (NFC) Hydraulic Systems . . .477

Proportional Solenoids in NFC Circuits 479

Pump Outlet Pressure 480

Cross Sensing Pressure 481

Pilot-Controlled DCV 482

Flow Limit Solenoid 484

ECM Logic 484

Case Excavators 486

Kobelco Dynamic Acera SK210-290 Excavators 487

Positive Flow Control (PFC) Hydraulic Systems . . .487

Pilot System 488

Deere G-Series and Hitachi Zaxis

Excavator PFC Pump Regulator Assemblies 492

Electro-Hydraulic (EH) PFC Systems . . .495

Standby Mode 496

Upstroked 497

Controlling the Proportional Solenoid Valve (PSV) 497

Chapter 21

Hydraulic Test Equipment 503

Introduction to Test Equipment . . .503

Flowmeters. . .

504

Mechanical Flowmeters 504

Electronic Flowmeters 506

Flowmeter Features 508

Installation of a Flowmeter .510

PQ Curve 511

Pressure Testing Equipment . . .512

Diagnostic Pressure Taps 512

Traditional Pressure Gauge. . 513

Differential Pressure Gauge 517

Quadrigage 517

Electronic Digital Pressure Meter 520

Snubbers 523

Selecting a Pressure Gauge . . .523

Pressure Gauge Accuracy 524

Measuring Pump Inlet Pressure 524

Miscellaneous Service Equipment . . .526

Infrared Temperature Meter.

526

Photocell Tachometer 527

Stopwatch 527

Pump and Motor Test Stand 528

Data Logger 528

Portable Particle Counter 529

Chapter 22

Hydrate Troubteshootiitg Principles 535

Introduction to Hydraulic Troubleshooting . . . 535

Understand the System 535

Question the Machine Operator 536

Operate the Hydraulic System 537

Examine the Hydraulic System 538

Identify Possible Causes 539

Isolate the True Cause 539

Test Your Conclusion 543

Additional Troubleshooting Principles . . . 544

Return Circuit 544

Art of Asking Good Questions 544

Noise 545

Heat 545

Pressures and Flows 546

Cycle Times 546

Chapter 23

Hydrostatic Qfwm 553

Introduction to Fluid Drives. . .

553

Hydrodynamic Drive 553

Basic Hydrostatic Drive 554

Applications of Hydrostatic Drives. . .

557

Single Path 557

Dual Path 558

One Pump and Two Motor Applications 563

Fixed- and Variable-Displacement Hydrostatic Motors 563

Hydrostatic Transmission Advantages 565

Hydrostatic Transmission Disadvantages 565

Configurations 566

Hydrostatic Charge Pumps and Main Piston Pumps . . .566

Sizing a Charge Pump 568

Styles of Piston Pump Frames 568

Types of Hydrostatic Pump Controls 568

Feedback Link 573

Hydrostatic Drive Operation and Oil Flow. . .

573

Servo Oil 574

Flushing Valve 574

Deceleration 576

High Pressure Relief Valves 578

Reverse Propulsion 579

Hydrostatic Transmission Filtration and Cooling 579

Variable Hydrostatic Drive Motor Applications . . .584

Two-Speed Motor Applications 584

Infinitely-Variable Motor Applications 588

Variability by Using One or Two Variable-Displacement Motors 589

Single-Speed, Fixed-Displacement Hydrostatic Motor 591

Additional Hydrostatic Valving . . .592

Inching Valve 592

Manual Bypass Valve 594

Electronic Pressure Release Solenoid 595

Internal Pressure Override 595

Pressure Cutoff Valve 596

Electronic Anti-Stall Control 597

Electronically Controlled Displacement .............. 598

Accumulator Effect. . .

598

Chapter 24

Hydrostatic Mm Service and Diagnostics 603

Centering Adjustments . . .603

Single-Servo Cradle Bearing Pump 604

Dual-Servo Trunion Bearing Pump Adjustments 609

Shaft Run-Out. . .

610

Startup (Commissioning) of a Hydrostatic Drive . . .611

Hydrostatic Drive Diagnostics by Symptom . . .

612

Overheating 612

Creeping Hydrostatic Transmission 615

Low Power or Sluggish in Forward and Reverse 615

Low Power or Sluggish in Just One Direction 618

Coasting or Freewheeling Transmission 620

Transmission Will Not Move in Either Direction 620

Effects of the Directional Control Valve Orifice 621

Charge Pressure Is Too High 621

Do Not Attempt to Isolate a Hydrostatic Pump . . .621

Using a Hydrostatic Transmission Test Stand. . .

622

Chapter 25

Steering 627

Steering Control Units. . .

627

SCU Components Design, and Operation . . .628

Open-Center SCU 630

Closed-Center Non-Load-Sensing SCU 630

Closed-Center Load-Sensing SCU 631

SCU Neutral Operation 632

SCU Left or Right Steering Mode of Operation 632

SCU Dead Engine Steering Mode 633

Optional SCU Internal Valves. . .

634

Inlet Check Valve 634

Inlet Relief Valve 634

Load-Sensing Relief Valve 635

Cylinder Port Relief Valves 635

Anti-Cavitation Check Valves 637

SCU Features. . .

637

Non-Load Reaction 637

Load Reaction 638

Wide-Angle Steering 638

Cylinder Dampening 639

Q-Amp Steering 639

Traditional Steering Priority Valves. . .

640

Steering Priority Valve Operation with the SCU in Neutral 640

Steering Priority Valve Operation with the SCU Steering Left or Right . . 640

Steering Priority Valve Load-Sensing Relief 641

Load-Sensing Line 641

Diagnosing Steering Systems . . .642

Electronic Steering Features. . .

644

John Deere ActiveCommand Steering 644

Caterpillar Quick Steer 644

Case IH 4WD Combination Steering . . .645

Image Credits 651

Glossary 652

index 666