Hydraulic systems for mobile equipment
Transcript of Hydraulic systems for mobile equipment
Uy/AmimS^dtDi for
M@Mte Eqmpm^
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