Principles of Hydraulic Systems Design
Principles of Hydraulic Systems Design
Second Edition
Peter Chapple
contents
List of figures ix
List of tabLes xvii
acknowLedgments xix
introduction to second edition xxi
chapter 1 hydrauLic power transmission and its controL 1
chapter 2 hydrostatic pumps and motors 5
chapter 3 hydrauLic cyLinders 29
chapter 4 pressure controL VaLVes 43
chapter 5 fLow controL VaLVes 53
chapter 6 anciLLary equipment 61
chapter 7 circuit design 75
chapter 8 fLow processes in hydrauLic systems 113
chapter 9 operating efficiencies of pumps and motors 129
chapter 10 controL system design 149
chapter 11 performance anaLysis 199
chapter 12 systems management 263
appendix 273
references 277
index
List of figures
Figure 2.1. External gear pump and motor. 7
Figure 2.2. Internal gear pump. 8
Figure 2.3. Balanced vane pump. 9
Figure 2.4. Variable displacement vane pump. 10
Figure 2.5. Axial piston variable displacement pump and motor. 11
Figure 2.6. Diagram of a pump port plate. 11
Figure 2.7. Bent axis type axial piston motor. 12
Figure 2.8. Pump performance characteristics. 15
Figure 2.9. Motor performance characteristics. 16
Figure 2.10. Radial piston eccentric motor (a) valve housing
(b) complete motor assembly. 19
Figure 2.11. Cam-type hydraulic motor. 19
Figure 2.12. Gerotor, or orbit-type low speed high torque motor. 20
Figure 2.13. Digital control valves for a radial piston motor. 21
Figure 2.14. Typical maximum speeds for motors of various types. 25
Figure 2.15. Typical mass values for a range of motor types. 26
Figure 3.1. Typical double-acting actuator. 30
Figure 3.2. Actuator of tie rod construction. 31
Figure 3.3. Actuator mountings (a) with position transducer (b). 31
Figure 3.4. Actuator mounting styles (a) Actuator flange mounted
to front or rear end cover with the rod end unguided (b)
Actuator trunnion mounted with the rod end guided (c)
Spherical coupling with the rod end guided (d) Actuator
flange mounted with the rod end guided. 32
Figure 3.5. Section view of a typical cylinder showing the
various seals. 33
ixx • LiSt Of figuRES
Figure 3.6. Telescopic cylinder. 35
Figure 3.7. Actuator cushioning. 36
Figure 3.8. Velocity and pressure variation. 38
Figure 3.9. Rack and pinion rotary actuator. 39
Figure 3.10. Vane rotary actuator. 39
Figure 4.1. Poppet and piston-type valves. 44
Figure 4.2. Two-stage poppet type relief valve. 44
Figure 4.3. Two-stage cartridge relief valve. 45
Figure 4.4. Dual relief valves in actuator circuit. 46
Figure 4.5. Reducing valve operating principles. 47
Figure 4.6. Reducing valve. 47
Figure 4.7. Cartridge type of counterbalance load control valve. 48
Figure 4.8. Flow characteristics of the counterbalance valve
in Figure 4.7. 48
Figure 4.9. Extending actuator controlled by a counterbalance valve
with a pulling load. 49
Figure 4.10. Operating pressures. 50
Figure 5.1. Four-way directional control valve (DCV). 54
Figure 5.2. Manually operated DCV. 54
Figure 5.3. Proportional control valve. 55
Figure 5.4. Adjustable restrictor valve. 56
Figure 5.5. Pressure compensated valve. 57
Figure 5.6. Pressure compensated flow control valve. 57
Figure 5.7. Central bypass valve. 59
Figure 5.8. Bypass valve connecting the pump flow to port A and
return to port B. 60
Figure 6.1. Accumulators: (a) bladder type and (b) typical
piston type. 62
Figure 6.2. Accumulator pressure. 63
Figure 6.3. Variation in adiabatic index with pressure and
temperature for nitrogen. 64
Figure 6.4. Important contamination aspects in vane and
gear pumps. 65
Figure 6.5. Wear particle generation in piston pumps. 66
Figure 6.6. High-pressure filter. 67LiSt Of figuRES • xi
Figure 6.7. Beta ratio for filters. 68
Figure 6.8. Downstream fluid quality and the beta ratio. 69
Figure 6.9. ISO 4406 standard code for contamination levels. 70
Figure 6.10. Cooler performance characteristics. 73
Figure 7.1. Flow and pressure variation. 76
Figure 7.2. Two-position four-way valve. 77
Figure 7.3. Two-position three-way valve. 77
Figure 7.4. Closed center valves. 78
Figure 7.5. Tandem center valves. 78
Figure 7.6. Open center valves 78
Figure 7.7. Open center valve connected to tank 79
Figure 7.8. Pilot-operated check valve. 80
Figure 7.9. Actuator circuit using a POCV. 80
Figure 7.10. Meter-in control for actuator extension. 81
Figure 7.11. Pressure and velocity variations with meter-in control. 82
Figure 7.12. Meter-out control. 83
Figure 7.13. Bleed-off control. 84
Figure 7.14. Multiple actuator circuit with meter-in control. 84
Figure 7.15. Four-way valve velocity control. 85
Figure 7.16. Valve pressures during extension. 87
Figure 7.17. Interaction between the flow and the force
characteristics during extension. 87
Figure 7.18. Actuator retracting. 89
Figure 7.19. Nonsymmetrical valve metering. 92
Figure 7.20. Load locus of velocity ratio against force ratio. 92
Figure 7.21. Central bypass valves in series. 93
Figure 7.22. Bypass valve characteristics. 93
Figure 7.23. Central bypass valve with notched metering edges
in three positions. 94
Figure 7.24. Pressure-compensated bypass valve with load sensing. 95
Figure 7.25. Variable displacement pump pressure limiting and load
sensing control. 97
Figure 7.26. Constant power control. 97
Figure 7.27. Pump operating characteristics. 98xii • LiSt Of figuRES
Figure 7.28. Accumulator charging circuit. 99
Figure 7.29. Rotary hydrostatic transmission circuit. 100
Figure 7.30. Motor brake circuit. 101
Figure 7.31. Linear actuator hydrostatic transmission circuit. 102
Figure 7.32. Secondary control system. 103
Figure 7.33. Radial piston motor with digitally operated valves
(as in Figure 2.12). 103
Figure 7.34. Poppet valve for cylinders. 104
Figure 7.35. Pilot circuit for active control of the motor
cylinder valves. 105
Figure 7.36. Wind turbine hydrostatic power transmission system. 106
Figure 7.37. Load control circuit using counterbalance valves. 107
Figure 7.38. Double pump system with unloading valve. 108
Figure 7.39. Sequence valve used for operation in a press circuit. 108
Figure 7.40. High pressure filter circuits. 109
Figure 7.41. High and low pressure filter circuits. 110
Figure 8.1. Oil viscosity variation with pressure and temperature. 114
Figure 8.2. Moody chart for determining the friction factor. 116
Figure 8.3. Flow between parallel plates. 117
Figure 8.4. Sharp-edged orifice. 118
Figure 8.5. Flow coefficient variation with Reynolds number. 120
Figure 8.6a. Single-stage poppet-type relief valve. 121
Figure 8.6b. The valve in open position. 121
Figure 8.7. Valve pressure flow characteristic from Equation 8.11. 123
Figure 8.8. Spool valve. 124
Figure 8A.1 Flow through a pipe. 125
Figure 9.1. Variation in overall efficiency. 134
Figure 9.2. Radial piston eccentric-type motor. 137
Figure 9.3. Slipper hydrostatic bearing. 138
Figure 9.4. The effect of outer bearing friction on the slipper. 140
Figure 9.5. Cross-sectional view of the hydrostatic slipper. 141
Figure 10.1. Valve actuator circuit. 150
Figure 10.2. Valve characteristics. 151
Figure 10.3. Open-loop time response. 152LiSt Of figuRES • xiii
Figure 10.4. System block diagram. 153
Figure 10.5. Simplified block diagram. 153
Figure 10.6. Step response. 154
Figure 10.7. Fluid compressibility. 155
Figure 10.8. The effect of load pressure on the valve characteristics.157
Figure 10.9. Valve flow coefficients. 159
Figure 10.10. Sinusoidal flow variations and actuator displacement. 163
Figure 10.11. Bode plot for valve actuator open-loop transfer
function. 165
Figure 10.12. Electrohydraulic position control system block
diagram. 167
Figure 10.13. Valve actuator block diagram. 168
Figure 10.14. Valve underlap. 169
Figure 10.15. Valve pressure gain. 170
Figure 10.16. Block diagram of steady state conditions. 171
Figure 10.17. Valve hysteresis. 172
Figure 10.18. Pressure control. 174
Figure 10.19. Frequency response for integral plus proportional
control. 176
Figure 10.20. Frequency response for proportional plus derivative
control. 178
Figure 10.21. Phase advance frequency response. 179
Figure 10.22. Pressure feedback control (fE = 0). 181
Figure 10.23. Hydrostatic system block diagram. 184
Figure 10.24. Steady state torque diagram of the load and
motor control. 187
Figure 10.25. Block diagram for secondary control system. 187
Figure 10.26. The relationship between turbine torque and speed
at a given wind speed. 191
Figure 10.27. Relationship between motor displacement and
turbine speed and closed-loop control for a fixed
speed of the motor [9, 10]. 193
Figure 10.28. Turbine speed control system block diagram. 193
Figure 10.29. Actuator control using a variable displacement pump. 195
Figure 11.1. Single-ended actuator. 202xiv • LiSt Of figuRES
Figure 11.2. Winch driven by motor and reduction gearbox. 204
Figure 11.3. Hydraulic winch with gearbox. 205
Figure 11.4. Gantry crane. 209
Figure 11.5. Circuit diagram. 214
Figure 11.6. Fluid resistance in fittings. 216
Figure 11.7. Weight loaded system. 220
Figure 11.8. Valve dimensions. 221
Figure 11.9. Equivalent circuit for actuator extension. 221
Figure 11.10. Valve performance characteristics. 226
Figure 11.11. Open-loop frequency response. 230
Figure 11.12. Injection-moulding machine schematic diagram. 231
Figure 11.13. Basic injection-moulding machine circuit. 233
Figure 11.14. Variation of actuator pressure and displacement. 234
Figure 11.15. Hydraulic circuit. 236
Figure 11.16. Cooler performance characteristics. 236
Figure 11.17. Oil inlet temperature. 239
Figure 11.18. Pump control strategy. 243
Figure 11.19. Variable displacement pump with pressure
compensation and flow control. 243
Figure 11.20. Pump power (torque) control. 244
Figure 11.21. Hydraulic potentiometer. 246
Figure 11.22. Vehicle crusher unloading pump circuit. 247
Figure 11.23. Bending machine schematic. 248
Figure 11.24. Bending machine circuit. 248
Figure 11.25. Alternative load sensing system. 249
Figure 11.26. Hydraulically operated crane. 250
Figure 11.27. The effect of changes in external forces on steady
state errors. 250
Figure 11.28. The effect of adding proportional plus integral
compensation. 251
Figure 11.29. Step response with the P + I compensator. 252
Figure 11.30. Dynamic responses using a PID compensator. 253
Figure 11.31. The application of load pressure feedback. 254LiSt Of figuRES • xv
Figure 11.32. Turbine torque variation with turbine speed at
different wind speeds and turbine blade pitch angle α. 260
Figure 11.33. Nonlinear simulation of turbine speed to change
of wind speed at 50 s. 260
Figure 12.1. The complete partnership. 266
Figure 12.2. The bathtub life curve. 267
Figure 12.3. Valve actuator system. 26
List of tAbLes
Table 2.1. Comparison of pump types 17
Table 2.2. Motor data 25
Table 3.1. Maximum piston rod extension (refer to Figure 3.4) 33
Table 3.2. Summary of typical rotary actuator performance 40
Table 11.1. Restrictor valve characteristics 201
Table 11.2. Motor data 206
Table 11.3. Cable information 210
Table 11.4. Motor performance 212
Table 11.5. Pipe pressure loss 213
Table 11.6. Valve flow characteristics 218
Table 11.7. Valve data 224
Table 11.8. Valve flow/pressure characteristic, x = 4 mm 225
Table 11.9. Valve flow/pressure characteristic, x = 5 mm 226
Table 11.10. Power dissipated in the cooler 238
Table 11.11. Dynamic performance parameters 256
Table 11.12. Dynamic performance parameters 257
Table 11.13. Hydrostatic transmission parameters 258index
A
Accumulators
adiabatic index variation,
64–65
pressure, 62–63
types, 61–62
Ancillary equipment
accumulators
adiabatic index variation,
64–65
pressure, 62–63
types, 61–62
contamination control
circuit design, 109–110
components, 65–66
filters, 67–70
coolers
characteristics, 73
thermodynamic aspects, 72
types, 71–72
reservoirs, 73
Axial piston motor
bent axis type, 11–12
variable displacement pump
type, 10–11
B
Bending machines, 247–249
Beta ratio, 66–68
BFPA. See British Fluid Power
Association (BFPA)
Bleed-off control, 83–84
British Fluid Power Association
(BFPA), 68, 273–275
British standards (BS), 273–275
BS. See British standards (BS)
Bulk modulus, 154
C
Central bypass valve
actuator force, 224
flow analysis, 221–223
valve characteristics, 223–224
valve dimensions, 220, 221
valve operation, 225–226
weight loaded system, 220
Central bypass valves, 58–60
Circuit design
contamination control,
109–110
directional control
three-position valves,
78–79
two-position valves, 76–77
hydrostatic transmissions
(see Hydrostatic
transmissions)
load holding valves, 79–80
pilot operated valve circuits,
106–108
pressure and flow, 75–76
types, 75280 • inDEX
variable displacement pump
control
accumulator charging,
98–99
load-sensing, 96, 97
power control, 96–98
velocity control
bleed-off control, 83–84
four-way valve restrictive
control (see
Four-way valve
restrictive
control)
meter-in control, 80–82
meter-out control, 82–83
Compensation techniques
integral plus proportional
compensation,
176–177
performance analysis
load pressure feedback,
253–254
outcomes, 254
PID compensation,
252–253
proportional plus integral
compensation,
251–252
steady state accuracy,
249–250
phase advance, 177–179
PID control, 179–180
pressure feedback, 180–181
proportional plus derivative
control, 177, 178
Contamination control
circuit design, 109–110
components, 65–66
filters
beta ratio, 67–68
downstream fluid quality,
68–69
high-pressure, 66–67
ISO 4406 standard code,
68, 70
Control system design
closed-loop position, stability
block diagram, 167–168
stability criterion, 166
system design, 166–167
valve leakage and
hysteresis,
168–172
closed-loop system
performance
position control, 172–173
pressure control, 174–175
velocity control, 173–174
compensation techniques
integral plus proportional
compensation,
176–177
phase advance, 177–179
PID control, 179–180
pressure feedback,
180–181
proportional plus
derivative
control, 177, 178
fluid compressibility
bulk modulus, 154
hydraulic stiffness,
155–156
frequency response
simple actuator, 163–164
valve actuator system,
164–166
hydrostatic systems (see
Hydrostatic systems)
pump-controlled systems,
195–196
simple valve actuator (see
Simple valve actuator
control)
system frequency response
tests, 194–195
valve actuator dynamic
response
actuator flows, 159–160
actuator force, 160–161
actuator position, 161–162
pressure shock control
in open-loop
systems,
162–163
valve flow, 156–159
valve selection, 162
Coolers
characteristics, 73
thermodynamic aspects, 72
types, 71–72
Coulomb friction torque, 132–133
Counterbalance valves
cartridge type, 47–48
extending actuator controlled,
49
flow characteristics, 48–49
operating pressures, 50–51
D
DCV. See Directional control valve
(DCV)
Digital valves
benefits, 22–23
high pressure supply, 20–21
low pressure supply, 21
Directional control
three-position valves, 78–79
two-position valves, 76–77
Directional control valve (DCV),
53–55
Double-acting actuator, 29–30
Dual relief valves, 46
E
EHSRs. See Essential Health and
Safety Requirements
(EHSRs)
EN. See European standards (EN)
Essential Health and Safety
Requirements (EHSRs),
269
European standards (EN), 273–275
F
Failure modes effects analysis
(FMEA), 266–268
Fault analysis
FMEA, 268–269
FTA, 267–268
methods, 266
parameters, 270–271
Fault tree analysis (FTA), 266–268
Filters
beta ratio, 67–68
downstream fluid quality,
68–69
high-pressure, 66–67
ISO 4406 standard code, 68, 70
Fixed displacement units
external gear pumps and
motors, 7–8
internal gear pumps, 8
vane pumps and motors, 8–9
Flow control valves
central bypass, 58–60
DCV, 53–55
pressure compensated, 56–58
restrictor, 55–56
types, 53
Flow processes. See Hydraulic
systems, flow processes
Fluid compressibility
bulk modulus, 154
hydraulic stiffness, 155–156
Fluid power system, 2–3
FMEA. See Failure modes effects
analysis (FMEA)
Four-way valve restrictive control
actuator extending
actuator force, 86–88
valve flow characteristics,
85–87
actuator retracting, 88–90
bypass control with fixed
displacement pumps
closed center valves,
95–96282 • inDEX
open center valves, 93–94
circuit diagram, 84–85
valve sizing, 90–91
valves with nonsymmetrical
metering, 91–92
FTA. See Fault tree analysis (FTA)
G
Gantry crane
cable information, 210
installation details, 208–209
low speed motor, 210
motor flow, 211
pipe sizes, 213, 214
wheel drive, 211–212
H
High-pressure filter, 66–67
circuits, 109–110
Hydraulic cylinders
actuator selection
actuator force, 35–36
cushioning, 36–38
rotary actuators, 39–40
double-acting actuator, 29–30
end covers, 30, 31
mounting methods
actuator mounting styles,
32
Euler failure criteria,
31–32
flange and trunnion
mounting, 30–31
maximum piston rod
extension, 32–33
position transducers and
proximity switches, 34
seals, 32–34
telescopic cylinders, 34–35
Hydraulic power
advantages, 1
fluid power system design, 2–3
Hydraulic stiffness, 155–156
Hydraulic systems, flow processes
annular space, 144–146
fluid properties, 113–114
laminar flow, 117–118
orifice flow, 118–120
pipes
flow and pressure loss
relationship,
125–127
Moody chart, 115–117
pressure loss, 114–115
tilted slipper, 146–147
valve force analysis
change in momentum,
119–120
poppet valves (see Poppet
valves)
spool valves, 123–124
Hydraulic systems management
aspects, 264–265
cleanliness, 265–267
fault analysis
FMEA, 268–269
FTA, 267–268
methods, 266
parameters, 270–271
objectives, 265
standards, 269–270 (see also
British Fluid Power
Association (BFPA))
Hydrostatic pumps and motors
digital valves
benefits, 22–23
high pressure supply,
20–21
low pressure supply, 21
equations
flow and speed
relationship, 13
pump selection parameters,
16, 17
torque and pressure
relationship,
14–16inDEX • 283
fixed displacement units
external gear pumps and
motors, 7–8
internal gear pumps, 8
vane pumps and motors,
8–9
general considerations, 23–24
influencing factors, 5
low speed motors
applications, 17–18
radial piston motors,
18–20
performance characteristics
comparison
displacements and
maximum
speeds, 24–25
typical mass values, 26–27
selection factors, 6
variable displacement unit
axial piston, 10–11
bent axis type axial piston
motor, 11–12
pump port plate, 10–11
vane pumps, 9–10
Hydrostatic systems
motor control systems
closed loop, 187–188
displacement controller,
186–187
torque, 186
pump-controlled
flow, 182–183
torque, 183–185
wind turbine
benefits and limitations,
189–190
speed control, 192–193
torque and speed
relationship,
190–192
Hydrostatic transmission
primary control system,
254–256
secondary control system,
256–258
wind turbine (see Wind
turbine)
Hydrostatic transmissions
digital operation, 102–105
linear actuator transmissions,
101–102
motor brake circuit, 101
motor controlled systems, 102,
103
pump controlled systems,
100–101
wind turbines, 105–106
I
Injection-moulding machine
accumulator, 232–233
actuator, 231–232
circuit, 233–234
motor, 232
pressure shocks, prevention,
234–235
system data, 231
International standards (ISO),
273–275
ISO. See International standards
(ISO)
L
Linear actuator transmissions,
101–102
Load holding valves, 79–80
Low speed motors
applications, 17–18
radial piston motors, 18–20
M
Mechanical loss modeling
generalised model assumptions,
135–136
hydrostatic bearing, 138–139284 • inDEX
hydrostatic bearing leakage
flow, 140–141
mechanical efficiency, 143
outer bearing friction, 139–140
radial piston motor analysis,
136–138
sliding contacts friction, 139
slipper and eccentric interface,
141–142
viscous and coulomb friction
torque, 132–133
Meter-in control, 80–82, 199–201
Meter-out control, 82–83
Motor brake circuit, 101
Motor controlled systems, 102,
103
Motor control systems
closed loop, 187–188
displacement controller,
186–187
torque, 186
Motors and pumps. See
Hydrostatic pumps and
motors
O
Oil cooling
duty cycle, 236
heat generated, 237–239
heat loss, 239
pump efficiency, 240
system data, 235–236
P
Performance analysis
central bypass valve
actuator force, 224
flow analysis, 221–223
valve characteristics,
223–224
valve dimensions, 220,
221
valve operation, 225–226
weight loaded system, 220
compensation techniques
load pressure feedback,
253–254
outcomes, 254
PID compensation,
252–253
proportional plus integral
compensation,
251–252
steady state accuracy,
249–250
control system design, 228–230
gantry crane (see Gantry crane)
hydrostatic transmission
primary control system,
254–256
secondary control system,
256–258
wind turbine (see Wind
turbine)
injection-moulding machine
(see Injectionmoulding machine)
meter-in control, 199–201
oil cooling (see Oil cooling)
pressure losses
at 20°C, 215–216
at 60°C, 216–217
components, 214–215
pump requirements, 217
pump and motor efficiencies,
226–228
pump control applications
bending machines,
247–249
vehicle crusher unloading
pump circuit,
246–247
simple actuator cushion,
218–220
single-ended actuator valve
control
actuator extension, 203inDEX • 285
actuator retraction,
202–203
data, 201–202
single stage relief valve,
217–218
vehicle transmission (see
Vehicle transmission)
winch application (see Winch
application)
PID. See Proportional, integral,
and derivative (PID)
compensation
Pilot-operated check valve
(POCV), 79–80
Pilot operated valve circuits,
106–108
POCV. See Pilot-operated check
valve (POCV)
Poppet and piston-type valves, 43
Poppet valves
flow, 122
momentum force, 120–122
pressure flow characteristics,
122–123
Pressure compensated valves,
56–58
Pressure control valves
counterbalance
cartridge type, 47–48
extending actuator
controlled, 49
flow characteristics, 48–49
operating pressures, 50–51
pressure reducing valves,
46–47
relief valves
single-stage, 43–45
two-stage, 44–46
types, 43
Proportional control valves, 54–55
Proportional, integral, and
derivative (PID)
compensation, 179–180
Proportional plus integral
plus derivative (PID)
compensation, 252–253
Pump control applications
bending machines, 247–249
vehicle crusher unloading
pump circuit, 246–247
Pump controlled systems,
100–101
Pump-controlled systems,
195–196
hydrostatic systems
flow, 182–183
torque, 183–185
Pump port plate, 10–11
Pumps and motors. See
Hydrostatic pumps and
motors
Pumps and motors, operating
efficiencies
loss analysis
theoretical performance,
130–131
volumetric flow loss,
131–132
mechanical and volumetric
efficiency, 129–130
mechanical loss modeling
generalised model
assumptions,
135–136
hydrostatic bearing,
138–139
hydrostatic bearing
leakage flow,
140–141
mechanical efficiency, 143
outer bearing friction,
139–140
radial piston motor
analysis,
136–138
sliding contacts friction,
139
slipper and eccentric
interface,
141–142286 • inDEX
viscous and coulomb
friction torque,
132–133
outcomes, 143–144
unit efficiency, 133–135
R
Rack and pinion rotary actuator,
39–40
Radial piston motor analysis,
136–138
Radial piston motors, 18–20
Relief valves
single-stage, 43–45
two-stage, 44–46
Reservoirs, 73
Restrictor valves, 55–56
Rotary actuators, 39–40
Rotary hydrostatic transmission
circuit, 100–101
S
Simple actuator cushion, 218–220
Simple valve actuator control
closed-loop system, 152–154
open-loop system
circuit and force
characteristics,
149–150
time response, 151–152
valve characteristics,
150–151
system response, 154
Single-ended actuator valve
control
actuator extension, 203
actuator retraction, 202–203
data, 201–202
Single-stage relief valve, 43–45
Single stage relief valve, 217–218
T
Telescopic cylinders, 34–35
Three-position valves, 78–79
Two-position valves, 76–77
Two-stage relief valves, 44–46
V
Valve force analysis
change in momentum, 119–120
poppet valves (see Poppet
valves)
spool valves, 123–124
Valves
central bypass valves, 58–60
circuit design
load holding valves, 79–80
three-position valves,
78–79
two-position valves, 76–77
digital valves
benefits, 22–23
high pressure supply,
20–21
low pressure supply, 21
dual relief valves, 46
flow control valves
central bypass, 58–60
DCV, 53–55
pressure compensated,
56–58
restrictor, 55–56
types, 53
four-way valve restrictive
control
closed center valves,
95–96
open center valves, 93–94
load holding valves, 79–80
poppet and piston-type valves,
43
poppet valves
flow, 122
momentum force, 120–122
pressure flow
characteristics,
122–123inDEX • 287
pressure compensated valves,
56–58
pressure control valves
counterbalance cartridge
type, 47–48
extending actuator
controlled, 49
flow characteristics, 48–49
operating pressures, 50–51
pressure reducing valves,
46–47
relief valves
single-stage, 43–45
two-stage, 44–46
types, 43
proportional control valves,
54–55
relief valves
single-stage, 43–45
two-stage, 44–46
restrictor valves, 55–56
three-position valves, 78–79
two-position valves, 76–77
two-stage relief valves, 44–46
Vane pumps and motors
fixed displacement units, 8–9
variable displacement unit,
9–10
Vane rotary actuator, 39–40
Variable displacement pump
control
accumulator charging, 98–99
load-sensing, 96, 97
power control, 96–98
Variable displacement unit
axial piston, 10–11
bent axis type axial piston
motor, 11–12
pump port plate, 10–11
vane pumps, 9–10
Vehicle crusher unloading pump
circuit, 246–247
Vehicle transmission
data, 240
fluid viscosity effects, 242
pressure and flow, 241–242
pump controls, 243–245
steady state pump power
control analysis,
245–246
vehicle speed, 241
Velocity control
bleed-off control, 83–84
four-way valve restrictive
control (see
Four-way valve
restrictive control)
meter-in control, 80–82
meter-out control, 82–83
Viscous friction torque,
132–133
W
Winch application
hydraulic motor
gear box, 205–206
minimum motor
displacement,
208
motor data and selection,
206–207
load lifting and lowering, 204
numerical values, 205
Wind turbine
benefits and limitations,
189–190
calculated values, 259–261
component details, 258–259
speed control, 192–193
system analysis, 259
torque and speed relationship,
190–192
Wind turbines, 105–106
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