Practical Hydraulic Systems

Practical Hydraulic Systems – Operation and Troubleshooting for Engineers & Technicians
Ravi Doddannavae, Andries Barnard
Table of Contents
1 Introduction to hydraulics 1
2 Pressure and flow 16
3 Hydraulic pumps 37
4 Hydraulic motors 69
5 Hydraulic cylinders 83
6 Control components in a hydraulic system 93
7 Hydraulic accessories 132
8 Hydraulic fluids 167
9 Applications of hydraulic systems 175
10 Hydraulic circuit design and analysis 181
11 Maintenance and troubleshooting
Index
Absolute pressure, 18
Absolute viscosity, 12
Absorbent filters, 141
Acceleration, 6-7
due to gravity, 7
Accumulators, 146-55
as auxiliary power source, 153
as hydraulic shock absorbers, 154-5
as leakage compensators, 154
gas-loaded, 148
non-separator, 148-9
separator, 149-53
spring-loaded, 147-8
weight-loaded, 147
Adjustable flow control valves, 115
Adsorbent filters, 141
Air-pressurized reservoir, 135
Air-to-hydraulic pressure booster, 2 3 ^
American National Standards Institute,
159, 181
Applications:
bendix hydro-boost brake system,
178-9
bridge maintenance, 180
high wire hydraulically driven overhead tram,
177-8
power steering, 179
welding, 179-80
Atmospheric pressure, 18
Axial piston motors, 76-9
bent-axis, 78
in-line, 78
principle of working, 78-9
Axial piston pumps, 53-5
Balanced vane pumps, 49-50
Ball valve, 117-18
Bendix hydro-boost brake system, 178-9
Bent-axis piston pumps, 53-4
Bernoulli’s equation, 30-2
Beta ratio filters, 138
Boiling point, effect of pressure on, 18-19
Bourdon pressure gage, 19-20
Bourdon tube-type sensing element, 128
Brake power, 82
Brake valve, 106, 114
Bramah’s press, 2
Bridge maintenance, 180
Bulk modulus, 11
Butterfly valve, 116-17
Check valves, 99-100
Circuit design, 181-9
control of double acting hydraulic cylinder, 183
counterbalance valve application, 185-6
fail-safe circuit, 187-8
hydraulic cylinder sequencing circuit, 186-7
mechanical hydraulic servo system, 189
pump unloading circuit, 185
regenerative circuit, 183-5
speed control of hydraulic motor, 188-9
symbols of hydraulic components, 181-2
Classification, 3
Cleanliness, 193
Compensator spring, 52
Continuous rotation hydraulic motors, 72-9
axial piston motors, 76-9
balanced and unbalanced-type vane motors,
74-5226 Index
Continuous rotation hydraulic motors (Continued)
gear motors, 72-3
piston motors, 75-6
radial piston motors, 76
vane motors, 73-4
Control valves, 94-123
direction control, 94-105
flow control, 94, 114-23
pressure control, 95, 106-7
Counterbalance valve, 106, 113-14
Darcy’ s equation, 31
Density, 5-6
relative see Specific gravity
Diaphragm pressure switch, 127
Direction control valves, 94-105
direct acting and pilot-operated, 95-7
normally open and normally closed, 95
open and closed center hydraulic circuits, 97-100
shuttle valves, 104-5
spool-type, 101-4
Discharge, 27-9
Displacement volume, 38
Double-acting hydraulic cylinders, 85-8
Drive shaft, 41
Duplex-type filters, 141-2
Eccentricity, 51
Edge-type filters, 142
Electro-hydraulic servo valves, 125-6
Electro-hydraulic stepping motors, 82
Elevation (potential) head, 31
Energy, 9
Energy head, 31
Eulerian method, 25
Excessive heat, 198, 201
Excessive noise, 198, 200
Expansion joints, 162
External gear pump, 41-5
internal leakage of oil, 44-5
theoretical flow rate, 44
volumetric displacement, 43
principle of working, 143-5
tell-tale, 142-3
Fire-resistant fluids, 171-2
Fixed flow valves, 115
Flexible hoses, 165-6
see also Pipes and hoses
Flow, 24-33
incorrect, 198, 202-3
laminar, 26, 32
mass, 25
meaning of, 25
non-rotational, 27
non-uniform, 26
rate, 27-9
rotational, 27
steady, 26
turbulent, 27, 32
uniform, 26
unsteady, 26
velocity, 25
volumetric, 25
Flow control valves, 94, 114-23
adjustable flow, 115
ball valve, 117-18
butterfly valve, 116-17
fixed flow, 115
globe valve, 116
meter-in/meter-out functions, 120-3
pressure-compensated, 116, 118-20
throttling valve, 115, 118
valve characteristics, 122-3
Flow measurement, 33-6
orifice plate-type flowmeter, 35-6
rotameter, 33-4
turbine-type flowmeter, 34-5
Flowmeters, 130
Fluids, 4-5, 36
pressure in, 17
Foam-resistant fluids, 172-3
Force, 7
Forced balanced pressure transducer, 21
Foreign particles in hydraulic pumps, 65
Filters, 136-45
absorbent, 141
beta ratio, 138
duplex-type, 141-2
edge-type, 142
filter location, 140
fluid cleanliness level, 138-40
mechanical, 140
micron, 137
number particles/ml, 139-40
Gage pressure, 18
Gas-loaded accumulators, 148
Gases, 5
Gaskets, 68
Gear motors, 72-3
Gear pumps, 40-7
external, 41-5
gerotor pump, 46
inspection of gears, 67
internal, 45-6Index 227
lobe pumps, 46, 47
principle of operation, 47
Gerotor pump, 46
Globe valve, 116
Hagen-Poiseuille equation, 32
Heat, 13
Heat dissipation, 4
Heat exchangers, 155-7
air-cooled, 155-6
water-cooled, 156-7
Herringbone gears, 45
High wire hydraulically driven overhead tram, 177-8
Horsepower, 11
Hydraulic cylinders, 83-92
cylinder cushioning, 89
cylinder mountings, 89-92
double acting, 85-8
single acting, 84-5
Hydraulic fluids, 3-15, 167-74
air, 173-4
contamination, 136, 207
entrained gas in, 191-2
fire-resistant, 171-2
foam-resistant, 172-3
functions of, 3-4
incorrect viscosity, 207
lubricating oils, 173
neutralization number, 170-1
oxidation and corrosion prevention, 168-70
petroleum-based fluids, 173
properties of, 174
HydrauUc fuses, 126-7
Hydraulic jack, 22-3
Hydraulic motors, 69-82
basic principles, 69-70
continuous rotation, 72-9
electro-hydraulic stepping motors, 82
limited rotation, 70-2
performance, 79-82
Hydraulic power, 82
HydrauUc pumps, 37-68
capacity, 61-2
gear pumps, 40-7
maintenance, 64-6, 67-8
mechanical efficiency, 59-61
noise, 63-4
non-positive displacement pumps, 38-40
performance curves, 62-3
performance of, 58
performance parameters, 63, 66
piston pumps, 53-8
positive displacement/hydrostatic pumps, 40
principle of operation, 37-8
selection of, 66-7
vane pumps, 47-52
volumetric efficiency, 59
Hydraulic rams, 83-4
Hydraulic systems:
advantages of, 176
components of, 176-7
Hydrodynamics, 3, 25
Hydrokinetics, 25
Hydrostatic law, 17
Hydrostatics, 3
Ideal fluids, 36
Industrial hydraulics, 2
Internal energy, 9-10, 29-30
Internal gear pumps, 45-6
Kinematic viscosity, 12
Kinetic energy, 9, 29
Lagrangian method, 25
Laminar flow, 26
frictional losses in, 32
Law of conservation of energy, 29
Limited rotation hydraulic motors, 70-2
Linear actuators, 83
Lobe pumps, 46, 47
Lubricating oils, 173
Lubrication, 3, 14-15
Maintenance, 190-207
causes of system breakdown, 190-1
cleanliness, 193
entrained gas in fluids, 191-2
preventive, 193-7
safety, 192-3
wear due to fluid contamination, 191
Manifolds, 130-1
Mass, 5
Mass flow, 25
Mechanical efficiency, 59-61
hydraulic motors, 79-80
Mechanical filters, 140
Mechanical servo valves, 125
Metal piping, 157-8
Micron filters, 137
Motor head, 31
Neutralization number, 170-1
Newtonian fluids, 36
Non-Newtonian fluids, 36
Non-positive displacement pumps, 38-40228 Index
Non-rotational flow, 27
Non-separator accumulators, 148-9
Non-uniform flow, 26
0-Rings, 68
Oil:
foamy, 65
hydraulics, 2
overheating, 65
viscosity, and pump capacity, 61
wrong selection, 65
Orifice plate-type flowmeter, 35-6
Pascal’slaw, 2, 3, 21-2
application of, 22-4
Petroleum-based fluids, 173
Pilot-operated check valve, 100-1
Pilot-operated control valves, 95-7
Pilot-operated relief valves, 108
Pipes and hoses, 157-62
color identification code, 159
metal piping, 157-8
pipe fittings, 160
pipe joints, 160-2
schedules and codes, 158-60
steel piping, 157
Piston cup packings:
non-metallic, 196-7
preventive maintenance, 195-7
Piston motors, 75-6
Piston pumps, 53-8
axial, 53-5
radial piston pump, 57-8
swash plate inline piston pump, 54-7
Positive displacement/hydrostatic pumps, 40
Potential energy, 9, 29
Power, 10-11
Power steering, 179
Power transmission, 3
Pre-commissioning, 205
Pressure, 16-17
absolute, 18
atmospheric, 18
effect on boiling point, 18-19
in fluids, 17
gage, 18
incorrect, 198, 203
measurement, 19-21
at point in liquid, 17
Pressure-compensated flow control valves, 116,
118-20
Pressure control valves, 94, 105-14
brake valve, 106, 114
counterbalance valve, 106, 113-14
reducing valve, 105, 108-10
sequencing valve, 106, 111-14
simple pressure relief valve, 106-7
unloading valve, 105, 110-11
Pressure-flow relationship, 32-3
Pressure head, 31
Pressure relief valves:
compound, 108
simple, 106-7
Pressure switches, 127-8
Preventive maintenance, 193-7
piston cup packings, 195-7
sealing devices, 194-5
V-ring packings, 195
Pump head, 31
Pump slippage, 45
Radial piston motors, 76
Radial piston pump, 57-8
Real fluids, 36
Reducing valve, 105, 108-10
Relief valve, 45, 105
Reservoir system, 132-5
air-pressurized, 135
non-pressurized, 133-5
pressurized, 135
Reynolds number, 26-7
Rotameter, 3 3 ^
Rotary actuators, 69, 83
Rotary four-way control valves,
103-4
Rotational flow, 27
Running clearance, and capacity, 61
Safety, 192-3
Seal rings, 68
Sealed piston-type sensing element, 128
Sealing, 4
Seals:
cleaning of, 67-8
installation, 68
Separator accumulators, 149-52
bladder-type, 152
diaphragm-type, 149-51
piston-type, 149, 150
Sequencing valve, 106, 111-13
Servo cylinders, 124
Servo motors, 124
Servo transducers, 124
Servo valves, 123-6
components, 124
electro-hydraulic type, 125-6
mechanical-type, 125Index 229
Shock absorbers, 129-30
Shuttle valves, 104-5
Single acting hydrauUc cylinders, 84-5
Snubber restrictions, 20
Solenoid-operated control valves, 102-3
Specific gravity, 6
Specific weight, 8
Spool-type control valves, 1 0 1 ^
rotary four-way, 103-4
solenoid-operated, 102-3
three-way and four-way, 101-2
two-way, 101
Spring-loaded accumulators, 147-8
Spur gears, 45
Steady flow, 26
Steel piping, 157
Steel tubing, 162-4
Strainers, 145
see also Filters
Supply pumps, 124
Swagelok fitting, 163-4
Swash plate inline piston pump, 54-7
Tell-tale filters, 142-3
Temperature switch, 128-9
Throttling valve, 115, 118
Torque, 14
Troubleshooting, 197-207
commissioning, 205-6
excessive heat, 198, 201
excessive noise, 198, 200
fault finding process, 197
faulty operation, 199, 203
fluid contamination, 207
high fluid temperature, 206
incorrect commissioning/adjustment, 207
incorrect flow, 198, 202-3
incorrect fluid viscosity, 207
incorrect pressure, 198, 203
instruments for, 204
investigation of failure, 207
pre-commissioning, 205
prevention of premature failure, 206-7
see also Maintenance
Turbine-type flowmeter, 34-5
Turbulent flow, 27
frictional losses in, 32
Uniform flow, 26
Unloading valve, 105, 110-11
Unsteady flow, 26
Vacuum, 18
Vane motors, 7 3 ^
balance and unbalanced-type, 74-5
Vane pumps, 47-52
balanced, 49-50
classification, 49
pump operation, 48-9
vane loading, 50
variable displacement, 50-2
Variable displacement vane pumps, 50-1
pressure compensation in, 52
Velocity, 6
Velocity head, 31
Velocity of flow, 25
Viscosity, 12-13
Viscosity index, 13
Volume, 5
Volumetric displacement, external gear pump, 43
Volumetric efficiency, 45
hydraulic motors, 80
hydraulic pumps, 59
Volumetric flow, 25
Water-glycol solutions, 172
Water hydraulics, 2
Water-in-oil emulsions, 172
Weight, 7-8
Weight-loaded accumulators, 147
Welding, 179-80
Work, 8-9
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