Hydraulic systemsare use din modern production plant sand manufacturing installations. By hydraulics,we meanthe generationof forces and motion using hydraulic fluids.
The hydraulic fluids represent the medium for power transmission. The objec tof this book is to teach you more about hydraulic sand its areas of application. We will begin with the latter by listing the main areas for the application of hydraulics.
The place held by hydraulics in (modern) automation technology illustrates the wide range of applications for which it can be used. A basic distinction is made between:
• stationaryhydraulics
• and mobile hydraulics
Mobile hydraulic systems move on wheel sortracks, for example, unlike stationary hydraulic systems which remain firmly fixed in one position. A characteristic feature of mobile hydraulics is that the valves are frequently manually operated. In the case of stationary hydraulics, however, mainly solenoid valve sare used.
Otherareas include marine, miningand air crafthy draulics. Aircraft hydraulics assumesaspecial position because safetymeasuresare of such critical importance here. In the next few pages, some typical examples of applications are given to clarify the tasks which can be carried out using hydraulic systems.

1 Tasksofa hydraulicinstallation__________________________________7
1.1Stationary hydraulics____________________________________________8
1.2Mobile hydraulics _____________________________________________10
1.3 Comparison ofhydraulics withothercontrol media__________________11
2 Fundamental physicalprinciplesofhydraulics_____________________13
2.1Pressure_____________________________________________________13
2.2Pressure transmission__________________________________________18
2.3Power transmission____________________________________________19
2.4 Displacement transmission_____________________________________21
2.5Pressure transfer______________________________________________23
2.6Flow rate_____________________________________________________25
2.7Continuity equation____________________________________________26
2.8Pressure measurement_________________________________________30
2.9Temperature measurement______________________________________31
2.10 Measurement of flow rate_______________________________________31
2.11Types of flow_________________________________________________31
2.12 Friction,heat, pressuredrop____________________________________35
2.13Energy and power_____________________________________________41
2.14 Cavitation____________________________________________________51
2.15Throttle points________________________________________________53
3 Hydraulic fluid________________________________________________57
3.1 Tasks for hydraulicfluids_______________________________________57
3.2 Types of hydraulic fluid_________________________________________58
3.3Characteristics and requirements_________________________________59
3.4 Viscosity_____________________________________________________60
4 Componentsofa hydraulic system_______________________________67
4.1 Power supply section__________________________________________67
4.2 Hydraulic fluid________________________________________________67
4.3 Valves_______________________________________________________68
4.4 Cylinders (linear actuators)______________________________________70
4.5 Motors(rotaryactuators)_______________________________________71
Tableofcontents
5 Graphic and circuitsymbols_____________________________________73
5.1Pumps and motors_____________________________________________73
5.2 Directional controlvalves_______________________________________74
5.3 Methods of actuation__________________________________________75
5.4 Pressure valves_______________________________________________76
5.5 Flow control valves____________________________________________78
5.6Non-return valves_____________________________________________79
5.7Cylinders ____________________________________________________80
5.8 Transferofenergy and conditioningofthe pressuremedium__________82
5.9Measuring devices_____________________________________________83
5.10 Combinationofdevices_________________________________________83
6 Designand representation of ahydraulic system___________________85
6.1Signal control section__________________________________________86
6.2Hydraulic power section________________________________________87
6.3Positional sketch______________________________________________90
6.4 Circuit diagram________________________________________________91
6.5 Components plus technical data__________________________________92
6.6Function diagram______________________________________________94
6.7Function chart ________________________________________________95
7 Componentsofthepower supplysection__________________________97
7.1Drive________________________________________________________97
7.2Pump_______________________________________________________99
7.3Coupling____________________________________________________107
7.4 Reservoir ___________________________________________________107
7.5Filters______________________________________________________109
7.6Coolers_____________________________________________________120
7.7Heaters_____________________________________________________122
8 Valves______________________________________________________123
8.1Nominal sizes________________________________________________123
8.2Design_____________________________________________________125
8.3Poppet valves________________________________________________126
8.4 Spool valves_________________________________________________127
8.5Piston overlap_______________________________________________129
8.6Control edges________________________________________________134
Tableofcontents
9 Pressure valves______________________________________________137
9.1Pressure relief valves _________________________________________137
9.2Pressure regulators___________________________________________144
10 Directionalcontrolvalves______________________________________149
10.12/2-way valve _______________________________________________153
10.23/2-way valve _______________________________________________157
10.34/2-way valve_______________________________________________159
10.4 4/3-way valve_______________________________________________162
11 Non-return valves____________________________________________167
11.1Non-return valve_____________________________________________168
11.2Piloted non-return valve_______________________________________172
11.3 Piloted doublenon-return valve_________________________________175
12 Flowcontrol valves___________________________________________179
12.1 Restrictorsand orificevalves___________________________________180
12.2 One-wayflow controlvalve_____________________________________184
12.3 Two-wayflow controlvalve_____________________________________185
13 Hydraulic cylinders___________________________________________193
13.1Single-acting cylinder _________________________________________194
13.2Double-acting cylinder ________________________________________196
13.3 Endpositioncushioning_______________________________________199
13.4 Seals_______________________________________________________200
13.5Types of mounting____________________________________________202
13.6Venting_____________________________________________________202
13.7Characteristics_______________________________________________203
13.8Buckling resistance___________________________________________205
13.9Selecting a cylinder___________________________________________207
14 Hydraulic motors_____________________________________________211
Tableofcontents
15 Accessories_________________________________________________215
15.1Flexible hoses _______________________________________________217
15.2Pipelines____________________________________________________223
15.3Sub-bases__________________________________________________226
15.4 Bleed valves_________________________________________________228
15.5Pressure gauges_____________________________________________229
15.6Pressure sensors_____________________________________________230
15.7Flow measuring instruments____________________________________231
16 Appendix___________________________________________________23