EBOOK - Hydraulics and Pneumatics Third Edition (Andrew Parr)


EBOOK - Thủy lực & Khí nén - Tài liệu hướng dẫn cho kỹ sư và kỹ thuật viên (Andrew Parr) - 210 Trang.

Practically every industrial process requires objects to be moved, manipulated or be subjected to some form of force. This is generally accomplished by means of electrical equipment (such as motors or solenoids), or via devices driven by air (pneumatics) or liquids (hydraulics).

Traditionally, pneumatics and hydraulics are thought to be a mechanical engineer’s subject (and are generally taught as such in colleges). In practice, techniques (and, more important, the fault-finding methodology) tend to be more akin to the ideas used in electronics and process control.
This book has been written by a process control engineer as a guide to the operation of hydraulic and pneumatic systems. It is intended for engineers and technicians who wish to have an insight into the components and operation of a pneumatic or hydraulic system. The mathematical content has been deliberately kept simple with the aim of making the book readable rather than rigorous. It is not, therefore, a design manual, and topics such as sizing of pipes and valves have been deliberately omitted.
The second edition was updated to include recent developments such as the increasing use of proportional valves, and an expanded section on industrial safety.
The third edition includes many changes based on suggestions from readers including a new chapter on sequencing applications and an appendix of hydraulic and pneumatic symbols. I would, in particular, like to thank Don MacDonald and  Kerry  Jones  of  IPS  International  (www.ips-international.com) for useful advice and the use of the simulation software described in Chapter 9.

CONTENTS:

1  Fundamental Principles .......................................................................1
Industrial Prime Movers ...............................................................................1
A Brief System Comparison ..........................................................................1
An electrical system ...................................................................................2
A hydraulic system .....................................................................................2
A pneumatic system ...................................................................................5
A comparison..............................................................................................6
Definition of Terms ........................................................................................6
Mass and force ............................................................................................9
Pressure.....................................................................................................10
Work, energy and power ...........................................................................12
Torque .......................................................................................................15
Pascal’s Law ...............................................................................................15
Pressure Measurement ................................................................................19
Fluid Flow ...................................................................................................21
Temperature.................................................................................................25
Temperature scales ...................................................................................25
Temperature measurement ........................................................................26
Gas Laws .....................................................................................................27
2  Hydraulic Pumps and Pressure Regulation .....................................31
Pressure Regulation ....................................................................................35
Pump Types .................................................................................................37
Gear pumps ...............................................................................................37
Vane pumps ..............................................................................................40
Piston pumps ............................................................................................42
Combination pumps..................................................................................45
Loading Valves ............................................................................................46
Pump Problems ...........................................................................................46
Filters ..........................................................................................................47
3  Air Compressors, Air Treatment and Pressure Regulation ............51
Compressor Types .......................................................................................53
Piston compressors ...................................................................................54
Screw compressors ...................................................................................57
Rotary compressors ..................................................................................57
Dynamic compressors ..............................................................................58
Air Receivers and Compressor Control ......................................................60
Air Treatment ..............................................................................................62
Stages of air treatment ..............................................................................64
Filters ........................................................................................................64
Air dryers ..................................................................................................65
Lubricators ................................................................................................67
Air classification .......................................................................................68
Pressure Regulation ....................................................................................69
Relief valves .............................................................................................70
Non-relieving pressure regulators ............................................................70
Relieving pressure regulators ...................................................................71
Service Units ...............................................................................................72
4  Control Valves .....................................................................................75
Graphic Symbols .........................................................................................76
Types of Control Valve .................................................................................79
Poppet valves ............................................................................................79
Spool valves ..............................................................................................81
Rotary valves ............................................................................................85
Pilot-Operated Valves .................................................................................85
Check Valves ................................................................................................87
Pilot-operated check valves ......................................................................89
Restriction check valves ...........................................................................92
Shuttle and Fast Exhaust Valves ..................................................................92
Sequence Valves ..........................................................................................95
Time-Delay Valves .......................................................................................96
Proportional Valves .....................................................................................97
Servo Valves ..............................................................................................107
Modular Valves and Manifolds .................................................................110
Cartridge Logic Valves ..............................................................................114
5  Actuators ................................................................................................117
Linear Actuators .......................................................................................117
Construction ...........................................................................................120
Mounting arrangements ..........................................................................125
Cylinder dynamics ..................................................................................125
Seals ..........................................................................................................128
Rotary Actuators .......................................................................................130
Constructional details .............................................................................132
Application Notes ......................................................................................135
Speed control ..........................................................................................135
Actuator synchronization........................................................................139
Regeneration ...........................................................................................141
Contents  vii
Counterbalance and dynamic braking ....................................................142
Pilot-operated check valves ....................................................................143
Pre-fill and compression relief................................................................144
Bellows Actuator .......................................................................................146
6  Hydraulic and Pneumatic Accessories ............................................149
Hydraulic Reservoirs ................................................................................149
Hydraulic Accumulators ...........................................................................151
Hydraulic Coolers and Heat Exchangers .................................................154
Hydraulic Fluids .......................................................................................156
Viscosity .................................................................................................159
Pour point ...............................................................................................160
Environmental fluids ...............................................................................160
Pneumatic Piping, Hoses and Connections ..............................................161
Cost of Air Leaks .......................................................................................164
Silencers ....................................................................................................164
Hydraulic Piping, Hosing and Connections .............................................165
Hydraulic and Pneumatic Fuses ...............................................................166
7  Process Control Pneumatics ............................................................169
Signals and Standards ...............................................................................170
The Flapper-Nozzle ...................................................................................171
Volume Boosters ........................................................................................173
The Air Relay and the Force Balance Principle ........................................174
Pneumatic Controllers ..............................................................................175
Process Control Valves and Actuators ......................................................179
Flow control valves .................................................................................179
Actuators.................................................................................................182
Valve positioners ....................................................................................184
Converters .................................................................................................187
I–P converters .........................................................................................187
P–I converters .........................................................................................187
8  Sequencing Applications ..................................................................189
Pneumatic Limit Switches .........................................................................189
Logic Elements ..........................................................................................193
Timers ........................................................................................................194
More Complex Sequences .........................................................................196
Pressure-Controlled Sequences.................................................................198
Modular Sequence Valves .........................................................................199
Programmable Controllers .......................................................................200
Distributed Systems ...................................................................................203
9  Safety, Fault-Finding and Maintenance .........................................205
Safety .........................................................................................................205
Cleanliness ................................................................................................211
Fault-Finding Instruments.........................................................................212
Fault-Finding ............................................................................................214
Preventive Maintenance ............................................................................224
Computer Simulation ................................................................................226
Appendix: Hydraulic and Pneumatic Symbols ........................................229

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