@LECTSOLUTIONSSTUVIA
All Chapters Covered
SOLUTION MANUAL
, @LECTSOLUTIONSSTUVIA
CONTENTS
PREFACE V
Part I Overview of Text Objectives 1
Part II Answers and Solutions to Text Exercises 9
Chapter 1 Introduction to Fluid Power 9
Chapter 2 Physical Properties of Hydraulic Fluids 12
Chapter 3 Energy and Power in Hydraulic Systems 21
Chapter 4 Frictional Losses in Hydraulic Pipelines 46
Chapter 5 Hydraulic Pumps 67
Chapter 6 Hydraulic Cylinders and Cushioning Devices 84
Chapter 7 Hydraulic Motors 97
Chapter 8 Hydraulic Valves 108
Chapter 9 Hydraulic Circuit Design and Analysis 121
i
, @LECTSOLUTIONSSTUVIA
Chapter 10 Hydraulic Conductors and Fittings 146
Chapter 11 Ancillary Hydraulic Devices 158
Chapter 12 Maintenance of Hydraulic Systems 167
Chapter 13 Pneumatics - Air Preparation and Components 177
Chapter 14 Pneumatics - Circuits and Applications 191
Chapter 15 Basic Electrical Controls for Fluid Power Circuits 202
Chapter 16 Fluid Logic Control Systems 205
Chapter 17 Advanced Electrical Controls for Fluid Power Systems
211
ii
, @LECTSOLUTIONSSTUVIA
Part I Overview of Text Objectives
Chapter 1 Introduction to Fluid Power
This chapter introduces the student to the overall field of fluid power. It answers
the question “What is fluid power?” and presents a corresponding historical background.
Advantages and applications of fluid power systems are discussed in detail.
Emphasis is placed on the fact that fluid power systems are designed to perform useful
work. A complete hydraulic system and a complete pneumatic system are individually
presented with identifications of the necessary components and their functions. The fluid
power industry is examined in terms of its bright, expanding future and the need for fluid
power mechanics, technicians and engineers.
Chapter 2 Physical Properties of Hydraulic Fluids
This chapter deals with the single most important material in a hydraulic system:
the working fluid. It introduces the student to the various types of hydraulic fluids and
their most important physical properties. The differences between liquids and gases are
outlined in terms of fundamental characteristics and applications. Methods for testing
various fluid properties (such as bulk modulus, viscosity, and viscosity index) are
presented. The student is introduced to the concepts of pressure, head and force. Units in
the Metric System are described and compared to units in the English System. This will
prepare the student for the inevitable United States adoption of the Metric System.
1
, @LECTSOLUTIONSSTUVIA
Chapter 3 Energy and Power in Hydraulic Systems
This chapter introduces the student to the basic laws and principles of fluid
mechanics, which are necessary for understanding the concepts presented in later chapters.
Emphasis is placed on energy, power, efficiency, continuity of flow, Pascal’s Law and
Bernoulli’s Theorem. Stressed is the fact that fluid power is not a source of energy but, in
reality, is an energy transfer system. As such, fluid power should be used in applications
where it can transfer energy better than other systems. Applications presented include the
hydraulic jack and the air-to-hydraulic pressure booster. Problem solving techniques are
presented using English and Metric units.
Chapter 4 Frictional Losses in Hydraulic Pipelines
This chapter investigates the mechanism of energy losses due to friction associated
with the flow of a fluid inside a pipeline. It introduces the student to laminar and turbulent
flow, Reynold’s Number and frictional losses in fittings as well as pipes. Hydraulic circuit
analysis by the equivalent length method is presented. Stressed is the fact that it is very
important to keep all energy losses in a fluid power system to a minimum acceptable level.
This requires the proper selection of the sizes of all pipes and fittings used in the system.
Problem solving techniques are presented using English and Metric units.
Chapter 5 Hydraulic Pumps
This chapter introduces the student to the operation of pumps, which convert
mechanical energy into hydraulic energy. The theory of pumping is presented for both
positive displacement and non-positive displacement pumps. Emphasized is the fact that
pumps do not pump pressure but instead produce the flow of a fluid. The resistance to this
flow, produced by the hydraulic system, is what determines the pressure. The operation
and applications of the three principal types of fluid power pumps (gear, vane and piston)
are described in detail. Methods are presented for selecting pumps and evaluating their
performance using Metric and English units. The causes of pump noise are discussed and
ways to reduce noise levels are identified.
2
, @LECTSOLUTIONSSTUVIA
Chapter 6 Hydraulic Cylinders and Cushioning Devices Chapter 7
Hydraulic Motors
These two chapters introduce the student to energy output devices (called actuators)
which include cylinders and motors. Cylinders are linear actuators, whereas motors are
rotary actuators. Emphasized is the fact that hydraulic actuators perform just the opposite
function of that performed by pumps. Thus actuators extract energy from a fluid and
convert it into a mechanical output to perform useful work. Included are discussions on the
construction, operation and applications of various types of hydraulic cylinders and
motors. Presented is the mechanics of determining hydraulic cylinder loadings when using
various linkages such as first class, second class and third class lever systems. The design
and operation of hydraulic cylinder cushions and hydraulic shock absorbers are discussed
along with their industrial applications. Methods are presented for evaluating the
performance of hydraulic motors and selecting motors for various applications.
Hydrostatic transmissions are discussed in terms of their practical applications as
adjustable speed drives.
Chapter 8 Hydraulic Valves
This chapter introduces the student to the basic operations of the various types of
hydraulic valves. It emphasizes the fact that valves must be properly selected or the entire
hydraulic system will not function as required. The three basic types of hydraulic valves
are directional control valves, pressure control valves and flow control valves. Each type of
valve is discussed in terms of its construction, operation and application. Emphasis is placed
on the importance of knowing the primary function and operation of the various types of
valves. This knowledge is not only required for designing a good functioning system, but it
also leads to the discovery of innovative ways to improve a fluid power system for a given
application. This is one of the biggest challenges facing the hydraulic system designer. Also
discussed are the functions and operational characteristics of servo valves, proportional
control valves and cartridge valves.
3
, @LECTSOLUTIONSSTUVIA
Chapter 9 Hydraulic Circuit Design and Analysis
The material presented in previous chapters dealt with basic fundamentals and
system components. This chapter is designed to offer insight into the basic types of
hydraulic circuits including their capabilities and performance. The student should be
made aware that when analyzing or designing a hydraulic circuit, three important
considerations must be taken into account: (1) Safety of operation, (2) Performance of
desired function, and (3) Efficiency of operation. In order to properly understand the
operation of hydraulic circuits, the student must have a working knowledge of components
in terms of their operation and their ANSI graphical representations.
Chapter 10 Hydraulic Conductors and Fittings
This chapter introduces the student to the various types of conductors and fittings
used to conduct the fluid between the various components of a hydraulic system.
Advantages and disadvantages of the four primary types of conductors (steel pipe, steel
tubing, plastic tubing and flexible hose) are discussed along with practical applications.
Sizing and pressure rating techniques are presented using English and Metric units. The
very important distinction between burst pressure and working pressure is emphasized as
related to the concept of factor of safety. The difference between tensile stress and tensile
strength is also explained. Precautions are emphasized for proper installation of conductors
to minimize maintenance problems after a fluid power system is placed into operation. The
design, operation and application of quick disconnect couplings are also presented.
Chapter 11 Ancillary Hydraulic Devices
Ancillary hydraulic devices are those important components that do not fall under
the major categories of pumps, valves, actuators, conductors and fittings. This chapter
deals with these ancillary devices which include reservoirs, accumulators, pressure
intensifiers, sealing devices, heat exchangers, pressure gages and flow meters. Two
exceptions are the components called
4
, @LECTSOLUTIONSSTUVIA
filters and strainers which are covered in Chapter 12 Maintenance of Hydraulic Systems.
Filters and strainers are included in Chapter 12 because these two components are
specifically designed to enhance the successful maintenance of hydraulic systems.
Chapter 12 Maintenance of Hydraulic Systems
This chapter stresses the need for planned preventative maintenance. The student is
introduced to the common causes of hydraulic system breakdown. Stressed is the fact that
over half of all hydraulic system problems have been traced directly to the fluid. Methods
for properly maintaining and disposing of hydraulic fluids are discussed in terms of
accomplishing pollution control and conservation of natural resources objectives. The
mechanism of the wear of mating moving parts due to solid particle contamination of the
fluid, is discussed in detail. Also explained are the problems caused by the existence of
gases in the hydraulic fluid. Components that are presented include filters and strainers.
Methods for trouble-shooting hydraulic circuits are described. Emphasized is the need for
human safety when systems are designed, installed, operated and maintained.
Chapter 13 Pneumatics - Air Preparation and Components
This chapter introduces the student to pneumatics where pressurized gases
(normally air) are used to transmit and control power. Properties of air are discussed and
the perfect gas laws are presented. Then the purpose, construction and operation of
compressors are described. Methods are presented to determine the power required to
drive compressors and the consumption rate of pneumatically driven equipment such as
impact wrenches, hoists, drills, hammers, paint sprayers and grinders. Fluid conditioners
such as filters, regulators, lubricators, mufflers and air dryers are discussed in detail. The
student is then introduced to the design, operation and application of pneumatic pressure
control valves, flow control valves, directional control valves and actuators (linear and
rotary).
5
, @LECTSOLUTIONSSTUVIA
Chapter 14 Pneumatics - Circuits and Applications
This chapter delves into the operation and analysis of basic pneumatic circuits and
with corresponding applications. A comparison is made between hydraulic and pneumatic
systems including advantages, disadvantages and types of applications. It is important for
the student to appreciate the performance, operating characteristics, cost and application
differences between pneumatic and hydraulic systems. The operation of pneumatic vacuum
systems is discussed along with the analysis method for determining vacuum lift capacities.
Techniques for evaluating the cost of air leakage into the atmosphere and frictional energy
losses are presented. Methods are also provided for sizing gas-loaded accumulators. In
addition, the trouble shooting of pneumatic circuits is discussed as a means of determining
the causes of system malfunction.
Chapter 15 Basic Electrical Controls for Fluid Power Circuits
This chapter introduces the student to fluid power systems where basic electrical
devices are used for control purposes.
There are seven basic electrical devices that are commonly used: manually actuated switches, limit
switches, pressure switches, solenoids, relays, timers and temperature switches.
Each type of electrical device is discussed in terms of its construction, operation and
function in various practical fluid power applications. Electrical circuits, containing these
electrical components, are represented in ladder diagram format. This chapter delves into
how the electrical ladder diagrams interact with corresponding hydraulic/pneumatic
circuits. Shown for example is how the manual actuation of an electric push button switch
can cause electrohydraulic/pneumatic equipment to perform a variety of industrial
operations.
Chapter 16 Fluid Logic Control Systems
This chapter introduces students to the theory and operation of MPL (Moving Part
Logic) control systems. It is pointed out that successful miniaturization of MPL devices and
also maintenance-free operation have resulted in increased utilization of MPL controls for a
wide variety of industrial fluid power
6
, @LECTSOLUTIONSSTUVIA
applications. Stressed is the fact that MPL is used for controlling fluid power systems. As
such, the MPL portion of the system is the brain and the fluid power portion provides the
brawn or muscle. Discussed in detail are the advantages and disadvantages of MPL control
systems as compared to electronic control systems. Illustrations, graphical symbols and
truth tables are provided to give the student a better understanding of how MPL control
devices function. Examples of MPL logic circuits are presented to illustrate the numerous
practical applications. Included are fluid logic circuits using general logic symbols and the
application of logic systems design techniques using Boolean Algebra.
Chapter 17 Advanced Electrical Controls for Fluid Power Systems
This chapter presents the theory, analysis and operation of electro-hydraulic servo systems.
Such a system is closed-loop and, thus, provides very precise control of the movement of
actuators. Also presented is the application of programmable logic controllers (PLCs) for
the control of fluid power systems. Unlike general-purpose computers, PLCs are designed
to operate in industrial environments where high ambient temperature and humidity levels
may exist, as is typically the case for fluid power applications. Unlike electro-mechanical
relays, PLCs are not hard-wired to perform specific functions. Thus when system operating
requirements change, a PLC software program is readily changed instead of having to
physically re-wire relays.
Chapter 18 Automation Studio Computer Software
This chapter presents the salient features and capabilities of Automation Studio.
Automation Studio is a computer software package that allows users to design, simulate
and animate circuits consisting of various automation technologies including hydraulics,
pneumatics, PLCs, electrical controls and digital electronics. Included with the Textbook is
a CD that illustrates how Automation Studio is used to create, simulate and animate the
following 16 fluid power circuits present throughout the book:
7
All Chapters Covered
SOLUTION MANUAL
, @LECTSOLUTIONSSTUVIA
CONTENTS
PREFACE V
Part I Overview of Text Objectives 1
Part II Answers and Solutions to Text Exercises 9
Chapter 1 Introduction to Fluid Power 9
Chapter 2 Physical Properties of Hydraulic Fluids 12
Chapter 3 Energy and Power in Hydraulic Systems 21
Chapter 4 Frictional Losses in Hydraulic Pipelines 46
Chapter 5 Hydraulic Pumps 67
Chapter 6 Hydraulic Cylinders and Cushioning Devices 84
Chapter 7 Hydraulic Motors 97
Chapter 8 Hydraulic Valves 108
Chapter 9 Hydraulic Circuit Design and Analysis 121
i
, @LECTSOLUTIONSSTUVIA
Chapter 10 Hydraulic Conductors and Fittings 146
Chapter 11 Ancillary Hydraulic Devices 158
Chapter 12 Maintenance of Hydraulic Systems 167
Chapter 13 Pneumatics - Air Preparation and Components 177
Chapter 14 Pneumatics - Circuits and Applications 191
Chapter 15 Basic Electrical Controls for Fluid Power Circuits 202
Chapter 16 Fluid Logic Control Systems 205
Chapter 17 Advanced Electrical Controls for Fluid Power Systems
211
ii
, @LECTSOLUTIONSSTUVIA
Part I Overview of Text Objectives
Chapter 1 Introduction to Fluid Power
This chapter introduces the student to the overall field of fluid power. It answers
the question “What is fluid power?” and presents a corresponding historical background.
Advantages and applications of fluid power systems are discussed in detail.
Emphasis is placed on the fact that fluid power systems are designed to perform useful
work. A complete hydraulic system and a complete pneumatic system are individually
presented with identifications of the necessary components and their functions. The fluid
power industry is examined in terms of its bright, expanding future and the need for fluid
power mechanics, technicians and engineers.
Chapter 2 Physical Properties of Hydraulic Fluids
This chapter deals with the single most important material in a hydraulic system:
the working fluid. It introduces the student to the various types of hydraulic fluids and
their most important physical properties. The differences between liquids and gases are
outlined in terms of fundamental characteristics and applications. Methods for testing
various fluid properties (such as bulk modulus, viscosity, and viscosity index) are
presented. The student is introduced to the concepts of pressure, head and force. Units in
the Metric System are described and compared to units in the English System. This will
prepare the student for the inevitable United States adoption of the Metric System.
1
, @LECTSOLUTIONSSTUVIA
Chapter 3 Energy and Power in Hydraulic Systems
This chapter introduces the student to the basic laws and principles of fluid
mechanics, which are necessary for understanding the concepts presented in later chapters.
Emphasis is placed on energy, power, efficiency, continuity of flow, Pascal’s Law and
Bernoulli’s Theorem. Stressed is the fact that fluid power is not a source of energy but, in
reality, is an energy transfer system. As such, fluid power should be used in applications
where it can transfer energy better than other systems. Applications presented include the
hydraulic jack and the air-to-hydraulic pressure booster. Problem solving techniques are
presented using English and Metric units.
Chapter 4 Frictional Losses in Hydraulic Pipelines
This chapter investigates the mechanism of energy losses due to friction associated
with the flow of a fluid inside a pipeline. It introduces the student to laminar and turbulent
flow, Reynold’s Number and frictional losses in fittings as well as pipes. Hydraulic circuit
analysis by the equivalent length method is presented. Stressed is the fact that it is very
important to keep all energy losses in a fluid power system to a minimum acceptable level.
This requires the proper selection of the sizes of all pipes and fittings used in the system.
Problem solving techniques are presented using English and Metric units.
Chapter 5 Hydraulic Pumps
This chapter introduces the student to the operation of pumps, which convert
mechanical energy into hydraulic energy. The theory of pumping is presented for both
positive displacement and non-positive displacement pumps. Emphasized is the fact that
pumps do not pump pressure but instead produce the flow of a fluid. The resistance to this
flow, produced by the hydraulic system, is what determines the pressure. The operation
and applications of the three principal types of fluid power pumps (gear, vane and piston)
are described in detail. Methods are presented for selecting pumps and evaluating their
performance using Metric and English units. The causes of pump noise are discussed and
ways to reduce noise levels are identified.
2
, @LECTSOLUTIONSSTUVIA
Chapter 6 Hydraulic Cylinders and Cushioning Devices Chapter 7
Hydraulic Motors
These two chapters introduce the student to energy output devices (called actuators)
which include cylinders and motors. Cylinders are linear actuators, whereas motors are
rotary actuators. Emphasized is the fact that hydraulic actuators perform just the opposite
function of that performed by pumps. Thus actuators extract energy from a fluid and
convert it into a mechanical output to perform useful work. Included are discussions on the
construction, operation and applications of various types of hydraulic cylinders and
motors. Presented is the mechanics of determining hydraulic cylinder loadings when using
various linkages such as first class, second class and third class lever systems. The design
and operation of hydraulic cylinder cushions and hydraulic shock absorbers are discussed
along with their industrial applications. Methods are presented for evaluating the
performance of hydraulic motors and selecting motors for various applications.
Hydrostatic transmissions are discussed in terms of their practical applications as
adjustable speed drives.
Chapter 8 Hydraulic Valves
This chapter introduces the student to the basic operations of the various types of
hydraulic valves. It emphasizes the fact that valves must be properly selected or the entire
hydraulic system will not function as required. The three basic types of hydraulic valves
are directional control valves, pressure control valves and flow control valves. Each type of
valve is discussed in terms of its construction, operation and application. Emphasis is placed
on the importance of knowing the primary function and operation of the various types of
valves. This knowledge is not only required for designing a good functioning system, but it
also leads to the discovery of innovative ways to improve a fluid power system for a given
application. This is one of the biggest challenges facing the hydraulic system designer. Also
discussed are the functions and operational characteristics of servo valves, proportional
control valves and cartridge valves.
3
, @LECTSOLUTIONSSTUVIA
Chapter 9 Hydraulic Circuit Design and Analysis
The material presented in previous chapters dealt with basic fundamentals and
system components. This chapter is designed to offer insight into the basic types of
hydraulic circuits including their capabilities and performance. The student should be
made aware that when analyzing or designing a hydraulic circuit, three important
considerations must be taken into account: (1) Safety of operation, (2) Performance of
desired function, and (3) Efficiency of operation. In order to properly understand the
operation of hydraulic circuits, the student must have a working knowledge of components
in terms of their operation and their ANSI graphical representations.
Chapter 10 Hydraulic Conductors and Fittings
This chapter introduces the student to the various types of conductors and fittings
used to conduct the fluid between the various components of a hydraulic system.
Advantages and disadvantages of the four primary types of conductors (steel pipe, steel
tubing, plastic tubing and flexible hose) are discussed along with practical applications.
Sizing and pressure rating techniques are presented using English and Metric units. The
very important distinction between burst pressure and working pressure is emphasized as
related to the concept of factor of safety. The difference between tensile stress and tensile
strength is also explained. Precautions are emphasized for proper installation of conductors
to minimize maintenance problems after a fluid power system is placed into operation. The
design, operation and application of quick disconnect couplings are also presented.
Chapter 11 Ancillary Hydraulic Devices
Ancillary hydraulic devices are those important components that do not fall under
the major categories of pumps, valves, actuators, conductors and fittings. This chapter
deals with these ancillary devices which include reservoirs, accumulators, pressure
intensifiers, sealing devices, heat exchangers, pressure gages and flow meters. Two
exceptions are the components called
4
, @LECTSOLUTIONSSTUVIA
filters and strainers which are covered in Chapter 12 Maintenance of Hydraulic Systems.
Filters and strainers are included in Chapter 12 because these two components are
specifically designed to enhance the successful maintenance of hydraulic systems.
Chapter 12 Maintenance of Hydraulic Systems
This chapter stresses the need for planned preventative maintenance. The student is
introduced to the common causes of hydraulic system breakdown. Stressed is the fact that
over half of all hydraulic system problems have been traced directly to the fluid. Methods
for properly maintaining and disposing of hydraulic fluids are discussed in terms of
accomplishing pollution control and conservation of natural resources objectives. The
mechanism of the wear of mating moving parts due to solid particle contamination of the
fluid, is discussed in detail. Also explained are the problems caused by the existence of
gases in the hydraulic fluid. Components that are presented include filters and strainers.
Methods for trouble-shooting hydraulic circuits are described. Emphasized is the need for
human safety when systems are designed, installed, operated and maintained.
Chapter 13 Pneumatics - Air Preparation and Components
This chapter introduces the student to pneumatics where pressurized gases
(normally air) are used to transmit and control power. Properties of air are discussed and
the perfect gas laws are presented. Then the purpose, construction and operation of
compressors are described. Methods are presented to determine the power required to
drive compressors and the consumption rate of pneumatically driven equipment such as
impact wrenches, hoists, drills, hammers, paint sprayers and grinders. Fluid conditioners
such as filters, regulators, lubricators, mufflers and air dryers are discussed in detail. The
student is then introduced to the design, operation and application of pneumatic pressure
control valves, flow control valves, directional control valves and actuators (linear and
rotary).
5
, @LECTSOLUTIONSSTUVIA
Chapter 14 Pneumatics - Circuits and Applications
This chapter delves into the operation and analysis of basic pneumatic circuits and
with corresponding applications. A comparison is made between hydraulic and pneumatic
systems including advantages, disadvantages and types of applications. It is important for
the student to appreciate the performance, operating characteristics, cost and application
differences between pneumatic and hydraulic systems. The operation of pneumatic vacuum
systems is discussed along with the analysis method for determining vacuum lift capacities.
Techniques for evaluating the cost of air leakage into the atmosphere and frictional energy
losses are presented. Methods are also provided for sizing gas-loaded accumulators. In
addition, the trouble shooting of pneumatic circuits is discussed as a means of determining
the causes of system malfunction.
Chapter 15 Basic Electrical Controls for Fluid Power Circuits
This chapter introduces the student to fluid power systems where basic electrical
devices are used for control purposes.
There are seven basic electrical devices that are commonly used: manually actuated switches, limit
switches, pressure switches, solenoids, relays, timers and temperature switches.
Each type of electrical device is discussed in terms of its construction, operation and
function in various practical fluid power applications. Electrical circuits, containing these
electrical components, are represented in ladder diagram format. This chapter delves into
how the electrical ladder diagrams interact with corresponding hydraulic/pneumatic
circuits. Shown for example is how the manual actuation of an electric push button switch
can cause electrohydraulic/pneumatic equipment to perform a variety of industrial
operations.
Chapter 16 Fluid Logic Control Systems
This chapter introduces students to the theory and operation of MPL (Moving Part
Logic) control systems. It is pointed out that successful miniaturization of MPL devices and
also maintenance-free operation have resulted in increased utilization of MPL controls for a
wide variety of industrial fluid power
6
, @LECTSOLUTIONSSTUVIA
applications. Stressed is the fact that MPL is used for controlling fluid power systems. As
such, the MPL portion of the system is the brain and the fluid power portion provides the
brawn or muscle. Discussed in detail are the advantages and disadvantages of MPL control
systems as compared to electronic control systems. Illustrations, graphical symbols and
truth tables are provided to give the student a better understanding of how MPL control
devices function. Examples of MPL logic circuits are presented to illustrate the numerous
practical applications. Included are fluid logic circuits using general logic symbols and the
application of logic systems design techniques using Boolean Algebra.
Chapter 17 Advanced Electrical Controls for Fluid Power Systems
This chapter presents the theory, analysis and operation of electro-hydraulic servo systems.
Such a system is closed-loop and, thus, provides very precise control of the movement of
actuators. Also presented is the application of programmable logic controllers (PLCs) for
the control of fluid power systems. Unlike general-purpose computers, PLCs are designed
to operate in industrial environments where high ambient temperature and humidity levels
may exist, as is typically the case for fluid power applications. Unlike electro-mechanical
relays, PLCs are not hard-wired to perform specific functions. Thus when system operating
requirements change, a PLC software program is readily changed instead of having to
physically re-wire relays.
Chapter 18 Automation Studio Computer Software
This chapter presents the salient features and capabilities of Automation Studio.
Automation Studio is a computer software package that allows users to design, simulate
and animate circuits consisting of various automation technologies including hydraulics,
pneumatics, PLCs, electrical controls and digital electronics. Included with the Textbook is
a CD that illustrates how Automation Studio is used to create, simulate and animate the
following 16 fluid power circuits present throughout the book:
7
