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FLUID POWER WITH APPLICATIONS ANTHONY ESPOSITO PDF

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Book Title: Fluid Power with Applications Author(s): Anthony Esposito Publisher : Pearson Education Edition: Fourth Pages: PDF Size. Book Title: Fluid Power with Applications Author(s): Anthony Esposito Publisher : Pearson Education Edition: Fourth Pages: PDF Size: Mb. SOLUTION!!!-Fluid-Power-With-Applications-ESPOSITO,Anthony-7th sppn.info - Free ebook download as PDF File .pdf), Text File .txt) or read book online for.


Fluid Power With Applications Anthony Esposito Pdf

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Uploaded by. Mike Fredskilde. Fluid Power Manual. Uploaded by. Chris Doherty. SOLUTION!!!-Fluid-Power-With-Applications-ESPOSITO,Anthony-7th sppn.info Download PDF Fluid Power with Applications (7th Edition) | PDF books Ebook Book Details Author: Anthony Esposito Pages: Binding. International Edition [PDF] [EPUB] Fluid Power with Applications by Anthony Esposito book coverage of fluid power technology in a readable.

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. 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.

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. 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: 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 5 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.

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: 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. 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 7 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. 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: Figures , , and Figures , 15, and Figures , 16, and By playing this CD on a personal computer, the student obtains a dynamic and visual presentation of the creation, simulation, analysis and animation of many of the fluid power circuits studied in class or assigned as homework excecises.

Fluid power is the technology which deals with the generation, control and transmission of power using pressurized fluids. Liquids provide a very rigid medium for transmitting power and thus can provide huge forces to move loads with utmost accuracy and precision. The terms fluid power and hydraulics and pneumatics are synonymous. Advantages of Fluid Power Systems 1. Not hindered by geometry of machine. Provides remote control.

Complex mechanical linkages are eliminated. Instantly reversible motion. Automatic protection against overloads. Infinitely variable speed control. Advantages of Mechanical System: No mess due to oil leakage problems. No danger of bursting of hydraulic lines. No fire hazard due to oil leaks. Fluid transport systems have as their sole objective the delivery of a fluid from one location to another to accomplish some useful purpose such as pumping water to homes. Fluid power systems are designed specifically to perform work such as power steering of automobiles.

Hydraulic fluid power uses liquids which provide a very rigid medium for transmitting power. Thus huge forces can be provided to move loads with utmost accuracy and precision. Pneumatic systems exhibit spongy characteristics due to the compressibility of air. However pneumatic systems are less expensive to build and operate. Hydraulic cylinder. Hydraulic motor. Liquids provide a very rigid medium. Power capacity of fluid systems is limited only by the strength capacity of the component material.

An electric motor or other power source to drive the pump or compressor. Prime mover. Compressed air tank. Plant tour. Power brakes. Power steering. Shock absorbers. Air conditioning. Automotive transmissions. Air has entered the hydraulic oil line and has greatly reduced the Bulk Modulus measure of stiffness or incompressibility of the oil-air combination fluid.

Hydraulic applications are: Pneumatic applications are: Fluid power mechanics. Fluid power technicians. Fluid power engineers. Research project. Transmit power. Lubricate moving parts. Seal clearances between mating parts. Good lubricity. Ideal viscosity 3. Chemical and environmental stability. Compatibility with system materials.

Large bulk modulus. Fire resistance. Good heat transfer capability. Low density. Foam resistance. Generally speaking, a fluid should be changed when its viscosity and acidity increase due to fluid breakdown or contamination. A liquid is a fluid which, for a given mass, will have a definite volume independent of the shape of its container. On the other hand, the volume of a gas will vary to fill the vessel which contains the gas.

Liquids are considered to be essentially incompressible. Gases, on the other hand, are fluids which are readily compressible. Advantages of air: Fire resistant.

pdf - Fluid Power with Applications Sixth Edition

Not messy. Disadvantages of air: Due to its compressibility, it cannot be used in an application where accurate positioning or rigid holding is required. Because it is compressible, it tends to be sluggish. Specific weight: Specific gravity: Pressure is force per unit area.

Gage pressures are measured relative to the atmosphere, whereas absolute pressures are measured relative to a perfect vacuum such as that which exists in outer space. To distinguish between them, gage pressures are labeled psig or simply psi Pa gage or kPa gage in Metric units.

Absolute pressures are labeled psia Pa abs or kPa abs in Metric units.

Bulk modulus is a measure of the incompressibility of a hydraulic fluid. Viscosity is a measure of the sluggishness with which a fluid flows. Viscosity index is a relative measure of an oils viscosity change with respect to temperature change. High resistance to flow which causes sluggish operation.

Increases power consumption due to frictional losses. Increased leakage losses past seals. Excessive wear due to breakdown of the oil film between moving parts. A Saybolt Universal Second is the viscosity an oil possesses which will allow it to fill a cubic- centimeter container in one second through a standard metering orifice. Pour point is the lowest temperature at which a fluid will flow.

The height of a column of liquid that represents the pressure it develops at its base. For example a 10 foot head of oil, having a density of 56 lb ft 3 , produces a pressure of 0. By atmospheric pressure at the base of the mercury column. As the temperature increases, the viscosity decreases and vice versa. When the fluid power system operates in an environment undergoing large temperature variations such as in outdoor machines like automobiles.

A high VI should be specified indicating small changes in viscosity with respect to changes in temperature. Hence we have: Therefore lb s ft N s m 1 2 2.

Using Eq. Pressure applied to a confined fluid is transmitted undimished in all directions throughout the fluid and acts perpendicular to the surfaces of the container. The total energy at upstream station 1 in a pipeline plus the energy added by a pump minus the energy removed by a motor minus the energy loss due to friction, equals the total energy at downstream station 2. If a section of horizontal pipe contains no pump or motor, the pressure at a small diameter location will be less than the pressure at a large diameter location.

Pressure energy is transformed into kinetic energy in the small diameter location. The weight flow rate is the same for all cross-sections of a pipe. Thus the smaller the pipe diameter, the greater the velocity and vice versa. Ideally the velocity of a free jet of fluid is equal to the square root of the product of two times the acceleration of gravity times the head producing the jet.

As shown in Figure , in order for a siphon to work, the following two conditions must be met: The elevation of the free end must be lower than the elevation of the liquid surface inside the container. The fluid must be initially forced to flow up from the container into the center portion of the U-tube.

This is normally done by temporarily providing a suction pressure at the free end of the siphon. Energy can neither be created nor destroyed. Per Figure , the volume of air flow is determined by the opening position of the butterfly valve.

As the air flows through the venturi, it speeds up and loses some of its pressure. This produces a differential pressure between the fuel bowl and the venturi throat.

This causes gasoline to flow into the air stream. Using Figure as a reference we have: Z is called elevation head or elevation energy per lb of fluid. A force is required to change the motion of a body. If a body is acted upon by a force, the body will have an acceleration proportional to the magnitude of the force and inversely to the mass of the body.

If one body exerts a force on a second body, the second body must exert an equal but opposite force on the first body. Energy is the ability to perform work. Power is the rate of doing work. Torque equals the product of a force and moment arm which is measured from the center of a shaft center of rotation perpendicularly to the line of action of the force.

Efficiency, another significant parameter when dealing with work and power, is defined as output power divided by input power. Mechanical power equals force times velocity. Electrical power equals voltage times electrical current. Hydraulic power or fluid power equals pressure times volume flow rate.

Elevation head is potential energy per unit weight of fluid. Pressure head is pressure energy per unit weight of fluid. Velocity head is kinetic energy per unit weight of fluid. First calculate the force applied to the air piston.

N m m N A p F piston air air air Pressure increases with depth and vice versa in accordance with the following equation: For example a pump discharge pressure of psi becomes psi at an elevation 10 ft above the pump. This is only a 0. S Hence S in Metric data are: Next calculate the pump discharge pressure p.

Pa m N A F area piston force rod p piston pump rod , N m m N A p F piston load load First find the booster discharge pressure. Pa psi Pa psi p , 7. This would increase the chances for having pump cavitation because the pump inlet pressure more closely approaches the vapor pressure of the fluid usually about 5 psi suction or -5 psig allowing for the formation and collapse of vapor bubbles.

First calculate the lever force applied to the small diameter piston. Pa m N A F p piston small piston small oil , Velocity value agrees with that of Example Writing Bernoullis Equation between stations 1 and 2, we have: Then using Equation yields: Thus psig ft in ft lb ft p 7.

Therefore we have from the previous equation: Writing Bernoullis Equation between stations 1 and 2 we have: We next solve for the pump head. Substituting values we have. Solving for v 2 we have: Therefore, we have from the previous equation: Per continuity equation: It is very important to keep all energy losses in a fluid power system to a minimum acceptable level.

Laminar flow is characterized by the fluid flowing in smooth layers. In turbulent flow, the movements of a particle becomes random and fluctuate up and down in a direction perpendicular as well as parallel to the mean flow direction. This causes a mixing motion as particles collide.

If N R is less than , the flow is laminar. If N R is greater than , the flow is turbulent. Reynolds numbers between and cover a transition region between laminar and turbulent flow. Relative roughness is defined as the pipe inside surface roughness divided by the pipe inside diameter. The K factor equals the head loss divided by the velocity head. The equivalent length of a valve or fitting is that length of pipe which, for the same flow rate, produces the same head loss as the valve or fitting.

High velocity and large pipe roughness. Since N R is less than , the flow is laminar. Assuming laminar flow we have: Thus the relative roughness can now be found. If the flow is laminar, the friction factor is: For a given opening position, a valve behaves as an orifice. Thus use Eq.

The flow coefficient and K factor values would be the same because these two parameters are dimensionless. First find the velocity. Then find the friction factor. Finally we calculate the equivalent length where the K factor equals 0. For the system of Figure , we have the following data: Reynolds Number can now be found. The flow is laminar. We can now find the head loss due to friction between stations 1 and 2.

We can now substitute values into Bernoullis equation to solve for. Using Equation allows us to solve for the pump head. Finally we solve for the pressure at station 2.

Writing Bernoullis equation between stations 1 and 2, we have: The pressure head at station 1 is: The Reynolds Number can now be found.

The flow is laminar so the friction factor is: Head loss across strainer ft SG p strainer 6. The Reynolds Number can now be found where the kinematic viscosity is: The flow is laminar so the friction depends only on N R.

Next use Bernoullis equation to solve for P 2. Solving for the pump head we have: Next we solve for the pressure head at station 2. For the system of Figure we have the following data: Writing Bernoullis equation stations 1 and 2, we have: P m 1 The Reynolds Number can now be found: Head loss across strainer m p strainer Next use Bernoullis equation to solve for.

Thus we have: MPa psi Pa psi p pump Pipe No. Length m Dia. Gear 2. Vane 3. Piston A positive displacement pump ejects a fixed amount of fluid into the hydraulic system per revolution of pump shaft rotation.

Thus, for positive displacement pumps, pump flow rate is directly proportional to pump speed. However, for centrifugal pumps, flow output is reduced as circuit resistance is increased. Thus, the flow rate from a centrifugal pump not only depends on the pump speed, but also on the resistance of the external system. All pumps operate on the principle whereby a partial vacuum is created at the pump inlet due to the internal operation of the pump.

This allows atmospheric pressure to push the fluid out of the oil tank into the pump intake. The pump then mechanically pushes the fluid out the discharge line as shown by Figure Volumetric efficiency equals actual flow rate produced by a pump, divided by the theoretical flow rate based on volumetric displacement and pump speed.

Actual flow rate is measured by a flow meter and theoretical flow rate is calculated from the equation: Mechanical efficiency is determined by using Equation where pump discharge pressure P, pump input torque T and pump speed N are measured.

The theoretical pump flow rate is calculated from the equation: After the volumetric efficiency q V and mechanical efficiency q m have been found, the overall efficiency q o is determined from the equation: A partial vacuum is created at the pump inlet due to the internal operation of the pump See Figure This allows atmospheric pressure to push the fluid out of the oil tank and into the pump intake because atmospheric pressure is greater than vacuum pressure.

A fixed displacement pump is one in which the amount of fluid ejected per revolution displacement cannot be varied. In a variable displacement pump, the displacement can be varied by changing the physical relationships of various pump elements. This change in pump displacement, produces a change in pump flow output even though pump speed remains constant.

Spur gear 2. Helical gear 3. Herringbone gear Lobe 2. Gerotor Three precision ground screws, meshing within a close- fitting housing, deliver non-pulsating flow See Figure 5- The two symmetrically opposed idler rotors are in rolling contact with the central power rotor and are free to float in their respective housing bores on a hydrodynamic oil film.

Flow rate requirements 2. Operating speed 3. Pressure rating 4. Performance 5. Reliability 6. Maintenance 7. Cost 69 8. Noise A pressure compensated vane pump is one in which system pressure acts directly on the cam ring via a hydraulic piston See Figure This forces the cam ring against the compensation spring-loaded piston.

If the discharge pressure is large enough, it overcomes the compensator spring force and shifts the cam ring. As the discharge pressure continues to increase, zero eccentricity and thus, zero flow is achieved. Therefore, such a pump has its own protection against excessive pressure buildup.

Pump cavitation occurs when suction lift is excessive and the inlet pressure falls below the vapor pressure of the fluid usually about 5 psi suction.

Fluid Power with Applications (7th Edition)

As a result, vapor bubbles which form in the low pressure inlet region of the pump, are collapsed when they reach the high pressure discharge region. This produces high fluid velocities and impact forces which erode the surfaces of metallic components. The result is shortened pump life. Pumps do not pump pressure.

Instead they produce fluid flow.

Cavitation can occur due to entrained vapor bubbles. This occurs when suction lift is excessive and the inlet pressure falls below the vapor pressure of the fluid usually about 5 psi suction. Cavitation produces very large fluid impact forces which erodes the surfaces of metallic components and thus shortens pump life. If there is no place for the fluid to go, the pressure will rise to an unsafe level unless a pressure relief valve opens to allow flow back to the oil tank.

Thus, the relief valve determines the maximum pressure level which the system will experience. The flow output of a centrifugal pump is reduced as circuit resistance is increased. Therefore, centrifugal pumps are rarely used in hydraulic systems. A balanced vane pump is one that has two intake and two outlet ports diametrically opposite each other.

Thus, pressure ports are opposite each other and a complete hydraulic balance is achieved. This eliminates the bearing side loads and, thus, permits higher operating pressures. Axial design 2. Radial design Pump speed 2. Pressure 3.

Pump size 4. Entrained gas bubbles The pressure rating is defined as the maximum pressure level at which the pump can operate safely and provide a good useful life.

Keep the pump inlet lines as short as possible. Minimize the number of fittings in the inlet line. Mount the pump as close as possible to the reservoir. Gear pumps are simple in design and compact in size. They are the least expensive. Vane pump efficiencies and costs fall in between gear and piston pumps. Piston pumps are the most expensive and provide the highest level of overall performance.

By specifying volumetric displacement and volumetric flow rate at a given pump speed. Vane and piston pumps. Thus, pressure ports are opposite each other, and a complete 71 hydraulic balance is achieved eliminating bearing side loads and thus permitting higher operating pressures.

By varying the offset angle between the cylinder block centerline and the drive shaft centerline. The eccentricity between the centerline of the rotor and the centerline of the cam ring can be changed by a hand wheel or by a pressure compensator.

The addition of pressure compensation prevents the manual setting of the rotor eccentricity to vary flow rate. Rather, the eccentricity is controlled by pump discharge pressure resulting in zero flow rate zero eccentricity at maximum pump discharge pressure.

Thus the pump is protected against excessive pressure because it produces no flow at the maximum pressure level. Noise is sound that people find undesirable. Intensity and loudness are not the same because loudness depends on each persons sense of hearing. The loudness of a sound may not be the same for two people sitting next to each other and listening to the same sound.

However the intensity of sound, which represents the amount of energy possessed by the sound, can be measured and thus does not depend on who hears it. One decibel equals the smallest change in intensity that can be detected by most people. The weakest sound intensity that the human ear can hear is designated as zero decibels. Prolonged exposure to loud noise can result in loss of hearing.

Noise can mask sounds that people want to hear. These include voice communication between people and warning signals emanating from safety equipment.

Make design changes to the source of the noise such as a pump. Modify the path along which the noise travels such as by clamping hydraulic piping at specifically located supports.

Use sound absorption materials in nearby screens or partitions. First find the displacement volume. Next find the theoretical flow rate. The volumetric efficiency can now be found. Next solve for the volumetric efficiency. HP Q p HP mover ime 7. The following metric data are applicable: External load on cyl. Thus when the cylinder is fully extended we have: For this case we have: Hydraulic HP lost with press-comp.

SOLUTION!!!-Fluid-Power-With-Applications-ESPOSITO,Anthony-7th ed..pdf

Per the solution to Exercise we have the following while the cylinder is extending: This is 1 gpm 0. Power lost with fixed displacement pump kW s m kPa Q p 1. A single acting cylinder can exert a force in only the extending direction. Single acting cylinders do not retract hydraulically.

Retraction is accomplished by using gravity or by the inclusion of a compression spring in the rod end. Double acting cylinders can be extended and retracted hydraulically. Flange mount.

Trunnion mount. Clevis mount. Foot and centerline lug mounts. Some cylinders contain cylinder cushions at the ends of the cylinder to slow the piston down near the ends of the stroke. This prevents excessive impact when the piston is stopped by the end caps as illustrated in Figure A double-rod cylinder is one in which the rod extends out of the cylinder at both ends. Since the force and speed are the same for either end, this type of cylinder is typically used when the same task is to be performed at either end.

Telescoping rod cylinders contain multiple cylinders which slide inside each other. They are used where long work strokes are required but the full retraction length must be minimized. The effective cylinder area is not the same for the extension and retraction strokes. This is due to the effect of the piston rod. Single acting cylinders are retracted by gravity or by the inclusion of a compression spring in the rod end of the cylinder. A first class lever is characterized by the lever fixed hinge pin located between the cylinder and load rod pins.

In a second class lever, the load rod pin is located between the fixed hinge pin and cylinder rod pin. For a third class lever, the cylinder rod pin lies in between the load rod pin and the fixed hinge pin.

A moment is the product a force and its moment arm relative to a given point. A moment arm is the perpendicular distance from a given point to the line of action of a force. The cylinder is clevis mounted to allow the rod pinned end to travel along the circular path of the lever as it rotates about its fixed hinge pin.

A torque is the product of a force and its torque arm relative to a given axis of rotation. The torque arm is the distance from the axis of rotation measured perpendicular to the line of action of the force. Thus for example, for the first class lever of Figure 6- 12, the axis of rotation is the fixed hinge pin centerline. The load torque that the cylinder must overcome thus equals the produce of the load force F load and its torque arm L 2 cos u relative to the hinge pin axis of rotation.

Hence a torque arm is a forces distance to an axis of rotation and a moment arm is a forces distance to a point. Hence a moment tends to bend a member about a point whereas a torque tends to rotate a member about an axis. The purpose is to bring a moving load to a gentle rest through the use of metered hydraulic fluid. Two applications are moving cranes and suspension systems of automobiles.

Therefore v does not change. Since the stroke is doubled the time increases by a factor of 2. Piston area A increases by a factor of 4. Therefore v decreases by a factor of 4. So the time imcreases by a factor of 4 and the force increases by a factor of 4. Since the stroke is doubled the time increases by a factor of 8 and the force increases by a factor of 4. Hence the answers are the same as those for the extension stroke.

There would be a net force to extend the cylinder. This net force would have the following value which is the same as that obtained in Exercise Per Newtons Law of Motion we have. The component of the weight W acting along the axis of the cylinder is W sin The component of the weight W acting normal to the incline surface is W cos The frictional force equals the coefficient of friction times the force normal to the sliding surfaces.

Therefore the frictional force f acting along the axis of the cylinder is lb lb W CF f 30 cos Per Newtons Law we have. Second Class Lever: Third Class Lever: Equating moments about fixed pin C yields: Equating moments about fixed pin A due to the cylinder force F and the lb weight yields: AE From trigonometry of right triangles we have: F F Therefore we have BC load sin: First, calculate the steady state piston velocity V prior to deceleration. Next, calculate the deceleration a of the piston during the 1 inch displacement S using the constant acceleration or deceleration equation.

Substituting into Newtons Law of Motion Equation yields: Hydr cyl dia in in ft in m ft m. Substituting into Newtons Law of Motion Equation and solving for 2 p yields: A limited rotation hydraulic actuator provides rotary output motion over a finite angle.

A hydraulic motor is an actuator which can rotate continuously. Simple design and subsequent low cost. Since vane motors are hydraulically balanced, they are fixed displacement units. The vanes must have some means other than centrifugal force to hold them against the cam ring. Some designs use springs while other types use pressure-loaded vanes. Yes and either fixed or variable displacement units can be used. Volumetric efficiency equals the theoretical flow rate the motor should consume, divided by the actual flow rate consumed by the motor.

Mechanical efficiency equals the actual torque delivered by the motor divided by the torque the motor should theoretically deliver. Overall efficiency equals the actual power delivered by the motor divided by the actual power delivered to the motor.

A motor uses more flow than it theoretically should because the motor inlet pressure is greater than the motor discharge pressure.

Thus, leakage flow passes through a motor from the inlet port to the discharge port. A hydrostatic transmission is a system consisting of a hydraulic pump, a hydraulic motor and appropriate valves and pipes, which can be used to provide adjustable speed drives for many practical applications. Four advantages of hydrostatic transmissions are: Infinitely variable speed and torque in either direction and over the full speed and torque range. Extremely high power per weight ratio. Can be stalled without damage.

Low inertia of rotating members permits fast starting and stopping with smoothness and precision. A hydraulic motor delivers less torque than it theoretically should because frictional losses exist in an actual hydraulic motor. The theoretical torque output is proportional to inlet pressure and volumetric displacement which is independent of motor speed.

Flow rate and volumetric displacement. Displacement is the volume of oil required to produce one revolution of the motor. Torque rating is the torque delivered by the motor at rated pressure. Some designs use springs, whereas other types use pressure-loaded vanes. Pressure exerts a force on the pistons. The piston thrust is transmitted to the angled swash plate causing torque to be created in the drive shaft. An increase in the working load results in an increase in volumetric displacement.

This decreases motor speed for a constant pump flow rate. Piston motor. By using the following equation: First, solve for the volumetric displacement. Then solve for the pressure that must be developed to overcome the load. The metric data are as follows: Pump disch e pressure psi kPa psi kPa arg. Friction This would, however, double the HP per the following equation: Note that the calculated values of V D and T are theoretical values. Actual values can be calculated as follows: Since a motor consumes more flow than it theoretically should we have: A relationship in terms of overall efficiency can be developed as follows: W Q p Power b AM motor to act , 14 Directional control valves determine the path through which a fluid traverses within a given circuit.

A check valve is a directional control valve which permits free flow in one direction and prevents any flow in the opposite direction.

A pilot check valve always permits free flow in one direction, but permits flow in the normally blocked opposite direction only if pilot pressure is applied at the pilot pressure port of the valve. A four-way directional control valve is one which has four different ports.

This valve contains a spool which can be actuated into three different functioning positions. The center position is obtained by the action of the springs alone. Manually 2. Air piloted 3. Solenoid actuated A solenoid is an electric coil. When the coil is energized, it creates a magnetic force that pulls the armature into the coil.

This causes the armature to push on the push rod to move the spool of the valve. The open-center type connects all ports together when the valve is unactuated. The closed-center design has all ports blocked when the valve is unactuated. A shuttle valve is another type of directional control valve.

It permits a system to operate from either of two fluid power sources. One application is for safety in the event that the main pump can no longer provide hydraulic power to operate emergency devices. To limit the maximum pressure experienced in a hydraulic system. A pressure reducing valve is another type of pressure control valve.

It is used to maintain reduced pressures in specified locations of hydraulic systems. An unloading valve is used to permit a pump to build up to an adjustable pressure setting and then allow it to discharge to the tank at essentially zero pressure as long as pilot pressure is maintained on the valve from a remote source.

A sequence valve is a pressure control device. Its purpose is to cause a hydraulic system to operate in a pressure sequence. To maintain control of a vertical cylinder so that it does not descend due to gravity.

This will prepare the student for the inevitable United States adoption of the Metric System. 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, Pascals Law and Bernoullis 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, Reynolds 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. 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. 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. 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. 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 5 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.Over half of all hydraulic system problems have been traced directly to the oil.

This requires the proper selection of the sizes of all pipes and fittings used in the system. Maintenance 7. Figure shows a compression-type fitting which can be repeatedly taken apart and reassembled and remain perfectly sealed against leakage. Thank you in advance to all those who take the time to send me the corrections. Cundiff did research at the University of Georgia for the first eight years of his academic career and has taught at Virginia Tech in the Biological Systems Engineering Department since The Reynolds Number can now be found.

A force is required to change the motion of a body.