File Name: industrial hydraulic systems and circuits .zip
Closed circuit ; Fluid power ; Hydraulic equipment ; Hydraulics ; Hydrostatic transmission ; Open circuit. Hydraulic circuits transmit and control power from a mechanical input to a mechanical output by means of liquids, mostly oils. Power is transmitted hydrostatically, where high pressures make static forces dominate over dynamic forces, and energy is transmitted mostly through static pressure at low flow velocities. Circuits are composed of a number of hydrostatic components which are connected to each other by means of piping, manifolds, or directly, to enable transmission and control of power or signals through liquids.
In Chapter 2, the rolling element bearings and their lubrication are discussed. An extremely important facet of any well-designed hydraulic system is uid ltration. Chapter 3 not only provides a detailed discussion of uid ltration and particle contamination and quanti cation, but also discusses uid lterability. An understanding of the physical properties of a uid is necessary to understand the performance of a hydraulic uid as a uid power medium.
Chapter 4 features a thorough overview of the physical properties, and their evaluation and impact on hydraulic system operation, which includes: viscosity, viscosity-temperature and viscosity-pressure behavior, gas solubility, foaming, air entrainment, air release, and uid compressibility and modulus.
Consequently, an abrupt local pressure variation will be propagated through the uid with a velocity equal to the uid sound velocity until the equilibrium has been re-established. This means that the uid will have a dynamic behavior alternating between the two equilibrium states. When a uid is treated as incompressible it is assumed that a local pressure perturbation is instantaneously transmitted throughout the uid.
This means that considering a uid as being compressible or incompressible is dependent on the observer's viewpoint and its validation depends on the use of the system and the particular design or analysis that is being carried out. Pascal's principle states that "a change in the pressure of an enclosed incompressible uid is conveyed undiminished to every part of the uid and to the surfaces of its container" [1,7].
Hence, when a uid is in a state of equilibrium, that is, in a steady state, the whole system is under the same internal pressure. The practical use of Pascal's principle can be exempli ed by the hydrostatic press principle whose objective is to amplify the force. As shown in Figure 1. The subscript indicates the quantity application and the superscript is used to indicate to which component or system the quantity is associated ISO , ISO -Fluid Power Systems and Components -Graphic symbols and circuit diagrams -Part 2: Circuit diagrams, Switzerland, Hence, according to Equation 1.
The behavioral description with temporal variation is carried out using the laws of hydrodynamics . In this chapter, two of these principles are studied; namely, the conservation of mass continuity equation and the conservation of energy Bernoulli's equation , which are essential to the comprehension of the hydraulic component behavior. From the conservation of mass principle, an important expression is obtained which describes the behavior of pressure in volumes.
Consider the hydraulic device shown in Figure 1. The ow rate in the inlet port is considered positive when entering the chamber and the ow rate in the outlet port is positive when leaving the chamber. The chamber volume changes with the piston movement. The result of the continuity equation [1,8,9] applied to this case is .
Therefore, Equation 1. The pressure change will take the piston out of equilibrium, causing its movement. As a consequence, the rst term on the right will be different from zero, in turn changing the pressure.
It is important to note that the continuity equation, as presented in Equation 1. Studying again the hydrostatic press Figure 1. Appling Equations 1. Cylinder A1, having reached the required displacement, will reach its stroke end much earlier than cylinder A2. Therefore, this basic circuit is not valuable for real uses. A typical circuit found in hydrostatic presses and hydraulic jacks is presented in Figure 1. In this circuit an external reservoir R , which compensates for the difference between the cylinder volumes, and two non-return valves V1 and V2 are included.
These valves allow uid suction from the reservoir on the upward movement of cylinder A1 and uid pumping to cylinder A2 on the downward movement. Valve register V3, when opened, allows the uid in cylinder A2 to return to the reservoir as a consequence of the external force F A2 applied to the piston.
Correlating Figure 1. The uid storage and conditioning is performed by both the reservoir R and the air lter F. The lter establishes the connection between the uid and the external environment in order to keep the reservoir cleaned and at atmospheric pressure. According to ISO , the pump has its own symbol, P, while the hydraulic motor is an actuator and, for this reason, it is designed as A. At the same time, a loading applied to the axis causes a torque T A in the opposite direction to the movement, inducing a pressure p increase.
This pressure, which is transmitted to the whole system, acts on the pump increasing the mechanical torque T P. However, as an ideal system is being considered, the load losses, leakages, and mechanical friction are neglected. In the same way as the hydrostatic press Figure 1. At each complete revolution of a hydrostatic machine rotor 1. For a rotor with vanes, as shown in Figure 1. According to this equation the sum of all forms of mechanical energy in a steady and unidimensional ow of an ideal and incompressible uid is the same at all points in the stream line.
One fundamental use of Bernoulli's equation is to describe the ow behavior through a sharp-edge ori ce in a pipe, which causes an abrupt reduction in the ow cross section, as shown in Figure 1.
In this case, the stream lines converge to a point where the diameter of the stream is the smallest. This point is called vena contracta and corresponds to cross section 2 in the gure. Furthermore, since the ori ce area A 0 and, consequently, the vena contracta area A 2 , are much smaller than the inlet area A 1 , the velocity in the inlet cross section v 1 is neglected.
Additionally, experimental data from the literature [9,10] correlate the vena contracta area A 2 with the real ori ce area A 0 such that Equation 1. Another important aspect is that the turbulence downstream of the ori ce causes a signi cant energy loss such that the velocity reduction in cross section 3 Figure 1. Hence p 3 is very close to p 2.
This hydraulic power difference is transformed into thermal energy, heating the uid and the environment. Typically, these circuits are represented by diagrams composed of graphical symbols that represent uid power components and devices. ISO  establishes basic elements for symbols and rules for devising uid power symbols for use in components and circuit diagrams.
ISO  establishes the rules for drawing uid power diagrams using symbols from ISO , including rules for identi cation of equipment. Furthermore, an identi cation code will be associated with these symbols following the rules shown in Figure 1. Figure 1. Since the pump theoretically supplies a constant ow rate, it is necessary to direct part of the ow through the relief valve V1 aiming to obtain velocity control in the cylinder A. Therefore, the effect of the ow control valve V3 is to cause a pressure loss such that the supply pressure p P is above the setting pressure p Pset at the relief valve V1 , and it opens.
As can be observed in the example in Figure 1. Therefore, the motor rotational frequency will be modi ed if the volumetric displacement of either the motor or the pump is varied or the pump rotational frequency is changed. The relationship between the ow rate, volumetric displacement, and rotational frequency of a pump or motor is described by Equation 1. In the circuit shown in Figure 1. A closed-loop circuit is always used in conjunction with a smaller replenishing circuit.
The replenishing circuit always works on the low-pressure side of the main loop. Its function is to pump freshly ltered uid into the closed loop through non-return valves V1 and V2 while bleeding-off a percentage of the hot uid through a directional control valve V3. This hot uid is then cooled by a cooler H and stored in a small reservoir R before returning to the main system. The pressure in the replenishing circuit is limited to bar MPa by the supercharge relief valve V6.
The cross-port relief valves V4 and V5 on the motor are there only to protect the actuator from load-induced pressure spikes. They are not intended to function like those found in open-loop circuits, which would cause severe overheating of the circuit due to the diverting of the unnecessary ow through the relief valve.
The advantages of a closed-loop circuit are that high-power systems are compact and ef cient and require less hydraulic uid storage. The high ef ciency of this circuit is the result of the pump control being designed to supply only the uid ow required by the actuator to operate at the load-induced pressure.
The pump is the heart of the system and controls the direction, acceleration, speed, and torque of the hydraulic motor, thus eliminating the need for pressure and ow control components.
In this type of circuit the energy control is transformative, instead of dissipative as in open-loop circuits, since it is the energy transformed in the pump or motor that is controlled. However, the secondary valves pressure, directional and ow-control valves impose energy losses-besides the internal mechanical and uid ow losses-in pumps and motors, thereby reducing the overall ef ciency. A major disadvantage of a closed-loop circuit is that a single pump can only operate a single output function or actuator.
In addition, this type of hydraulic circuit is generally used only with motor actuators. The third general con guration is the half-closed-loop circuit as shown in Figure 1. This circuit is similar to the closed-loop circuit except that it can be used with cylinder actuators with different areas. As can be seen from the gure, during cylinder extension, the pump P must generate a higher ow rate from its left-hand port than that being returned to its right-hand port from the cylinder A.
The extra uid needed by the pump P is supplied by its left-hand inlet nonreturn valve, which is an integral part of the pump. When the pump control moves the pump over the center, the ow from the pump P is reversed and the cylinder A begins to retract. During retraction, the larger area of the cylinder piston causes a higher ow rate than needed at the inlet of the pump P.
This excess ow is directed to the reservoir R through the unloading valve V3. The unloaded uid is ltered and cooled prior to its return to the reservoir. In this way, a portion of the closed-loop uid is ltered by F and cooled by C in an open-loop circuit each time the cylinder A is cycled. In this case, the uid volume and reservoir size reductions are not as signi cant as in the closedloop scenario. As can be seen in the above examples, each hydraulic component has a basic function, but it is the circuit itself that determines the hydraulic system behavior.
You do not have to provide any information to download free software downloads. We will screen all donated downloads, for validity and relevance. Industrial Hydraulic Systems and Circuits sample. Sample of another popular ebook, detailed to the point of being a great desk top reference for all who work on hydraulic systems. This book covers the literature regarding various types of standard hydraulic system components like different types of pumps, pressure controlling components, flow control valves, check valves and direction control valves. Details of different types of tailor made auxiliaries like hydraulic tank and their accessories, filters, piping, fittings and accumulator etc. In addition to the above, special devices right from the conventional copying attachment system to latest electro-hydraulic system like proportional valves and servo valve with electronic controls are given in this book.
The first edition of this book was intended to provide knowledge of hydraulic components, their operating characteristics and available circuit arrangements to assist in the design of hydraulic systems for a range of applications. For some circuits it is important to predict the dynamic performance of the overall system particularly where closed loop control is being employed. For this purpose and to provide a general understanding of how parameters vary transiently analytical methods are developed that provide techniques for studying the dynamics of systems. In this second edition these features have been retained and expanded upon so as to evaluate the performance of some hydrostatic transmission examples. In the period since the first edition there has been a considerable expansion in the use of digital computers for control purposes which has been accompanied by developments in the instrumentation field and use of electromechanical valves. This technology often involves closed loop control methods for example, the control of motor speed in a hydrostatic transmission.
Below are some common illustrations of equipment located on fluids circuit diagrams, followed by descriptions of the most common elements. Later in this article series we will describe some simple hydraulic and pneumatic circuits composed of these circuit elements. Needle valves are used to throttle or shut-off flow of fluids. They usually will vary flow with pressure or viscosity change.
Беккер терял терпение. А ведь он мог быть сейчас в Смоки-Маунтинс, со Сьюзан. Что он делает здесь, в Испании, зачем спорит с этим психованным подростком. Беккер резким движением взял парня под мышки, приподнял и с силой посадил на столик. - Слушай, сопливый мозгляк. Убирайся отсюда немедленно, или я вырву эту булавку из твоих ноздрей и застегну ею твой поганый рот. Парень побелел.
И весь мир сразу же узнает о ТРАНСТЕКСТЕ. Сьюзан вопросительно смотрела на. - Это совсем просто, Сьюзан, мы позволим правде выйти за эти стены. Мы скажем миру, что у АНБ есть компьютер, способный взломать любой код, кроме Цифровой крепости, - И все бросятся доставать Цифровую крепость… не зная, что для нас это пройденный этап. Стратмор кивнул: - Совершенно. - Повисла продолжительная пауза.
Graphic and circuit symbols_____________________________________ 73 Hydraulic systems are used in modern production plants and manufacturing.
Мелкая любезность, которую он оказал Стратмору, забрав личные вещи Танкадо, вылилась в поиски таинственного кольца, как в известной игре, где нужно находить спрятанные предметы. Дэвид только что позвонил Стратмору и рассказал о немецком туристе. Новость не обрадовала коммандера. Выслушав подробности, он долго молчал. Дэвид, - сказал наконец Стратмор мрачным голосом, - обнаружение этого кольца - вопрос национальной безопасности.
Читайте медленно и очень внимательно. Беккер кивнул и поднес кольцо ближе к глазам. Затем начал читать надпись вслух: - Q… U… 1…S… пробел… С, Джабба и Сьюзан в один голос воскликнули: - Пробел? - Джабба перестал печатать. - Там пробел. Беккер пожал плечами и вгляделся в надпись. - Да, их тут немало.
Наверное, стоит выключить ТРАНСТЕКСТ, - предложила Сьюзан. - Потом мы запустим его снова, а Филу скажем, что ему все это приснилось. Стратмор задумался над ее словами, затем покачал головой: - Пока не стоит. ТРАНСТЕКСТ работает пятнадцать часов. Пусть пройдут все двадцать четыре часа - просто чтобы убедиться окончательно. Сьюзан это показалось разумным.
Халохот, спустившись вниз по улочке, смачно выругался.
Дэвид на экране застыл в глубокой задумчивости. - Разница, - бормотал он себе под нос. - Разница между U235 и U238. Должно быть что-то самое простое.
Северная Дакота - это Хейл. Но Стратмор смотрел на молодого сотрудника лаборатории систем безопасности.
Сьюзан неохотно кивнула. План неплохой. Когда служба безопасности извлечет Хейла из подсобного помещения и обвинит в убийстве Чатрукьяна, он скорее всего попытается шантажировать их обнародованием информации о Цифровой крепости. Но все доказательства к этому моменту будут уничтожены, и Стратмор сможет сказать, что не знает, о чем речь. Бесконечная работа компьютера.
El vuelo a los Estados Unidos. Стоявшая за стойкой симпатичная андалузка посмотрела на него и ответила с извиняющейся улыбкой: - Acaba de salir. Вы на чуть-чуть опоздали. - Ее слова словно повисли в воздухе. Все-таки он опоздал.
Если нужно, используйте против всех нас слезоточивый газ. Если мистер Хейл не образумится, снайперы должны быть готовы стрелять на поражение. Всю ответственность я беру на .
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