can be kept clean inside and variations fromnormal operation can easily be detected andremedied.OPERATION OF HYDRAULICCOMPONENTSTo transmit and control power throughpressurized fluids, an arrangement of inter-connected components is required. Such anarrangement is commonly referred to as a system.The number and arrangement of the componentsvary from system to system, depending on theparticular application. In many applications, onemain system supplies power to several subsystems,which are sometimes referred to as circuits. Thecomplete system may be a small compact unit;more often, however, the components are locatedat widely separated points for convenient controland operation of the system.The basic components of a fluid power systemare essentially the same, regardless of whether thesystem uses a hydraulic or a pneumatic medium.There are five basic components used in a system.These basic components are as follows:1.2.3.4.5.Reservoir or receiverPump or compressorLines (pipe, tubing, or flexible hose)Directional control valveActuating deviceSeveral applications of fluid power requireonly a simple system; that is, a system which usesonly a few components in addition to the fivebasic components. A few of these applications arepresented in the following paragraphs. We willexplain the operation of these systems briefly atthis time so you will know the purpose of eachcomponent and can better understand howhydraulics is used in the operation of thesesystems. More complex fluid power systems aredescribed in chapter 12.HYDRAULIC JACKThe hydraulic jack is perhaps one of thesimplest forms of a fluid power system. Bymoving the handle of a small device, an individualcan lift a load weighing several tons. A smallinitial force exerted on the handle is transmittedby a fluid to a much larger area. To understandthis better, study figure 2-19. The small inputpiston has an area of 5 square inches and isdirectly connected to a large cylinder with anoutput piston having an area of 250 square inches.The top of this piston forms a lift platform.If a force of 25 pounds is applied to the inputpiston, it produces a pressure of 5 psi in the fluid,that is, of course, if a sufficient amount ofresistant force is acting against the top of theoutput piston. Disregarding friction loss, thispressure acting on the 250 square inch area of theoutput piston will support a resistance force of1,250 pounds. In other words, this pressure couldovercome a force of slightly under 1,250 pounds.An input force of 25 pounds has been transformedinto a working force of more than half a ton;however, for this to be true, the distance traveledby the input piston must be 50 times greater thanthe distance traveled by the output piston. Thus,for every inch that the input piston moves, theoutput piston will move only one-fiftieth of ani n c h .This would be ideal if the output piston neededto move only a short distance. However, in mostinstances, the output piston would have to becapable of moving a greater distance to serve apractical application. The device shown in figure2-19 is not capable of moving the output pistonfarther than that shown; therefore, some othermeans must be used to raise the output piston toa greater height.Figure 2-19.—Hydraulic jack.2-15
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