Quantcast Operation of Hydraulic Components

can  be  kept  clean  inside  and  variations  from normal   operation   can   easily   be   detected   and remedied. OPERATION  OF  HYDRAULIC COMPONENTS To  transmit  and  control  power  through pressurized  fluids,  an  arrangement  of  inter- connected   components   is   required.   Such   an arrangement  is  commonly  referred  to  as  a  system. The number and arrangement of the components vary  from  system  to  system,  depending  on  the particular application. In many applications, one main system supplies power to several subsystems, which are sometimes referred to as circuits. The complete  system  may  be  a  small  compact  unit; more often, however, the components are located at widely separated points for convenient control and  operation  of  the  system. The basic components of a fluid power system are essentially the same, regardless of whether the system 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  receiver Pump  or  compressor Lines  (pipe,  tubing,  or  flexible  hose) Directional  control  valve Actuating  device Several  applications  of  fluid  power  require only a simple system; that is, a system which uses only  a  few  components  in  addition  to  the  five basic components. A few of these applications are presented  in  the  following  paragraphs.  We  will explain the operation of these systems briefly at this  time  so  you  will  know  the  purpose  of  each component   and   can   better   understand   how hydraulics   is   used   in   the   operation   of   these systems.  More  complex  fluid  power  systems  are described  in  chapter  12. HYDRAULIC  JACK The   hydraulic   jack   is   perhaps   one   of   the simplest  forms  of  a  fluid  power  system.  By moving the handle of a small device, an individual can  lift  a  load  weighing  several  tons.  A  small initial force exerted on the handle is transmitted by a fluid to a much larger area. To understand this  better,  study  figure  2-19.  The  small  input piston  has  an  area  of  5  square  inches  and  is directly  connected  to  a  large  cylinder  with  an output 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 input piston,  it  produces  a  pressure  of  5  psi  in  the  fluid, that  is,  of  course,  if  a  sufficient  amount  of resistant  force  is  acting  against  the  top  of  the output   piston.   Disregarding   friction   loss,   this pressure acting on the 250 square inch area of the output  piston  will  support  a  resistance  force  of 1,250 pounds. In other words, this pressure could overcome a force of slightly under 1,250 pounds. An  input  force  of  25  pounds  has  been  transformed into  a  working  force  of  more  than  half  a  ton; however, for this to be true, the distance traveled by the input piston must be 50 times greater than the distance traveled by the output piston. Thus, for  every  inch  that  the  input  piston  moves,  the output  piston  will  move  only  one-fiftieth  of  an i n c h . This would be ideal if the output piston needed to move only a short distance. However, in most instances,  the  output  piston  would  have  to  be capable  of  moving  a  greater  distance  to  serve  a practical application. The device shown in figure 2-19 is not capable of moving the output piston farther  than  that  shown;  therefore,  some  other means must be used to raise the output piston to a greater height. Figure  2-19.—Hydraulic  jack. 2-15


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