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General Gas Law
Contamination Control - 14105_172

Fluid Power - Intro to Hydraulics, Pneumatics, and how it all works
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75  psig,  T1  is   800,  P1  is  237.8  psig,  and  T2  is 300°F: Solution: Substituting: PNEUMATIC   GASES In  chapter  1,  you  learned  that  many  factors are  considered  in  determining  whether  to  use hydraulics or pneumatics as a power source in a fluid  power  system.  Once  it  is  determined  that pneumatics will be used as the source of power, some  of  the  same  factors  are  considered  in selecting the pneumatic gas. QUALITIES The  ideal  fluid  medium  for  a  pneumatic system   is   a   readily   available   gas   that   is nonpoisonous  (nontoxic),  chemically  stable,  free from  any  acids  that  cause  corrosion  of  system components,  and  nonflammable.  It  also  will  not support  combustion  of  other  elements. Gases that have these desired qualities may not have  the  required  lubricating  power.  Therefore, lubrication of the components of some pneumatic systems  must  be  arranged  by  other  means.  For example, some air compressors are provided with a   lubricating   system,   some   components   are lubricated  upon  installation  or,  in  some  cases, lubrication is introduced into the air supply line. Two  gases  meeting  these  qualities  and  most commonly  used  in  pneumatic  systems  are  com- pressed  air  and  nitrogen. COMPRESSED  AIR Compressed   air   is   a   mixture   of   all   gases contained  in  the  atmosphere.  In  this  manual, compressed air is referred to as a gas when it is used  as  a  fluid  medium. The  unlimited  supply  of  air  and  the  ease  of compression  make  compressed  air  the  most  widely used  fluid  for  pneumatic  systems.  Although moisture  and  solid  particles  must  be  removed from  the  air,  it  does  not  require  the  extensive distillation or separation process required in the production  of  other  gases. Compressed  air  has  most  of  the  desired properties  and  characteristics  of  a  gas  for pneumatic   systems.   It   is   nonpoisonous   and nonflammable  but  does  contain  oxygen,  which supports  combustion.  One  of  the  most  undesirable qualities of compressed air as a fluid medium for pneumatic  systems  is  moisture  content.  The atmosphere  contains  varying  amounts  of  moisture in  vapor  form.  Changes  in  the  temperature  of compressed  air  will  cause  condensation  of moisture  in  the  pneumatic  system.  This  condensed moisture  can  be  very  harmful  to  the  system,  as it  increases  corrosion,  dilutes  lubricants,  and  may freeze  in  lines  and  components  during  cold weather.  Moisture  separators  and  air  driers (dehydrators) are installed in the compressed air lines   to   minimize   or   eliminate   moisture   in systems  where  moisture  would  deteriorate  system performance. The supply of compressed air at the required volume  and  pressure  is  provided  by  an  air compressor. (For information on air compressors, refer to Naval Ships’ Technical Manual,  chapter 551.)  In  most  systems  the  compressor  is  part  of the system with distribution lines leading from the compressor  to  the  devices  to  be  operated.  In  these systems  a  receiver  is  installed  in-line  between  the compressor and the device to be operated to help eliminate pulsations in the compressor discharge line, to act as a storage tank during intervals when the   demand   for   air   exceeds   the   compressor’s capacity,  and  to  enable  the  compressor  to  shut down during periods of light load. Other systems receive  their  supply  from  cylinders  which  must  be filled  at  a  centrally  located  air  compressor  and then  connected  to  the  system. Compressed  air  systems  are  categorized  by their  operating  pressures  as  follows:  high-pressure (HP)  air,  medium-pressure  (MP)  air,  and  low- pressure  (LP)  air. High-Pressure Air Systems HP  air  systems  provide  compressed  air  at  a nominal  operating  pressure  of  3000  psi  or  5000 psi and are installed whenever pressure in excess 11-7







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