TM 5-3895-374-24-1 OVERVIEW BASIC AIR COMPRESSOR COMPONENTS The  basic  components  of  the  air  compressor  are  the electric motor, pump, and receiver The receivers may be vertical  or  horizontal,  varying  In  size  and  capacity  See Fig 1. Electric Motor The  electric  motor  powers  the  compressor  pump  The motor drives a pulley and two belts, which transfer power from the motor to the pump pistons via a flywheel and a crankshaft  The  flywheel  fan  helps  cool  the  compressor pump. IMPORTANT: These compressors require installation of  a  magnetic  starter,  to  prevent  motor  damage  in the  event  of  a  thermal  overload.  Failure  to  Install  a magnetic   starter   will   void   the   manufacturer’s   warranty See  page  9  for  further  Information  on  magnetic  starter installation  and  wiring  (Some  units  are  supplied  with  a factory-installed magnetic starter ). Compressor Pump The pump compresses the air and discharges it Into the receiver. Two-stage air compressors have a minimum of two pump cylinders. By compressing the air twice, first In a  larger,  low  pressure  cylinder,  then  in  a  smaller,  high pressure  cylinder,  two-stage  compressors  can  produce pressures from 145-175 psi. As the piston in the pump cylinder moves downward, air enters the large cylinder through the filter and air Intake valves at atmospheric pressure. On    the    upstroke,    the    piston    in    the    large    cylinder compresses    the    air    to    approximately    50    psi,    and discharges    It    to    the    smaller    cylinder     through     the intercooler tube. The air is cooled by the flywheel fan as It  passes  through  the  intercooler  and  into  the  smaller cylinder. In the smaller cylinder, the air  is  compressed  to  its  final pressure.  As  the  piston  moves  upward,  it  compresses the   air   and   discharges   It   into   the   receiver   through   a check valve. Receiver The  receiver  (tank)  stores  the  compressed  air  A  check valve at the receiver inlet prevents the compressed air in the   receiver   from   flowing   back   Into   the   compressor pump. Pressure Switch When   the   air   pressure   in   the   receiver   reaches   the factory-set  limit,  the  pressure  switch  shuts  down  the motor. As compressed air Is used and the pressure level in  the  tank  drops  to  a  pre-set  level,  the  pressure  switch restarts the motor and the compressor resumes pumping air. TYPICAL INSTALLATION Fig  2  Illustrates  a  typical  Installation  of  an  electric  two- stage air compressor Air Dryers and Aftercoolers Two  types  of  aftercoolers  are  available  The  type  shown In Fig 2 is Installed directly in the air line It both cools and dries the air. Another  type  mounts  directly  on  the  belt  guard  of  the compressor  It  functions  like  a  radiator,  using  fan-driven air   to   cool   the   compressed   air   before   it   enters   the receiver. Moisture Removal and Air Filtration As the air cools, moisture will condense in the lines This moisture must be removed before it reaches the tool. To remove this moisture, run the main air line downhill to a trap   and   drain,   as   specified   in   Fig   2   Air/water   filters should also be Installed In the positions shown. Air Pressure Regulation The     air     pressure     gauge     on     the     pressure     switch measures     air     pressure     inside     the     receiver,     not pressure in the airline. Install an air regulator in the drop line  for  each  tool,  to  regulate  air  pressure  to  that  tool. Never  exceed  the  maximum  pressure  rating  of  the tool. Air Lubrication Install   an   air   lubricator   only   for   those   tools   requiring lubrication. Do not use a lubricator for paint spraying or   similar   applications.   The   oil   will   contaminate   the paint and ruin the job. Shut-Off Valves Install shut-off valves in each drop line, to isolate the tool and  Its  accessories  for  servicing  You  can  also  Install  a bypass line around an accessory, as shown in Fig 2. WARRANTY/REGISTRATION CARD Please   fill   out   the   enclosed   warranty/registration   card and mail it to the factory. 200-2009 (page 3-628)